Next Article in Journal
Effects of Fertilization Approaches on Plant Development and Fertilizer Use of Citrus
Next Article in Special Issue
Challenges Inherent in Controlling Prickly Pear Species; a Global Review of the Properties of Opuntia stricta, Opuntia ficus-indica and Opuntia monacantha
Previous Article in Journal
Nematicidal Potential of Sulla (Hedysarum coronarium L.) against the Root-Knot Nematode Meloidogyne incognita
Previous Article in Special Issue
Assessing Seedbank Longevity and Seed Persistence of the Invasive Tussock Grass Nassella trichotoma Using in-Field Burial and Laboratory-Controlled Ageing
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Plants
Volume 11
Issue 19
10.3390/plants11192551
plants-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Allelopathy and Allelochemicals of Imperata cylindrica as an Invasive Plant Species

by
Hisashi Kato-Noguchi
Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki 761-0795, Kagawa, Japan
Plants 2022, 11(19), 2551; https://doi.org/10.3390/plants11192551
Submission received: 8 September 2022 / Revised: 23 September 2022 / Accepted: 26 September 2022 / Published: 28 September 2022
(This article belongs to the Special Issue Plant Invasion 2022)
Browse Figures
Versions Notes

Abstract

:
Imperata cylindrica is native to Southeast Asia and East Africa and has become naturalized in humid tropics, subtropics and warmer temperate zones of the world. The species is one of the top ten worst weeds in the worlds and is listed among the world’s top 100 worst invasive alien species. It is an aggressive colonizer and forms large monospecific stands in several countries. Possible evidence of the allelopathy of I. cylindrica has been accumulated in the literature over three decades. The extracts, leachates, root exudates, decomposing residues and rhizosphere soil of I. cylindrica were found to suppress the germination and growth of several plant species, including woody plant species, and to reduce their rhizobium nodulation and mycorrhizal colonization. Several allelochemicals, such as fatty acids, terpenoids, simple phenolics, benzoic acids, phenolic acids, phenolic aldehydes, phenylpropanoids, flavonoids, quinones and alkaloids, were also found in the extracts, leachates, root exudates and/or growth medium of I. cylindrica. These observations suggest that allelochemicals may be synthesized in I. cylindrica and released into the rhizosphere soil and surrounding environments either by the leachates, root exudation or decomposition process of plant parts, and certain allelochemicals may contribute to the alteration of the microbial community, including rhizobia and mycorrhizal fungi, suppressing the regeneration process of native plant species through the inhibition of their germination and growth. Therefore, the allelopathy of I. cylindrica may support its invasiveness, naturalization and formation of large monospecific stands. This is the first review article focusing on the allelopathy of I. cylindrica.

1. Introduction

Imperata cylindrica (L.) Beauv., belonging to Poaceae, is a C4 perennial rhizomatous grass species (Figure 1). This species has an extensive rhizome network. The rhizome development of I. cylindrica occurs 3–12 weeks after germination, beginning with downward growth. When the rhizome develops cataphylls, it grows horizontally, and the tip of the rhizome begins to turn upward between the fifth and sixth leaf stages. Then, a secondary shoot and rhizome arise from the apical bud and subapical bud of the first rhizome, respectively. The secondary rhizome produces the third shoot and rhizome, continuing the following shoot and rhizome formations [1,2,3,4,5]. It was reported that one plant produced 31 rhizomes in 10 months, with a total rhizome length of 12 m [6]. The shoots form loose to compact tufts. Several leaf sheaths are often tightly rolled together, forming a cylindrical culm. I. cylindrica is virtually stemless, except for the flowering stalks. The leaves are flat, slender (4–10 mm in wide) and linear–lanceolate (15–150 cm in length, depending on the growth condition), possessing serrated margins embedded with sharp silica crystals. Stomata are present on both surfaces of the leaves [7,8,9,10].
I. cylindrica is native to Southeast Asia and East Africa and has become naturalized in humid tropics, subtropics and warmer temperate zones of the world [1,11,12,13,14]. The species is considered one of the top ten worst weeds in the world and is listed among the world’s top 100 worst invasive alien species [1,12,13]. I. cylindrica thrives in the 10 southeastern states of the USA, the Mediterranean region, northern Africa to the Middle East, tropical and subtropical Asia, Australia and the Pacific Islands, covering more than 500 million hectares worldwide [3,12,13,15,16,17]. Very large monospecific stands of I. cylindrica of more than 10,000 hectares in size, known as mega grasslands, are often observed in Indonesia as a climax species [18,19]. Large monospecific stands are also observed in Africa from Egypt to Ethiopia [1]. The species grows between latitudes 45° N (e.g., Japan) and 45° S (New Zealand) and from sea level to more than 2000 m in elevation [20,21].
The characteristics of life history, such as high reproduction and growth rates, competitive ability and phenotypic plasticity, of the plants are important for the naturalization of invasive plants into non-native ranges [22,23,24,25]. I. cylindrica is also a prolific seed producer, although its flowering is variable, depending on the environmental conditions. The inflorescence of I. cylindrica is 10–20 cm in length, with approximately 400 spikelets, which are 3–6 cm in length and covered with short, white hairs [5,7,8]. (Figure 1). A single plant produces 500–3000 seeds, which are contained in the spikelets. The movement of the seeds was reported to generally span 15 m, traveled distances of as much as 24 km with the spikelets through wind dispersal [1,26,27]. The germination rate is 30–98%, depending on the conditions [8,28,29].
Vegetative reproduction maintains local stands of I. cylindrica and contributes to spread the plant in its vicinity. When rhizome pieces are dispersed by human activities and other disturbing factors, such as a hurricane, the establishment of new populations arises from rhizome pieces. The regeneration of I. cylindrica can occur within a small amount of rhizomes—as much as 0.1 g [30]. I. cylindrica rhizomes are also very fertile [31]. It was estimated that I. cylindrica produces 6 tons of rhizome biomass per hectare, with more than 4.5 million shoots and 10 metric tons of leaf biomass [32]. Terry et al. [33] also estimated a rhizome biomass of 40 tons per hectare. Over the course of 6 weeks, rhizomes were reported to develop 350 shoots, covering an area of 4 m2 [34]. The extensive growth of I. cylindrica results dense mats of rhizomes in the soil, forming thick monospecific patches [32,33] (Figure 1).
I. cylindrica is an excellent competitor for nutrients. Its ability to absorb phosphorus, nitrogen and potassium is higher than that of native pine savanna plants, including Pinus taeda L. [35,36,37]. The species was reported to reduce the availability of water and nitrogen in surrounding soil, suppressing the establishment of juvenile P. taeda by 50% [38].
I. cylindrica has also been reported to increase wildfire occurrence and maximum wildfire temperatures [39,40]. High-temperature fire increases the mortality of native herbaceous and juvenile woody plant spices. Because I. cylindrica allocates a significant amount of biomass (over 60%) in below-ground rhizomes, it is able to regenerate quickly from its rhizomes after fires [37,39,41,42]. Therefore, frequent intense fires may result in the conversion of native ecosystems of herbaceous and juvenile woody plants into I. cylindrica-dominated grasslands.
The phenotypic plasticity of I. cylindrica is high, and the species has adapted to a wide range of environmental conditions, such as various soil types, pH values (4.4 to 8.0), organic matter (0.9 to 5%) and nutrients (P; 6 to190 kg/ha, K; 46 to 734 kg/ha) [43]. It thrives in tropical, subtropical and warm temperate areas, where annual rainfall is 750–5000 mm [7]. Its characteristics in terms of floral traits (such as spikelets, anthers and glumes) and leaf traits (such as length and width) vary within the species [27,44,45]. The species can be separated into five major varieties based on growth and morphological characteristics, as well as geographic origin: I. cylindrica var. europa (2n = 40), major (2n = 20), Africana (2n = 60), latifolia (not available) and condensate (not available). The genetic diversity of I. cylindrica in 676 samples from seven southern US states was determined using amplified fragment length polymorphisms, with two genetic lineages identified [46]. Random amplified polymorphic DNA analysis conducted in Florida showed that the species was highly outcrossed [8]. Hybridization may have facilitated the expansion of the species.
The interactions of these invasive plants with natural enemies, such as herbivores and pathogens, are critical for their naturalization. [23,24,47]. Multiple insect predators and fungal pathogens have been identified in I. cylindrica stands. However, none of them caused the extensive damage to the population of I. cylindrica [21]. In addition, methanol extracts of shoots, roots and inflorescences of I. cylindrica showed antifungal activity against the plant pathogen Macrophomina phaseolina (Tassi) Goid. [48].
The chemical interactions of the invasive plants with native plants are also crucial [24,49,50]. Several observations suggest that some invasive plants are allelopathic and that their allelochemicals are toxic to native plant species in the invasive ranges [51,52]. Therefore, allelopathy may among the factors allowing the invasive plants to establish their habitats and naturalize within the invasive ranges [52]. Allelopathy is the chemical interaction between a donor plant and receiver plants through the specific secondary metabolites defined as allelochemicals [53]. Available data from a number of observations under field and laboratory conditions suggest that I. cylindrica is also allelopathic, and possible evidence for the compounds involved in this allelopathy has been accumulated. However, no review papers have been published focusing on the allelopathy of I. cylindrica. Therefore, in this review, we provide an overview of the allelopathy and allelochemicals of the I. cylindrica and discuss the possible involvement of allelopathy in the invasiveness of the species.

2. Effects of I. cylindrica on Microbial Community

Several investigations under field and greenhouse conditions have showed that I. cylindrica altered the microbial community in the rhizosphere soil and affected the growth of several plant species, including crop plants. The decomposition process of an I. cylindrica residue was reported to be significantly faster than that of a local native grass species, Andropogon glomeratus (Walt.) Britton, Sterns & Poggenb. I. cylindrica was reported to affect the microbial flora in the soil of invaded areas and enhance the decomposition process of the plant residue [54]. The enhanced decomposition process of the plant residue may enable increasing nutrient cycling and availability. Although there are many possible explanations for the alteration of the microbial community in the soil, certain compounds of I. cylindrica may be involved in this alteration.
The abundance of mycorrhizal colonization and biomass of fine feeder roots of Pinus taeda L. was significantly suppressed in I. cylindrica-infested plantations compared with plantations not infested by I. cylindrica. The diversity of understory vegetation in pine plantations was also reduced by the presence of I. cylindrica [55]. The invasion of I. cylindrica into a Pinus palustris Mill. community caused significant loss of native plant species and reduced the distinctiveness of the native flora [56]. Arbuscular mycorrhizal colonization of Mesicago denticulata Greene and Trifolium resupinatum L. was decreased in I. cylindrica-infested fields compared with non-infested fields [57]. The mycorrhizal colonization of some weed species was also suppressed by the presence of I. cylindrica [58]. In addition, the rhizobium nodulation, nitrogen fixation and root growth of Melilotus parviflora Desf. were suppressed when M. parviflora was grown together with I. cylindrica. The populations of some fungi, such as Aspergillus spp., also differed between I. cylindrica-infested soil and non-infested soil [59]. When I. cylindrica was grown with Zea mays L. or Sorghum bicolor (L.) Moench for 8 weeks, the biomass of I. cylindrica was not affected by the presence of Z. mays and S. bicolor. However, the biomass of Z. mays and S. bicolor was significantly reduced by the presence of I. cylindrica even under the conditions that eliminated possible nutrient competition [60]. These observations suggest that I. cylindrica may suppress the mycorrhizal colonization and rhizobium nodulation in native plant species, leading to the growth inhibition of these plant species. Although some authors found no direct evidence of allelopathy, they suggested the involvement of I. cylindrica allelopathy in the suppression of mycorrhizal colonization and rhizobium nodulation [54,58,59,60].

3. Allelopathy of I. cylindrica

Allelochemicals are synthesized in certain plant parts and released into the vicinity of the plants either by rainfall leachates and volatilization from the plants, root exudation or decomposition of plant litter and residues [61,62,63]. The allelopathic activity of leachates, residues and plant extracts of I. cylindrica was evaluated over three decades (Table 1). Those observations suggest that I. cylindrica may synthesize some allelochemicals and release them into the neighboring environments either by rainfall leachates, exudation or the decomposition process of the plants.

3.1. Plant Leachates and Exudates

Water was sprinkled onto the chopped leaves of I. cylindrica as an artificial rain, and dripped water from the leaves was pumped up and sprinkled again onto the leaves. After 11 days of water circulation, dripped water was collected as artificial rainfall leachates and evaluated in terms of its allelopathic activity. The leachates suppressed the growth of Brachiaria mutica (Forssk.) Stapf and Digitaria decumbens Stent but not I. cylindrica itself [64]. Crushed dry shoots and roots of I. cylindrica were placed onto a large funnel containing a sheet of filter paper, which was kept in the open air and exposed to natural rainfall. Collected rainfall leachates from the crushed shoots and roots inhibited the germination of Dichanthium annulatum (Forssk.) Stapf and the radical growth of D. annulatum, Chrysopogon montanus Trin., Medicago polymorpha L. and Pinus roxburghii Sarg. [65].
I. cylindrica was grown in pots filled with a fine sand and irrigated with water twice a week, and drain water from holes at bottom of the pots was collected as I. cylindrica leachates. The leachates suppressed the aboveground biomass of Aristida stricta Michex. var. beyrichiana by 35.7%, its total root length by 24.9% and its mycorrhizal colonization by 23.5%. It also suppressed mycorrhizal colonization of Pinus elliottii Engelm by 19.5% [66]. The collected leachates may also contain its root exudates. I. cylindrica was grown in an agar medium for 7 day, and the medium was centrifuged after removing the plants. The resulting supernatant, which may contain root exudates of I. cylindrica, inhibited the roots and shoots growth of Echinochloa crus-galli (L.) Beauv. [67]. Soil obtained in I. cylindrica-dominated areas was extracted with water. The soil extracts inhibited the germination of Dichanthium annulatum (Forssk.) Stapf and Chrysopogon montanus Trin., as well as the radical growth of Setaria italica P. Beauv., D. annulatum, C. montanus, Medicago polymorpha L. and Pinus roxburghii Sarg. [65]. These observations suggest that the leachates and root exudates may contain allelochemicals, causing the growth inhibition and suppression of mycorrhizal colonization. These observations also imply that certain allelochemicals may be released from the leaves and below-ground parts of I. cylindrica into the rhizosphere soil or neighboring environments as plant leachates and exudates.

3.2. Plant Residues

The leaves of I. cylindrica were mixed with soil (0 g, 1.6 g and 3.2 g leaves per 100 g soil) in plastic trays (32 × 25 × 7 cm3), and those trays were kept in a greenhouse with occasional watering. Weeds that emerged in the trays were identified, counted and removed every week for one year. There was no significant difference in the total number of emerged weeds among treatments. However, the total biomass of the weeds was 38.8%, and that of the control was 27.1% (0 g leaf) for the soil mixed with 1.6 g and 3.2 g leaves, respectively. The predominant weed species were Erigeron canadensis L. and Portulaca oleracea L., which were also predominant weeds in the nearest experimental crop field [68].
Foliage or rhizomes and roots of I. cylindrica were mixed with sterilized sand medium, and the seeds of Sida spinosa L., Brachiaria ramosa (L.) Stapf., Echinochloa crus-galli (L.) Beauv., Cynodon dactylon (L.) Pers. and Lolium multiflorum Lam. were sown into the mixture and incubated for 10 days and 30 days to determine the rate of the germination and growth, respectively. All treatments resulted in the suppression of the germination of S. spinosa, B. ramosa, E. crus-galli, C. dactylon and L. multiflorum and the growth of S. spinosa, B. ramosa and E. crus-galli [69]. Whole plants of I. cylindrica were cut and mixed with a sand–peat medium. Rice seeds were then sown into the medium and incubated for 38 days. The treatments resulted in a reduction in the growth of Oryza sativa L. and the concentration of nitrogen and phosphate in rice seedlings [70].
Tillers, roots or rhizomes of I. cylindrica were incorporated into a soil mixture of sandy loam and sand and kept for 4 weeks. The I. cylindrica-incorporated soil mixtures were then extracted with water. The extracts of all soil mixtures inhibited the growth of Trifolium subterraneum L. radicles. However, the extract of the tiller mixture was the most effective [71]. These observations suggest that the whole plants, including leaves, roots and rhizomes, of I. cylindrica may contain certain allelochemicals, some of which may be released into the soil during the decomposition processes of plant residues.

3.3. Plant Extract

Because allelochemicals are synthesized and accumulated in some plant parts [61,62,63], many researchers have investigated the allelopathic activity of the extracts from different plant parts of I. cylindrica. Aqueous extracts of whole plants of I. cylindrica showed the inhibitory activity with respect to the germination of Oryza sativa L. [70]. Frequency and density of Parthenium hysterophorus L. was significantly lower in I. cylindrica-dominated areas than that in non-infested areas, and inhibition of the germination and seedling growth of P. hysterophorus was observed in association with treatments of the aqueous extracts of roots and shoots of I. cylindrica [72]. Aqueous extracts of roots and shoots of I. cylindrica also inhibited the germination and growth of Cucumis sativus L., Lolium perenne L. [73] and Centrosema pubescens Benth. [74].
Leaves, roots and rhizomes of I. cylindrica were soaked in water, and the obtained soaking water inhibited the germination and growth of Raphanus sativus L., Brassica juncea var. cernua Jorb. et Hem., Trigonella foenum-graecum L. and Lycopersicon esculentum Mill. [59]. Aqueous leaf extracts of I. cylindrica exhibited growth inhibitory activity on the radicals of Solanum lycopersicum L. (synonym; S. lycopersicum L.) [75]. Aqueous extracts of foliage and below-grand parts of I. cylindrica inhibited the germination and seedling growth of Sida spinosa L., Brachiaria ramosa (L.) Stapf., Echinochloa crus-galli (L.) Beauv., Cynodon dactylon (L.) Pers. and Lolium multiflorum Lam. [76]. Aqueous extracts of inflorescences, shoots and roots of I. cylindrica suppressed the germination and radicle growth of Setaria italica P. Beauv., Dichanthium annulatum (Forssk.) Stapf, Chrysopogon montanus Trin., Medicago polymorpha L. and Pinus roxburghii Sarg. [65]. It was also reported that aqueous extracts of I. cylindrica shoots suppressed the rhizobium nodulation and arbuscular mycorrhizal colonization of Vigna radiata (L.) Wilczek and Phaseolus vulgaris L. [77].
Aqueous methanol extracts of I. cylindrica rhizomes inhibited the root and shoot growth of three monocotyledonous plants, Echinochloa crus-galli (L.) Beauv., Lolium multiflorum Lam. and Phleum pratense L., as well as that of three dicotyledonous plants, Lepidium sativum L., Lactuca sativa L. and Medicago sativa L. [78]. Leaf and rhizome powder of I. cylindrica was extracted with methanol, and the extract was concentrated. The concentrated extract was dissolved in water and sprayed onto the plant surface of Amaranthus spinosus L. The treatments resulted in a significant reduction in the growth of A. spinosus [79]. In addition, essential oil of roots and aerial parts of I. cylindrica suppressed the germination and seedlings of Lactuca sativa L. and Agrostis stolonifera L. [80].
Observations reported in this section suggest that the aqueous and methanol extracts of every part of I. cylindrica exhibit allelopathic activity with respect to the germination, growth, rhizobium nodulation and/or mycorrhizal colonization of several plant species and probably contain water- and methanol-extractable allelochemicals, which may cause the suppression of germination, growth, mycorrhizal colonization and/or rhizobium nodulation.

4. Allelochemicals of I. cylindrica

Many secondary metabolites were isolated and identified in the leachates, exudates and extracts of I. cylindrica, as well as its allelopathic agents (Figure 2, Table 2). p-Hydroxybenzoic acid and p-coumaric acid were identified in artificial rainfall leachates from leaves of I. cylindrica [64]. Benzoic acid, salicylic acid, gallic acid, cinnamic acid, caffeic acid, sinapinic acid (sinapic acid), emodin and hexadecahydro-1-azachrysen-8-yl ester were identified in the drain water from the I. cylindrica growth medium. However, their concentrations were 0.6–18 μM [66], which may be lower than their biologically active concentrations.
Four compounds, palmitic acid, phytol, tabanone (4,6,8-megastigmatrien-3-one) and p-vinylguaiacol, were identified in the essential oil obtained from roots and aerial parts of I. cylindrica. Phytol, palmitic acid and p-vinylguaiacol did not show significant growth inhibitory activity against Lactuca sativa L. and Agrostis stolonifera L. Tabanone inhibited the growth of Lemna aequinoctialis Welw., L. sativa and Allium cepa L. The concentrations required for 50% growth inhibition of tabanone on L. aequinoctialis, L. sativa and A. cepa were 0.094, 6.5 and 3.6 mM, respectively. Tabanone also caused the electrolyte leakage of the cotyledon discs of Cucumis sativus L. and reduced photosynthetic electron transport of the discs. However, tabanone was not found in the soil under I. cylindrica [80].
Three allelochemicals, methyl caffeate, 5-methoxyflavone and 5,2′-dimethoxyflavone, were isolated from the aqueous methanol extracts of I. cylindrica rhizomes, and these compounds significantly inhibited the root and shoot growth of Lepidium sativum L. The concentrations required for 50% growth inhibition of 5-methoxyflavone, 5,2′-dimethoxyflavone and methyl caffeate were 0.24, 0.079 and 1.1 mM for L. sativum roots, and 0.23, 0.88 and 0.59 mM for L. sativum shoots, respectively [78]. Benzoic acid, gentisic acid, p-hydroxybenzoic acid, vanillic acid, vanillin, p-hydroxybenzaldehyde, p-coumaric acid and o-coumaric acid were also identified in the aqueous leaf extracts [75].
A total of 36 compounds were identified: 27 compounds in the aqueous rhizome extracts of I. cylindrica and 24 compounds in its root exudates. Fifteen of these compounds were identified in both the extracts and exudates. Major compounds in the rhizome extracts were isoeugenol (392 μg/rhizome), isoferulic acid (289 μg/rhizome), linoleic acid (253 μg/rhizome), ferulic acid (217 μg/rhizome) and vanillin (217 μg/rhizome), and those in the root exudates were 4-acetyl-2-methoxyphenol (acetoguaiacone; 872 μg/plant) and palmitic acid (221 μg/plant). Isoeugenol (100 ppm) inhibited the growth of Bidens pilosa L., Leucaena leucocephala (Lam.) de Wit and Echinochloa crus-galli (L.) Beauv. Isoferulic acid inhibited the growth of B. pilosa, L. leucocephala and E. crus-galli. Ferulic acid, vanillin, 4-acetyl-2-methoxyphenol and palmitic acid inhibited the growth of B. pilosa and L. leucocephala. 2,4-Di-tert-butylphenol was also found in the rhizome extract at a concentration of 19.7 μg/rhizome. Its inhibitory activity was the most active of all compounds, followed by isoeugenol and 4-acetyl-2-methoxyphenol [67]. However, 2,4-di-tert-butylphenol is a synthetic phenolic antioxidant and the most widely used additive globally [81,82]. The contamination of 2,4-di-tert-butylphenol into the natural environment was also reported through the degradation of multiphenolic rings of synthetic phenolic antioxidants [83].

5. Contribution of Allelopathy of I. cylindrica to Its Invasiveness

I. cylindrica shows high reproductive ability through seeds and rhizomes; its high growth rate and highly competitive ability with native plant species is described in the “Introduction” section [1,27,31,33,36,37]. Its phenotypic plasticity is also high, and it has adapted to a wide range of soil and climate conditions [7,43]. The species alters wildfire regimes and increases mortality of native plant species. None insects, fungi or other predators cause extensive damage to I. cylindrica populations [21]. These characteristics may contribute to the invasiveness of I. cylindrica and its naturalization. Many studies also suggest that its allelopathy may contribute to its invasiveness and naturalization [5,15,54,84].
The leachates, root exudates, residues and extracts of the plant parts of I. cylindrica exhibit allelopathic activity against the seed germination and growth of several plant species, including native plant species (Table 1). Several allelochemicals, such as fatty acids, terpenoids, simple phenolics, benzoic acid, phenolic acids, phenolic aldehydes, phenylpropanoids, flavonoids, quinone and alkaloids, were also isolated and identified in the leachates, root exudates, essential oil and extracts of I. cylindrica (Table 2; Figure 2). The derivatives of cinnamic acid and benzoic acid have been found in a wide range of plants and soils. Their inhibitory activity with respect to plant growth and germination is concentration-dependent. These compounds are often mentioned as putative allelochemicals, although their levels in soil and plants are differ significantly between publications. The derivatives of cinnamic acid and benzoic acid are synthesized by the shikimic acid pathway and serve as precursors for a wide variety of important compounds, playing crucial roles in plant fitness, including plant hormones and defense compounds [85]. Cinnamic acid and benzoic acid derivatives affect cell membrane permeability and reduce the potential of ion and nutrient uptake. They also affect stomatal functions and water balance and interfere with several enzyme activities involved in major physiological processes, such as respiration, protein synthesis, phytohormone synthesis and metabolism of some other secondary metabolites [86,87,88,89]. Therefore, cinnamic acid and benzoic acid derivatives found in I. cylindrica, such as benzoic acid, gentisic acid, gallic acid, p-hydroxybenzoic acid, vanillic acid, isoeugenol, cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapinic acid, may affect some of those physiological processes of native plant species and decrease their germination, growth and fitness. Salicylic acid is a signaling molecule involved in plant defense systems against insect and fungal attacks, as well as other stress conditions [90,91]. Tabanone was reported to reduce photosynthetic electron transport [80]. Information on the mode of action of other compounds found in I. cylindrica is limited.
Recent pharmacological investigations showed that I. cylindrica contains secondary metabolites in many chemical classes, such as saponins, flavonoids, phenols and glycosides. in its rhizomes and other parts of the plants. Some of those compounds exhibited anti-inflammatory, antitumor, antibacterial, hematuria and diuretic activity in previous studies [92,93,94,95,96,97,98]. Although the allelopathic activity of most identified compounds has not yet been reported to date, a number of secondary metabolites in the invasive plants showed multiple effects, such as antiherbivore, antifungal and allelopathic activity [24,51,99]. Therefore, some of those compounds may exhibit growth inhibitory activity as allelopathic agents. It was reported that I. cylindrica may alter the microbial community in invaded soil and enhance the decomposition process of plant residues [54]. The rhizobium nodulation and mycorrhizal colonization of native plant species were significantly lower in I. cylindrica-infested plantations [59]. The leachates and exudates of I. cylindrica suppressed the mycorrhizal colonization of Aristida stricta Michex. var. beyrichiana and Pinus elliottii Engelm [66]. In addition, aqueous extracts of I. cylindrica shoots suppressed the rhizobium nodulation and arbuscular mycorrhizal colonization of Vigna radiata (L.) Wilczek and Phaseolus vulgaris L. [77]. These observations suggest that certain compounds of I. cylindrica may be involved in the alteration of the microbial community, including rhizobia and mycorrhizal fungi. Symbiosis with arbuscular mycorrhizal fungi is important for most territorial plants, and rhizobium nodulation is also important for leguminous plants. Arbuscular mycorrhizal fungi increase the ability of plants to absorb water and nutrients and enhance the defense function against several stress conditions and pathogen attacks [100,101,102]. Rhizobia establish root nodules of legumes, fix nitrogen and supply ammonium to host plants [103,104]. These observations suggest that I. cylindrica may be able to degrade the fungal and bacterial mutualisms of nearby plants. Reductions in rhizobium nodulation and mycorrhizal colonization weaken the ability of native plants to absorb water and nutrients, as well as their defense functions, which may result in growth inhibition of the native plants. It was also reported that other invasive plant species, such as Lantana camara L. and Fallopia japonica (Houtt.) Ronse Decraene, alter the microbial community, which is involved in the mycorrhizal colonization and the decomposition process of plant residues [105,106,107,108,109,110]. As described above, I. cylindrica may directly interrupt the regeneration process of native plant species by decreasing their germination and growth and indirectly via the suppression of mycorrhizal colonization and rhizobium nodulation of native plant species through its allelopathy. Therefore, the allelopathy of I. cylindrica may contribute to its enhanced competitive ability, as well as its invasiveness (Figure 3). Catechin (flavonoid) was once considered to contribute to the invasion of Centaurea stoebe L. from Europe into North America [49,50]. According to the novel weapon hypothesis, C. stoebe would release a certain amount of catechin into the rhizosphere soil, and the released catechin could suppress the regeneration process of indigenous plant species in North America through the inhibition of their germination and growth, contributing to the formation of C. stoebe monospecific stands [50,51]. However, the actual catechin levels in the rhizosphere soil were very low and could not induce significant inhibition of indigenous plant species [111]. The consequence suggests that the levels of allelochemicals in the rhizosphere soil and/or surrounding environments of invasive plants should be determined. Some allelochemicals were found in leachates, root exudate and growth medium of I. cylindrica [64,66,67]. However, it was also reported that some allelochemicals were absorbed onto soil particles. Some of those allelochemicals were not liberated with soil water and could not work as allelopathic agents [112,113,114].
Therefore, a discussion of the specific inhibitory activity of the identified allelochemicals and their concentrations in the rhizosphere soil water and/or surrounding environments is necessary to evaluate the contribution of these allelochemicals to the invasiveness of I. cylindrica.

6. Conclusions

I. cylindrica is highly invasive and has been naturalized in humid tropics, subtropics and warmer temperate zones of the world. Large monospecific stands of I. cylindrica are often observed in several countries. Its characteristics of life history, such as high reproduction and growth rates, competitive ability, phenotypic plasticity and defense ability against natural enemies may contribute to the invasiveness of the species. It was also shown that I. cylindrica possesses allelopathic properties (Table 1) and contains allelochemicals (Table 2, Figure 2), some of which were found in leachates, root exudates and growth medium of I. cylindrica, suggesting that certain allelochemicals may be released into the rhizosphere soil and/or surrounding environments. The leachates, exudates and extracts of I. cylindrica also altered the microbial community and suppressed the rhizobium nodulation and mycorrhizal colonization of native plant species, suggesting that certain compounds of I. cylindrica may be involved in the alteration of the microbial community, including rhizobia and mycorrhizal fungi. Mycorrhizal colonization increases the ability of plants to absorb water and nutrients and enhances the defense ability against several stress conditions and pathogen attacks. Rhizobia induce the root nodulation of legumes and supply nitrogen to the host plants. Therefore, the suppression of rhizobium nodulation and mycorrhizal colonization reduces the competitive ability and vigor of native plant species. Allelochemicals of the species may also suppress the regeneration process of native plant species through the inhibition of their germination and growth. Therefore, allelochemicals released from I. cylindrica may provide the species with a competitive advantage against native plant species, interrupting the regeneration process of native plants. The allelopathy of I. cylindrica may contribute to its invasiveness and naturalization as an invasive plant species.

Funding

This research received no external funding.

Institutional Review Statement

Not applicable.

Informed Consent Statement

Not applicable.

Conflicts of Interest

The author declares no conflict of interest.

References

  1. Holm, L.G.; Pucknett, D.L.; Pancho, J.B.; Herberger, J.P. The World’s Worst Weeds. Distribution and Biology; University Press of Hawaii: Honolulu, HI, USA, 1977; pp. 1–609. [Google Scholar]
  2. Dozier, H.; Gaffney, J.; McDonald, S.; Johnson, E.; Shilling, D. Cogongrass in the United States: History, ecology, impacts, and management. Weed Technol. 1998, 12, 737–743. [Google Scholar] [CrossRef]
  3. MacDonald, G.E. Cogongrass (Imperata cylindrica): Biology, ecology, and management. Crit. Rev. Plant Sci. 2004, 23, 367–380. [Google Scholar] [CrossRef]
  4. Tominaga, T. Growth of seedlings and plants from rhizome pieces of co gongrass (Imperata cylindrica (L.) Beauv). Weed Biol. Manage. 2003, 3, 193–195. [Google Scholar] [CrossRef]
  5. Tominaga, T.; Nishiwaki, A.; Mizuguti, A.; Ezaki, T. Weed monograph 5: Imperata cylindrica (L.) Beauv. J. Weed Sci. Tech. 2007, 52, 17–27. [Google Scholar] [CrossRef]
  6. Tominaga, T. Rhizome systems and sprouting pattern of shoots in Imperata cylindrica. Jpn. J. Trop. Agric. 1993, 37, 120–123. [Google Scholar]
  7. Bryson, C.T.; Carter, R. Cogongrass, Imperata cylindrica, in the United States. Weed Technol. 1993, 7, 1005–1009. [Google Scholar] [CrossRef]
  8. Shilling, D.G.; Bewick, T.A.; Gaffney, J.F.; McDonald, S.K.; Chase, C.A.; Johnson, E.R.R.L. Ecology, Physiology, and Management of Cogongrass (Imperata cylindrica); Final Report; Florida Institute of Phosphate Research: Gainesville, FL, USA, 1997; pp. 1–128. [Google Scholar]
  9. Sellers, B.A.; Ferrell, J.A.; MacDonald, G.E.; Langeland, K.A.; Floy, S.L. Cogongrass (Imperata cylindrica) biology, ecology, and management in Florida grazing land. EDIS 2012, 2012, 8. [Google Scholar] [CrossRef]
  10. Rusdy, M. Imperata cylindrica: Reproduction, dispersal, and controls. CAB Rev. 2020, 15, 38. [Google Scholar] [CrossRef]
  11. Evans, H.C. Fungal pathogens of some subtropical and tropical weeds and the possibilities for biological control. Biocontrol. News Info. 1987, 8, 7–30. [Google Scholar]
  12. Global Invasive Species Database, Species Profile: Imperata cylindrica. Available online: http://www.iucngisd.org/gisd/speciesname/Imperata+cylindrica (accessed on 8 August 2022).
  13. Invasive Species Compendium. Imperata cylindrica. Available online: https://www.cabi.org/isc/datasheet/28580 (accessed on 8 August 2022).
  14. National Invasive Species Information Center, Cogongrass. Available online: https://www.invasivespeciesinfo.gov/terrestrial/plants/cogongrass#cit (accessed on 8 August 2022).
  15. Holzmueller, E.J.; Jose, S. Invasion success of cogongrass, an alien C4 perennial grass, in the southeastern United States: Exploration of the ecological basis. Boil. Invasions 2011, 13, 435–442. [Google Scholar] [CrossRef]
  16. Holzmueller, E.J.; Jose, S. Response of the invasive grass Imperata cylindrica to disturbance in the southeastern forests, USA. Forests 2012, 3, 853–863. [Google Scholar] [CrossRef]
  17. EDDMapS. Early Detection & Distribution Mapping System. The University of Georgia-Center for Invasive Species and Ecosystem Health. Available online: http://www.eddmaps.org/ (accessed on 8 August 2022).
  18. Suryatna, E.S.; McIntosh, J.L. Food Crops Production and Control of Imperata cylindrica (L.) Beauv. on Small Farms. In Proceedings of BIOTROP Workshop on Alang-Alang in Bogor, 27–29 July 1976; Biotropica Special Publication: Bogor, Indonesia, 1980; pp. 135–147. [Google Scholar]
  19. Garrity, D.P.; Aqustin, P.C. Historical land use evolution in a tropical acid upland agroecosystem. Agric. Ecosyst. Environ. 1995, 53, 83–95. [Google Scholar] [CrossRef]
  20. Pacific Island Ecosystems at Risk (PIER). Imperata cylindrica. Available online: http://www.hear.org/pier/species/imperata_cylindrica.htm (accessed on 8 August 2022).
  21. van Loan, A.N.; Meeker, J.R.; Minno, M.C. Cogon Grass. In Biological Control of Invasive Plants in the Eastern United States; van Driesche, R., Hoddle, M., Blossy, B., Reardon, D., Riffe, M., Eds.; USDA Forest Service Publication: Morgantown, WV, USA, 2002; pp. 36–372. [Google Scholar]
  22. Thompson, J.D.; McNeilly, T.; Gray, A.J. Population variation in Spartina anglica C.E. Hubbard. I. Evidence from a common garden experiment. New Phytol. 1991, 117, 115–128. [Google Scholar] [CrossRef]
  23. Mack, R.M. Predicting the identity and fate of plant invaders: Emergent and emerging approaches. Biol. Conserv. 1996, 78, 107–121. [Google Scholar] [CrossRef]
  24. Chengxu, W.; Mingxing, Z.; Xuhui, C.; Bo, Q. Review on allelopathy of exotic invasive plants. Procedia Engin. 2011, 18, 240–246. [Google Scholar] [CrossRef]
  25. Warren, R.J.; Matt Candeias, M.; Labatore, A.; Olejniczak, M.; Yang, L. Multiple mechanisms in woodland plant species invasion. J. Plant Ecol. 2019, 12, 201–209. [Google Scholar] [CrossRef]
  26. Tominaga, T.; Kobayashi, H.; Ueki, K. Intra- and inter-populational variation of Imperata cylindrica var koenigii on Kii-ohshima island of Japan. J. Weed Sci. Tech. 1989, 34, 273–279. [Google Scholar] [CrossRef]
  27. Hubbard, C.E.; Whyte, R.O.; Brown, D.; Gray, A.P. Imperata cylindrica.: Taxonomy, Distribution, Economic Significance and Control; Commonwealth Agriculture Bureaux: Aberystwyth, UK, 1944; pp. 1–63. [Google Scholar]
  28. Santiago, A. Studies on the Autecology of Imperata cylindrica (L) Beauv. In Proceedings of the Ninth International Grassland Congress, San Paulo, Brazil, 7–20 January 1965; pp. 499–502. [Google Scholar]
  29. McDonald, S.K.; Shilling, D.G.; Bewick, T.A.; Okoli, C.A.N.; Smith, R. Sexual reproduction by cogongrass, Imperata cylindrica. Proc. South Weed Sci. Soc. 1995, 48, 188. [Google Scholar]
  30. King, S.E.; Grace, J.B. The effects of soil flooding on the establishment of cogongrass (Imperata cylindrica), a nonindigenous invader of the southeastern United States. Wetlands 2000, 20, 300–306. [Google Scholar] [CrossRef]
  31. Ayeni, A.O.; Duke, W.B. The influence of rhizome features on subsequent regenerative capacity in speargrass (Imperata cylindrica (L.) Beauv.). Agric. Ecosyst. Environ. 1985, 13, 309–317. [Google Scholar] [CrossRef]
  32. Soerjani, M. Alang-alang Imperata cylindrica (L.) Beav., pattern of growth as related to its problem of control. Biol. Trop. Bull. 1970, 1, 88–96. [Google Scholar]
  33. Terry, P.J.; Adjers, G.; Akobundu, I.O.; Anoka, A.U.; Drilling, M.E.; Tjitrosemito, S.; Utomo, M. Herbicides and mechanical control of Imperata cylindrica as a first step in grassland rehabilitation. Agroforest Syst. 1997, 16, 151–179. [Google Scholar] [CrossRef]
  34. Eussen, J.H.H. Biological and Ecological Aspects of Alang-Alang [Imperata cylindrica (L) Beauv.]. In Proceedings of BIOTROP Workshop on Alang-Alang in Bogor, 27–29 July 1976; Biotropica Special Publiation: Bogor, Indonesia, 1980; pp. 15–22. [Google Scholar]
  35. Brewer, J.S.; Cralle, S.P. Phosphorus addition reduces invasion of longleaf pine savanna (Southeastern USA) by an non-indigenous grass (Imperata cylindrica). Plant Ecol. 2003, 167, 237–245. [Google Scholar] [CrossRef]
  36. Collins, A.R.; Jose, S. Cogongrass Invasion Alters Soil Chemical Properties of Natural and Panted Forestlands. In Invasive Plants and Forest Ecosystems; Kohli, R.K., Jose, S., Batish, D., Singh, H., Eds.; CRC press: Boca Raton, FL, USA, 2008; pp. 237–247. [Google Scholar]
  37. Daneshgar, P.; Jose, S. Imperata cylindrica, an alien invasive grass, maintains control over nitrogen availability in an establishing pine forest. Plant Soil 2009, 320, 209–218. [Google Scholar] [CrossRef]
  38. Daneshgar, P.; Jose, S.; Ramsey, C.; Collins, A.R. Impacts of an invasive grass on the productivity of an establishing pine forest. For. Sci. 2008, 54, 579–587. [Google Scholar]
  39. Lippincott, C.L. Effects of Imperata cylindrica (L.) Beauv. (Cogongrass) invasion on fire regime in Florida sandhill (USA). Nat. Areas J. 2000, 20, 140–149. [Google Scholar]
  40. Fuscoa, E.J.; Finnb, J.T.; Balchc, J.K.R.; Nagyc, R.C.; Bradley, B.A. Invasive grasses increase fire occurrence and frequency across US ecoregions. PNAS 2019, 116, 47. [Google Scholar] [CrossRef]
  41. Sajise, P.E. Evaluation of cogon [Imperata cylindrica (L.) Beauv.] as a serial stage in Philippine vegetational succession. Diss. Abstr. Int. B 1973, 33, 3040–3041. [Google Scholar]
  42. King, S.E.; Grace, J.B. The effects of gap size and disturbance type on invasion of wet pine savanna by cogongrass, Imperata cylindrica (Poaceae). Am. J. Bot. 2000, 87, 1279–1286. [Google Scholar] [CrossRef]
  43. Bryson, C.T.; Krutz, L.J.; Ervin, G.N.; Reddy, K.N.; Byrd, J.D., Jr. Ecotype variability and edaphic characteristics for cogongrass (Imperata cylindrica) populations in Mississippi. Invasive Plant Sci. Manag. 2010, 3, 199–207. [Google Scholar] [CrossRef]
  44. Santiago, A. Gene ecological aspects of the Imperata weed and practical implications. In Proceedings of BIOTROP Workshop on Alang-Alang in Bogor, 27–29 July 1976; Biotropica Special Publication: Bogor, Indonesia, 1980; pp. 23–24. [Google Scholar]
  45. Hiatt, D.S.; Flory, S.L. Populations of a widespread invader and co-occurring native species vary in phenotypic plasticity. New Phytol. 2020, 225, 584–594. [Google Scholar] [CrossRef] [PubMed]
  46. Lucardi, R.D.; Wallace, L.E.; Ervin, G.N. Patterns of genetic diversity in highly invasive species: Cogongrass (Imperata cylindrica) expansion in the invaded range of the Southern United States (US). Plants 2020, 9, 423. [Google Scholar] [CrossRef] [PubMed]
  47. Keane, R.M.; Crawley, M.J. Exotic plant invsions and the enemy release hypothesis. Trends Ecol. Evol. 2002, 17, 164–169. [Google Scholar] [CrossRef]
  48. Javaid, A.; Naqvi, S.F.; Shoaib, A.; Iqbal, S.M. Management of Macrophomina phaseolina by extracts of an allelopathic grass Imperata cylindrica. Pak. J. Agric. Sci. 2015, 52, 37–41. [Google Scholar]
  49. Callaway, R.M.; Aschehoug, E.T. Invasive plants versus their new and old neighbors: A mechanism for exotic invasion. Science 2000, 290, 521–523. [Google Scholar] [CrossRef]
  50. Callaway, R.M.; Ridenour, W.M. Novel weapons: Invasive success and the evolution of increased competitive ability. Front. Ecol. Environ. 2004, 2, 419–426. [Google Scholar] [CrossRef]
  51. Cappuccino, N.; Arnason, J.T. Novel chemistry of invasive exotic plants. Biol. Lett. 2006, 2, 189–193. [Google Scholar] [CrossRef]
  52. Meiners, S.J.; Kong, C.H.; Ladwig, L.M.; Pisula, N.L.; Lang, K.A. Developing an ecological context for allelopathy. Plant. Ecol. 2012, 213, 1861–1867. [Google Scholar] [CrossRef]
  53. Rice, E.L. Allelopathy, 2nd ed.; Academic Press: Cambridge, MA, USA, 1984; pp. 1–422. [Google Scholar]
  54. Holly, D.C.; Ervin, G.N.; Jackson, C.R.; Diehl, S.V.; Kirker, G.T. Effect of an invasive grass on ambient rates of decomposition and microbial community structure: A search for causality. Biol Invasions 2009, 11, 1855–1868. [Google Scholar] [CrossRef]
  55. Trautwig, A.N.; Eckhardt, L.G.; Loewenstein, N.G.; Hoeksema, J.D.; Carter, E.A.; Nadel, R.L. Cogongrass (Imperata cylindrica) affects above and belowground processes in commercial loblolly pine (Pinus taeda) stands. For. Sci. 2017, 63, 10–16. [Google Scholar] [CrossRef]
  56. Brewer, S. Declines in plant species richness and endemic plant species in longleaf pine savannas invaded by Imperata cylindrica. Biol. Invasions 2008, 10, 1257–1264. [Google Scholar] [CrossRef]
  57. Bajwa, R.; Javaid, A.; Tasneem, Z.; Nasim, G. Allelopathy and VA mycorrhiza I. Suppression of VA mycorrhiza in Leguminous plants by phytotoxic exudates of Imperata cylindorica (L.) Beauv. Pak. J. Phytopathol. 1996, 8, 25–27. [Google Scholar]
  58. Bajwa, R. Effects of arbuscular mycorrhizae (AM) and effective microoganisms (EM) on various plant under allelopathic stress. Allelopath. J. 2005, 16, 261–271. [Google Scholar]
  59. Inderjit, S.; Dakshini, K.M.M. Investigations on some aspects of chemical ecology of cogongrass, Imperata cylindrica (L.) Beauv. J. Chem. Ecol. 1991, 17, 343–352. [Google Scholar] [CrossRef] [PubMed]
  60. Eussen, J.H.H. Some competitive experiments with alang-alang (Imperta cylindrica (L.) Beauv.) in replacement series. Oecologia 1979, 40, 351–356. [Google Scholar] [CrossRef]
  61. Bais, H.P.; Weir, T.L.; Perry, L.G.; Gilroy, S.; Vivanco, J.M. The role of root exudates in rhizosphere interactions with plants and other organisms. Annu. Rev. Plant Biol. 2006, 57, 233–266. [Google Scholar] [CrossRef]
  62. Bonanomi, G.; Sicurezza, M.G.; Caporaso, S.; Esposito, A.; Mazzoleni, S. Phytotoxicity dynamics of decaying plant materials. New Phytol. 2006, 169, 571–578. [Google Scholar] [CrossRef]
  63. Belz, R.G. Allelopathy in crop/weed interactions-an update. Pest Manag. Sci. 2007, 63, 308–326. [Google Scholar] [CrossRef]
  64. Chou, C.H. Comparative phytotoxic nature of leachate from four subtropical grasses. J. Chem. Ecol. 1989, 15, 2149–2159. [Google Scholar] [CrossRef]
  65. Hussain, F.; Abidi, N. Allelopathy exhibited by Imperata cylindrica (L.) Beauv. Pak. J. Bot. 1991, 23, 15–25. [Google Scholar]
  66. Hagan, D.L.; Jose, S.; Lin, C.H. Allelopathic exudates of cogongrass (Imperata cylindrica): Implications for the performance of native pine savanna plant species in the southeastern US. J. Chem. Ecol. 2013, 39, 312–322. [Google Scholar] [CrossRef] [PubMed]
  67. Xuan, T.D.; Toyama, T.; Fukuta, M.; Khanh, T.D.; Tawata, S. Chemical interaction in the invasiveness of cogongrass (Imperata cylindrica (L.) Beauv.). J. Agric. Food Chem. 2009, 57, 9448–9453. [Google Scholar] [CrossRef] [PubMed]
  68. Tominaga, T.; Watanabe, O. Weed growth suppression by cogongrass (Imperata cylindrica) leaves. Weed Sci. Tech. 1997, 42, 289–293. [Google Scholar] [CrossRef]
  69. Koger, C.H.; Bryson, C.T. Effect of cogongrass (Imperata cylindrica) extracts on germination and seedling growth of selected grass and broadleaf species. Weed Technol. 2004, 18, 236–242. [Google Scholar] [CrossRef]
  70. Casini, P.; Vecchio, V. Allelopathic interaction pf itchgrass and cogongrass: Germination and early development of rice. Trop. Agric. 1998, 75, 445–451. [Google Scholar]
  71. Rajan, A.; Lovett, J.V.; Anderws, A.C. Evaluation of potential source of allelochemical in lalang (Imperata cylindrica). Pertanika 1988, 11, 175–189. [Google Scholar]
  72. Anjum, T.; Bajwa, R.; Javaid, A. Biological control of Parthenium I: Effect of Imperata cylindrica on Distribution, Germination and Seedling Growth of Parthenium hysterophorus L. Int. J. Agri. Biol. 2005, 7, 448–450. [Google Scholar]
  73. Salim, M.A.A.; Linatoc, A.C.; Jikan, S.S.; Jamil, S.; Latif, M.S. Allelopathic effects of Imperata cylindrica aqueous extract on the germination of Cucumis sativus and Lolium perenne. Int. J. Recent. Technol. Eng. 2020, 8, 2503–2508. [Google Scholar] [CrossRef]
  74. Rusdy, M.; Riadi, M.; Sari, A.M.; Normal, A. Comparative allelopathic effect of Imperata cylindrica and Chromolaena odorata on germination and seedling growth of Centrosema pubescens. Int. J. Sci. Res. Pub. 2015, 5, 1–5. [Google Scholar]
  75. Eussen, J.H.H.; Niemann, G.J. Growth inhibiting substances from leaves of Imperata cylindrica (L.) Beauv. Z. Pflanzenphysiol. 1981, 102, 262–266. [Google Scholar] [CrossRef]
  76. Koger, C.H.; Bryson, C.T.; Byrd, J.D., Jr. Response of selected grass and broadleaf species to cogongrass (Imperata cylindrica) residues. Weed Technol. 2004, 18, 353–357. [Google Scholar] [CrossRef]
  77. Afzal, B.; Bajwa, R.; Javaid, A. Allelopathy and VA mycorrhiza VII: Cultivation of Vigna radiata and Phaseolus vulgaris under allelopathic stress caused by Imperata cylindrica. Pak. J. Biol. Sci. 2000, 3, 1926–1928. [Google Scholar] [CrossRef]
  78. Suzuki, M.; Tominaga, T.; Ohno, O.; Iwasaki, A.; Suenaga, K.; Kato-Noguchi, H. Plant growth inhibitory activity and active substances with allelopathic potential of cogongrass (Imperata cylindrica) rhizome. Weed Biol. Manag. 2018, 18, 92–98. [Google Scholar] [CrossRef]
  79. Erida, G.; Saidi, N.; Hasanuddin, S. Allelopathic screening of several weed species as potential bioherbicides. IOP Conf. Ser. Earth Environ. Sci. 2019, 334, 012034. [Google Scholar] [CrossRef]
  80. Cerdeira, A.L.; Cantrell, C.L.; Dayan, F.E.; Byrd, J.D.; Duke, S.O. Tabanone, a new phytotoxic constituent of cogongrass (Imperata cylindrica). Weed Sci. 2012, 60, 212–218. [Google Scholar] [CrossRef]
  81. Lu, Z.; Smyth, S.A.; De Silva, A.O. Distribution and fate of synthetic phenolic antioxidants in various wastewater treatment processes in Canada. Chemosphere 2019, 219, 826–835. [Google Scholar] [CrossRef]
  82. Shi, Z.; Liang, X.; Zhao, Y.; Liu, W.; Martyniuk, C.J. Neurotoxic effects of synthetic phenolic antioxidants on dopaminergic, serotoninergic, and GABAergic signaling in larval zebrafish (Danio rerio). Sci. Total Environ. 2020, 830, 154688. [Google Scholar] [CrossRef]
  83. Löschner, D.; Rapp, T.; Schlosser, F.U.; Schuster, R.; Stottmeister, E.; Zanderm, S. Experience with the application of the draft european standard prEN 15768 to the identification of leachable organic substances from materials in contact with drinking water by GC-MS. Anal. Method 2011, 3, 2547–2556. [Google Scholar] [CrossRef]
  84. Estrada, J.A.; Flory, S.L. Cogongrass (Imperata cylindrica) invasions in the US: Mechanisms, impacts, and threats to biodiversity. Glob. Ecol. Conserv. 2015, 3, 1–10. [Google Scholar] [CrossRef]
  85. Widhalm, J.R.; Dudareva, N. A familiar ring to it: Biosynthesis of plant benzoic acids. Mol. Plant 2015, 8, 83–97. [Google Scholar] [CrossRef]
  86. Dalton, B.R. The Occurrence and Behavior of Plant Phenolic Acids in Soil Environments and their Potential Involvement in Allelochemical Interference Interactions: Methodological Limitations in Establishing Conclusive Proof of Allelopathy. In Principals and Practices in Plant Ecology: Allelochemical Interactions; Inderjit Dakshini, K.M.M., Foy, C.L., Eds.; CRC Press: Boca Raton, FL, USA, 1999; pp. 57–74. [Google Scholar]
  87. Inderjit. Plant phenolics in allelopathy. Bot. Rev. 1996, 62, 186–202. [Google Scholar] [CrossRef]
  88. Einhellig, F.A. Mode of Action of Allelochemical Action of Phenolic Compounds. In Chemistry and Mode of Action of Allelochemicals; Macías, F.A., Galindo, J.C.G., Molino, J.M.G., Cutler, H.G., Eds.; CRC Press: Boca Raton, FL, USA, 2004; pp. 217–238. [Google Scholar]
  89. Li, Z.H.; Wang, Q.; Ruan, X.; Pan, C.D.; Jiang, D.A. Phenolics and plant allelopathy. Molecules 2010, 15, 8933–8952. [Google Scholar] [CrossRef] [PubMed]
  90. Li, Z.G.; Xiang, R.H.; Wang, J.Q. Hydrogen sulfide-phytohormone interaction in plants under physiological and stress conditions. J. Plant Growth Regul. 2021, 40, 2476–2484. [Google Scholar] [CrossRef]
  91. Nakano, M.; Omae, N.; Tsuda, K. Inter-organismal phytohormone networks in plant-microbe interactions. Curr. Opin. Plant Biol. 2022, 68, 102258. [Google Scholar] [CrossRef] [PubMed]
  92. Yoon, J.S.; Lee, M.K.; Sung, S.H.; Kim, Y.C. Neuroprotective 2-(2-phenylethyl)chromones of Imperata cylindrica. J. Nat. Prod. 2006, 69, 290–291. [Google Scholar] [CrossRef]
  93. An, H.J.; Nugroho, A.; Song, B.M.; Park, H.J. Isoeugenin, a novel nitric oxide synthase inhibitor. Molecules 2015, 20, 21336–21345. [Google Scholar] [CrossRef]
  94. Nayim, P.; Mbaveng, A.T.; Ntyam, A.M.; Kuete, V. A botanical from the antiproliferative cameroonian spice, Imperata cylindrica is safe at lower doses, as demonstrated by oral acute and sub-chronic toxicity screenings. BMC Complement. Med. Ther. 2020, 20, 273. [Google Scholar] [CrossRef]
  95. Jung, Y.K.; Shin, D. Imperata cylindrica: A review of phytochemistry, pharmacology, and industrial applications. Molecules 2021, 26, 1454. [Google Scholar] [CrossRef]
  96. Maryati, M.; Widyaningrum, I.; Sulistyowati, E. Effects of Imperata cylindrica on anti-hyperlipidemia: A review. Biointerface Res. App. Chem. 2022, 12, 8184–8194. [Google Scholar]
  97. Nago, R.D.T.; Nayim, P.; Mbaveng, A.T.; Mpetga, J.D.S.; Bitchagno, G.T.M.; Garandi, B.; Tane, P.; Lenta, B.N.; Sewald, N.; Tene, M.; et al. Prenylated dlavonoids and C-15 isoprenoid analogues with antibacterial properties from the whole plant of Imperata cylindrica (L.) Raeusch (Gramineae). Molecules 2021, 26, 4717. [Google Scholar] [CrossRef]
  98. Ruan, J.Y.; Cao, H.N.; Jiang, H.Y.; Li, H.M.; Hao, M.M.; Zhao, W.; Zhang, Y.; Han, Y.; Zhang, Y.; Wang, T. Structural characterization of phenolic constituents from the rhizome of Imperata cylindrica var major and their anti-inflammatory activity. Phytochemistry 2022, 196, 113076. [Google Scholar] [PubMed]
  99. Lockwood, J.L.; Simberloff, D.; McKinney, M.L.; Von Holle, B. How many, and which, plants will invade natural areas. Biol. Inva. 2001, 3, 1–8. [Google Scholar] [CrossRef]
  100. Smith, S.E.; Read, D.J. Mycorrhizal Symbiosis, 3rd ed.; Academic Press: London, UK, 2008; pp. 1–815. [Google Scholar]
  101. Diagne, N.; Ngom, M.; Djighaly, P.I.; Fall, D.; Hocher, V.; Svistoonoff, S. Roles of Arbuscular Mycorrhizal Fungi on Plant Growth and Performance: Importance in Biotic and Abiotic Stressed Regulation. Diversity 2020, 12, 370. [Google Scholar] [CrossRef]
  102. Tang, H.; Hassan, M.U.; Feng, L.; Nawaz, M.; Shah, A.N.; Qari, S.H.; Liu, Y.; Miao, J. The critical role of arbuscular mycorrhizal fungi to improve drought tolerance and nitrogen use efficiency in crops. Front. Plant Sci. 2022, 13, 919166. [Google Scholar] [CrossRef]
  103. Tsyganova, A.V.; Brewin, N.J.; Tsyganov, V.E. Structure and development of the legume-rhizobial symbiotic interface in infection threads. Cells 2021, 10, 1050. [Google Scholar] [CrossRef]
  104. Mathesius, U. Are legumes different? Origins and consequences of evolving nitrogen fixing symbioses. J. Plant Physiol. 2022, 276, 153765. [Google Scholar] [CrossRef]
  105. Hale, A.N.; Kalisz, S. Perspectives on allelopathic disruption of plant mutualisms: A framework for individual- and population-level fitness consequences. Plant Ecol. 2012, 213, 1991–2006. [Google Scholar] [CrossRef]
  106. Pinzone, P.; Potts, D.; Pettibone, G.; Warren, R. Do novel weapons that degrade mycorrhizal mutualisms promote species invasion? Plant Ecol. 2018, 219, 539–548. [Google Scholar] [CrossRef]
  107. Mutshekwa, T.; Cuthbert, R.N.; Wasserman, R.J.; Murungweni, F.M.; Dalu, T. Macroinvertebrate colonisation associated with native and invasive leaf litter decomposition. Knowl. Manag. Aquat. Ecosyst. 2020, 421, 32. [Google Scholar] [CrossRef]
  108. Zubek, S.; Majewska, M.L.; Błaszkowski, J.; Stefanowicz, A.M.; Nobis, M.; Kapusta, P. Invasive plants affect arbuscular mycorrhizal fungi abundance and species richness as well as the performance of native plants grown in invaded soils. Biol. Fertil. Soil 2016, 52, 879–893. [Google Scholar] [CrossRef]
  109. Zubek, S.; Kapusta, P.; Stanek, M.; Woch, M.W.; Błaszkowski, J.; Stefanowicz, A.M. Reynoutria japonica invasion negatively affects arbuscular mycorrhizal fungi communities regardless of the season and soil conditions. Appl. Soil Ecol. 2022, 169, 104152. [Google Scholar] [CrossRef]
  110. Řezáčová, V.; Řezáč, M.; Gryndler, M.; Hršelová, H.; Gryndlerová, H.; Michalová, T. Plant invasion alters community structure and decreases diversity of arbuscular mycorrhizal fungal communities. Appl. Soil Ecol. 2021, 167, 104039. [Google Scholar] [CrossRef]
  111. Duke, S.O.; Blair, A.C.; Dayan, F.E.; Johnson, R.D.; Meepagala, K.M.; Cook, D.; Bajsa, J. Is (−)-catechin a novel weapon of spotted knapweed (Centaurea stoebe)? J. Chem. Ecol. 2009, 35, 141–153. [Google Scholar] [CrossRef] [PubMed]
  112. Ito, I.; Kobayashi, K.; Yoneyama, T. Fate of dehydromatricaria ester added to soil and its implications for the allelopathic effect of Solidago altissima L. Ann. Bot. 1998, 82, 625–630. [Google Scholar] [CrossRef]
  113. Blum, U. Fate of Phenolic Allelochemicals in Soils-the Role of Soil and Rhizosphere Microorganism. In Chemistry and Mode of Action of Allelochemicals; Macías, F.A., Galindo, J.C.G., Molino, J.M.G., Cutler, H.G., Eds.; CRC Press: Boca Raton, FL, USA, 2004; pp. 57–76. [Google Scholar]
  114. Kobayashi, K.; Koyama, H.; Shim, I.S. Relationship between behavior of dehydromatricaria ester in soil and the allelopathic activity of Solidago altissima L. in the laboratory. Plant Soil 2004, 259, 97–102. [Google Scholar] [CrossRef]
Plants 11 02551 g001 550
Figure 1. Imperata cylindrica. Photos were kindly provided by Dr. T. Tominaga.
Figure 1. Imperata cylindrica. Photos were kindly provided by Dr. T. Tominaga.
Plants 11 02551 g001
Plants 11 02551 g002 550
Figure 2. Allelochemicals identified in Imperata cylindrica. Compound numbers and names are listed in Table 2.
Figure 2. Allelochemicals identified in Imperata cylindrica. Compound numbers and names are listed in Table 2.
Plants 11 02551 g002
Plants 11 02551 g003 550
Figure 3. A possible scheme of I. cylindrica to establish the new habitats.
Figure 3. A possible scheme of I. cylindrica to establish the new habitats.
Plants 11 02551 g003
Table
Table 1. Allelopathic activities of leachates, exudates, residues, soil and plant extracts of Imperata cylindrica.
Table 1. Allelopathic activities of leachates, exudates, residues, soil and plant extracts of Imperata cylindrica.
SourceInhibitionTarget Plant SpeciesReference
GerminationGrowthMycorrhizal colonization, nodulation
Leachate ✓ Brachiaria mutica, Digitaria decumbens[64]
✓✓ Dichanthium annulatum[65]
✓ Chrysopogon montanus, Medicago polymorpha, Pinus roxburghii[65]
Leachate/
exudate		 ✓✓Aristida stricta[66]
Exudate ✓Pinus elliottii[66]
✓ Echinochloa crus-galli[67]
Plant residue ✓ Erigeron candensis, Portulaca oleracea[68]
✓✓ Sida spinosa, Brachiaria ramosa, Echinochloa crus-galli, Lolium multiflorum[69]
✓ Lolium multiflorum[69]
✓ Oryza sativa[70]
✓ Trifolium subterraneum[71]
Soil extract✓✓ Dichanthium annulatum, Chrysopogon montanus[65]
✓ Setaria italica, Medicago polymorpha, Pinus roxburghii[65]
Plant extract✓ Oryza sativa[70]
✓✓ Parthenium hysterophorus[72]
✓✓ Cucumis sativus, Lolium perenne[73]
✓✓ Centrosema pubescens[74]
✓✓ Raphanus sativus, Brassica juncea, Trigonella foenum-graecum, Lycopersicon esculentum[59]
✓ Solanum lycopersicum (syn; L.esculentum)[75]
✓✓ Sida spinosa, Brachiaria ramosa, Echinochloa crus-galli, Cynodon dactylon, Lolium multiflorum[76]
✓✓ Setaria italica, Dichanthium annulatum, Chrysopogon montanus, Medicago polymorpha, Pinus roxburghii[65]
✓Vigna radiata, Phaseolus vulgaris[77]
✓ Echinochloa crus-galli, Lolium multiflorum, Phleum pratense, Lepidium sativum, Lactuca sativa, Medicago sativa[78]
✓ Amaranthus spinosus[79]
✓✓ Lactuca sativa, Agrostis stolonifera[80]
Table
Table 2. Allelochemicals identified in Imperata cylindrica and their sources.
Table 2. Allelochemicals identified in Imperata cylindrica and their sources.
Chemical ClassCompoundSourceReference
LeachateExudateEssential oilRhizome extractLeaf extract
Fatty acid1: Palmitic acid ✓✓ [67,80]
2: Linoleic acid ✓ [67]
Terpenoid3: Phytol ✓ [80]
4: Tabanone ✓ [80]
Simple phenolic5: p-Vinylguaiacol ✓ [80]
6: 2,4-Di-tert-butylphenol ✓ [67]
Benzoic acid7: Benzoic acid ✓ ✓[66,75]
Phenolic acid8: Salicylic acid ✓ [66]
9: Gentisic acid ✓[75]
10: Gallic acid ✓ [66]
11: p-Hydroxybenzoic acid✓ ✓[64,75]
13: van ilic acid ✓[75]
Phenolic aldehyde14: van illin ✓✓[67,75]
15: p-Hydroxybenzaldehyde ✓[75]
Acetophenone16: 4-Acetyl-2-methoxyphenol (acetoguaiacone) ✓ [67]
Phenylpropanoid17: Isoeugenol ✓ [67]
18: cinnamic acid ✓ [66]
19: p-coumaric acid✓ ✓[64,75]
20: o-coumaric acid ✓[75]
21: Caffeic acid ✓ [66]
22: Ferulic acid ✓ [67]
23: Isoferulic acid ✓ [67]
24: Sinapinic acid (sinapic acid) ✓ [66]
25: Methyl caffeate ✓ [78]
Flavonoid26: 5-Methoxyflavone ✓ [78]
27: 5,2′-Dimethoxyflavone ✓ [78]
Quinone28: Emodin ✓ [66]
Alkaloid29: Hexadecahydro-1-azachrysen-8-yl ester ✓ [66]
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Kato-Noguchi, H. Allelopathy and Allelochemicals of Imperata cylindrica as an Invasive Plant Species. Plants 2022, 11, 2551. https://doi.org/10.3390/plants11192551

AMA Style

Kato-Noguchi H. Allelopathy and Allelochemicals of Imperata cylindrica as an Invasive Plant Species. Plants. 2022; 11(19):2551. https://doi.org/10.3390/plants11192551

Chicago/Turabian Style

Kato-Noguchi, Hisashi. 2022. "Allelopathy and Allelochemicals of Imperata cylindrica as an Invasive Plant Species" Plants 11, no. 19: 2551. https://doi.org/10.3390/plants11192551

APA Style

Kato-Noguchi, H. (2022). Allelopathy and Allelochemicals of Imperata cylindrica as an Invasive Plant Species. Plants, 11(19), 2551. https://doi.org/10.3390/plants11192551

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop