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Article

Rhizome Weight and Number of Sectioning per Rhizome Determine Plantlet Growth and Propagation Rate of Hemerocallis citrina Baroni in Cutting Propagation

by
Yue Xie
1,2,*,
Tong Chen
1 and
Huazhong Ren
1
1
Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetables, China Agricultural University, Beijing 100193, China
2
Department of Food Science, Aarhus University, N 8200 Aarhus, Denmark
*
Author to whom correspondence should be addressed.
Agronomy 2022, 12(11), 2777; https://doi.org/10.3390/agronomy12112777
Submission received: 5 September 2022 / Revised: 27 October 2022 / Accepted: 2 November 2022 / Published: 8 November 2022
(This article belongs to the Section Horticultural and Floricultural Crops)
Browse Figures
Review Reports Versions Notes

Abstract

:
Rhizome cutting is prevalent in propagation for Hemerocallis citrina Baroni. This study aimed to reveal the influence of rhizome weight on plantlet growth, and evaluate a new cutting protocol. Three levels of rhizome weight (big (BR), medium (MR) and small (SR)) were compared by measuring plantlet growth four times during cutting propagation. Sectioning rhizomes longitudinally along shaft axis of crown into 2, 3 or 4 parts (S2, S3 and S4), was tested on rhizomes with two bud sizes (Large bud (LB), Small bud (SB)). Propagation coefficient, the number of plantlets obtained per rhizome, kept similar regardless of rhizome weight, while S3 and S4 increased propagation coefficient. Rhizome weight changed the relative growth rates on different dates. SR resulted in lower aboveground dry biomass, leaf area, total fibrous root length, relative total fibrous root length growth rate and N deficiency compared to BR. Sucrose concentration in rhizome decreased with time and fructose concentration was lowest in MR at the end of experiment. Aboveground dry biomass and total fibrous root length were lowest in S4, followed by S3 and S2. Rhizome weight and number of sectioning per rhizome influence cutting propagation, and sectioning rhizomes into three pieces has higher propagation coefficient and less retardation on growth. According to N deficiency in plantlets during the propagation, N fertiliser is probably needed during cutting.

1. Introduction

Hemerocallis citrina Baroni (H. citrina) is commonly planted in open field for harvesting unopened flower buds. The fresh and dried unopened flower buds of H. citrina, known as “golden needle” or “huang hua cai” in Chinese, have been used as a vegetable with high nutrition value in Asian cuisine for a long history. The compounds in its flowers are with medical functions, such as anti-bacteria, antioxidation, anti-inflammation, sleep quality improvement and likely anti-depression [1]. The flowering period of H. citrina starts from middle June to early August in North China. The high nutritious and medical values but short flowering period drive up the economic value of the flower buds, which contributed to poverty reduction in Shanxi province during the 13th Five-year Plans. The lack of colchicine biosynthesis in H. citrina proven recently eliminates consumers’ concern on food safety, and may lead to an increased consumption on the flower buds [2].
Efficient propagation techniques guarantee the expanding production of H. citrina. Sexual and asexual propagations are both available for H. citrina productions. Sexual propagation method, seed propagation, shows low efficiency due to low seed germination rate and high trait differentiation in offspring. Additionally, H. citrina propagated from seeds has a long juvenile or vegetative phase, taking three years before flowering. In general, asexual propagation methods preserve genetic identity of parent plants, and shorten propagation periods and the time from planting to harvesting the first flowers. For instance, H. citrina propagated from division can start flowering in the same year that it is planted. One of the asexual propagation methods is in vitro propagation, in which young leaf, pollen and nearly mature capsules of H. citrina are used as explants [3,4]. However, regeneration of H. citrina depends on plant materials and cultivars used as explants, as most plants do [5]. Moreover, in vitro propagation requires input of technique and skilled technicians, which is unpractical and expensive for poorly educated smallholders, the major producers in China. Therefore, propagation methods with low input-cost techniques are essential for current H. citrina production in China.
Several methods with low input-cost techniques have been developed [6]. For instance, division is the most prevalent method due to its low cost, convenient operation and high survival rate. Applying plant growth regulators (PGR) on wounded crowns can further promote production of ramets or offshoots for division. However, this is not efficient enough and damages parent plants [7].
Cutting is another efficient asexual propagation method using short rhizome or scape of H. citrina as propagules [8]. Studies stated that short rhizomes can be sectioned into pieces according to bud numbers. Each piece comprises only an intact bud and enough rhizomes and/or fleshy roots [8,9]. The rhizomes and fleshy roots provide carbohydrates (especially non-structural ones) and nutrients for root initiation, bud emergence, and shoot growth [10,11,12,13]. However, no studies have revealed the relationship between carbohydrates and development of H. citrina plantlets during the cutting process. This method requires rhizomes being at least 6 years of age, so that rhizomes can have enough buds and sufficient length for being cut into several pieces [8,9]. The requirement on rhizome age resulted in limited resource for propagules. Moreover, sectioning should be delicately conducted since some axillary buds are invisible.
A cutting protocol has been developed to overcome these limits in the present study: apical buds and short rhizomes were longitudinally sectioned along shaft axis of crown into equal sections as propagules. Although the apical bud is mechanically injured in this protocol, the leaves in the injured bud can keep growing in an imbalanced way: uninjured part of leaves grows as normal, and injured part grows slower. Additionally, rhizomes at any age can be used for propagation, since rhizomes are not sectioned based on number of buds. However, like in other cutting protocols, each propagule should contain enough rhizome or/and fleshy roots, and apical bud in this protocol. Thus, it is important to determine number of sections for maximising number of plantlets produced per rhizome. In the present study, we first investigated the effects of H. citrina rhizome weight on plantlet development when buds were intact. Furthermore, we identified the optimal number of sections per rhizome for two sizes of buds, based on the performance of plantlet. We hypothesised that (1) the growth of plantlets is influenced by rhizomes weight, which links to energy and nutrient supplies; (2) sectioning rhizomes into three pieces can produce more plantlets per rhizome and has less adverse effects on growth of plantlets.

2. Materials and Methods

2.1. Experimental Site and Materials

Two experiments were conducted in a solar-greenhouse at the Research Park of China Agricultural University, Beijing, China (39°54′ N, 116°23′ E). The solar-greenhouse was 85 m long and 7 m wide. Experiments were set up in the middle section of the solar-greenhouse.
H. citrina rhizomes, with age of 3–5 years and an intact apical bud, were collected in autumn 2020 from a field in Datong, Shanxi province, China. Rhizomes were kept in a dark and cool room (4 °C) to avoid emergence of leaf buds until the experiments started. A mixture of peat, vermiculite and perlite (2:1:1, v/v/v) was chosen as substrates, in which rhizomes had good performance on survival rates, aboveground and belowground growth in a pre-experiment (data not shown). The substrates had total porosity of 67.8%, a pH value of 5.42 and an EC value of 0.75 mS cm−1. Substrates were filled into square pots (width and length: 7 cm, height: 8 cm) and reached to a bulk density of 0.31 g cm−3.

2.2. Experiment 1 (EXP.1)

Experiment 1 was conducted to investigate the effects of rhizome weight on growth of plantlets during the period of 15 November to 17 December in 2020. A completely randomised design was applied with three treatments and three replicates. The three treatments consisted of three levels of rhizome weight: big rhizome (BR, weight of 20.2 ± 0.5 g), medium rhizome (MR, weight of 12.2 ± 0.4 g) and small rhizome (SR, weight of 6.3 ± 0.3 g). Each replicate contained five randomly selected rhizomes which were grown at a plant density of one rhizome per pot. Plants were destructively sampled 17 days after planting (DAP), 22 DAP, 27 DAP and 32 DAP for biomass and chemical analysis. In total, this experimental setup yielded 180 rhizomes.

2.3. Experiment 2 (EXP.2)

Experiment 2 was carried out during the period of 13 January to 1 March 2021 at the same site as in EXP.1. Bud size (n = 2 treatments) and Section Number (n = 3 treatments) were investigated by using a completely randomised design with three replicates, yielding 6 treatments. The buds were classified into two groups according to the transverse diameter of the bud: large bud (LB, Ø: >1 cm) and small bud (SB, Ø: <1 cm). Rhizomes were longitudinally sectioned along shaft axis of crown into equal parts: two equal sections (S2), three equal sections (S3) and four equal sections (S4) (Figure 1). Each replicate contained five propagules. Three destructive samplings were conducted at 32 DAP, 39 DAP and 46 DAP. The sampling dates were set later in EXP.2 compared to in EXP.1, due to lower air temperature. This experiment contained 270 rhizomes in total.

2.4. Growing Conditions

In both experiments, each propagule was planted into substrate in one square pot after removing the dead leaf on the rhizome. A saucer was placed underneath the pot to prevent water and nutrient loss. Before planting, substrates received tap water until water holding capacity reached. Rhizomes within each replicate were grouped and placed together, and each replicate was placed randomly in the greenhouse. After planting, 50 mL of tap water was given every three days until the end of the experiment. In EXP.2, 50 mL of a full-strength nutrient solution (Yamazaki formula), instead of tap water was given every three days from 39 DAP to 46 DAP. The Yamazaki formula contained 196 mg L−1 of N, 31 mg L−1 of P and 20 mg L−1 of K. Heat coils were placed on the top of ground, and were turned on when temperature was below 5 °C to avoid cold damage on plantlets. No artificial lights were supplied during the experimental periods.

2.5. Plant Analysis

Apical bud sprouting rates of propagules, the number of propagules with sprouting bud divided by the number of total propagules, were recorded 3, 6 and 9 days after planting in EXP.1 and 3, 7 and 9 days after planting in EXP.2. Afterwards, plantlets were delicately taken out from pots for keeping fibrous roots intact on each sampling date. The plantlets were divided by scissors into aboveground and belowground parts. Belowground part was carefully washed with tap water to remove substrates attached to fibrous roots. All fibrous roots were carefully detached from rhizomes. The total leaf area and total fibrous root length was measured by scanning all leaves and fibrous roots (Epson Perfection V800 photo scanner) and analysing images in WinRHIZO (LC4800-II LA2400, Regent Instruments, Quebec, QC, Canada). Leaf area was not measured in EXP.2, because it is difficult to scan curly leaves caused by unbalanced growth. A subsample of belowground parts from 17, 27 and 32 DAP was taken and frozen at −20 ℃ for carbohydrate analysis in EXP.1. Glucose, fructose, sucrose and starch concentrations were measured using assay kits and following the manufacturer’s instructions (Su Zhou Keming Bioengineer Company, China). The rest plant materials were oven-dried at 80 °C to constant weight for measuring biomass (dry weight). In both experiments, N concentration in dry biomass was analysed by using the Kjeldahl procedure [14]. P, K, Ca, Mg and S concentrations were analysed by inductively coupled plasma-atomic emission spectroscopy (ICP6300, UK), after digestion with nitric acid [15].

2.6. Calculation and Statistical Analysis

Propagation coefficient is calculated as the number of plantlets obtained per rhizome. Specific leaf area was calculated by dividing fresh leaf area by aboveground dry biomass. Specific root length was calculated by dividing total fibrous root length by dry biomass of fibrous roots [16]. The relative aboveground dry biomass growth rates (RGR-AB), the relative leaf area growth rate (RGR-LA) and the relative root length growth rate (RGR-ROOT) were calculated according to the equation below [17]:
RGR = (lnN2 − lnN2)/(t2 − t1)
where N2 and N1 are aboveground dry biomass, leaf area and fibrous root length at times t1 and t2 respectively.
Analysis of variance was conducted by using general linear model procedure in R (version 4.0.3). In EXP.1, the effect of rhizome weight on plantlet growth was analysed with Rhizome weight as a factor. Additionally, the relative growth rates were analysed by taking Rhizome weight and Date as factors. In EXP.2, the plantlet growth and nutrient concentrations were analysed with Bud size, Section number and their interaction as factors. A square root transformation or log transformation of data were carried out to obtain homogeneity of variance. Tukey’s Student test was applied for multiple comparisons among treatments in each factor when no interaction between factors. When there was an interaction, multiple comparisons among treatments were conducted by using function “emmeans” (Package emmean Version 1.6.3).

3. Results

3.1. Bud Sprouting Rates of Propagules and Propagation Rate

In both experiments, apical bud sprouting rates increased with time till 9 DAP. In EXP.1, the bud sprouting rate was higher in BR treatment than in MR treatment and SR treatment on 3 DAP (p < 0.05). The sprouting rates were similar on 6 DAP and 9 DAP and reached to 96–99% on 9 DAP (Table 1). There was no significant difference among three levels of rhizome weight on 9 DAP.
In EXP.2, the bud sprouting rate and propagation coefficient was influenced by the interaction between Bud size and Section number on each date. The sprouting rate was highest in S2 across Bud size on each date. On 9 DAP, the sprouting rates were similar in S2 and S3 treatments, when large buds were used. When small buds were used, the sprouting rate was 66.7% in S4, lower than 78.9% in S3 and 96.7% in S2 on 9 DAP (p < 0.05). Propagation coefficient was 3.2 in S4, higher than that in S3 (2.8) and S2 (1.9) when large buds were used. When small buds were used, the highest propagation coefficient was 2.7 in S4, followed by 2.4 in S3 and 1.9 in S2. The small buds decreased propagation coefficients in S3 and S4 relative to large buds (p < 0.05) (Table 1).

3.2. Aboveground and Belowground Growth of Plantlets

In EXP.1, leaf area of plantlet was only statistically different on 32 DAP. The leaf area in BR treatment was larger than those in MR treatment and SR treatment (p < 0.05). The aboveground dry biomass was lower in SR treatment than in BR treatment on all four sampling dates (p < 0.05). The aboveground dry biomass was lower in MR treatment than in BR treatment on 17 DAP and 32 DAP (p < 0.05). Specific leaf area in SR treatment were higher than those in BR treatment (p < 0.05) (Table 2). The total fibrous root length was higher in BR treatment than in SR treatment on 22 DAP (p < 0.05). The total fibrous root length in BR treatment was highest among all treatments on 32 DAP (p < 0.05) (Table 2).
The relative growth rates of aboveground dry biomass, leaf area and total fibrous root length were influenced by interaction between Date and Rhizome weight. When big rhizome was used as propagule, the relative growth rates of aboveground dry biomass and leaf area were higher on 32 DAP compared to on 22 DAP and on 27 DAP (p < 0.05). The medium-rhizome plantlets had steady relative growth rates of aboveground dry biomass, leaf area and total fibrous root length through time. The relative root length growth rate was only different among dates when the small rhizomes was used, showing slower growth rate on 32 DAP relative to on 22 DAP and 27 DAP (p < 0.05) (Figure 2).
In EXP.2, aboveground dry biomass of seedlings was affected by Section number on three dates (p < 0.05), not by Bud size. Aboveground dry biomass was always higher in S2 than in S3 and S4 across bud sizes. The aboveground dry biomass was lower in S3 treatment than in S2 treatment on 32 DAP and 46 DAP (p < 0.05). Total fibrous root length of plantlets was influenced by both Section number and Bud size. The total fibrous root length was lowest in S4 treatment compared to in S2 and S3 treatments, on all three sampling dates (p < 0.05). Meanwhile, plantlets had lower total fibrous root length in SB treatment than in LB treatment on all three dates (Table 3).
Section number did not influence the relative aboveground dry biomass growth rate in the period of 32 DAP to 46 DAP. However, the relative total fibrous root length growth rate was higher in LB treatment than in SB treatment (p < 0.05) (Figure 3).

3.3. Carbohydrates in Rhizomes in EXP.1

In EXP.1, glucose concentration in rhizome was influenced by interactions between Date and Rhizome weight. All glucose concentration significantly decreased from 17 DAP to 32 DAP, regardless of weights of rhizome (p < 0.05). Glucose concentrations in big rhizomes were only different between 17 DAP and 32 DAP. Glucose concentrations in medium and small rhizomes were different between 27 DAP and 32 DAP (p < 0.05) (Figure 4).
Fructose concentration was influenced by Rhizome weight (p < 0.05), while sucrose, starch and total soluble sugar (sum of glucose, fructose and sucrose) were similar among rhizome weights and dates (Table 4).

3.4. Nutrients Concentrations of Plantlets

At the end of EXP.1 (32 DAP), N concentration in aboveground dry biomass was lower in SR treatment compared to in BR treatment and MR treatment (p < 0.05) (Table 5). There is no significant difference in other nutrient concentrations.
In EXP.2, plantlets had higher N, P and K concentrations in S4 treatment than in S2 and S3 treatments before nutrient solution was given (39 DAP) (p < 0.05). N concentration in aboveground dry biomass was higher in small buds than in large buds (p < 0.05). Seven days after nutrient solution was given (46 DAP), N, P and K concentration in aboveground dry biomass was similar among Section number and Bud size (Figure 5). No significant difference was found in Mg and S concentrations on 39 and 46 DAP.

4. Discussion

4.1. The Influence of Rhizome Weight and Section Number on Propagation Coefficients

Rhizome weight did not influence propagation coefficient when buds were intact. The higher bud sprouting rate of big-rhizome plantlets on 3 DAP indicated earlier initiation of sprouting, which was probably due to more carbohydrates provided by rhizomes and fleshy fibrous roots in big rhizome at the beginning [18]. Since 6 DAP, similar bud sprouting rate and propagation coefficient among three levels of rhizome weight indicated small rhizomes contained enough carbohydrates for wound healing and bud sprouting (Table 1).
In our new cutting protocol, the propagation coefficient of H. citrina increased when buds were sectioned into more pieces. In general, bud sprouting rate of propagules decreased with the increase of sectioning number. It also decreased with bud size when rhizomes were sectioned into 3 or 4 pieces (Table 1). The decrease of bud sprouting rate could be attributed to smaller propagules and more severe mechanical injuries on leaves on each propagule. Sectioning rhizomes into more pieces per bud could yield more propagules per rhizomes, and overshadowed adverse effect of the decreased bud sprouting rate on propagation coefficient, leading to higher propagation coefficients in the end.

4.2. The Influence of Rhizome Weight on Plantlet Development Pattern

Rhizome weight influenced the aboveground (aboveground dry biomass and leaf area) and belowground (total fibrous root length) development patterns of plantlets, which were probably related to alteration of photosynthetic organ (leaf area), N status and carbohydrate concentrations in rhizomes. Medium-rhizome plantlets had steady relative growth rate in both aboveground and belowground parts. Big-rhizome plantlets and small-rhizome plantlets showed steady relative growth rates on 22 DAP and 27 DAP, while big-rhizome plantlets showed an increased relative growth rate in aboveground part and small-rhizome plantlets showed a decreased relative growth rate in belowground part on 32 DAP (Figure 2). This confirmed our first hypothesis. The increased relative growth rates in aboveground part of big-rhizome plantlets on 32 DAP corresponding to the highest biomass could be ascribed to a higher leaf area (Table 1) which is a determinant of photosynthesis. The decreased relative growth rate in small-rhizome plantlets on 32 DAP could be ascribed to severe N deficiency shown by lower N concentration aboveground (Figure 5). Although root proliferation can be stimulated by nutrient (i.e., N and P) deficiency in order for a larger exploiting volume of soil [19], severe N deficiency could inhibit root growth and accelerate root death [20], due to suppression of photosynthesis and decreased assimilate allocation to roots [21]. Moreover, carbohydrates in rhizomes, such as glucose and fructose, could play a role in plantlet growth in the present study. The gradually decreased glucose concentrations in rhizomes from 17 DAP to 32 DAP (Figure 4) indicated that glucose was involved in plantlet development [22], such as rooting and leaf growth. It has been recorded that carbohydrates, especially glucose, act as an important energy source for rooting [23]. Similarly, the decrease of glucose contents with time has also been found in other species, such as olive (Olea europaea L.) [24] and mangroves [25]. Glucose and fructose can also modulate auxin metabolism and consequently regulate rooting process [26,27]. A lower fructose concentration in medium-rhizome plantlets at 27 and 32 DAP (Table 4) might lead to a higher expression of auxin responsive genes [27], resulting in a slightly higher relative root length growth rate than that in small-rhizome plantlets on 32 DAP (p = 0.0904).

4.3. The Influence of Rhizome Weight on Plantlet Performance

Rhizome weight determined the sizes of photosynthetic (leaf area) and fibrous roots of plantlets, by influencing initiation of growth (bud sprouting) and growth rates of plantlets. The aboveground part (aboveground dry biomass) showed earlier response to rhizome weights (17 DAP) than the belowground part (22 DAP) (Table 2). The similar leaf area and relative growth rates of aboveground dry biomass among rhizome weights indicated similar photosynthesis during the period of 17 to 27 DAP (Table 1, Figure 1 and Figure 2). Thus, rather than photosynthesis, less carbohydrates provided by rhizomes for bud sprouting and reallocation to the aboveground part might be a reason for the lower aboveground dry biomass in small-rhizome plantlets [28]. The delay of initiation of bud sprouting, indicated by lower bud sprouting rate in MR and SR treatments on 3 DAP (Table 1), could postpone the initial growth aboveground (photosynthesis), and consequently biomass accumulation. N deficiency in small-rhizome plantlets could be an integrated result of less N provided by small rhizomes and fewer fibrous roots for N uptake. This deficiency signified the necessity of N fertilization during the cutting procedure.
However, rhizome weight did not change the strategy of plantlets for assimilate investment, indicated by similar specific leaf area and specific root length among rhizome weights. Specific leaf area and specific root length are parameters showing response of plant morphology to growth stage and environmental stress, such as light, water and soil N [29,30]. Higher specific leaf area in small-rhizome plantlets on 17 and 22 DAP indicated it invested less dry matter per leaf area for capturing more solar energy. However, the higher specific leaf area did not lead to higher relative growth rate which is also related to other factors, such as N uptake by roots [30]. Weak correlation between specific leaf area and relative growth rates was also reported by Shipley [31].

4.4. The Influence of Section Numbers and Bud Size on Plantlet Growth

Sectioning rhizomes into more pieces and small bud led to smaller H. citrina plantlets, due to fewer leaves per propagule and alternation of assimilates allocation or translocation strategy. Sectioning rhizomes into more pieces resulted in smaller portion of apical bud, equivalent to fewer leaf primordia per propagule. The smallest amount of rhizome and fleshy fibrous roots in S4 treatment indicated less energy for bud sprouting, leading to a lowest bud sprouting rate on 9 DAP (Table 1). Meanwhile, propagules suffered mechanical damage stress caused by sectioning procedure, and consequently called for carbohydrates for recovery [32]. Due to the less rhizome and fleshy fibrous roots, propagules in S4 treatment might invest more photoassimilate for recovery, but less to aboveground and fibrous roots. This was confirmed by the fact that aboveground dry biomass in S4 treatment was disproportionately less than half of biomass in S2 treatment (Table 2). The poorer initial growth was the main cause for smaller plantlets in the end, since the relative growth rates kept similar regardless of the number of sectioning. Therefore, sectioning rhizomes into three pieces showed less adverse effects on growth and nutrient concentrations of plantlets, compared to sectioning into four pieces. This confirmed our second hypothesis. Distinctly different total fibrous root length but similar aboveground dry biomass of plantlets in two bud sizes indicated that bud sizes changed the strategy of plantlets for carbohydrate allocation or/and translocation. Plantlets from small buds allocated less carbohydrates to roots, resulting in a lower total fibrous root length as well as a lower relative total root length growth rate (Figure 3). Similar amounts of carbohydrates allocated or/and translocated to leaves were probably due to similar bud compositions between two sizes of buds, such as number of leaf primordia, which is determined by ambient conditions, such as light and temperature [33,34].
Higher N, P and K concentrations in leaves were found in S4 treatment before nutrient solution was given. The higher concentrations were mainly due to the retardation of biomass accumulation aboveground as forementioned (Table 3). The higher concentrations did not imply a better nutrient uptake by roots, of which length was lower in S4 (Table 3). After nutrient solution was given, nutrient concentrations in leaves were similar among section numbers and bud sizes (Figure 5). The similarity in nutrient concentrations was probably due to improved biomass accumulation in S4 treatment, confirmed by the fact that aboveground dry biomass increased by 78% from 39 DAP to 46 DAP. No increase of nutrient concentrations after nutrient solution given indicated that there were no significant nutrient deficiencies on 39 DAP.

5. Conclusions

Rhizome weight did not influence propagation coefficient of H. citrina when buds were intact. However, it influenced growing patterns of plantlets by retarding initial growth and changing the relative growth rates on different dates. Small rhizomes decreased aboveground and belowground growth. However, rhizome weight did not alter the strategy of plantlet for assimilate investment. Longitudinally sectioning apical buds and short rhizomes along shaft axis of crown into equal sections as propagules increased propagation coefficient when sectioning rhizome into more pieces. Retarded growth of plantlets appeared when rhizomes were sectioned into three or four pieces, and was more severe when sectioning into four pieces. Small bud resulted in less total fibrous root length, probably due to fewer carbohydrates allocated to biomass. In conclusion, rhizome weight and sectioning number per rhizome did play an important role in plantlet development. Sectioning rhizomes into three pieces should be recommended with smaller plantlets but higher propagation coefficient. N fertiliser might be requested during the cutting procedure, while the N dose needs to be determined in the future work.

Author Contributions

Conceptualization, Y.X.; methodology, Y.X.; formal analysis, Y.X.; investigation, T.C.; resources, H.R.; writing—original draft preparation, Y.X.; writing—review and editing, Y.X. and H.R.; visualization, Y.X.; supervision, Y.X.; project administration, H.R.; funding acquisition, H.R. All authors have read and agreed to the published version of the manuscript.

Funding

The research was financially supported by Research and Development on Efficient Propagation of Virus-free Plantlets of Huang Hua Cai (201904710121629) and The Construction of Beijing Science and Technology Innovation and Service Capacity in Top Subjects (CEFF-PXM2019_014207_000032).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Agronomy 12 02777 g001 550
Figure 1. Schematic diagram of sectioning rhizomes in EXP.2. Note: S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in Experiment 2.
Figure 1. Schematic diagram of sectioning rhizomes in EXP.2. Note: S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in Experiment 2.
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Agronomy 12 02777 g002 550
Figure 2. The relative growth rates of aboveground dry biomass, leaf area and total fibrous root length on 22, 27 and 32 DAP in EXP.1. Note: BR, MR and SR refer to the big, medium and small rhizome weight in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
Figure 2. The relative growth rates of aboveground dry biomass, leaf area and total fibrous root length on 22, 27 and 32 DAP in EXP.1. Note: BR, MR and SR refer to the big, medium and small rhizome weight in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
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Agronomy 12 02777 g003 550
Figure 3. The relative growth rates of aboveground dry biomass, leaf area and total fibrous root length from 32 to 46 DAP in EXP.2. Note: The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
Figure 3. The relative growth rates of aboveground dry biomass, leaf area and total fibrous root length from 32 to 46 DAP in EXP.2. Note: The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
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Figure 4. The glucose concentration in rhizomes on 17, 27 and 32 DAP in EXP.1. Note: BR, MR and SR refer to big, medium and small rhizome weight in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
Figure 4. The glucose concentration in rhizomes on 17, 27 and 32 DAP in EXP.1. Note: BR, MR and SR refer to big, medium and small rhizome weight in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among sampling dates. The error bars represent standard errors (n = 3).
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Agronomy 12 02777 g005 550
Figure 5. The N, P and K concentrations in leaves on 39 and 46 DAP in EXP.2. Note: S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in EXP.2. The different lower-case letters indicate significant probability difference at p < 0.05 among numbers of sectioning. The error bars represent standard errors (n = 3).
Figure 5. The N, P and K concentrations in leaves on 39 and 46 DAP in EXP.2. Note: S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in EXP.2. The different lower-case letters indicate significant probability difference at p < 0.05 among numbers of sectioning. The error bars represent standard errors (n = 3).
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Table
Table 1. The sprouting rate of apical buds on propagules during first 9 days and the propagation coefficients of each treatment in EXP.1 and EXP.2.
Table 1. The sprouting rate of apical buds on propagules during first 9 days and the propagation coefficients of each treatment in EXP.1 and EXP.2.
TreatmentSprouting Rate (%)Propagation Coefficients
EXP.1 3 DAP6 DAP9 DAP
BR86.7 ± 6.2 a93.3 ± 2.498.9 ± 1.41.00 ± 0.00
MR68.9 ± 4.9 b85.6 ± 3.695.6 ± 2.70.98 ± 0.01
SR64.4 ± 4.9 b88.9 ± 1.496.7 ± 2.40.97 ± 0.02
EXP.2 3 DAP7 DAP9 DAP
Large budS287.8 ± 3.6 a97.8 ± 1.4 a98.9 ± 1.4 a1.98 ± 0.03 c
S384.4 ± 1.4 a91.1 ± 2.7 a93.9 ± 2.4 a2.80 ± 0.07 b
S470.0 ± 4.1 b73.3 ± 7.1 b81.1 ± 3.6 b3.24 ± 0.14 a
Small budS282.2 ± 1.4 a88.9 ± 1.4 a96.7 ± 0.0 a1.93 ± 0.00 c
S334.4 ± 2.7 b43.3 ± 4.1 b78.9 ± 3.6 b2.37 ± 0.11 b
S433.3 ± 0.0 b38.9 ± 5.9 b66.7 ± 2.4 c2.67 ± 0.09 a
Note: BR, MR and SR refer to the big, medium and small rhizome, respectively, in Experiment 1. Large bud and Small bud refer to large bud (Ø: >1 cm) and small bud (Ø: <1 cm) in Experiment 2. S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in Experiment 2. The different lower-case letters indicate significant probability difference at p < 0.05 among rhizome weights in Experiment 1 or among numbers of sectioning in Experiment 2. Values are mean ± s.e (n = 3).
Table
Table 2. The height, leaf area, fibrous root length, aboveground dry biomass, root dry weight, specific leaf area and specific root length of propagules on four dates in EXP.1.
Table 2. The height, leaf area, fibrous root length, aboveground dry biomass, root dry weight, specific leaf area and specific root length of propagules on four dates in EXP.1.
DAPTreatmentLeaf Area (cm2)Fibrous Root Length (cm)Aboveground Dry Biomass (mg)Root Dry Weight (mg)Specific Leaf Area (cm2 g−1)Specific Root Length (cm)
17BR120.11 ± 5.4023.87 ± 3.21577.50 ± 24.02 a-206.95 ± 12.95 b-
MR116.21 ± 8.7117.25 ± 2.47448.33 ± 24.04 b-260.59 ± 13.37 ab-
SR98.92 ± 7.0915.83 ± 0.49348.33 ± 17.22 c-284.21 ± 15.83 a-
22BR139.49 ± 16.8770.37 ± 11.06 a586.67 ± 50.09 a-237.04± 17.64 b-
MR142.21 ± 7.4434.40 ± 5.44 b514.12 ± 13.72 ab-276.23± 7.92 b-
SR128.53 ± 10.8236.86 ± 1.48 b386.67 ± 22.93 b-331.58 ± 10.34 a-
27BR195.60 ± 12.14176.78 ± 28.50691.67 ± 32.83 a121.11 ± 22.55282.48 ± 5.4814.96 ± 1.52
MR197.68 ± 12.9093.60 ± 3.68607.50 ± 20.36 a62.22 ± 23.28324.74 ± 11.2725.26 ± 13.89
SR179.48 ± 21.34125.47 ± 34.70470.83 ± 34.11 b65.56 ± 28.57379.14 ± 20.1125.07 ± 9.50
32BR391.59 ± 11.01 a304.13 ± 29.43 a1233.33 ± 103.30 a180.00 ± 17.50 a321.00 ± 21.3817.09 ± 1.99
MR301.17 ± 24.25 b218.96 ± 27.68 ab832.50 ± 53.87 b105.83 ± 4.17 b361.23± 9.2620.80 ± 2.86
SR223.66 ± 22.88 b160.20 ± 9.59 b595.83 ± 45.56 b63.33 ± 6.51 b373.95± 9.2425.56 ± 1.50
Note: BR, MR and SR refer to the big, medium and small rhizome, respectively in Experiment 1. The different lower-case letters indicate significant probability difference at p < 0.05 among rhizome weights. Values are mean ± s.e (n = 3).
Table
Table 3. The aboveground dry biomass and fibrous root length on three dates in EXP.2. Data shown are Mean ± s.e. (n = 3).
Table 3. The aboveground dry biomass and fibrous root length on three dates in EXP.2. Data shown are Mean ± s.e. (n = 3).
DAPTreatmentAboveground Dry Biomass (mg)Fibrous Root Length (cm)
32S2264.33 ± 15.75 a88.57 ± 8.42 a
S3164.67 ± 9.30 b41.06 ± 5.76 b
S497.67 ± 6.9 c21.14 ± 3.53 c
39S2306.67 ± 18.89 a133.22 ± 19.78 a
S3257.00 ± 16.34 a152.48 ± 17.40 a
S4118.00 ± 13.64 b40.31± 6.75 b
46S2698.00 ± 67.43 a438.52 ± 44.34 a
S3403.00 ± 32.51 b250.28 ± 18.61 b
S4210.00 ± 29.25 c108.94 ± 9.20 c
Note: S2, S3 and S4 refer to two equal sections, three equal sections and four equal sections, respectively in EXP.2. The different lower-case letters indicate significant probability difference at p < 0.05 among numbers of sectioning. Values are mean ± s.e (n = 3).
Table
Table 4. The fructose, sucrose, soluble sugar and starch concentration in rhizomes on 17, 27 and 32 DAP in EXP.1. Data shown are Mean ± s.e. (n = 3).
Table 4. The fructose, sucrose, soluble sugar and starch concentration in rhizomes on 17, 27 and 32 DAP in EXP.1. Data shown are Mean ± s.e. (n = 3).
Fructose (mg g−1)Sucrose (mg g−1)Soluble Sugar (mg g−1)Starch (mg g−1)
Dates
1710.46 ± 0.4518.19 ± 0.8632.46 ± 1.452.06 ± 0.18
2710.31 ± 0.6016.72 ± 1.6530.44 ± 2.842.68 ± 0.22
3210.90 ± 0.9119.21 ± 1.3632.65 ± 1.152.32 ± 0.18
Rhizome weight
Big11.59 ± 0.45 a19.30 ± 1.2234.36 ± 1.452.70 ± 0.27
Medium8.98 ± 0.67 b19.03 ± 1.4031.07 ± 1.752.22 ± 0.14
Small11.11 ± 0.53 a15.80 ± 1.1430.12 ± 0.902.15 ± 0.15
Date × Rhizome weightn.s.n.s.n.s.n.s.
Note: Big, Medium and Small refer to the big, medium and small rhizome in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among rhizome weights. Values are mean ± s.e (n = 3).
Table
Table 5. The nutrient concentrations in aboveground and belowground parts of plantlets at the end of EXP.1 (32 DAP).
Table 5. The nutrient concentrations in aboveground and belowground parts of plantlets at the end of EXP.1 (32 DAP).
TreatmentN (mg g−1)P (mg g−1)K (mg g−1)Ca (mg g−1)Mg (mg g−1)S (mg g−1)
AbovegroundBR7.05 ± 0.25 a3.04 ± 0.2016.97 ± 0.974.15 ± 0.091.88 ± 0.032.30 ± 0.03
MR6.97 ± 0.63 a3.03 ± 0.0417.52 ± 0.634.08 ± 0.121.87 ± 0.052.54 ± 0.37
SR4.76 ± 0.34 b3.13 ± 0.0919.60 ± 0.164.50 ± 0.332.03 ±0.063.80 ± 0.96
BelowgroundBR2.7 ± 0.201.78 ± 0.057.29 ± 0.387.42 ± 0.38 b1.38 ± 0.051.27 ± 0.24
MR2.30 ± 0.071.92 ± 0.127.23 ± 0.608.27 ± 0.35 b1.41 ± 0.082.07 ± 0.31
SR2.77 ± 0.191.88 ± 0.087.68 ± 0.239.81 ± 0.03 a1.47 ± 0.021.53 ± 0.23
Note: BR, MR and SR refer to the big, medium and small rhizome weight in EXP.1, respectively. The different lower-case letters indicate significant probability difference at p < 0.05 among rhizome weights. Values are mean ± s.e (n = 3).
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Xie, Y.; Chen, T.; Ren, H. Rhizome Weight and Number of Sectioning per Rhizome Determine Plantlet Growth and Propagation Rate of Hemerocallis citrina Baroni in Cutting Propagation. Agronomy 2022, 12, 2777. https://doi.org/10.3390/agronomy12112777

AMA Style

Xie Y, Chen T, Ren H. Rhizome Weight and Number of Sectioning per Rhizome Determine Plantlet Growth and Propagation Rate of Hemerocallis citrina Baroni in Cutting Propagation. Agronomy. 2022; 12(11):2777. https://doi.org/10.3390/agronomy12112777

Chicago/Turabian Style

Xie, Yue, Tong Chen, and Huazhong Ren. 2022. "Rhizome Weight and Number of Sectioning per Rhizome Determine Plantlet Growth and Propagation Rate of Hemerocallis citrina Baroni in Cutting Propagation" Agronomy 12, no. 11: 2777. https://doi.org/10.3390/agronomy12112777

APA Style

Xie, Y., Chen, T., & Ren, H. (2022). Rhizome Weight and Number of Sectioning per Rhizome Determine Plantlet Growth and Propagation Rate of Hemerocallis citrina Baroni in Cutting Propagation. Agronomy, 12(11), 2777. https://doi.org/10.3390/agronomy12112777

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