Figures
Abstract
Current knowledge on responses of aquatic clonal plants to resource availability is largely based on studies manipulating limited resource levels, which may have failed to capture the “big picture” for aquatic clonal plants in response to resource availability. In a greenhouse experiment, we grew the floating clonal plant Spirodela polyrhiza under ten nutrient levels (i.e., 1/64×, 1/32×, 1/16×, 1/8×, 1/4×, 1/2×, 1×, 2×, 4× and 8×full-strength Hoagland solution) and examined their responses in terms of clonal growth, morphology and biomass allocations. The responses of total biomass and number of ramets to nutrient availability were unimodal. A similar pattern was found for frond mass, frond length and frond width, even though area per frond and specific frond area fluctuated greatly in response to nutrient availability. In contrast, the responses of root mass and root length to nutrient availability were U-shaped. Moreover, S. polyrhiza invested more to roots under lower nutrient concentrations. These results suggest that nutrient availability may have distinct influences on roots and fronds of the aquatic clonal plant S. polyrhiza, resulting in a great influence on the whole S. polyrhiza population.
Citation: Jin Y, Zhang Q, Zhang L-M, Lei N-F, Chen J-S, Xue W, et al. (2021) Distinct responses of frond and root to increasing nutrient availability in a floating clonal plant. PLoS ONE 16(10): e0258253. https://doi.org/10.1371/journal.pone.0258253
Editor: Jian Liu, Shandong University, CHINA
Received: July 14, 2021; Accepted: September 23, 2021; Published: October 11, 2021
Copyright: © 2021 Jin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: This study was supported by the National Natural Science Foundation of China (grant no. 31800341). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Clonal plants, i.e., those with the ability of clonal growth or asexual reproduction, are widespread in various natural habitats [1–3]. They are also the dominant species in many ecosystems, including grasslands, wetlands and alpine and arctic tundra, where they play a key role in regulating ecosystem functions and stability [2, 4–6]. Clonal plants, via clonal growth, are able to produce offspring ramets (asexual individuals) that have exactly the same genetic information as their mother ramet [3, 7].
Most aquatic plants are capable of clonal growth [8–12]. Aquatic clonal plants are a common component of aquatic communities and play important roles in many aquatic ecosystems [13, 14]. For instance, aquatic clonal plants such as floating and submerged clonal plants can reduce turbidity, thereby inhibiting the growth of algae and improving the quality of water [15, 16]. Another example is that oxygen released from the roots of aquatic clonal plants may create an oxidized rhizosphere [17] that facilitates processes contributing to waste degradation [18, 19]. Many aquatic ecosystems are degraded due to, e.g., eutrophication, and a huge amount of efforts have been spent to restore such degraded ecosystems [20–24]. To make better use of aquatic clonal plants for restoration of degraded aquatic ecosystems, we need to assess the detailed responses of their clonal growth, morphology and biomass allocation to a wide range of changes in single environmental factors such as nutrient availability.
Nutrient availability can substantially affect the growth and development of aquatic clonal plants [25, 26]. Excessive nutrient load in aquatic ecosystems can have great consequences on the distribution of aquatic plants, including floating clonal plants [27–31]. For instance, total biomass and ramet number of Salvinia natans in high nutrient availability were greater than those in low nutrient availability, and floating mass was mostly higher and submerged mass lower at high than at low nutrient availability [11]. However, in the low ammonia nitrogen (<8 mg L-1) of water column, an increase in nutrient availability led to increased total biomass and chlorophyll concentration of Vallisneria natans [32]. An increase in nutrient availability in the water column leads to a decreased specific root length in V. natans [33]. However, plants exhibit slowed growth and altered intrinsic nutrient uptake in a nutrient-poor environment because dry weight production is related to the demand for nutrients [26]. So far, however, studies testing effects of nutrient availability on clonal growth, morphology and biomass allocation of aquatic clonal plants, especially floating clonal plants, have mostly included only a few (e.g., 2–4) nutrient levels [12, 34–38]. To better understand their responses, therefore, we need to test their responses to a wider range of nutrient levels.
We grew the floating clonal plant Spirodela polyrhiza in ten concentrations of Hoagland solution and evaluated the effects of nutrient availability on clonal growth, morphology and biomass allocation. Specifically, we addressed the following questions. (1) How does nutrient availability affect clonal growth of S. polyrhiza as measured by biomass, ramet production and total frond area? (2) How does nutrient availability influence clonal morphology of S. polyrhiza as measured by frond length, frond width, the longest root length, area per frond and specific frond area? (3) How does nutrient availability impact root to shoot ratio of S. polyrhiza?
Materials and methods
Species and sampling
Spirodela polyrhiza (L.) Schleiden is a perennial, floating, clonal plant of Lemnaceae (duckweed family). It has the simplest morphology among flowering plants [39]. The species rarely flowers and mainly reproduces vegetatively [40, 41]. A ramet (i.e., asexual individual) of S. polyrhiza commonly consists of one or two fronds and some roots [12]. When environmental conditions are favorable, a parent ramet can produce offspring ramets that are connected to it by a stipe at their early stage of development [39]. Offspring ramets can be detached from the parent ramet and become completely independent due to aging or disturbance [12]. Each frond of S. polyrhiza is 5–10 mm long and 3–8 mm wide. It is flat and obovate, with a green surface towards the air and purple back towards the water. This species is widely distributed across the world, and typically found in eutrophic freshwater systems, such as slow-moving streams, ditches, and shallow pools [12, 41].
Plants of S. polyrhiza were collected on June 2, 2018 from a slow-moving stream (28°3′N, 121°21′E) in Jiaojiang District, Taizhou City, Zhejiang Province, China. Plants were transported to the greenhouse at the Jiaojiang campus of Taizhou University in Jiaojiang District, Taizhou City, Zhejiang Province, China. The plants were washed several times with double distilled water and rinsed with 0.01 M NaClO for 30 s to reduce microbial and algal growth [42]. Before the experiment, the plants were propagated vegetatively in plastic tanks with 10% Hoagland solution.
Experimental design
The experiment started on June 19, 2018. Healthy ramets of S. polyrhiza with uniform size and two fronds were selected and grown in 250 mL containers (9.5 cm in diameter and 6.5 cm in height). Each container initially contained two ramets of S. polyrhiza. Plants were subjected to ten levels of full-strength Hoagland nutrient solution (1/64×, 1/32×, 1/16×, 1/8×, 1/4×, 1/2×, 1×, 2×, 4× and 8×), with 12 replicates for each treatment. The composition of 1×full-strength Hoagland solution included: 0.945 g L-1 Ca(NO3)2·4H2O, 0.506 g L-1 KNO3, 0.08 g L-1 NH4NO3, 0.136 g L-1 KH2PO4, 0.493 g L-1 MgSO4, 0.0139 g L-1 FeSO4·7H2O, 0.01865 g L-1 EDTA·2Na, 0.00415 g L-1 KI, 0.031 g L-1 H3BO3, 0.1115 g L-1 MnSO4, 0.043 g L-1 ZnSO4, 0. 00125 g L-1 Na2MoO4, 0.000125 g L-1 CuSO4, and 0.000125 g L-1 CoCl2. Each container was filled with 200 mL of nutrient solution. Every four days, nutrient solution was replaced in all containers. Containers were placed completely randomly. After 14 days, on July 3, 2018, plants were harvested. The experiment ran within a relative short period because the surface of the solution was already fully covered with the ramets of S. polyrhiza in some containers where intraspecific competition would occur if the experiment ran for a longer time. During the experiment, the mean air temperature was 24.3°C and the mean relative humidity was 81.3% in the greenhouse, as measured hourly using temperature loggers (iButton DS1923; Maxim Integrated Products, San Jose, CA, USA).
Measurements
At harvest, we counted ramets and fronds of S. polyrhiza in each container. We randomly selected five ramets in each container, and measured their frond length, frond width and longest root length. Total area of all fronds in each container was scanned and measured with ImageJ 2006 (Bethesda, MD, USA). All ramets in each container were separated into roots and fronds, dried at 75°C for 24 h, and weighed.
Data analysis
We calculated area per frond (total frond area/number of fronds), root to shoot ratio (total root mass/total frond mass) and specific frond area (total frond area/total frond mass). We also obtained mean frond length, mean frond width and mean longest root length based on the measures on the five ramets in each container. The data of fourteen containers were excluded from the analyses due to missing values.
One-way ANOVA was used to evaluate the effects of nutrient availability on clonal growth (total mass, frond mass, root mass, number of ramets and total frond area), morphology (frond length, frond width, longest root length, area per frond and specific frond area) and biomass allocation (root to shoot ratio). Before analysis, data on number of ramets, total frond area, frond mass, total mass, and SLA were transformed to logarithmic, data on root mass were transformed to square root, data on longest root length was transformed to trigonometric. Other data required no transformation to meet requirements for homoscedasticity and normality; figures showed untransformed data. Duncan’s multiple range test was used to compare mean values among treatments. All analyses were conducted using SPSS 22.0 (IBM, Armonk, NY, USA).
Results
Effects of nutrient availability on clonal growth
Nutrient availability highly significantly affected biomass (F9,96 = 2.8–48.9, all P < 0.01), number of ramets (F9,96 = 94.7, P < 0.001) and total frond area (F9,96 = 34.2, P < 0.001) of S. polyrhiza (Figs 1 and 2). Total mass and frond mass of S. polyrhiza initially increased and then declined as nutrient availability increased, and the maximum value was observed at 4×full-strength Hoagland solution (Fig 1A and 1B). Root mass initially decreased, then increased and finally decreased again, showing the greatest value at 4×full-strength Hoagland solution, smallest values at 1/8× and 1/4×full-strength Hoagland solution and intermediate values at other concentrations (Fig 1C). Number of ramets and total frond area showed the similar patterns as total mass and leaf mass (Fig 2).
Total mass (A), frond mass (B), and root mass (C) of Spirodela polyrhiza grown in ten concentrations of Hoagland nutrient solution. Bars and vertical lines indicate means and SE (n = 12). F-statistics, df and P-values of one-way ANOVA for the effect of nutrient level are also given. Bars sharing the same letters are not different at P = 0.05.
Ramet number (A) and total frond area (B) of Spirodela polyrhiza grown in ten concentrations of Hoagland nutrient solution. Bars and vertical lines indicate means and SE (n = 12). F-statistics, df and P-values of one-way ANOVA for the effects of nutrient level are also given. Bars sharing the same letters are not different at P = 0.05.
Effects of nutrient levels on biomass allocation
Nutrient availability highly significantly affected root to shoot ratio of S. polyrhiza (F9,96 = 24.5, P < 0.001; Fig 3). Root to shoot ratio of S. polyrhiza at 1/64× and 1/32×full-strength Hoagland solution did not differ significantly, but was much larger than that at all other eight concentrations (Fig 3). Root to shoot ratio of S. polyrhiza also also greater in 1/16×, 2× and 4× full-strength Hoagland solution than in 1/8× full-strength Hoagland solution (Fig 3).
Bars and vertical lines indicate means and SE (n = 12). F-statistics, df and P-values of one-way ANOVA for the effects of nutrient level are also given. Bars sharing the same letters are not different at P = 0.05.
Effects of nutrient availability on clonal morphology
Clonal morphology of S. polyrhiza was significantly affected by nutrient availability (F9,96 = 2.1–12.6, all P < 0.05; Fig 4). Both frond length and frond width first gradually increased with increasing nutrient level, maximized at 4×full-strength Hoagland solution, and then decreased at 8×full-strength Hoagland solution (Fig 4A and 4B). With increasing nutrient availability, length of the longest root first decreased sharply, minimized at 1/8×full-strength Hoagland solution, and then increased, with the greatest values occurring at the two lowest concentrations (1/64× and 1/32×) of Hoagland solution (Fig 4E). Neither specific frond area nor area per frond showed a clear pattern, and they fluctuated with increasing nutrient availability (Fig 4C and 4D).
Frond length (A), frond width (B), specific frond area (SFA, C), area per frond (D), and longest root length (E) of Spirodela polyrhiza grown in ten concentrations of Hoagland nutrient solution. Bars and vertical lines indicate means and SE (n = 12). F-statistics, df, and P-values of one-way ANOVA for the effect of nutrient levels are also given. Bars sharing the same letters are not different at P = 0.05.
Discussion
Our results showed that the responses of total biomass and number of ramets to increasing nutrient availability were hump-shaped. Similar patterns were found for frond mass, frond length and frond width, despite that no clear pattern was found for area per frond and specific frond area. In contrast, the responses of root mass and root length to increasing nutrient availability were U-shaped. These results indicated that fronds and roots of the same clonal plant may had different response strategies to increasing nutrient availability, which may have largely determined the performance of the whole S. polyrhiza population.
Hump-shaped growth patterns in response to nutrient availability
Our results showed an overall hump-shaped growth pattern of S. polyrhiza in response to increasing nutrient availability, in agreement with many theoretic and experimental studies [41, 43–46]. The initial increase of the biomass was likely due to the very low water nutrient supply as plant production is generally positively correlated with the demand for nutrients [26, 41, 47]. The declined growth at higher levels of nutrient availability can be explained by four reasons in our study. First, the biomass gained from the newly ramets did not level off the biomass lost from the older ramets, which may have resulted in the decreased growth at the whole pot level. Second, intraspecific competition increased as the growth of the S. polyrhiza population, which may have led to the decreased growth at higher nutrient levels [8, 10, 32, 48, 49]. Third, it was also likely that ammonia nitrogen and heavy metal elements in Hoagland’s solutions of high concentrations may have reduced the growth of S. polyrhiza, which has also been found in other species [32, 44, 50, 51]. Moreover, we cannot rule out the possibility that the complex interactions among elements (ions) in Hoagland’s solutions of high concentrations played a role in shaping growth pattern of S. polyrhiza [52–54].
Contrasting responses of frond and root to nutrient availability
Fronds are the main photosynthetic organs of S. polyrhiza, and therefore their morphology may have great influences on plant growth [12, 38, 55–57]. We observed that total frond area, frond length and width and frond mass of S. polyrhiza increased with increasing nutrient availability but decreased afterwards. The response of frond to nutrient availability may have largely determined the growth pattern of S. polyrhiza in response to nutrient availability. In general, a greater specific leaf area would be expected under shaded or crowded environments where light is limited [58–61]. However, we did not observe a clear pattern for specific frond area in response to nutrient levels, despite that the population density in terms of total biomass and number of ramets changed a lot with the applied nutrient levels. This result indicated that specific frond area may not be a good predictor for light competition driven by nutrient-induced population growth.
In contrast, a U-shaped pattern was observed in root length and root mass in response to increasing nutrient levels. This is likely because, at lower level of nutrient concentrations, plants may need to invest more to roots in order to uptake more nutrients [43, 62–64], which could explain the greater root length and root mass at lower nutrient concentration treatments in the present study [65]. However, we also observed a greater root length and root mass at higher nutrient concentrations. This is likely because at higher levels of nutrient concentration, plants may suffer from strong intraspecific competitions due to rapidly clonal growth. In this case, a longer and bigger root would be more beneficial for the plants to obtain resources in order to fight against their intraspecific competitors [11, 43, 64, 66].
Trade-offs between root and shoot growth in response to nutrient availability
Plants can respond to varying resources through changing biomass allocations to above- and below-ground organs [67, 68]. In general, many terrestrial plants would allocate more biomass to below-ground organs under low-nutrient soils [66, 69–71], and this is also frequently observed for many aquatic macrophytes [72, 73]. We also observed a greater root to shoot ratio at lower nutrient concentrations in the floating clonal plant S. polyrhiza. However, we do not know whether it is a common strategy in floating clonal plants in response to increasing nutrient availability, as clonal plants are characterized by highly plasticity in morphology [74–76]. Therefore, more studies on other floating clonal plants are required to generalize our findings.
Conclusions
We conclude that the floating clonal plant S. polyrhiza varied in terms of growth and morphology in response to increasing nutrient availability. In general, S. polyrhiza showed a hump-shaped growth pattern as increased nutrient availability, but shoots and roots of S. polyrhiza differed in their responses to the nutrient availability. Our results have important implications for the control of eutrophication which is common in natural ecosystem [77–80]. However, one should be noted that in this study we only used one floating clonal plant and our experiment only ran for a short period, we do not know how S. polyrhiza and many other floating clonal plants may vary in their responses to increasing nutrient availability in the long run. Therefore, to generalize our findings, future research should focus on the long-term effects of changing nutrients or other biological factors on various floating clonal plants.
References
- 1. Klimeš L, Klimešová J. CLO-PLA2—a database of clonal plants in central Europe. Plant Ecology. 1999;141: 9–19.
- 2. Dorken ME, Eckert CG. Severely reduced sexual reproduction in northern populations of a clonal plant, Decodon verticillatus (Lythraceae). Journal of Ecology. 2010;89: 339–350.
- 3. Latzel V, Klimešová J. Transgenerational plasticity in clonal plants. Evolutionary Ecology. 2010;24: 1537–1543.
- 4. Oudot-Canaff J, Bornette G, Viricel MR, Piola F, Mousset S, Martel E. The short-term impact of wetland restoration on the genetic diversity of a predominantly clonal plant species. Aquatic Botany. 2013;110: 16–23.
- 5. Zhang JY, Wu YX. Changes in diversity and importance of clonal plants during sand dune succession in northeastern China. Ecological Research. 2014;29: 393–399.
- 6. Portela R, Dong BC, Yu FH, Barreiro R, Roiloa SR, Matos DMS. Trans-generational effects in the clonal invader Alternanthera philoxeroides. Journal of Plant Ecology. 2020;13: 122–129.
- 7. Stuefer JF, Erschbamer B, Huber H, Suzuki J-I. The ecology and evolutionary biology of clonal plants: An introduction to the proceedings of Clone-2000. Evolutionary Ecology. 2002;15: 223–230.
- 8. Wang P, Xu YS, Dong BC, Xue W, Yu FH. Effects of clonal fragmentation on intraspecific competition of a stoloniferous floating plant. Plant Biology. 2014;16: 1121–1126. pmid:24661501
- 9. Holt R, Kwok A, Dorken ME. Increased spatial-genetic structure in a population of the clonal aquatic plant Sagittaria latifolia (Alismataceae) following disturbance. Heredity. 2019;124: 514–523. pmid:31827265
- 10. Si C, Zhang LM, Yu FH. Effects of physical space and nutrients on the growth and intraspecific competition of a floating fern. Aquatic Ecology. 2019;53: 295–302.
- 11. Zhang LM, Yao SM, Jin Y, Song MH, Lei NF, Chen JS, et al. Effects of clonal fragmentation and nutrient availability on the competitive ability of the floating plant Salvinia natans. Folia Geobotanica. 2020;55: 63–71.
- 12. Zhang LM, Jin Y, Yao SM, Lei NF, Chen JS, Zhang Q, et al. Growth and morphological responses of duckweed to clonal fragmentation, nutrient availability and population density. Frontiers in Plant Science. 2020;11: 618. pmid:32523592
- 13. Cazzanelli M, Warming TP, Christoffersen KS. Emergent and floating-leaved macrophytes as refuge for zooplankton in a eutrophic temperate lake without submerged vegetation. Hydrobiologia. 2008;605: 113–122.
- 14. Kanoun-Bouléa M, Vicentea JAF, Nabaisa C, Prasadb MNV, Freitasa H. Ecophysiological tolerance of duckweeds exposed to copper. Aquatic Toxicology. 2009;91: 1–9. pmid:19027182
- 15. Lou M, Liao BH, Liu HY, Zou YZ. Study of three aquatic floating plants to treat the water eutrophication. Chinese Journal of Eco-Agriculture. 2005;13: 194–195.
- 16. Hilt S, Gross EM. Can allelopathically active submerged macrophytes stabilise clear-water states in shallow lakes? Basic and Applied Ecology. 2008;9: 422–432.
- 17. Armstrong W. The oxidising activity of roots in waterlogged soils. Physiologia Plantarum. 1967;20: 920–926.
- 18. Pilon-Smits EAH, Souza MPD, Hong G, Amini A, Bravo RC, Payabyab ST, et al. Selenium volatilization and accumulation by twenty aquatic plant species. Journal of Environmental Quality. 1999;28: 1011–1018.
- 19.
Babourina O, Rengel Z. Nitrogen removal from eutrophicated water by aquatic plants. A A., SG S., L G., R W., editors. Springer, Dordrecht: Eutrophication: Causes, Consequences and Control; 2010. 355–372 pp.
- 20. Chislock MF, Doster E, Zitomer RA, Wilson AE. Eutrophication: Causes, consequences, and controls in aquatic ecosystems. Nature Education Knowledge. 2013;4: 10.
- 21. Immers AK, Vendrig K, Ibelings BW, Donk EV, Heerdt GNJT, Geurts JJM, et al. Iron addition as a measure to restore water quality: Implications for macrophyte growth. Aquatic Botany. 2014;116: 44–52.
- 22. Neagu C. Degree of water eutrophication in the terminal basin of the Danube. Case study. Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca Agriculture. 2014;71: 274–281.
- 23. Huang J, Xu CC, Ridoutt BG, Chen F. Reducing agricultural water footprints at the farm scale: A case study in the Beijing region. Water. 2015;7: 7066–7077.
- 24. Sand-Jensen K, Bruun HH, Nielsen TF, Christiansen DM, Hartvig P, Schou JC, et al. The dangers of being a small, oligotrophic and light demanding freshwater plant across a spatial and historical eutrophication gradient in southern Scandinavia. Frontiers in Plant Science. 2018;9: 66. pmid:29456545
- 25. Schachtman DP, Shin R. Nutrient sensing and signaling: NPKS. Annual Review of Plant Biology. 2007;58: 47–69. pmid:17067284
- 26. Krouk G, Ruffel S, Gutiérrez RA, Gojon A, Crawford NM, Coruzzi GM, et al. A framework integrating plant growth with hormones and nutrients. Trends in Plant Science. 2011;16: 178–182. pmid:21393048
- 27.
Kennedy JA, Matthews MA, Waterhouse AL. Effects of submerged aquatic macrophytes on nutrient dynamics, sedimentation, and resuspension. In: Caldwell MM, Heldmaier G, Lange OL, Mooney HA, Schulze ED, Sommer U, editors. The structuring role of submerged macrophytes in lakes. 131. Springer, New York, NY: Ecological Studies (Analysis and Synthesis); 1998. pp. 197–214.
- 28. Hart BT, Dok WV, Djuangsih N. Nutrient budget for Saguling Reservoir, West Java, Indonesia. Water Research. 2002;36: 2152–2160. pmid:12092591
- 29. Lu J, Wang ZX, Xing W, Liu GH. Effects of substrate and shading on the growth of two submerged macrophytes. Hydrobiologia. 2013;700: 157–167.
- 30. Chanc LMG, Brunt SCV, Majsztrik JC, White SA. Short- and long-term dynamics of nutrient removal in floating treatment wetlands. Water Research. 2019;159: 153–163. pmid:31091480
- 31. Wang T, Hu JT, Wang RQ, Liu CH, Yu D. Trait convergence and niche differentiation of two exotic invasive free-floating plant species in China under shifted water nutrient stoichiometric regimes. Environmental Science Pollution Research. 2019;26: 35779–35786. pmid:31705409
- 32. Zhu ZJ, Yuan HZ, Wei Y, Li PS, Zhang PH, Xie D. Effects of ammonia nitrogen and sediment nutrient on growth of the submerged plant Vallisneria natans. CLEAN-Soil, Air, Water. 2015;43: 1653–1659.
- 33. Xie YH, An SQ, Yao X, Xiao KY, Zhang C. Short-time response in root morphology of Vallisneria natans to sediment type and water-column nutrient. Aquatic Botany. 2005;81: 85–96.
- 34. Sun LF, Sun YX, Zhou CF, An SQ. Effects of plant species combination and water body nutrient level on the biomass accumulation and allocation of three kinds functional plants. Chinese Journal of Applied Ecology. 2009;20: 2370–2376. pmid:20077692
- 35. Szabo S, Scheffer M, Roijackers R, Waluto B, Braun M, Nagy PT, et al. Strong growth limitation of a floating plant (Lemna gibba) by the submerged macrophyte (Elodea nuttallii) under laboratory conditions. Freshwater Biology. 2010;55: 681–690.
- 36. Yu LF, Yu D. Differential responses of the floating-leaved aquatic plant Nymphoides peltata to gradual versus rapid increases in water levels. Aquatic Botany. 2011;94: 71–76.
- 37. Hao ZJ, Li YH, Cai WK, Wu PP, Liu YD, Wang GH. Possible nutrient limiting factor in long term operation of closed aquatic ecosystem. Advances in Space Research. 2012;49: 841–849.
- 38. Tan BC, He H, Gu J, Li KY. Effects of nutrient levels and light intensity on aquatic macrophyte (Myriophyllum aquaticum) grown in floating-bed platform. Ecological Engineering. 2019;128: 27–32.
- 39. Hillman WS. The Lemnaceae, or duckweeds: A review of the descriptive and experimental literature. Botanical Review. 1961;27: 221–287.
- 40. Stomp AM. The duckweeds: A valuable plant for biomanufacturing. Biotechnology Annual Review. 2005;11: 69–99. pmid:16216774
- 41. Stirk WA, Kulkarni MG, Staden JV. Effect of smoke-derived extracts on Spirodela polyrhiza, an aquatic plant grown in nutrient-rich and -depleted conditions. Aquatic Botany. 2016;129: 31–34.
- 42. Xing W, Huang WM, Liu GH. Effect of excess iron and copper on physiology of aquatic plant Spirodela polyrrhiza (L.) Schleid. Environmental Toxicology. 2010;25: 103–112. pmid:19260045
- 43. Si C, Xue W, Lin J, Zhang JF, Yu FH. No evidence of greater biomass allocation to stolons at moderate resource levels in a floating plant. Aquatic Ecology. 2020;54: 421–429.
- 44. Gosselin JR, Haller WT, Gettys LA, Griffin T, Crawford ES. Effects of substrate nutrients on growth of three submersed aquatic plants. Journal of Aquatic Plant Management. 2018;56: 39–46.
- 45. Nichols DS, Keemey DR. Nitrogen nutrition of Myriophyllum spicatum: Uptake and translocation of 15N by shoots and roots. Freshwater Biology. 1976;6: 145–154.
- 46. Best MD, Mantai KE. Growth of Myriophyllum: Sediment or lake water as the source of nitrogen and phosphorus Ecology. 1978;59: 1075–1080.
- 47. Kleczewski NM, Herms DA, Bonello P. Nutrient and water availability alter belowground patterns of biomass allocation, carbon partitioning, and ectomycorrhizal abundance in Betula nigra. Trees. 2012;26: 525–533.
- 48. Bonser SP, Reader RJ. Plant competition and herbivory in relation to vegetation biomass. Ecology. 1995;76: 2176–2183.
- 49. Tiffin P. Competition and time of damage affect the pattern of selection acting on plant defense against herbivores. Ecology. 2002;83: 1981–1990.
- 50. Zhu ZJ, Song SY, Wang PH, Leng X, Li PS, Jeelani N, et al. Growth and physiological responses of submerged plant Vallisneria natans to water column ammonia nitrogen and sediment copper. Peer J. 2016;4: e1953. pmid:27123381
- 51. Wang PF, Wang C, Ouyang P, Qian J, Shi RJ. Physiological responses of Vallisneria spiraslis L. induced by different hydraulic conditions when exposed to copper and nitrogen. African Journal of Biotechnology. 2013;10: 7441–7452.
- 52. Xie KL, Cakmak I, Wang SY, Zhang FS, Guo SW. Synergistic and antagonistic interactions between potassium and magnesium in higher plants. The Crop Journal. 2021;9: 249–256.
- 53. Gransee A, Führs H. Magnesium mobility in soils as a challenge for soil and plant analysis, magnesium fertilization and root uptake under adverse growth conditions. Plant and Soil. 2013;368: 5–21.
- 54. Juang KW, Lee YI, Lai HY, Chen BC. Influence of magnesium on copper phytotoxicity to and accumulation and translocation in grapevines. Ecotoxicology Environmental Safety. 2014;104: 36–42. pmid:24632121
- 55. Bornette G, Puijalon S. Response of aquatic plants to abiotic factors: A review. Aquatic Sciences. 2011;73: 1–14.
- 56. Kennedy TL, Horth LA, Carr DE. The effects of nitrate loading on the invasive macrophyte Hydrilla verticillata and two common, native macrophytes in Florida. Aquatic Botany. 2009;91: 253–256.
- 57. Wersal RM, Madsen JD. Influences of light intensity variations on growth characteristics of Myriophyllum aquaticum. Journal of Freshwater Ecology. 2013;28: 147–164.
- 58. Sack L, Scoffoni C, McKown AD, Frole K, Rawls M, Havran JC, et al. Developmentally based scaling of leaf venation architecture explains global ecological patterns. Nature Communications. 2012;3: 837. pmid:22588299
- 59. Boyce CK, Brodribb TJ, Feild TS, Zwieniecki MA. Angiosperm leaf vein evolution was physiologically and environmentally transformative. Proceedings Biological Sciences. 2009;276: 1771–1776. pmid:19324775
- 60. Brodribb TJ, Feild TS, Jordan GJ. Leaf maximum photosynthetic rate and venation are linked by hydraulics. Plant Physiology. 2007;144: 1890–1898. pmid:17556506
- 61. Hines PJ. Light tuning of leaf size. Science. 2019;366: 69.61–69.
- 62. Mcconnaughay KDM, Colema JS. Biomass allocation in plants: Ontogeny or optimality? A test along three resource gradients. Ecology. 1999;80: 2581–2593.
- 63. Müller I, Schmid B, Weiner J. The effect of nutrient availability on biomass allocation patterns in 27 species of herbaceous plants. Perspect Plant Ecol Evol Syst. 2000;3: 115–127.
- 64. Hermans C, Hammond JP, White PJ, Verbruggen N. How do plants respond to nutrient shortage by biomass allocation? Trends in Plant Science. 2006;11: 610–617. pmid:17092760
- 65. Rosolem CA, Witacker JPT, Vanzolini S, Ramos VJ. The significance of root growth on cotton nutrition in an acidic low-P soil. Plant and Soil. 1999;212: 183–188.
- 66. Kumar A, Duijnen RV, Delory BM, Reichel R, Brüggemann N, Temperton VM. Barley shoot biomass responds strongly to N:P stoichiometry and intraspecific competition, whereas roots only alter their foraging. Plant and Soil. 2020;453: 515–528.
- 67. Linkohr BI, Williamson LC, Fitter AH, Leyser HMO. Nitrate and phosphate availability and distribution have different effects on root system architecture of Arabidopsis. The Plant Journal. 2002;29: 751–760. pmid:12148533
- 68. Trubat R, Cortina J, Vilagrosa A. Plant morphology and root hydraulics are altered by nutrient deficiency in Pistacia lentiscus (L.). Trees. 2006;20: 334–339.
- 69. Güsewell S. N: P ratios in terrestrial plants: Variation and functional significance New Phytologist. 2010;164: 243–266.
- 70. Dong BC, Zhang LM, Li KY, Hu XT, Wang P, Wang YJ, et al. Effects of clonal integration and nitrogen supply on responses of a clonal plant to short-term herbivory. Journal of Plant Ecology. 2019;12: 624–635.
- 71. Zhang SJ, Wang L, Ma F, Bloomfield KJ, Yang JX, Atkin OK. Is resource allocation and grain yield of rice altered by inoculation with arbuscular mycorrhizal fungi? Journal of Plant Ecology. 2014;8: 436–448.
- 72. Idestam-Almquist J, Kautsky L. Plastic responses in morphology of Potamogeton pectinatus L. to sediment and above-sediment conditions at two sites in the northern Baltic proper. Aquatic Botany. 1995;52: 205–216.
- 73. Crossley MN, Dennison WC, Williams RR, Wearing AH. The interaction of water flow and nutrients on aquatic plant growth. Hydrobiologia. 2002;489: 63–70.
- 74. Douhovnikoff V, Dodd RS. Epigenetics: A potential mechanism for clonal plant success. Plant Ecology. 2014;216: 227–233.
- 75. Fazlioglu F, Bonser SP. Phenotypic plasticity and specialization in clonal versus non-clonal plants: A data synthesis. Acta Oecologica. 2016;77: 193–200.
- 76. Guo J, Li HY, Yang YF. Phenotypic plasticity in sexual reproduction based on nutrients supplied from vegetative ramets in a Leymus chinensis population. Frontiers in Plant Science. 2020;10: 1681. pmid:32010165
- 77. Liu CG, Dai Z, Sun HW. Potential of duckweed (Lemna minor) for removal of nitrogen and phosphorus from water under salt stress. Journal of Environmental Management. 2017;187: 497–503. pmid:27856035
- 78. Sharip Z, Schooler SS, Hipsey MR, Hobbs RJ. Eutrophication, agriculture and water level control shift aquatic plant communities from floating-leaved to submerged macrophytes in Lake Chini, Malaysia. Biological Invasions. 2012;14: 1029–1044.
- 79. Huang XL, Xu X, Liu SL, Song SL, Chang SW, Liu CH, et al. Impact of eutrophication on root morphological and topological performance in free-floating invasive and native plant species. Hydrobiologia. 2019;836: 123–139.
- 80. Colares GS, Dell’Osbel N, Wiesel PG, Oliveira GA, Lemos PHZ, Silva FPd, et al. Floating treatment wetlands: A review and bibliometric analysis. Science of the Total Environment. 2020;714: 136776. pmid:31991269