Abstract
The allocation of limiting elements among plant organs is an important aspect of the adaptation of plants to their ambient environment. Although eutrophication can extremely alter light and nutrient availability, little is known about nutrient partitioning among organs of submerged macrophytes in response to eutrophication. Here, we analyzed the stoichiometric scaling of carbon (C), nitrogen (N), and phosphorus (P) concentrations among organs (leaf, stem, and root) of 327 individuals of seven common submerged macrophytes (three growth forms), sampled from 26 Yangtze plain lakes whose nutrient levels differed. Scaling exponents of stem nutrients to leaf (or root) nutrients varied among the growth forms. With increasing water total N (WTN) concentration, the scaling exponents of stem C to leaf (or root) C increased from <1 to >1, however, those of stem P to root P showed the opposite trend. These results indicated that, as plant nutrient content increased, plants growing in low WTN concentration accumulated leaf C (or stem P) at a faster rate, whereas those in high WTN concentration showed a faster increase in their stem C (or root P). Additionally, the scaling exponents of stem N to leaf (or root) N and stem P to leaf P were consistently large than 1, but decreased with a greater WTN concentration. This suggested that plants invested more N and P into stem than leaf tissues, with a higher investment of N in stem than root tissues, but eutrophication would decrease the allocation of N and P to stem. Such shifts in plant nutrient allocation strategies from low to high WTN concentration may be attributed to changed light and nutrient availability. In summary, eutrophication would alter nutrient allocation strategies of submerged macrophytes, which may influence their community structures by enhancing the competitive ability of some species in the process of eutrophication.
Highlights
Anthropogenic activity and industrial development have extremely altered the availability of nitrogen (N) and phosphorus (P) in terrestrial and freshwater ecosystems across the globe (Dodds et al, 2009; Rockstrom et al, 2009; Marklein and Houlton, 2012; Penuelas et al, 2013)
We divided all sampled individuals into five subgroups based on the lakes’ water total N (WTN) to examine the effects of eutrophication on the relationships of nutrient content among plant organs (WTN ≤ 0.5, 0.5 < WTN ≤ 1, 1 < WTN ≤ 1.5, 1.5 < WTN ≤ 2, and WTN > 2 mg L−1 for total N (TN)-1, TN2, TN-3, TN-4, and TN-5, respectively)
We focused on seven species of common submerged macrophytes widely distributed in lakes of the Yangtze plain, each of which could be classified into one of three types of growth forms: canopy former, erect and rosette (Chambers and Kalff, 1987)
Summary
Anthropogenic activity and industrial development have extremely altered the availability of nitrogen (N) and phosphorus (P) in terrestrial and freshwater ecosystems across the globe (Dodds et al, 2009; Rockstrom et al, 2009; Marklein and Houlton, 2012; Penuelas et al, 2013). The allocation of limiting resources, as an important adaptive strategy for how plants respond to different and changeable environments, reflects the influences of evolutionary history, environmental stresses and trade-offs of functional traits (Xie et al, 2005; Kerkhoff et al, 2006; Dulger et al, 2017; Scartazza et al, 2017; Li et al, 2019). To maximize their multiple functions, namely growth, reproduction, and nutrient storage of plants, plants need to rebalance the allocation of elements across organs under various environmental stresses (Schreeg et al, 2014; Yang et al, 2014). Considerable attention has focused on the nutrient allocation strategies of terrestrial plants (Yang et al, 2014; Yan et al, 2016; Zhao et al, 2019), relatively little is known about aquatic plants
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