Nitrogen Uptake by Two Plants in Response to Plant Competition as Regulated by Neighbor Density

Abstract

Plant species may acquire different forms of nitrogen (N) to reduce competition for the same resource, but how plants respond to neighbors with different densities in their N uptake is still poorly understood. We investigated the effects of competition regime on the uptake of different N forms by two hygrophytes, Carex thunbergii and Polygonum criopolitanum, by conducting a hydroponic test of excised roots and an in situ experiment in a subtropical wetland ecosystem. The two species were grown either in monocultures or mixtures with various neighbor densities. Root functional traits and N uptake rates of different N forms were measured. Our results showed that N uptake was mainly determined by N form, rather than species identity. Both species were able to use organic N sources, but they took up relatively more N supplied as NO3- than as NH4+ or glycine, irrespective of competition treatments. Both species preferred NO3- when grown in monoculture, but in the presence of competitors, the preference of fast-growing C. thunbergii persisted while P. criopolitanum acquired more NH4+ and glycine, with stronger responses being observed at the highest neighbor density. The hydroponic test suggested that these divergences in N acquisition between two species might be partially explained by different root functional traits. To be specific, N uptake rates were significantly positively correlated with root N concentration and specific root length, but negatively correlated with root dry matter content. Our results implicated that C. thunbergii has a competitive advantage with relatively more stable N acquisition strategy despite a lower N recovery than P. criopolitanum, whereas P. criopolitanum could avoid competition with C. thunbergii via a better access to organic N sources, partly mediated by competition regimes.

Melatonin confers tolerance to nitrogen deficiency through regulating MdHY5 in apple plants

“…Previous studies have shown that N use efficiency is closely related to amino acid metabolism, and the level of free amino acids is significantly decreased when N supply is insufficient (Dellero, 2020; Sung et al., 2015). Enhanced absorption contributes to the maintenance of the amino acid pool under N deficiency (Jia et al., 2020). N‐deficiency‐tolerant wild soybean can enhance amino acid synthesis and the TCA cycle to improve the low‐N tolerance (Liu et al., 2020).…”

Melatonin biosynthesis gene MdASMT9 confers tolerance to nitrogen deficiency in an MdHY5-dependent manner in apple plants

“…Previous studies have shown that N use efficiency is closely related to amino acid metabolism, and the level of free amino acids is significantly decreased when N supply is insufficient (Dellero, 2020;Sung et al , 2015). Enhanced NO 3 uptake contributes to maintenance of the amino acid pool under N deficiency (Jia et al , 2020). N-deficiency-tolerant wild soybean can enhance amino acids synthesis and the TCA cycle to improve the low-N tolerance (Liu et al , 2020).…”

Plant N economics and the extended phenotype: Integrating the functional traits of plants and associated soil biota into plant–plant interactions

“…A recent global meta‐analysis corroborated this claim and highlighted the importance of nutrient resource availability in resorption plasticity (Drenovsky et al, 2019). If plant species use the same N source, they may also spatially and temporally differentiate their N acquisition from the rest of the plant community to escape the influence of neighbours (Figure 1, arrow A and circle 4, Jia et al, 2020; Persson et al, 2003).…”