Effects of the supply levels and ratios of nitrogen and phosphorus on seed traits of <i>Chenopodium glaucum</i>

Abstract

Aims Global nitrogen (N) deposition not only alters soil N and phosphorus (P) availability, but also changes their ratio. The levels and ratios of N and P supply and their interaction may simultaneously influence plant seed traits. However, so far there has been no experiments to distinguish these complex impacts on plant seed traits in the field. Methods A pot experiment with a factorial design of three levels and ratios of N and P supply was conducted in the Nei Mongol grassland to explore the effects of levels and ratios of N and P supply and their interaction on seed traits of Chenopodium glaucum. Important findings We found that the relative contribution (15%-24%) of N and P supply levels in affecting the N concentrations, P concentrations and germination rates of seeds was larger than that (3%-7%) of N:P supply ratios, whereas seed size was only significantly influenced by N:P. Simultaneously, seed N and P concentrations were impacted by the interaction of N and P supply levels and ratios. At the same N:P, decrease in nutrient supply levels increased seed N concentrations, P concentrations and germination rates. N:P supply ratios only had a significant effect on seed size and germination rates under low nutrient levels. Overall, these results indicate that different seed traits of C. glaucum show different sensitivities to N or P limitations, leading to adaptive and passive responses under different nutrient limitations. This study presents the the first field experiment to distinguish the effects of nutrient supply levels, ratios and their interactions on plant seed traits, which provides a new case study on the influences of global N deposition on future dynamics of plant population and community.