Morphological and physiological responses and plasticity in Robinia pseudoacacia to the coupling of water, nitrogen and phosphorus

Abstract

AbstractBackground: Under the background of drought and nitrogen deposition, global climate change is changing the supply of resources and environmental conditions that are crucial to plant growth, and plants respond to climate change by environmentally induced phenotypic changes.Aims: The objective of this study was to assess the differences in the plasticity responses of the morphological, photosynthetic, fluorescence and antioxidant parameters of Robinia pseudoacacia seedlings under water, nitrogen and phosphorus interaction conditions.Methods: We analyzed the above parameters of R. pseudoacacia seedlings using methods of morphological measurements, gas exchanges, fluorescence emission and antioxidant assays under two water levels (75% and 55% of field capacity), four nitrogen levels (no urea; 0.2 g kg−1, 0.4 g kg−1, 0.8 g kg−1), and two phosphorus levels (no superphosphate, 0.6 g kg−1).Results: The results showed that drought stress significantly reduced the morphological parameters, actual photochemical efficiency of photosystem II (ΦPSII), superoxide dismutase (SOD) activity, peroxidase (POD) activity and catalase (CAT) activity of R. pseudoacacia seedlings, and significantly increased nonphotochemical quenching (NPQ) and the malondialdehyde (MDA) content. Excessive application of nitrogen (N) fertilizer inhibited plant growth, and phosphorus (P) deficiency significantly weakened the positive effect of the high nitrogen treatment on morphological parameters under drought stress. The high nitrogen treatment effectively weakened the inhibitory effect of drought and phosphorus deficiency on chlorophyll formation. Proper N and P fertilizers increased the SOD, POD and CAT activities and decreased the MDA content under drought stress. The mean plasticity index of POD and CAT activities in response to water, nitrogen and phosphorus was the highest, which indicated that R. pseudoacacia seedlings can adapt to changes in water and nutrients mainly by adjusting their POD and CAT activities.Conclusions: These results may explain the better survival of R. pseudoacacia under the condition of limited water and nutrient resources, which is helpful for understanding the response mechanism of R. pseudoacacia to changes in environmental factors in the future. The results also provide scientific data and a theoretical basis for vegetation restoration and sustainable development of the regional ecological environment.