Independent and combined influence of drought stress and nitrogen deficiency on physiological and proteomic changes of barley leaves

Abstract

Drought stress and nitrogen (N) deficiency often interact mutually during crop growth, yet the combinational effects of both stresses are still poorly understood. In the present study, physiological changes of barley were determined under drought stress, N deficiency and combined both stresses. Barley leaf proteomes were detected by label-free proteomic techniques under drought stress or/and N deficiency. The results showed that few proteins involved in photosynthesis were changed, and the main reason for the reduction in photosynthetic rate (An) was the decrease in stomatal conductance (gs) under drought stress. The increased photorespiration as well as decreased gs and chlorophyll reduced An under combined stresses. Compared to drought stress and N deficiency, the combined stresses led to the greater expression of proteins related to energy, carbohydrate and amino acid metabolism, causing the development of more extensive signaling pathways. Barley plants generated more energy by enhancing aerobic respiration to maintain growth under combined stresses. The synthesis of proteins in plant leaves was decreased under drought stress or/and N deficiency, while the degradation of proteins was enhanced to provide free amino acids under N deficiency and combined stresses. Our results provided further information for the mechanisms of crop response to combined drought stress and N deficiency, and helped to understand the response and adaptation of plants to adverse environmental conditions.