High Nitrogen Enhance Drought Tolerance in Cotton through Antioxidant Enzymatic Activities, Nitrogen Metabolism and Osmotic Adjustment.

Asif Iqbal,Xiling Zhang,Huiping Gui,Xiangru Wang,Hengheng Zhang,Meizhen Song,Qiang Dong

doi:10.3390/plants9020178

Abstract

Drought is one of the most important abiotic stresses and hampers many plant physiological processes under suboptimal nitrogen (N) concentration. Seedling tolerance to drought stress is very important for optimum growth and development, however, the enhancement of plant stress tolerance through N application in cotton is not fully understood. Therefore, this study investigates the role of high N concentration in enhancing drought stress tolerance in cotton. A hydroponic experiment supplying low (0.25 mM) and high (5 mM) N concentrations, followed by 150 g L−1 polyethylene glycol (PEG)-induced stress was conducted in a growth chamber. PEG-induced drought stress inhibited seedling growth, led to oxidative stress from excessive malondialdehyde (MDA) generation, and reduced N metabolism. High N concentrations alleviated oxidative damage and stomatal limitation by increasing antioxidant enzymatic activities, leaf relative water content, and photosynthesis in cotton seedlings under drought stress. The results revealed that the ameliorative effects of high N concentration may be ascribed to the enhancement of N metabolizing enzymes and an increase in the amounts of osmoprotectants like free amino acids and total soluble protein. The present data suggest that relatively high N concentrations may contribute to drought stress tolerance in cotton through N metabolism, antioxidant capacity, and osmotic adjustment.

Highlights

Drought is one of the most important abiotic stresses and is associated with the hydrology and climate of an area [1]
The growth and dry biomass of cotton plants supplied with nitrogen were greatly affected by Thestress, growth and dry biomass of cotton plants supplied with nitrogen were greatly affected by drought which led to a significant reduction in shoot length
(29%) and shoot and total drought stress, which led to a significant reduction in shoot length and total plant dry weight (35%), while root dry weight increased by 27% under low supply concentration

Summary

Introduction

Drought is one of the most important abiotic stresses and is associated with the hydrology and climate of an area [1]. Drought stress adversely affects many plant physiological processes [4] such as photosynthesis and carbon and nitrogen metabolism [5]. The limitations to photosynthesis induced by drought are attributed to either stomatal or non-stomatal limitations [8]. The drought induced non-stomatal limitations include decreases in linear electron transport, maximum quantum yield, and actual quantum yield of electron flow through photosystem II [9]. These decreases are, in part, associated with the downregulation of the light reactions through processes such as increased

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Discussion

Conclusion