Urea amendment alleviated morphological and physiological damages and yield loss of winter wheat subjected to low temperature stress at jointing stage

Low temperature stress in spring is an abiotic stress limiting the growth and productivity of winter wheat. A controlled pot experiment was done to explore the possibility of applying urea to alleviate the low temperature (3 degrees C/-4 degrees C, day/night) damage to wheat cultivar Yangmai 16 at jointing stage. Urea at different rates was applied on the 5th day after low temperature stress. Low temperature stress decreased grain yield and plant height. Compared with the unstressed control, the content of soluble sugar, proline, zeatin riboside (ZR), and abscisic acid (ABA) in the leaves was increased under longer low temperature stress. These above parameters in the stressed treatments without urea amendment were higher than those with urea amendment on the 10th day. The change in GA(3) concentration was opposite to the concentrations of ABA and ZR. The decline in the concentrations of osmotic adjustment substances, balanced hormone concentrations, and increased grain number per ear and ear number were the main reasons for the increased grain yield after urea application. Remedial effects was enhanced with the higher urea remedial level under the same low temperature stress duration. Our study suggested that suitable urea remedial rates are recommended based on the freezing index in wheat to alleviate the impacts of low temperature on wheat production at jointing stage.