Effects Of Low Temperature At Anther Connective Formation,Meiosis And Anthesis Stages On Grain Yield In Wheat And Remedial Techniques

As global warming intensifies, low temperature in later spring occurs more frequently in the middle and lower reaches of Yangtze River region, which severely hampers and restricts the production security of wheat. In order to investigate the effects of low temperature in spring on wheat growth and yield formation, the present study was conducted on the Experimental Farm of Jiangsu Provincial Key Lab of Crop Genetics and Physiology of Yangzhou University from 2013 to 2015. Spring wheat cultivar Yangmai 16 and semi-winter wheat cultivar Xumai 30 were used as the varieties. The effects of low temperature on wheat yield and its components, the changes in physical properties at anther connective formation stage, meiosis stage and anthesis stage were analyzed. The remedial effects of fertilizer amendment on improving yield and physiological characteristics after cold damage were also studied. This study was of critical importance for providing theoretical basis and technical support for relieving cold stress to achieve high and stable yield in wheat. The main results were as follows:1. Low temperature stress had a significant impact on wheat yield at anther connective formation stage (Day/Night:5/-3’C), meiosis stage (Day/Night:8/-1℃). and anthesis stage (Day/Night:12/4℃). The longer of the stress duration was, the more serious cold damage on wheat yield was. The loss of grain number per ear was the main reason for the decline in yield, followed by the loss of ear, when low temperature stress at connective stage (Day/Night:5/-3℃). The loss of grain number per ear was also the main reason for the decline in yield, followed by the grain weight when low temperature stress at both meiosis stage (Day/Night:8/-1℃) and anthesis stage (Day/Night:12/4℃). The loss of yield in Xumai 30 after cold damage was greater as compared with that in Yangmai 16.2. The stress of low temperature at anther connective stage made the weak tillers dead and significantly reduced the percentage of productive tillers and the number of ear at maturity. The longer the stress duration was, the more serious the cold damage was. The effect of low temperature at meiosis and blooming stages on ear number was not significant. The low temperature at anther connective stage reduced the length of I and II basal internodes. The uppermost internode length was reduced by low temperature at meiosis stage. Pollen vigor and the grain number per ear were reduced when wheat plants were treated with low temperature at both anther connective and meiosis stages, while the number of degenerated spikelet was increased. Meanwhile, ear length and plant height were shortened.3. The activities of SOD, POD, CAT, and the content of MDA in the leaves of the cold treatments increased with the progress of low temperature stress at anther connective stage. On the 5th day after treatment, the antioxidant enzymes activities and the content of MDA were significantly increased as compared with the control. On the 10th day after cold damage, the activities of these enzymes and the content of MDA were reduced closely to the levels of the control. The activities of SOD, POD, CAT, and the content of MDA in leaves on the last day of cold stress,5th day and 10th day after stress at meiosis and anthesis stages had the similar trends to those at anther connective stage. The differences only existed in the amplitudes of variation.4. Leaf senescence was accelerated and leaf photosynthetic function was declined significantly after low temperature stress from anther connective stage to anthesis stage. At anther connective stage, the reading of SPAD in the treatment of 5/-3℃(Day/Night) lasting for 24 h and 48 h decreased on the 5th day and then increased on the 10th day after cold stress, which was still lower than that in the control. The reading of SPAD decreased continuously in the treatment of 5/-3℃(Day/Night) lasting for 72 h at anther connective stage. The SPAD reading declined persistently after cold stress at meiosis stage and anthesis stage, and the SPAD reading of treatments on 10th day was significantly lower as compared with the control. The SPAD reading, photosynthetic rate, stomata conductance, and transpiration rate in the leaves of all treatments from anthesis to the 28th day after anthesis were significantly lower than that in the control. However, the intercellular CO2 concentration was significantly higher than the control after anthesis. Low temperature stress at this three stages accelerated the senescence of flag leaves, reduced the production of photosynthetic material and grain filling substance, which were the main reasons for the reduced number of gain per ear and grain weight.5. Fertilizer amendment after cold stress at anther connective and meiosis stages effectively decreased the loss of yield to a certain degree. With increased fertilizer applying amount under the same treatment duration, the loss of grain yield was better compensated. The grain yield of the treatment under slight cold stress at anther connective and meiosis stages were better remedied after remedial fertilizer was applied, whose yield was almost close to the yield level of the control. Increasing the number of ear and grain per ear by fertilizer amendment was the main reason for increasing grain yield at connective stage. At meiosis stage, fertilizer amendment mainly improved grain yield by increasing the number of grain per spike and grain weight.