Effects Of Physiological Factors On Wheat Dormancy With Different Seed Coat Colors

Wheat pre-harvest sprouting is a world problem,which seriously affects the yield and quality of wheat.Seed dormancy was the primary factor to determine the resistance to pre-harvest sprouting of wheat varieties,and seed coat color was closely related to dormancy of wheat seeds.In order to understand the relationship between seed coat color and seed dormancy in wheat,and to explore the physiological factors affecting seed dormancy in wheat,wheat varieties with different seed coat colors i.e.15 red wheat and 15white wheat were selected to determine color strength of seed coat and seed dormancy level in the study.Four wheat varieties with significant dormancy differences were selected:White wheat i.e.Huachengmai 1688（W1）and Annong 0711（W15）,red wheat i.e.Baihumai 1（R1）and Yangmai 27（R15）,physiological characteristics were further analyzed.The main experimental results are as follows:1.The average of R value,R/（R+G+B）value,hue（H）,saturation（S）and intensity（I）of white wheat are 128.33（CV=11.26%）,0.52（CV=3.02%）,0.66（CV=7.73%）,0.99（CV=0.17%）and 81.64（CV=14.01%）respectively;Similarly,these value of red wheat are90.50（CV=7.47%）,0.56（CV=6.40%）,0.59（CV=7.99%）,0.98（CV=0.24%）and 55.88（CV=10.92%）,respectively.Except the R/（R+G+B）value,the average of all the measured indexes of white wheat were higher than those of red wheat.2.The germination index of 15 white wheat ranged from 24.90%to 96.00%,with an average of 60.35%;The germination rate of 15 white wheat ranged from 44.70%to98.70%,with an average of 80.86%.The maximum and minimum of germination index of15 red wheat were 92.70%and 95.30%,respectively,and the maximum and minimum of germination rates were 19.30%and 11.30%,respectively,which were lower than those of white wheat.3.The index hue（H）,saturation（S）and intensity（I）derived from RGB values that extracted from digital camera images could reflect the depth of seed coat color.The values of R,H,S and I were negatively correlated with seed dormancy（P<0.05）,and R/（R+G+B）was significantly positively correlated with seed dormancy（P<0.05）though there were exceptions in both red and white wheat.Weak dormancy variety（W1）and strong dormancy variety（W15）of white wheat,weakly dormancy variety（R1）and strong dormancy variety（R15）of red wheat were used as experimental materials for further physiological analysis.4.The varieties with significant dormancy differences had differences in water absorption,water content,α-amylase activity,β-amylase activity,acid phosphatase activity,soluble sugar content,soluble protein content,starch content,gibberellin and abscisic acid content during germination.It was found that the water absorption and water content in weak dormancy varieties i.e.W1 and R1 were higher than in strong dormancy varieties i.e.W15 and R15,which means faster seed germination.The contents of soluble sugar,protein,amylose and amylopectin in W1 and R1 were also higher,which provided energy and matter for seed germination.In addition,the higher activities ofα-amylase andβ-amylase in W1 and R1 mainly accelerated the decomposition of starch in seeds and the higher activity of acid phosphatase during late germination increased the transport and metabolic rate of stored substances in seeds.The content of gibberellin（GA₃）increased while the content of abscisic acid（ABA）decreased gradually in W1 and R1,which promoted the release of seed dormancy.On the contrary,strong dormancy varieties i.e.W15 and R15had lower amylase activity,lower contents of soluble sugar,soluble protein,amylose,amylopectin and GA₃,and higher content of ABA,which inhibited the breaking of dormancy.5.Compared to the materials with the same dormancy level,the water absorption and water content in white wheat varieties were higher than that in red wheat varieties,and the overall trend was W1>R1>W15>R15.The soluble sugar content,protein consumption and GA₃content in seeds showed the similar trend,while the comparison of ABA content in seeds was opposite,showing R15>W15>R1>W1.In conclusion,R,H,S,and I values can be used to quickly identify red and white wheat varieties,which indirectly assist the screening of pre-harvest sprouting resistant varieties.The physiological indicators i.e.the water content,the activity ofα-amylase,β-amylase and acid phosphatase,the content of soluble sugar and ABA,can be taken as the reference index for identification of pre-harvest sprouting resistance.