| It is of great significance to study the difference of response of rice to weak light stress,so as to alleviate the adverse effect of overcast and rainless climate on rice production and improve rice yield in Sichuan basin.In this study,58 hybrid rice varieties commonly used in the upper reaches of the Yangtze river were used as the material,and artificial shading method was used to simulate weak light stress.By comparing plant height,leaf length,plant type,yield and RVA of different varieties under different low light treatments,the agronomic traits,chlorophyll dynamics,yield and rice quality of different types of rice were identified,which laid a necessary theoretical foundation for the breeding and application of rice varieties with low light tolerance in Sichuan.The results show that:(1)Compared with normal light,the plant heights of all the tested varieties were significantly increased under low light treatment from the green stage to the tillering stage,among Nei5 you 768 in the low-light tolerant rice had the smallest increase(12.22 cm).There was no significant increase in plant height of all tested cultivars under low light treatment from the green stage to heading stage.Low light sensitive rice plant height increased significantly under low light treatment during the period of rejuvenation to maturity.There was no significant increase in plant height of both low light tolerance and intermediate rice varieties.There was no significant difference in plant height between heading stage and ripening stage under low light treatment.(2)Compared with normal light,the leaves of rice treated with low light from the green stage to tillering stage and the light treated with low light from the green stage to heading stage showed that the leaf length of all the participating rice significantly increased.The leaf length of Nei5you768 in the low-light tolerant rice varieties did not increase significantly compared with that of the normal light treatment during the low-light treatment from the green stage to the tillering stage.The other types of rice varieties were significantly higher than the normal light treatment.Compared with normal light,the upper second leaf of each type of rice cultivars increased significantly in the period of low light treatment from returning green stage to heading stage.The leaf area of the upper three leaves of each type of rice was higher than that of the normal low light treatment under the low light treatment from the green stage to the mature stage.The leaf areas of all the three inverted leaves were of low light tolerance type(Nei5you 768)> intermediate type(Byou 268)> sensitive type(Yixiangyou 1108).(3)Compared with normal light,the dry weight of all rice leaves significantly decreased under low-light treatment during the period of returning to green and tillering,of which Yi Xiangyou 1108 had the smallest reduction,followed by Nei5 you 768.The stem dry weight of all the tested rice was significantly reduced,among which weak light sensitive rice(Yi Xiangyou 1108)had the smallest reduction,followed by intermediate rice(Byou 268).Under the low light treatment from the green stage to the heading stage,the total dry matter amount of all rice leaves in the test decreased,the light tolerance type(Nei5you 768)did not decrease significantly,and the total dry matter weight of the other two rice varieties significantly decreased.Under the low light treatment during the period of rejuvenation to maturity,the light tolerance rice varieties significantly increased,the intermediate type significantly decreased,and the weak light sensitive type was the second.Compared with the control,the stem dry weight of all three cultivars decreased significantly and reached a significant level.(4)compared with the normal light treatment,the theoretical yield of all rice varieties under the low-light treatment from the rejuvenation period to the maturity period was significantly reduced.The thousand-grain weight of the low-light tolerance type(Nei5you 768)was significantly reduced,and that of the other two varieties was significantly reduced.The total grain number of each tested variety decreased significantly.The seed setting rate of Nei5 you 768 in low light tolerance rice varieties was significantly reduced,and the other two varieties reached an extremely significant level.The theoretical yield of all rice varieties tested was significantly lower than that of the normal light treatment during the period of returning to green and heading,but the low-light tolerance rice varieties were not lower than that of the low-light treatment during heading to maturity.The 1000-grain weight of Nei5 you 768 in the low-light tolerant rice variety was significantly lower than that of the normal light treatment,the intermediate rice variety was not significantly different from that of the normal light treatment,and the low-light sensitive rice variety was significantly lower than that of the normal light treatment.However,there was no significant difference in seed setting rate between the tested varieties and the normal light treatment.Compared with the normal light treatment,the theoretical yield of all the tested varieties was significantly reduced in the period from heading stage to maturity stage under the low-light treatment.The thousand-grain weight of both light-tolerant and light-sensitive rice varieties was significantly reduced,but the total grain weight was not significantly reduced.The seed setting rate of the three tested varieties was significantly reduced.There was an extremely significant negative correlation between the difference of cultivars and the seed setting rate during the period of returning to green and the period of maturity,and the difference between cultivars and the grain number during the period of heading to maturity.(5)compared with normal light treatment,amylose content of rice in each type of lowlight treatment was significantly lower than that in the control treatment.Moreover,amylose content of rice was the lowest in the low light treatment from the green stage to the heading stage.The amylose content of the intermediate rice variety(Byou 268)was the maximum value in each treatment,and the decrease rate of amylose content after the weak light treatment was the maximum value of the three types of rice.After low light treatment,the RVA curves of the three types of rice varieties all changed to different degrees.In summary,after low-light treatment,rice will grow upper leaves to obtain more material energy,but dry matter weight will not increase.However,the degree of reduction of rice varieties with low light tolerance was less than that of intermediate and low light sensitive varieties.In all types of weak light treatment,the weak light treatment during the whole growth period made the photosynthetic materials synthesized by rice unable to meet all the survival requirements.When the early weak light treatment changed to normal light,rice would provide more materials for vegetative reproduction,so the panicle development was weakened.However,in the later period of low light treatment,the material of rice could not supply the growth demand of grains,so the setting rate of rice was reduced. |
