Effects Of Sowing Date And Shading During Different Rice Duration On The Physiological Characteristics And Rice Quality

Five varieties with low amylose content varietiy Mirukikuin, the moderate amylose content varieties Toyonishiki and Koshihikari, high amylose content varieties Hoshiyutaka and Gangyou527 were used to study the influence of different sowing date on rice quality. (Six sowing date were designed on march 13, on march 23, on April 2, on April 12,on April 22, on may 2) ;Three varieties Mirukikuin, Hoshiyutaka and Toyonishiki were used to study the influence of different rice duration shading (transplanting date to initial period of young spike, initial period of young spike to heading date, heading date to maturity date, shading rate 50%) on rice quality. The results were as follows: 1. The influence on rice quality in different sowing-date1.1 The average temperature changes during grain filling stage: The growth periods of varieties Koshihikari, Toyonishiki and Mirukikuin were short and their growth periods were 143d, 143d and 142d respectively. The average temperature of the grain filling stage decreased after increase on the first five sowing date and the average temperature of the grain filling stage always decreased on the six sowing date. The growth periods of varieties Hoshiyutaka and Gangyou527 were long and their growth periods were respectively 165d and 164d. With the postponement of the sowing date, the average temperature of grain filling stages declined gradually and the change trends were similar among different sowing date.1.2. The influence on fountain apparatus: On the different sowing date, the green leaves areas of the top leaves diminished after increase, the chlorophyll content of superior three leaves decreased step by step, the content of soluble sugar in superior three leaves declined after increase and the soluble protein content of the superior three leaves, stemsand sheaths decreased gradually during the whole grain filling stage. 1.3 The influence on rice quality:1.3.1 The influence on milling and appearance quality: As for the same variety, the brown rice rate and milled rice rate changed a little and head rice rate declined and chalky rate enhanced with the increase of the grain filling temperature.1.3.2 The influence on amylose content: The research about the dynamic changes of amylose accumulation indicated that the main formation period of amylose content were 0 —30d after anthesis, amylose content changed a little after 30d, so it is proper to use the temperature change of the first 30 days of grain filling stage to describe the relation between amylose accumulation and temperature. Judging from the relation between temperature during grain filling stage and amylose content, the amylose content of varieties with high and low amylose content increased with the decrease of the grain filling temperature and the amylose content of varieties with moderate amylose content declined with the decrease of the grain filling temperature. The difference of amylose content was significant or very significant among different sowing dates.1.3.3 The influence on protein content: the rice protein accumulation was correlated to do with the changes of the grain filling temperature. As for short growth period varieties Koshihikari, Toyonishiki and Mirukikuin, the protein content had the trendence of increase with the postponement of the sowing date and the increase of the grain filling temperature. As for varieties with long growth period Hoshiyutaka and Gangyou527, the protein content had the tendency of increase with the postponement of the sowing date and the decrease of the grain filling temperature. According to the dynamic changes of the protein content, the protein content of grains was high at the beginning of grain filling stage and the protein content decreased gradually with the continuance of grain filling.2. The influence on rice quality in shading of different rice duration2.1 The influence on fountain apparatus and grain filling: As for shading of different rice duration, the green areas of the top leaf and chlorophyll content of superior three leaves were higher than control during the whole grain filling stage. As for varieties Hoshiyutaka, the effect of shading from the heading date to maturity date was the most obvious in all shading treatment, as for varieties Toyonishiki and Mirukikuin, the effect ofthe shading from transplanting date to initial period of young spike was the most obvious in all shading treatment and the soluble protein content of superior three leaves, stems and sheaths was higher than control during the whole grain filling stage. The accumulation speed of dry matter in grain was lower than control during the whole grain filling stage. The effect of shading from the heading date to maturity date was the most obvious in all shading treatment.2.2.The influence on rice quality2.2.1 The influence on milling and appearance quality: The distinction of the influence of the shading in different rice duration on brown rice rate and milled rice rate was not transparent, head rice rate and amylose content were different in different varieties, shading during grain filling stage could enhance chalky rate.2.2.2 The influence on amylose content: Intrinsic amylose content of different varieties resulted in the different influence of different rice duration shading on amylose content. The amylose content of every treatment of high amylose content varieties was lower than control while moderate and low amylose content varieties had higher amylose content than control.2.2.3 The influence on protein content: The shading in different rice duration had different influence on protein content. The difference of the protein content of varieties which were shaded from transplanting date to initial period of young spike and from initial period of young spike to heading date was not significant. The effect of shading from the heading date to maturity date on the protein content was much higher than control and the degree of influence was different because of the distinction of varieties intrinsic protein content. Varieties with high protein content had big increase degree and the varieties with low protein content had small increase degree.