Effect Of Shading On The Floret And Grain Growth And Development In Winter Wheat Mianyang 26

In order to explore the mechanisms of shading damage in wheat, effects of shade on the floret development and degradation, mesophyll cell, grain, photosynthesis and the transformation of photosynthate were investigated in winter wheat cultivar mianyan-26 by measuring the growth of wheat flowers and its degradation; the mesophyll cell size, shape, ring the number, height and stomata traits; the dry height of leaf blade, leaf sheath, internodes and spike; maturing rate and thousand seed weight; the value of chlorophyll SPAD and photosynthesis. The main results are as follows:1 The process of wheat florets development were significantly delayed after shade treatment, and most florets were stopped growth before pollen maturity. The number of degraded wheat florets increased and the deterioration were in advance. The lower spikelet and the upper florets suffered a biggest influence; The rate of Mature florets was only 21.3% on the shade treatment, which was just half of the normal treatment about 46.7%. And the number of mature grain was 15.2, obviously less than normal conditions of 50. The rate of grain 47.5% was greatly lower than the normal setting 71.4%, thousand seed weight declined by 1.3g, the weight of single spike exists very significant difference.2 The mesophyll growth in shade treatment was poorer than normal condition after shading, where some mesophyll cells have white transparent substance and while the granule formed from chloroplast appears in normal mesophyll. The average number of ring of mesophyll was 4.34, which was less than that in normal condition of 4.51,but not notable. The frequency of much ring-cells was lower than the normal. The average height also was unobservable declined by 0.36um. But there was not significant difference in term of the stomata character.3 The transfer and distribution of assimilates in wheat changed clearly in the shading treatment. The total export number and export rate of shading treatment was lower than normal treatment and the total transfer rate was 73.1%, which is the characteristic of production and distribution of the substance-dependent from vegetative organs stored before flowering. The total transfer rate in normal treatment was 44.7%, which is the characteristic of production and distribution of the substance double-dependent from vegetative organs stored before flowering and the accumulation of photo synthetic substance after flowering. The trend of chlorophyll relative content in the two treatments after flowering period was from slow decrease to rapid decrease. Under the shading treatment the content and reduction trend of chlorophyll in backward first leaf during flowering period was similar to the normal treatment, and in the late the reduction trend was lower than normal treatment and the chlorophyll content was higher than normal treatment clearly; Under the shading treatment the content and reduction trend of chlorophyll in backward second leaf and third leaf during flowering period was similar to the normal treatment, which was from slow reduction to fast reduction and the trend of reduction in the shading treatment was slower than normal treatment.4 The flag leaf photosynthesis on 8:00,10:30 and 15:30(strong light, high temperature, the recovery stage after humidity stress) were measured. The results showed that the net photosynthesis rate of shading treatment in the 8:00 am during flowering period was relatively high and the net photosynthesis rate of normal treatment in the 10:30 am and 15:30 pm was relatively higher than shading treatment to lead to the trend of the amount of all-day photosynthetic assimilation increased. The net photosynthesis rate of shading treatment on 8:00,10:30 and 15:30 after 20 days from flowering period were higher than normal treatment slightly.