Response of Rice Organ Morphology and Dry Matter Accumulation to High Temperature at Different Panicle Initiation Stages
A pot experiment in controlled-environment chambers was conducted to determine the effects of high temperature(40℃)on the rice organ morphology and dry matter accumulation during panicle initiation stage.Two mid-indica rice cultivars(Huanghuazhan,heat-tolerant;Fengliangyou 6,heat-sensitive)were planted and exposed to high temperature(40℃,10:00-15:00),and normal temperature(32℃,10:00-15:00)during branch-spikelet differentiation stage(I)and pollen mother cell formation-meiosis stage(Ⅱ),meanwhile rice was grown in ambient conditions as CK.The results indicated that,1 )at stage I high temperature inhibited panicle initiation,extending the panicle initiation stage by 2.5-8.8 d,while at stage Ⅱ,by 6.8-7.1d,which shortened the length of the top internode and reduced the heading degree,especially in Fengliangyou 6.2)Heat stress at panicle initiation stage significantly decreased the number and the size of spikelets,which might be due to the significant difference in treatment period. High temperature at stage I inhibited spikelet differentiation,while at stageⅡ,heat stress mainly promoted spikelet degeneration,the degeneration rate of the two cultivars were up to 50%,with'Fengliangyou6'having a higher ratio. High temperature exposure at stage Ⅱ also significantly declined the size of anther,and the spikelet fertility.3)High temperature promoted the growth of the top three leaves,especially at stage Ⅱ.Heat stress at the two stages had no significant effect on the leaf photosynthesis and dry matter accumulation of single main stem.Heat stress (40℃) exerted no significant influence on dry matter accumulation of culm,leaves and panicle at stage I,but significantly decreased the dry matter accumulation of culm and panicle at stage Ⅱ,leading to upper-internode tillering and resultant dry matter accumulation.
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