Effect Of High Temperature Stress On Flowering And Fertilization And Quality Of Rice

The experiment with two early rice lines differed extremely in heat tolerance including thermo-resistant line996and thermo-sensitive line4628,was carried out in the controlled greenhouse high temperature(9:00-17:00,37℃,17:00-09:00,30℃) and suitable temperature(09:00-17:00,30℃,17:00-09:00,25℃) to study the effect of high temperature stress on flowering and fertilization and quality of rice from flowering habit,anther physiologicalcharacteristics and rice quality.The main results are as follows:1. The flowering period shortened,flowering clock decentralized and the flowering peak value decreased,daily number of spikelet flowering increased and flowering clock delayed under high temperature stress during flowering period,compared to heat-sensitive line4628, heat tolerant line996showed more obvious. The glume opening time prolonged,glume opening angle,pollen diameter and stigma surface area increased under high temperature stress, and anther dehiscence coefficient,pollen vigor,stigma exsertion,stigma vigor and seed set rate decreased. The glume opening angle, anther dehiscence coefficient, pollen diameter, pollen vigo and stigma vigor in heat tolerant line996were greater than that of heat-sensitive line4628.2. Souble sugar content, souble protein content and vitamin C content of anther decreased under high temperature stress; The increase scope of MDA content and relative conductivity in heat-sensitive line4628was greater under high temperature stress than that of in heat-tolerant line996; Under high temperature stress, GA3and IAA content of anther decreased, while ABA content of anther increased, compared with heat-sensitive line4628, the decreasing scope of GA3and IAA content, the increasing scope of ABA content in heat tolerant line996was less.3. Under high temperature stress the ratio of grain length to width, the brow rice rate, milled rice rate, head rice rate and gel consistency of both lines decreased during heading and filling stages,while chalkness rate, chalkness,amylose content, protein content and gelatinization temperature increased.Under high temperature treatments,gelatinization temperature,final viscosity, set back and peak time increased,break dowm decreased, Mg content and K content increased,Mg/K decreased.The observation of starch structure with scanning electron microscope showed that the starch granules arranged loosely,most of the starch granules existed in the form of single starch granule,refractive index decreased,endosperm transparency decreased,and chalkiness was formed.Under same treatment,the extent of rice quality of heat-tolerant line996affected by high temperature was lower than that of heat-sensitive line4628. Rice qualities had different responses to different high temperature treatments,the rice qualities were affected by high temperature treatment8-14d after heading mostly,moderatedly by high temperature treatment15-21d and1-7d after heading,while least by high temperature treatment22-28d after heading. Therefore,8-21d after heading is the vital stage for whole rice quality in response to highe temperature,which affects rice qualities decisively; while the effect of the temperature in the later stage(beyond22days from heading) is slight.