灌浆初期高温影响水稻籽粒充实和剑叶理化特性摘要：为探明灌浆初期高温热害降低水稻籽粒充实度的可能生理原因，本文以遗传背景相近而灌浆期耐热性存在显著差异的2个水稻纯系XN0437T（耐热）和XN0437S（热敏感）为材料，于水稻抽穗后第10天进行高温处理，调查了水稻籽粒充实度，测定了与水稻剑叶光合效率、细胞膜透性和渗透调节有关的生理指标。结果表明，高温处理后水稻籽粒充实度、叶绿素含量、剑叶的净光合速率和可溶性糖含量降低，热敏感纯系的下降幅度大于耐热纯系；超氧化物歧化酶（SOD）活性、细胞膜透性、丙二醛（MDA）和脯氨酸（Pro）含量增加，其中热敏感纯系的MDA含量、细胞膜透性增加幅度大于耐热纯系，而其SOD活性、脯氨酸含量的增加幅度小于耐热纯系。灌浆初期高温抑制水稻剑叶光合效率，增加细胞膜透性和改变细胞内环境是高温热害降低水稻籽粒充实度的生理原因。关键词:水稻;高温;籽粒充实度;理化特性Effectsofhightemperatureonricegrain-fillingofcaryopsisandphysiologicalbiochemicalcharacteristicofflagleaveatearlymilkystageofriceTheaimofthisexperimentwastoascertainpossiblephysiologicalcausesofhightemperaturedecreasinggrain-fillingrateatearlymilkystageofrice.Tworiceinbredlines,namedXN0437T(heat-sensitive)andXN0437S(heat-tolerant),wereselectedandtreatedbyhightemperatureatthe10thdayafterheading.Thegrainplumpnessrate,indexesrelatedtophotosyntheticefficiency,cellmembranepermeabilityandosmoticadjustmentinflagleavesweredetectedinricelinesXN0437TandXN0437S.TheresultshowedthatthegrainplumpnessratewasreducedunderhightemperatureinbothXN0437TandXN0437Sandthereducedrangeofheat-sensitivelinewasgreaterthanthatofheat-tolerantline.Thenetphotosyntheticrate,chlorophyllcontentandsolublesugarcontentweredecreasedincomparisonwithcontrolbothinheat-sensitiveandheat-tolerantricelines,andthedecreaserangeofthesephysiologicalmattercontentsweregreaterintheheat-sensitivelinethanthatoftheheat-tolerantline.Thesuperoxidedismutase(SOD)activity,malonaldehyde(MDA)content,cellmembranepermeabilityandproline(Pro)contentwereincreasedunderhightemperature,andtheincreasedrangeofMDAcontentandmembranepermeabilityinheat-sensitivelinewerehigherthanthatinheat-tolerantline,whiletheincreasedrangeofSODactivity,Procontentinheat-sensitivelinewaslessthanthatinheat-tolerantline.Thepresentstudysuggestedthatdecreasingthephotosyntheticefficiencyofflagleaves,damagingthestructureandfunctionofcellmembrane,andresultintheintracellularenvironmentalteringwerethephysiologicalcausesofhightemperatureatearlymilkystagelimitingthegrainplumpn