中文摘要：

本试验以小偃54×8602高代分离品系中的早衰与对照品系近等基因系为试验材料，研究了早衰对小麦旗叶光合速率、籽粒灌浆速率及产量的影响。结果表明，早衰小麦旗叶叶绿素含量较低，而且在生育后期下降较快；在整个灌浆期，旗叶光合速率、PSⅡ最大光化学效率Fv／Fm均低于对照；光饱和点低而光补偿点高，可利用的光强范围较窄，一天之中Pn都比对照低，光合“午休”现象严重；表观量子效率和CO2羧化效率均较对照低；早衰小麦叶片积累了较多的丙二醛，细胞膜脂过氧化程度高。由于叶片功能的衰退，使早衰小麦籽粒灌浆速率低，灌浆持续期短，粒重下降，最终减产20％以上．

英文摘要：

Early aging before maturity can cause serious loss in wheat （ Triticum aestivum L. ） grain yield. In order to understand how and why early aging affected wheat productivity, we compared net photosynthetic rate （ Pn ）, chlorophyll content （Ch1）, malondialdehyde （MDA） content, chlorophyll fluorescence parameters of flag leaf, and grain filling rate between the early aging line （EAL） and the normal line （NL） derived from winter wheat Xiaoyan 54×8602 during grain filling stage. The responses of P, to light intensity and carbon dioxide concentration, and diurnal variation of P, of flag leaf at 14 days post anthesis （ DPA）, photooxidation tolerance of flag leaf at 7 DPA, the biomass and grain yields at maturity were also compared. According to the results, early aging of EAL was reflected in the following four respects. Firstly, the Chl of EAL were lower and decreased earlier than that of NL; consequently the P, values of EAL were lower and decreased much earlier than that of NL during the grain filling stage. Secondly, the flag leaf of EAL had higher Fo （minimal fluorescence intensity）, DIo/CS （dissipated excitation energy at time zero per cross-section） and lower Fv/Fm （maximal quantum yield of Photosystem Ⅱ ）, RC/CSm （active reaction centers at maximum fluorescence per cross-section）, and P. I. （ perform index） than that of NL during grain filling stage, although other chlorophyll fluorescence parameters did not differ significantly between these two lines （data not shown）. Thirdly, EAL had lower apparent quantum yield and carboxylation efficiency as revealed by the responses of P, to light intensity and carbon dioxide concentration at 14 DPA. Finally,investigation on the diurnal variation of P,, at 14 DPA revealed that EAL had lower Pn than NL at all the measuring time points; the P,, of EAL was 25.2% lower at noon than its maximum Pn in the morning, while that of NL was 14.2% lower, reflecting that EAL was more. suseeptive to photoinhibition than NL under fiel