In the present study,photosynthetic parameters (photosynthetic rate,photosynthetic contribution rate)and biomass parameters (leaf biomass,inflorescence biomass,1000-seed weight,seed yield)of leaves at different positions were measured during seed development of Elymus sibiricus .The aim of this study was to investigate changes in photosynthetic parameters and biomass parameters with the advance of seed develop-ment,and to determine the relationship between seed yield and photosynthetic performance of leaves at differ-ent positions during seed development.There were significant differences in photosynthetic rate and photosyn-thetic contribution rate of leaves at different positions at different stages of seed development,and among leav-es of different positions at the same stage.Leaf biomass and leaf water content of different leaf positions changed significantly with seed development.At the flowering stage,seed yield was positively correlated with photosynthetic rate,leaf biomass and total leaf biomass in leaves at positions 1 to 5.At the seed filling stage photosynthetic rate of the first and third leaves and leaf biomass of the first two leaves were correlated with seed yield.At the milk stage,seed yield had a negative correlation with photosynthetic rate and leaf biomass from the fourth to fifth leaf.At the dough and ripe stages,seed yield had a positive correlation with photosyn-thetic rate of the first leaf and with leaf biomass of the first two leaves,but a significant negative correlation with photosynthetic rate from the third to fifth leaf and with leaf biomass from the third to fifth leaf.Seed yield was negatively correlated with total leaf biomass after the filling stage and with inflorescence biomass at the filling and milk stages,but a positive correlation with inflorescence biomass at the dough and ripening stages. It was concluded that crop management should promote growth and nutrient accumulation of leaves at different positions during vegetative growth to promote seed production.After the filling stage,it is very important to protect the integrity and health of the first three leaves to increase seed yield and seed quality.%本文通过在开花期、灌浆期、乳熟期、蜡熟期、完熟期测定不同位叶的光合速率和生物量，分析种子发育过程中各位叶的光合速率、光合贡献率、叶生物量及含水量、花穗生物量和种子千粒重的变化，研究种子产量与不同发育期不同位叶光合性能的关系。结果表明，1）种子发育过程中，不同位叶的光合速率和光合贡献率均存在显著变化，同一发育期各位叶的光合速率和光合贡献率表现出显著差异。2）不同位叶的叶生物量和含水量随种子发育均发生显著变化，同一位叶在种子发育不同时期的叶生物量和含水量表现出显著差异。3）种子产量与开花期1～5叶的光合速率和生物量及叶总生物量均呈正相关；与灌浆期第1，3叶光合速率和第1，2叶生物量呈显著正相关（P ＜0．05）；与乳熟期第4，5叶的光合速率及叶生物量为负相关；与蜡熟期、完熟期第1叶光合速率为正相关，与第3～5叶光合速率为极显著负相关，与第1，2叶生物量呈正相关，与第3～5叶生物量呈显著负相关。4）种子产量与灌浆期之后的叶总生物量均为负相关，与灌浆期和乳熟期花穗生物量呈负相关，与蜡熟期和完熟期花穗生物量为显著正相关。所以，在营养生长阶段要采取合理栽培措施，促进不同位叶叶片生长和营养累积，为种子发育奠定物质基础，而灌浆期后要注意调控各位叶的生物量和光合速率，着重保护第1～3叶的完整性与健康度，以提高老芒麦种子产量与千粒重。
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