中文摘要：

为了解胡桃楸幼苗对光的需求及适应规律,采用Li-6400便携式光合测定系统研究了不同光环境处理（100%、60%、30%和15%自然光）条件下3年生胡桃楸幼苗（适应1年后）叶片光合能力的季节变化及其对光强的响应.结果表明：在春季,胡桃楸幼苗对光反应不敏感,夏季和秋季随着光强的增加,叶片的最大光合速率、最大羧化速率和最大电子传递速率均显著增加（P〈0.05）.光饱和点随光强的下降而降低（P〈0.05）,表观量子效率、暗呼吸速率和光补偿点在不同光环境下未发现显著差异.100%和60%自然光处理的幼苗相对生长率差异不显著,但是随着光强下降,相对生长率显著下降（P〈0.05）,为60%〉30%〉15%自然光处理.胡桃楸幼苗对不同的光环境表现出较强的适应性和可塑性;同时,通过降低光饱和点和减少碳积累,也能适应15%～30%自然光环境.

英文摘要：

In order to understand the light requirement and adaptability of Juglans mandshurica seedlings,two-year-old J.mandshurica seedlings were grown under four light regimes（100%,60%,30%,and 15% of natural irradiance）.After 1-year adaptation,the seasonal variations of the seedlings photosynthetic variables were measured by a Li-6400 portable photosynthesis system.The J.mandshurica seedlings were insensitive to the changes of light environment in spring,but their maximum net photosynthetic rate,maximum carboxylation rate,and maximum electron transport rate increased significantly with increasing light intensity in summer and autumn（P0.05）.The light saturation point declined with decreasing light intensity（P0.05）,but the apparent quantum yield,dark respiration rate,and light compensation point under different light environments had no significant changes.The relative growth rate under 100% and 60% of natural irradiance had no significant difference（P0.05）,but declined significantly in the order of 60%30%15% of natural irradiance（P0.05）.These results indicated that J.mandshurica seedlings had the maximum relative growth rate under 100% and 60% of natural irradiances,and could tolerate 15%-30% of natural irradiance by reducing light saturation point and carbon accumulation,exhibiting strong adaptability and plasticity to light environment.