光照对辽东栎种子萌发和幼苗生长的影响

Effects of light intensity on Quercus liaotungensis seed germination and seedling growth

研究了不同光照梯度[55.4%自然全光照(natural sunlight,NS)、18.9%NS、5.5%NS、2.2%NS、0.5%NS和0.3%NS]对辽东栎种子萌发和幼苗生长的影响.结果表明:辽东栎种子的萌发率和萌发指数在55.4%NS处理达到最大,分别为72.5%和0.22,然后随着光照减弱而逐渐减小,在0.3%NS处理下最小,分别为42.5%和0.11;强光照对种子萌发进程有一定的延迟作用,萌发活力指数随着光照的减弱而增大(0.5%NS处理最大);强光下种子萌发的延迟可能是其对多种命运的权衡性选择.强光照有利于辽东栎幼苗基径和根系生长,以及幼苗干物质的积累,但株高最小(6.06 cm);不同光强处理的辽东栎幼苗具有较大的形态学可塑性,其幼苗阶段对光环境的适应性较强,0.5%NS处理的幼苗比叶面积、比枝长、比根长、叶片叶绿素b含量及叶绿素总量均最大,分别为142.57 cm2.g-1、156.86 cm.g-1、271.87 cm.g-1、0.07 g.cm-2和0.24 g.cm-2,55.4%NS处理下最小,分别为44.89 cm2.g-1、52.84 cm.g-1、101.98 cm.g-1、0.04 g.cm-2和0.15 g.cm-2;不同光照强度下幼苗根冠比的变化可能是光照和水分共同影响的结果.

This paper studied the effects of different shading（55.4%,18.9%,5.5%,2.2%,0.5%,and 0.3% natural sunlight） on the seed germination and seedling growth of Quercus liaotungensis.The seed germination rate and germination index were the highest（72.5% and 0.22,respectively） at 55.4% natural sunlight,declined with decreasing light intensity,and were the lowest（42.5% and 0.11,respectively） at 0.3% natural sunlight.Strong light had definite delaying effect on the germination.The index of germination vigor increased with decreasing light intensity,being the maximum at 0.5% natural sunlight.The delay of seed germination under strong light could be the selective tradeoff on varied seed fates. Strong light benefited the basal stem diameter and root system growth and dry mass accumulation of Q.liaotunensis seedling,but resulted in the minimum seedlings height（6.06 cm）.Greater morphological plasticity was observed for the seedlings under different shading,which lent support to the higher adaptability of the seedlings to light environment.For example,the specific leaf area,specific shoot length,specific root length,and chlorophyll b and total chlorophyll contents were the maximum at 0.5% natural sunlight,being 142.57 cm2·g-1,156.86 cm·g-1,271.87 cm·g-1,0.07 g·cm-2,and 0.24 g·cm-2,respectively,and the minimum at 55.4% natural sunlight,being 44.89 cm2·g-1,52.84 cm·g-1,101.98 cm·g-1,0.04 g·cm-2,and 0.15 g·cm-2,respectively.The variation of the root/shoot ratio of Q.liaotungensis seedlings under different shading could be the effects of the combination of light intensity and water availability.