控制光照强度条件下1年生连翘幼苗的生理生态响应

为了调查连翘在发育早期对于不同光照强度条件的生理生态响应和适应性,提高苗期管理质量和出苗率,以1年生连翘幼苗为材料,在人工控制大田环境中设置100%、50%、25%和12.5%4个光照强度水平,通过测量1个生长季后连翘幼苗的存活率、光合生理、地上地下形态、生物量积累和分配等生理生态指标,研究控制光照强度条件下1年生连翘幼苗的生理生态响应。结果表明:1)1年生连翘幼苗在50%光照强度条件下的最大净光合速率、光饱和点和叶绿素b含量显著下降,苗高、地径、总根长、根表面积以及各器官的生物量积累增加显著,根质量比减小,茎质量比和冠根质量比增大;2)在25%光照强度条件下,幼苗的存活率、最大净光合速率、苗高、地径、总根长、根表面积以及各器官的生物量积累增加显著且达到最大值,茎质量比增大;3)在12.5%光照强度条件下,仅最大净光合速率、地径和根系形态指标显著增加,但增幅小于50%和25%光照强度,叶质量比减小。1年生连翘幼苗在光合生理特性上对于遮荫处理表现出不一致的响应,形态和生物量积累在中等光照强度下响应积极一致,且能够通过增加对地上结构生物量的分配比例而适应中等光照强度条件,建议在今后的苗圃培育和管理中应当重视连翘在发育早期的光环境要求。

Ecophysiological responses of one-year-old Forsythia suspensa seedlings to controlled light intensity conditions

To investigate the light response and acclimation of Forsythia suspensa in seedling stage,improving seedling quality and production,one year old Forsythia suspensa seedlings were selected to test under four light intensities（100%,50%,25% and 12.5% relative transmittance levels） under field conditions.Survival rates,photosynthetic traits,morphology,biomass accumulation and allocation patterns of these seedlings after one growing season were measured.The results showed that at 50% relative transmittance level,the maximum net assimilation rate（Amax）,light saturation point and chlorophyll b content of one year old Forsythia suspensa seedlings decreased significantly,but seedling height（H）,root collar diameter（RCD）,total root length（RL）,root surface area（RS） and biomass accumulation of all organs significantly increased,while root mass ratio（RMR） decreased and stem mass ratio（SMR） and above/belowground mass ratio increased.At 25% relative transmittance level,survival rates,Amax,H,RCD,RL,RS and biomass accumulation of all organs of the seedlings significantly increased and were highest among all light intensities,while only SMR increased in all biomass allocation variables.Moreover,at 12.5% relative transmittance level,only Amax,RCD,RL,RS significantly increased with smaller increments than that at 50% and 25% relative transmittance levels,while only leaf mass ratio（LMR） decreased in all biomass allocation variables.Therefore,one year old Forsythia suspensa seedlings showed inconsistent photosynthetic responses to all shade treatments and consistent morphological and biomass accumulation responses to medium shades,and were capable of acclimating medium shade by increasing biomass allocation of aboveground structure.Thus,the light requirements and habit of Forsythia suspensa in seedling stage should be emphasized in future management works of nurseries.