植物生态学报 ›› 2003, Vol. 27 ›› Issue (5): 617-623.DOI: 10.17521/cjpe.2003.0089

• 论文 • 上一篇    下一篇

6种热带雨林木本植物幼苗光合诱导的研究

蔡志全, 曹坤芳, 郑丽   

  • 发布日期:2003-05-10
  • 通讯作者: 蔡志全

Photosynthetic Induction in Seedlings of Six Tropical Rainforest Tree Species

CAI Zhi-Quan, CAO Kun-Fang, ZHENG Li   

  • Published:2003-05-10
  • Contact: YU Hua and Bee-Lian ONG

摘要:

在晴天上午适宜条件下,测定了生长在模拟林下光环境中的6种热带雨林木本植物幼苗的光合特性和光合诱导特征。6种植物分别为先锋树种大穗野桐(Mallotus macrostachys),冠层树种绒毛番龙眼(Pometia tomentosa)、玉蕊(Barringtonia pendala)、望天树(Shorea chinensis)、滇南插柚紫(Linociera insignis)和林下灌木睫毛粗叶木(Lasianthus hookeri)。研究结果表明:暗处理3 h的叶片经连续饱和强光照射后,6种植物的净光合速率呈s形到双曲线形。6种植物达到90%最大净光合速率的时间为4.4~12.5 min,这与所报道的其它热带雨林中一些阴生植物的诱导速率相近。大穗野桐和睫毛粗叶木的诱导速率最快,达到50%和90%最大净光合速率的时间为其它4种冠层植物幼苗的1/2至1/3。诱导过程中,最大气孔导度对强光的响应明显滞后于净光合速率。充分诱导的叶片在黑暗中20 min后,6种植物的诱导状态都较高。其中,大穗野桐的诱导状态消失相对较快,这可能与其气孔导度和羧化能力的快速降低有关。玉蕊诱导状态的消失主要与生化限制有关,因为此时它的气孔导度仍维持相对较高的值。而睫毛粗叶木较高的气孔导度和羧化能力的维持导致了很高的诱导状态。林下植物这种对强光的快速反应和黑暗中高的维持状态对有效利用光斑具有重要的意义,这与其一生中在林下生长和更新的特点是一致的。

Abstract:

In order to investigate the differences in capacity of sunfleck utilization between species with different ecological characteristics, the photosynthetic characteristics and photosynthetic induction responses were examined with LI-6400 portable photosynthesis system in seedlings of six tropical rainforest species acclimated in simulated understory light environment for more than one and a half years. The species studied were Mallotus macrostachys, a pioneer species, Pometia tomentosa, Shorea chinensis, Barringtonia pendala, Linociera insignis, Lasianthus hookeri, four canopy species and an extremely shade-tolerant understory shrub. After leaves were shaded in darkness for 3 h, photosynthetic induction was measured under optimum temperature ((26±1.2) ℃) and humidity (75%±5%) and normal ambient CO2 ((400±0.5) μmol CO2·mol-1 air) in the morning. The time courses of induction varied from a sigmoidal to a hyperbolic increase in net photosynthesis. The time required to reach 90% of maximum net photosynthetic rate differed among species, and was short (4.4-12.5 min), which was consistent with induction times reported in other tropical shade-tolerant species. Seedlings of M. macrostachys and L. hookeri were induced two to three times more quickly than the other four canopy species. The response of attaining maximal stomatal conductance significantly lagged behind the increase in net photosynthetic rate during the induction course. When fully induced leaves were shaded in darkness for 20 min, loss of induction was moderate in all species. Among these species, seedlings of M. macrostachys had a relatively rapid induction loss, which was due to rapid loss of stomatal conductance and biochemical factors. The loss of B. pendala was mainly due to biochemical limitation as stomatal conductance decreased only slowly. Seedlings of L. hookeri showed the slowest loss of induction as a result of maintaining higher relative stomatal conductance and maximum carboxylation capacity. Thus this effective utilization of sunflecks is likely to be a critical determinant of growth and generation for understory species.