摘要
测定了生长于 3种光强下 (10 0 %、4 2 %和 14 %自然光强 )热带雨林演替早期 (思茅蒲桃Syzygiumlatilim bum)、中期 (乌墨S .cumini)和后期 (阔叶蒲桃S .szemaoense)出现的蒲桃属 (Syzygium) 3个树种幼苗叶片气体交换参数和叶绿素荧光参数的日变化、比叶重和叶绿素含量。发现演替早期树种光合能力和光合可塑性最大、中期树种次之 ,后期树种光合能力最弱且在强光下受到显著抑制。但是 ,生长在强光下 ,3个树种均未发生长期光抑制和光破坏。随生长光强增加 ,3个树种热耗散速率都升高。不过在强光下 ,中期和后期树种通过热耗散消耗的过剩光能较多 ,通过叶黄素循环的热耗散可能对于这两个树种在强光下避免光合机构的光破坏起到了重要作用。 14 %光强下 ,3个树种最大净光合速率、光合作用的光饱和点、光补偿点、暗呼吸速率、比叶重降低 ,叶片单位干重叶绿素含量提高 ,对低光环境有了较好的形态学和生理学适应。但是 ,在 4 %光强下思茅蒲桃和乌墨幼苗全部死亡 ,只有阔叶蒲桃幼苗仍能存活 ,说明阔叶蒲桃幼苗适应弱光环境的能力高于思茅蒲桃和乌墨 。
Light is one of the most important factors that affect the regeneration and succession of tropical rain forests. Tropical trees with different successional status have different acclimation capacities to different growth light environments. In the present study, gas exchange and diurnal variation of chlorophyll fluorescence parameters were measured in the seedlings of three tropical rainforest Syzygium species, which are early (S. szemaoense), middle (S. cumini) and late (S. latilimbum) successional species. The seedlings were cultivated under three different light regimes (fully open site, 42% and 14% daylight). Their leaf mass per unit area (LMA) and chlorophyll content were also determined. The early successional species had the highest light- saturated photosynthetic rate (P max) and photosynthetic acclimation capacity to the variation of growth light environments, the next was the middle successional species. The late successional species had the lowest P max values and its photosynthesis was strongly suppressed when grown in full light. Nevertheless, grown under both the full light and 42% daylight, all the three species did not suffer from irreversible photoinhibition, as indicated by their dawn values of maximal photochemical efficiency of PS Ⅱ (F v/F m) larger than 0.8, and their φPSⅡ was able to recover on the same day. Dynamic (reversible) photoinhibition occurred in all species, the degree of which increased with growth light level. Among species, the degrees of dynamic photoinhibition were similar. The non-photochemical fluorescence-quenching rate (NPQ) increased with the growth light level for all species. However, in the fully open site, the NPQ rates in the morning were higher in the late and middle successional species than in the early successional species. This compensated for the lower photosynthetic rates of the former two species, and probably plays a role in preventing photodamage to these species under full light. Leaf dark respiration rate per unit area (R d) and leaf mass per area (LMA) tended to increase with the growth light level. Under the same light regimes, R d was higher in early than in middle and late successional species. The LMA values of late successional species were higher than for the other two species. This could be favorable for this shade-tolerant species to prevent herbivory. For all of the three species grown in 14% daylight, area-based P max, photosynthetic light saturation point, light compensation point, R d and LMA were reduced, while chlorophyll content per unit dry weight were increased compared to those in the other two light regimes. This showed their favorable acclimation to low light. Nevertheless, under 14% daylight the seedlings of both the early and middle species died, only the seedlings of the late successional species were still alive. This indicates that this late successional species has high capacity to acclimate to low light.
出处
《植物生态学报》
CAS
CSCD
北大核心
2004年第1期31-38,共8页
Chinese Journal of Plant Ecology
基金
中国科学院"百人计划"项目资助
关键词
热带雨林
树苗
演替状态
光合能力
光适应
蒲桃属
Tropical rainforest, Tree seedlings, Successional status, Light acclimation, Photosynthetic capacity
