Strauss-Debenedetti S, Bazzaz F A
Yale School of Forestry & Environmental Studies, 06511, New Haven, CT, USA.
Department of Organismic and Evolutionary Biology, Harvard University, 02138, Cambridge, MA, USA.
Oecologia. 1991 Sep;87(3):377-387. doi: 10.1007/BF00634595.
We evaluated both the photosynthetic plasticity and acclimation to light of seedlings of five co-occurring tropical tree species in the Moraceae,Cecropia obtusifolia, Ficus insipida, Poulsenia armata, Brosimum alicastrum, andPseudolmedia oxyphyllaria. Distinct differences in the species' abilities to respond to increasing irradiance correlated with their known habitat breadths and successional status. The early successinalsCecropia andFicus exhibited the highest photosynthetic rates and conductance values in high light. There was a several-fold difference in assimilation across light regimes, consistent with a high physiological plasticity. When individuals grown at low light were transferred to higher irradiances, seedlings of bothCecropia andFicus produced leaves which photosynthesized at rates as high or higher than those of plants continuously grown in high light, indicating a high photosynthetic acclimation potential. In contrast, the late successionals were characterized by both a more restricted physiological plasticity and acclimation potential. Higher light levels resulted in only moderate increases in assimilation among the late successionals, and onlyBrosimum acclimated fully to increased irradiances. NeitherPoulsenia norPseudolmedia increased appreciably their photosynthetic rates when transferred to high light. This suggests that acclimation potential cannot always be inferred from plasticity responses, and calls for a reevaluation of arguments developed solely from plasticity studies. Finally, differences between the early and late successional species in the allocation of nitrogen into RuBP carboxylase and thylakoid nitrogen pools or non-photosynthetic compounds are suggested by the distinct relationships between maximum photosynthetic capacity and nitrogen content.
我们评估了桑科同时出现的五种热带树种钝叶塞克罗皮亚树、无味榕、武装波尔森木、面包树和尖叶假胶木幼苗的光合可塑性和对光照的适应性。这些物种对光照增强的响应能力存在明显差异，这与它们已知的栖息地宽度和演替状态相关。早期演替物种塞克罗皮亚树和榕属植物在高光下表现出最高的光合速率和导度值。不同光照条件下的同化作用存在几倍的差异，这与高生理可塑性一致。当在低光照下生长的个体转移到更高光照强度时，塞克罗皮亚树和榕属植物的幼苗产生的叶片光合作用速率与在高光下持续生长的植物一样高或更高，这表明它们具有很高的光合适应潜力。相比之下，晚期演替物种的特点是生理可塑性和适应潜力更为有限。较高的光照水平只会使晚期演替物种的同化作用适度增加，只有面包树能完全适应光照强度的增加。当转移到高光下时，波尔森木和尖叶假胶木的光合速率均未明显增加。这表明适应潜力不能总是从可塑性反应中推断出来，这就需要重新评估仅从可塑性研究得出的观点。最后，最大光合能力与氮含量之间的明显关系表明，早期和晚期演替物种在将氮分配到核酮糖-1,5-二磷酸羧化酶、类囊体氮库或非光合化合物方面存在差异。
