Dynamic Variations in the Photosynthetic Capacity in a Leaf's Lifetime for Five Taiwanese Tree Species at Different Successional Stages

台灣五種不同演替階段樹種葉片存活期間光合潛力的動態變化

郭耀綸(Yau-Lun Kuo) ； 黃明鍇(Ming-Kai Huang) ； 楊月玲(Yeh-Lin Yang)

《台灣林業科學》 28卷1期 (2013/03) Pp. 17-28

https://doi.org/10.7075/TJFS.201303_28(1).0002

摘要

本研究測定5種台灣原生闊葉樹種的葉壽命，以及一個葉片在發育過程光合作用潛力隨葉齡的動態變化。供試樹種包括演替早期的蟲屎與血桐，演替中期的江某，以及演替後期的黃心柿與毛柿。試驗結果發現，葉壽命以蟲屎107天最短，血桐為140天，江某、黃心柿及毛柿則分別為236、309及374天，5樹種的葉壽命間均具顯著差異。各樹種葉片存活期間光合作用潛力的變化樣式呈現偏斜的鐘型分布。葉片到達最大光合作用潛力的葉齡會早於或晚於充分伸展時的葉齡。蟲屎與血桐達到最大光合作用潛力（分別為27.3及25.4 μmol m^(-2) s^(-1)）的葉齡（分別為第33及43天），是在葉片充分伸展前1～2週；黃心柿及毛柿達到最大光合作用潛力（分別為9.8及10.4 μmol m^(-2) s^(-1)）的葉齡（分別為第76及106天），則是在葉片充分伸展後第2及第5週，而江某達到最大光合作用潛力（17.7 μmol m^(-2) s^(-1)）的葉齡與葉片充分伸展同時發生。蟲屎及血桐的最大光合作用潛力顯著大於江某、黃心柿及毛柿。樹種間比較，發現不同樹種最大光合作用潛力與葉壽命間具顯著負相關。但是，同一樹種不同葉片間，此兩性狀並不具顯著負相關。各樹種維持最大光合潛力90%的日數（生理旺盛期）均約為葉壽命的9%。本研究發現演替早期的樹種，具較高的光合作用潛力，葉壽命較短，在葉片充分伸展前光合作用潛力已達最高，而演替晚期樹種的光合作用潛力較低，葉壽命較長，通常光合作用潛力在葉片充分伸展後才達最高。

關鍵字

葉片充分伸展 ； 葉齡 ； 葉壽命 ； 最大光合作用潛力 ； 生理旺盛期

並列摘要

This research investigated the leaf lifespan and dynamic variations in the photosynthetic capacity during the developmental process of a leaf from unfolding, morphological maturity, then to senescence for 5 native broadleaf tree species of Taiwan. Chosen species represent species at different successional stages, including Melanolepis multiglandulosa and Macaranga tanarius (representing early-successional species), Schefflera octophylla (representing a mid-successional species), and Diospyros maritima and D. philippensis (representing late-successional species). For mean leaf lifespans, Mel. multiglandulosa was shortest (107 d), followed by Mac. tanarius (140 d), S. octophylla (236 d), D. maritima (309 d), and D. philippensis (374 d), with significant differences among the 5 species. Patterns of photosynthetic capacity through a leaf's lifetime exhibited a skewed bell-shaped distribution with maximum photosynthetic capacity (Amax) reached either before or after full leaf expansion. Amax values of Mel. multiglandulosa (27.3 μmol m^(-2) s^(-1)) and Mac. tanarius (25.4 μmol m^(-2) s^(-1)) were reached at 33 and 43 d of leaf age, respectively, which was 1~2 wk before full leaf expansion; Amax values of D. maritima (9.8 μmol m^(-2) s^(-1)) and D. philippensis (10.4 μmol m^(-2) s^(-1)) were reached at 76 and 106 d of leaf age, respectively, which was 2 and 5 wk after full leaf expansion; Amax values and full leaf expansion occurred at the same time for S. octophylla (17.7 μmol m^(-2) s^(-1)). Amax values of both Mel. multiglandulosa and Mac. tanarius were significantly higher than these of S. octophylla, D. maritima, and D. philippensis. Interspecific comparisons revealed significant negative relationships between leaf lifespan and Amax. This relationship, however, was not significant intraspecifically. In each species, the duration when photosynthesis was maintained above 90% of Amax (referred to as a stage of optimal photosynthesis) was approximately 9% of the leaf lifespan. In conclusion, early-successional species possessed a higher photosynthetic capacity and a shorter leaf lifespan, and reached Amax before full leaf expansion, while late-successional species possessed a lower photosynthetic capacity and a longer leaf lifespan, and generally reached Amax after full leaf expansion.

並列關鍵字

full leaf expansion ； leaf age ； leaf lifespan ； maximum photosynthetic capacity ； optimal photosynthesis