Dynamics of the Photosynthetic Capacity during the Lifetime of Leaves in Three Subtropical Tree Species

三種亞熱帶樹種葉片－生光合作用潛力的動態變化

郭耀綸(Yau-Lun Kuo) ； 黃慈薇(Tsu-Wei Hwang) ； 楊月玲(Yeh-Lin Yang)

《台灣林業科學》 24卷3期 (2009/09) Pp. 169-182

https://doi.org/10.7075/TJFS.200909.0169

摘要

光合潛力及葉壽命是植物重要的兩項功能性性狀，兩者間常呈負相關。本研究連續測定茄冬、大頭茶及大葉楠由幼葉、充分展葉到落葉，同一葉片一生光合作用潛力的動態變化。結果發現茄冬平均葉壽命為224±7天，大頭茶與大葉楠則分別為345±21及515±28天。茄冬葉片在葉齡27天時完全展開，此時其光合潛力亦同步達最適期。大頭茶及大葉楠在葉齡約20天時葉片完全展開，但分別要到葉齡32及59天時才達光合潛力最適期。此三樹種的最高光合潛力並無顯著差異，在12.7~13.8μmolm^(-2)s^(-1)間，維持最高光合潛力90%的期間（光合潛力最適期）只有40~50天。茄冬光合潛力隨葉齡的增加而呈直線下降，但大頭茶與大葉楠在葉齡200至350天期間，其光合潛力可穩定維持在最高光合潛力的30~40%。本研究三樹種無論種間或種內比較，葉壽命較長者其光合潛力並不會比葉壽命較短者低，此結果與其他研究有所不同。光合潛力隨葉齡變化的迴歸分析顯示，葉壽命較短的茄冬，其直線迴歸線下降的斜率較另兩葉壽命較長的樹種陡。然而，同一樹種不同葉片間，僅有大頭茶其葉壽命較短者迴歸線下降的斜率會較陡，另兩樹種並不如此。

關鍵字

葉齡 ； 葉壽命 ； 一生的光合作用 ； 光合作用旺盛期 ； 光合潛力

並列摘要

Two important functional traits of plants, the photosynthetic capacity and leaf lifespan, are usually negatively correlated. To compare the lifetime pattern of photosynthetic activity in leaves of Bischofia javanica, Gordonia axillaris, and Machilus japonica var. kusanoi, we monitored the dynamics of the photosynthetic capacity of leaves from a young age to full expansion then abscission. The mean leaf lifespans of B. javanica, G. axillaris, and M. japonica were 224±7, 345±21, and 515±28 d, respectively. Leaves of B. javanica had fully expanded at 27 d of leaf age and had reached a stage of optimal photosynthesis (see below), while leaves of G. axillaris and M. japonica had fully expanded at around 20 d but did not reach the optimal photosynthetic stage until 32 and 59 d, respectively. No significant differences in the maximum photosynthetic capacity (A(subscript max)) were observed among the 3 species, and all were in the range of 12.7 to 13.8 μmol m^(-2) s^(-1). The photosynthetic capacity was maintained above 90% of A(subscript max) (referred to as a stage of optimal photosynthesis) for only 40~50 d in the 3 species. The photosynthetic capacity linearly declined as leaves aged in B. javanica. However, leaves of both G. axillaris and M. japonica maintained their photosynthetic capacity steadily at 30~40% of A(subscript max) for about 5 mo at the leaf ages of 200~350 d. Our study showed that leaves with a longer lifespan did not always have a significantly lower photosynthetic capacity than leaves with a shorter lifespan in either interspecific or intraspecific comparisons, a result which differs from findings of other researchers. Regression analysis of the photosynthetic capacity vs. leaf age of B. javanica (with a shorter leaf lifespan) yielded a slope steeper than that of G. axillaris and M. japonica (with longer leaf lifespans). Compared within each species, leaves with a shorter lifespan having steeper slopes was only found in leaves of G. axillaris, but not in those of the other 2 species.

並列關鍵字

leaf age ； leaf lifespan ； lifetime photosynthesis ； stage of optimal photosynthesis ； photosynthetic capacity