田字草浮水葉、挺水葉和陸生葉葉部特徵和光合作用表現

Leaf Characteristics and Photosynthetic Performance of Floating, Emergent and Terrestrial Leaves of Marsilea quadrifolia

田字草是一種水陸兩棲的蕨類，在不同環境下會長出異形葉。本研究比較田字草浮水葉、挺水葉和陸生葉上、下表皮氣孔和表皮毛密度、葉和葉柄單位重量比、葉反射、穿透和吸收光譜特性以及光合作用表現；目的在探討異形葉的形成在生態上的意義。結果發現這三型葉在下表皮氣孔密度、表皮毛密度、葉柄單位重量以及在波長500和650 nm間之葉反射光譜係數有顯著差異；但在不同光度下的電子傳遞鏈速率則沒有顯著差異；穩定性碳同位素分析顯示三者都使用C3型光合途徑進行固碳作用。

Individuals of Marsilea quadrifolia, an amphibious fern, experiencing extreme variation in environment develop heterophyll. In this study, we compared stomatal and trichome density on upper and lower surfaces, leaf and petiole area mass ratio, spectral properties and photosynthetic performance of floating, emergent and terrestrial leaves of M. quadrifolia, to explore the ecological advantages of producing different leaf types. Morphological measurement reveals that these three types of leaf display highly differences in stomatal density on lower epidermis, trichome density on both surfaces and petiole dry mass per length, and reflectance coefficient between 500 and 650 nm. In contrast, no significant difference was found in the PSII electron transport rate of the three types of leaves. The analysis of stable carbon isotope ratio of the three types of leaves indicates that they all use C3 photosynthetic pathway.