De Lucia Evan H, Shenoi Hemanth D, Naidu Shawna L, Day Thomas A
Department of Plant Biology, University of Illinois, 289 Morrill Hall, 505 South Goodwin Avenue, 61801, Urbana, IL, USA.
Oecologia. 1991 Jun;87(1):51-57. doi: 10.1007/BF00323779.
The photosynthetic responses to light of leaves irradiated on the adaxial or abaxial surfaces, were measured for plants with contrasting leaf orientations. For vertical-leaf species of open habitats (Eryngium yuccifolium and Silphium terebinthinaceum), photosynthetic rates were identical when irradiated on either surface. However, for horizontal-leaf species of open habitats (Ambrosia trifida and Solidago canadensis), light-saturated rates of photosynthesis for adaxial irradiation were 19 to 37% higher than rates for abaxial irradiation. Leaves of understory plants (Asarum canadense and Hydrophyllum canadense) were functionally symmetrical although they had horizontal orientation. Photosynthetic rates were measured at saturating CO, thus differences in the response to incident irradiance presumably resulted from complex interactions of light and leaf optical properties rather than from stomatal effects. Differences in absorptance (400-700 nm) among leaf surfaces were evident for horizontal-leaf species but the primary determinant of functional symmetry was leaf anatomy. Functionally symmetrical leaves had upper and lower palisade layers of equal thickness (vertical leaves of open habitats) or were composed primarily of a single layer of photosynthetic cells (horizontal leaves of understory habitats). Photosynthetic symmetry of vertical-leaf species may be an adaptation to maximize daily integrated carbon gain and water-use efficiency, whereas asymmetry of horizontal-leaf species may be an adaptation to maximize daily integrated carbon gain and photosynthetic nutrient-use efficiency.
针对具有不同叶片取向的植物，测量了照射在叶片正面或背面的光合光响应。对于开阔生境中的垂直叶物种（刺果蓟和松香草），无论照射哪一面，光合速率都相同。然而，对于开阔生境中的水平叶物种（豚草和加拿大一枝黄花），正面照射的光合光饱和速率比背面照射高19%至37%。林下植物（加拿大细辛和加拿大水叶）的叶片虽然呈水平取向，但功能上是对称的。在饱和二氧化碳浓度下测量光合速率，因此对入射辐照度响应的差异可能是由光和叶片光学特性的复杂相互作用导致的，而非气孔效应。水平叶物种的叶片表面在400-700纳米的吸收率存在差异，但功能对称的主要决定因素是叶片解剖结构。功能对称的叶片具有厚度相等的上下栅栏层（开阔生境的垂直叶），或者主要由单层光合细胞组成（林下生境的水平叶）。垂直叶物种的光合对称性可能是一种适应机制，可使每日综合碳增益和水分利用效率最大化，而水平叶物种的不对称性可能是一种适应机制，可使每日综合碳增益和光合养分利用效率最大化。
