Ehleringer J R, Björkman O
Department of Biological Sciences, Stanford University, 94305, Stanford, CA, USA.
Department of Plant Biology, Carnegie Institution of Washington, 94305, Stanford, CA, USA.
Oecologia. 1978 Jan;36(2):151-162. doi: 10.1007/BF00349805.
The effects of leaf hairs (pubescence) on leaf spectral characteristics were measured for the drought-deciduous desert shrub Encelia farinosa. Leaf absorptance to solar radiation is diminished by the presence of pubescence. The pubescence appears to be reflective only after the hairs have dried out. There are seasonal changes in leaf absorptance; leaves produced at the beginning of a growing season have high absorptances, whereas leaves produced during the growing season are more pubescent and have lower absorptances. The decrease in leaf absorptance is the result of an increase in pubescence density and thickness. Between 400 and 700 nm (visible wavelengths), pubescence serves as a blanket reflector. However, over the entire solar spectrum (400-3000 nm), the pubescence preferentially reflects near infrared radiation (700-3000 nm) over photosynthetically useful solar radiation (400-700 nm). Leaf absorptance to solar radiation (400-3000 nm) varies between 46 and 16%, depending on pubescence; whereas leaf absorptance to photosynthetically useful radiation (400-700 nm) may vary from 81 to 29%.
针对干旱落叶沙漠灌木粉叶毛头鬼伞，测量了叶毛（柔毛）对叶片光谱特征的影响。柔毛的存在会降低叶片对太阳辐射的吸收率。柔毛似乎只有在变干后才具有反射性。叶片吸收率存在季节性变化；在生长季开始时产生的叶片具有较高的吸收率，而在生长季期间产生的叶片柔毛更多且吸收率较低。叶片吸收率的降低是柔毛密度和厚度增加的结果。在400至700纳米（可见光波长）之间，柔毛起到了类似毯子的反射作用。然而，在整个太阳光谱（400 - 3000纳米）范围内，柔毛优先反射近红外辐射（700 - 3000纳米）而非光合有效太阳辐射（400 - 700纳米）。叶片对太阳辐射（400 - 3000纳米）的吸收率因柔毛情况而异，在46%至16%之间；而叶片对光合有效辐射（400 - 700纳米）的吸收率可能从81%变化到29%。
