Gausman H W, Allen W A, Cardenas R, Richardson A J
Appl Opt. 1970 Mar 1;9(3):545-52. doi: 10.1364/AO.9.000545.
Cotton plants were grown hydroponically with controlled environment. Third, growth chamber grown true leaves of cotton plants were tagged on the day they became macroscopically visible. Beginning 3.0 days after tagging,five leaf harvests representing maturity dates were made at successive 2- or 3-day intervals. Measurements with a spectrophotometer made on the leaves showed that the largest increase in reflectance, about 5%, and decrease in transmittance, about 8%, occurred between average values for after-tagging-ages of 3.5 days and 8.0 days over the 0.75-1.35-micro wavelength interval. Between after-tagging-ages of 3.5 days and 8.0 days, leaves expanded approximately fivefold, numbers of intercellular spaces approximately doubled, and thicknesses increased 14%. The theory of diffuse reflectance and transmittance of a compact leaf of equivalent water thickness (EWT) specified by D is generalized to include also the noncompact leaf characterized by many intercellular air spaces, can be regarded as a pile of N compact layers separated by infinitesimal air spaces. The void area index (VAI) of a noncompact leaf is given by N - 1, where N is not necessarily an integer. Predictions from the generalized theory include a measure of the water, air, and plant pigments in a leaf. An effective dispersion curve associated with the leaf surfaces is also obtained. A derived parameter D/N largely determines the reflectance and transmittance of a typical leaf over the 1.40-2.50-micro spectral range. A cotton leaf is highly compact when it first unfolds. At this point D/N ~ 180 micro. This value is essentially the leaf thickness. Intercellular air spaces develop rapidly during the next few days, and D/N decreases in value to about 130 micro Subsequently, the leaf cells increase in size with no substantial further increase in the number of intercellular air spaces. This final growth phase is characterized by a slight increase in D/N to a maximum value of about 140 micro. Maximum reflectance of the leaf corresponds to a minimum value of D/N. The parameter D/N is highly correlated with the amount of intercellular air spaces in a leaf.
棉花植株在可控环境下进行水培种植。第三，对生长箱中生长的棉花植株真叶在肉眼可见当天进行标记。标记后3.0天开始，每隔2天或3天进行5次叶片采收，代表不同的成熟日期。用分光光度计对叶片进行测量，结果显示，在0.75 - 1.35微米波长区间内，标记后3.5天至8.0天的平均龄期之间，反射率最大增加约5%，透过率最大降低约8%。在标记后3.5天至8.0天之间，叶片面积大约扩大了五倍，细胞间隙数量大约增加了一倍，厚度增加了14%。由D规定的等效水厚度（EWT）的致密叶片的漫反射和透射理论被推广，以包括具有许多细胞间隙的非致密叶片，这种叶片可被视为由无限小的空气间隙分隔的N个致密层的堆叠。非致密叶片的空隙面积指数（VAI）由N - 1给出，其中N不一定是整数。广义理论的预测包括对叶片中水分、空气和植物色素的一种度量。还获得了与叶片表面相关的有效色散曲线。一个推导参数D/N在很大程度上决定了典型叶片在1.40 - 2.50微米光谱范围内的反射率和透射率。棉花叶片刚展开时非常致密。此时D/N约为180微米。这个值基本上就是叶片厚度。在接下来的几天里，细胞间隙迅速发育，D/N值降至约130微米。随后，叶片细胞增大，细胞间隙数量没有进一步大幅增加。这个最终生长阶段的特征是D/N略有增加，达到最大值约140微米。叶片的最大反射率对应于D/N的最小值。参数D/N与叶片中细胞间隙的数量高度相关。
