PROSPECT模型的特定吸收系数的测定方法和叶绿素a和b的反演研究

In vivo determination of specific coefficients in PROSPECT model is critical since they link the optical and biochemical properies together. PROSPECT model has long been not successful for retrieval of chlorophyll a and b due to lack of methodology for measurement of the specific coefficients. The main objectives of this study are to establish an experimental method for in vivo measurement of the specific absorption coefficients of chlorophyll a and b in intact leaves and improve the PROSPECT model for retrieval of chlorophyll a and b by input of the determined specific coefficients and those derived by minimizing the merit function.Direct comparison between simulated and measured reflectance (and transmittance) will be made to assess the performance of the improved model in terms of accuracy of fit. The experimental method is based on derivation of a large size of leaf samples with special compositions of chlorophyll a and b by use of chlorophyll b deficient rice mutant and low chlorophyll b rice mutant，induction of far red light and low nitrogen treatment under greenhouse conditions.The in vivo specific absorption coefficients of chlorophyll a and b will be determined by calculating the difference in absorptance of the leaves very close in the biophysical and biochemical parameters (e.g. leaf area, water, dry weight, cellulose, lignin, carotenoids) but only different in chlorophyll a or b.The leaf spectral features of the chlorophyll b deficient rice mutant and low chlorophyll b rice mutant will be extracted for construction of new spectral vegetation indices for retrieval of chlorophyll a and b by using new constructed hyperspectral vegetation indices.

由于缺乏在活体条件下测定叶片的特定吸收系数的实验方法，长期以来PROSPECT模型不能分别反演叶绿素a和b。本研究通过选用低叶绿素b突变体和叶绿素b缺失突变体水稻以及常规水稻品种为材料，在温室条件下采用远红光诱导和低氮处理的方法培养出大量的在叶绿素a和b方面组成特殊的叶片样品，从中筛选出其他生物物理化学参数（干物重、叶面积、木质素、纤维素、类胡萝卜素、水分）相近而只在叶绿素含量有差异的叶片样本，进而找出只有叶绿素a或b含量差异的特殊样本，测定叶片的吸收光谱，通过分析计算这些样本间在叶绿素吸收区域的吸收率差异，计算叶绿素a和b的特定吸收系数。将测得的特定吸收系数输入PROSPECT模型，用最小化代价函数方法获得其他特定吸收系数，建立改进的模型，以能分别反演叶绿素a和b。同时，在提取叶绿素b缺失突变体叶片光谱特性基础上，研究用新构建的高光谱植被指数分别反演叶绿素a和b的方法。

我们选择了8个叶绿素b缺失水稻突变体材料和6个野生型水稻品种，设计三个供氮/供磷水平，在温室条件下连续进行了三年的水培试验，测定了水稻叶片在400-900nm区域的吸收光谱和在350-2500nm区域的反射光谱，并分析了水稻叶片的色素（叶绿素a/b、类胡萝卜素、花菁素）组成、水分、叶面积、叶厚度等参数。对数据进行了多种模型分析，并研究了用新构建的高光谱植被指数分别反演叶绿素a和b的方法。主要成果如下：..1 通过实测数据，计算获得了在活体条件下水稻叶绿素a和b的特定吸收系数曲线（400-900nm）,从而为PROSPECT模型的改进奠定了基础。.2 构建了基于叶绿素中心波段（The in-chlorophyll centre waveband (ICCW)）反射的新型植被指数DFDS_ICCW，该植被指数能分别精确反演水稻的叶绿素a和b的浓度。在此基础上，发现用DFDS_ICCW代替其他叶绿素植被指数的红波反射，可得到改进的植被指数，改进的植被指数比原植被指数在反演叶绿素时精度显著提高。.3 在做水稻水培实验时，我们偶然发现植物与藻具有显著的共生互惠关系，在此基础上我们发明了生态水培方法。该技术在作物和藻的农场化生产及废水的生态修复方面具有广阔的应用前景。