Abstract
Relatively little research has assessed the impact of spectral differences among dorsiventral leaves caused by leaf structure on leaf chlorophyll content (LCC) retrieval. Based on reflectance measured from peanut adaxial and abaxial leaves and LCC measurements, this study proposed a dorsiventral leaf adjusted ratio index (DLARI) to adjust dorsiventral leaf structure and improve LCC retrieval accuracy. Moreover, the modified Datt (MDATT) index, which was insensitive to leaves structure, was optimized for peanut plants. All possible wavelength combinations for the DLARI and MDATT formulae were evaluated. When reflectance from both sides were considered, the optimal combination for the MDATT formula was ( R 723 − R 738 ) / ( R 723 − R 722 ) with a cross-validation R2cv of 0.91 and RMSEcv of 3.53 μg/cm2. The DLARI formula provided the best performing indices, which were ( R 735 − R 753 ) / ( R 715 − R 819 ) for estimating LCC from the adaxial surface (R2cv = 0.96, RMSEcv = 2.37 μg/cm2) and ( R 732 − R 754 ) / ( R 724 − R 773 ) for estimating LCC from reflectance of both sides (R2cv = 0.94, RMSEcv = 2.81 μg/cm2). A comparison with published vegetation indices demonstrated that the published indices yielded reliable estimates of LCC from the adaxial surface but performed worse than DLARIs when both leaf sides were considered. This paper concludes that the DLARI is the most promising approach to estimate peanut LCC.
Highlights
Peanut (Arachishypogaea L.) is one of the major food legumes as well as oilseed crops being grown in 118 countries around the world on about 28 million ha of land [1], and offers multiple benefits to meet human nutritional needs as well as being an important resource in the context of food security and hunger issues [2]
The objectives of this work were to (1) analyze spectral differences in the adaxial and abaxial surfaces of peanut leaves; (2) identify the optimal wavelengths of the modified Datt (MDATT) for estimating peanut Leaf chlorophyll content (LCC); (3) develop a novel index based on a four-band combination to reduce spectral differences in dorsiventral leaves for improving LCC retrieval; (4) compare the performance of the indices developed in this study with those widely used in the literature
The results demonstrated that the wavelengths used in the dorsiventral leaf adjusted ratio index (DLARI) were similar to those used in the MDATTs (Table 2)
Summary
Peanut (Arachishypogaea L.) is one of the major food legumes as well as oilseed crops being grown in 118 countries (or regions) around the world on about 28 million ha of land [1], and offers multiple benefits to meet human nutritional needs as well as being an important resource in the context of food security and hunger issues [2]. Leaf chlorophyll content (LCC) is an important indicator of plant photosynthesis [3], nutritional state [4], and stress [5]. Decades of research have gone into determining wavelength regions sensitive to LCC in order to develop indices to maximize the accuracy of retrieval for different types of plants [9,10,11]. Datt [12] developed a three-band index for retrieval of LCC in higher plants based on the different response of reflectance at 710 nm and 850 nm to LCC. Gitelson et al [14] proposed an index (RnirRred-edge − 1), which is an effective LCC predictor for maple, chestnut, wild vine, and beech leaves
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