Abstract

Leaf water status information is highly needed for assessing high temperature stress. Leaf equivalent water thickness (fresh weight − dry weight)/area) is commonly used functional plant trait. Retrieval of leaf equivalent water thickness based on hyperspectral remote sensing has been shown to be rapid and accurate. However, a universal index that is applicable to various plants remains a considerable challenge. Few attempts had been made to monitor kiwifruit leaf equivalent water thickness using hyperspectral vegetation indexes under high temperature stress. In this study, a high temperature stress experiment was conducted in ambient conditions on 29 July–1 August 2021 during the kiwifruit expansion period to obtain a leaf spectrum dataset in the laboratory after the high temperature (above 35 °C) duration time for 1, 2, 3, and 4 days. This study systematically analyzed the performance of hyperspectral vegetation indexes of kiwifruit in estimating leaf equivalent water thickness with the range of 0.02–0.04 g/cm². Newly developed and published spectral indexes were calculated to estimate kiwifruit leaf equivalent water thickness. Results showed that the newly developed three-band vegetation index (R₂₀₃₉ − R₂₄₃₈)/R₇₅₂ generated the optimal testing performance for estimating kiwifruit leaf equivalent water thickness, with the coefficient of determination of 0.771, root mean square error of 0.0024 g/cm², and residual prediction deviation of 2.09, respectively. This study suggests that the kiwifruit leaf equivalent water thickness under high temperature stress could be accurately estimated based on leaf level spectral indexes.

摘要

评估高温胁迫非常需要叶片水分状态信息。叶当量水分厚度（鲜重-干重）/面积）是常用的植物功能性状。基于高光谱遥感的叶片等效水厚度的反演已被证明是快速和准确的。然而，适用于各种植物的通用指数仍然是一个相当大的挑战。在高温胁迫下使用高光谱植被指数监测猕猴桃叶片等效水厚度的尝试很少。本研究于 2021 年 7 月 29 日至 8 月 1 日在奇异果膨大期在环境条件下进行了高温胁迫实验，以在实验室获得高温（35 °C 以上）持续时间 1, 2、3 和 4 天。² . 计算新开发和公布的光谱指数来估计猕猴桃叶等效水厚度。结果表明，新开发的三波段植被指数(R ₂₀₃₉  − R ₂₄₃₈ )/R ₇₅₂对估计猕猴桃叶片等效水厚度的测试性能最优，决定系数为0.771，均方根误差为0.0024 g/ cm ²和残差预测偏差分别为 2.09。本研究表明，基于叶级光谱指数可以准确估算高温胁迫下猕猴桃叶片等效水分厚度。