基于红光波段日光诱导叶绿素荧光逃逸率的小麦条锈病遥感监测

    Remote sensing monitoring of wheat stripe rust based on red solar-induced chlorophyll fluorescence escape rate

    • 摘要: 小麦条锈病是影响小麦产量的主要病害之一,及时探测到病害信息对小麦条锈病的防控具有重要意义。红光波段日光诱导叶绿素荧光(red solar-induced chlorophyll fluorescence,RSIF)能够敏感反映植物光合生理状态,SIF逃逸率与冠层几何结构、叶片光学特性和植被光能利用率密切相关。为实现小麦条锈病及时准确的探测,该研究基于SIF逃逸率函数计算方式,利用野外实测数据计算不同尺度SIF(冠层尺度SIFCanopy、光系统尺度SIFPS)及其逃逸率(εCP),分析了RSIF逃逸率(RεCP)监测小麦条锈病的生理基础,探讨了条锈病胁迫下RεCP的响应特性,并将其与SIF及其衍生参数(荧光产率ФF、表观SIF产量SIFy)、归一化植被指数(normalized difference vegetation index,NDVI)、MERIS陆地叶绿素指数(MERIS terrestrial chlorophyll index,MTCI)、简单比值植被指数(simple ratio vegetation index,SR)进行比较。结果表明:RεCP与氮平衡指数(nitrogen balance index,NBI)、叶绿素(chlorophyll,Chl)、类黄酮(flavonoid,Flav)和花青素(anthocyanin,Anth)4个生理参数的相关性均达到了极显著性水平,且优于光系统尺度RSIF和远红光波段SIF(far-red solar-induced chlorophyll fluorescence,FRSIF),与叶面积指数(leaf area index,LAI)的相关性则优于冠层尺度FRSIF,RεCP能够更好地反映病害胁迫引起的作物生理和冠层结构的变化。在冠层尺度FRSIF(FRSIFCanopy)、光系统尺度FRSIF(FRSIFPS)和RSIF(RSIFPS)、红光波段表观SIF产量(RSIFy)及其荧光产率(RФF)、NDVI、MTCI、SR等特征变量中,RεCP与病情严重度(severity level,DSL)的相关性最高。低叶绿素含量(Chl≤30)和中高叶绿素含量(Chl>30)下,RεCP对小麦条锈病胁迫的响应均最为敏感,其与DSL的相关性均优于达到极显著性水平的SIF及其衍生参数和植被指数。RεCP是小麦条锈病遥感监测的适宜因子,研究结果对提高小麦条锈病的遥感监测精度具有重要意义,同时亦对其他作物胁迫的遥感监测具有一定的参考价值。

       

      Abstract: Wheat stripe rust, caused by Puccinia striiformis, is one of the most serious diseases on wheat yield. It is of great significance to timely and accurately detect the disease, in order to monitor and prevent the wheat stripe rust. The stripe rust can infect the internal physical and chemical characteristics and external morphological structure of wheat. Solar-induced chlorophyll fluorescence (SIF) can be expected for the remote sensing detection of crop stress. The red-band sunlight-induced chlorophyll fluorescence (RSIF) has more information about photosystem II (PSII), thus sensitively representing the photosynthetic physiological state of plants. The SIF escape rate is closely related to the canopy geometry, leaf optical properties, and light energy utilization efficiency of vegetation. In this study, field-measured data was used to invert and calculate the SIF and its escape rate (εCP) at different scales (canopy scale SIFCanopy and photosystem scale SIFPS) in the red and far-red band. The contents of four wheat pigments were obtained to combine the leaf area index (LAI) closely related to vegetation growth. The physiological basis of RSIF escape rate (RεCP) was determined to monitor the wheat stripe rust. Subsequently, the response characteristics of RεCP under stripe rust stress were explored to compare with the SIF and its derived parameters (fluorescence yield ФF, apparent SIF yield SIFy) in the red and far-red light bands, the normalized difference vegetation index (NDVI), the MERIS terrestrial chlorophyll index (MTCI) and the simple ratio vegetation index (SR). We also systematically analyzed the response characteristics of RεCP to disease severity level (DSL) under different DSL and chlorophyll (Chl) levels. The results revealed that the correlations between nitrogen balance index (NBI), Chl, flavonoids (Flav), anthocyanins (Anth), LAI, and DSL were all extremely significant, with the highest correlation observed between Chl and DSL. RεCP showed extremely significant correlations with NBI, Chl, Flav, and Anth, outperforming RSIF and far-red Sun-induced chlorophyll fluorescence (FRSIF) at the photosystem scale and being superior to FRSIF at the canopy scale in relation to LAI. This indicates that RεCP better reflects crop physiological and canopy structural changes induced by disease stress. Among various characteristic variables such as canopy-scale FRSIF (FRSIFCanopy), photosystem-scale FRSIF (FRSIFPS), RSIF (RSIFPS), apparent SIF yield in the red band (RSIFy), its fluorescence yield (RФF), NDVI, MTCI, and SR, RεCP exhibited the highest correlation with DSL. For both mild to moderate (0<DSL≤45%) and severe (DSL>45%) disease conditions, the correlation between RεCP and DSL was higher than that of SIF, its derived parameters, and vegetation indices, all reaching extremely significant levels. RεCP was more sensitive to changes in DSL, surpassing other parameters. Whether under low (Chl≤30) or medium-to-high (Chl>30) Chl content, RεCP demonstrated the most sensitive response to wheat stripe rust stress, with its correlation with DSL superior to the extremely significant levels achieved by SIF and its derived parameters, as well as vegetation indices. Therefore, RεCP can serve as a suitable factor for remote sensing monitoring of wheat stripe rust, which is of great significance for disease prevention and yield enhancement. This study also provides a robust reference and tool for remote sensing monitoring of crops in agricultural production, incorporating RSIF and escape ratio into remote sensing monitoring to significantly enhance the detection and monitoring of plant health status.

       

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