小麦条锈病胁迫下光合速率与光谱指数关系研究

Study on Relationship Between Photosynthetic Rate and Hyperspectral Indexes of Wheat Under Stripe Rust Stress

为应用遥感技术进行小麦条锈病的实时监测以及大范围作物病害识别,明确条锈病胁迫下小麦光谱反射率和净光合速率与病情指数的关系,利用光谱植被指数预测小麦光合速率的变化,在2018年—2019年度冬小麦生长季节,以易感条锈病的济麦15号小麦品种为对照,以生产上播种面积较大的济麦22和鲁原502为供试品种,基于大田小区条锈病接种试验,从抽穗期到乳熟期,每隔7~10 d进行小麦旗叶光合速率、光谱反射率测定及病情指数调查。研究发现,随感病程度加重,小麦旗叶光合速率呈显著下降趋势,扬花期济麦22光合速率高于鲁原502。灌浆期可见光波段,病斑部位的光谱反射率始终高于正常部位,这是由于病斑部位叶片单位面积上叶绿素含量较低,对光吸收的少;而在反射平台区域,病斑部位的光谱反射率较正常叶低得多。利用与病害胁迫、生长状况以及产量相关较大的光化学反射指数(photochemical reflectance index,PRI)、植被衰减指数(plant senescence reflectance index,PSRI)和比值植被指数(ratio vegetation index,RVI)来反映病情指数变化,结果显示,病斑部位的光化学反射指数和植被衰减指数大于正常部位,且植被衰减指数变化率较大,而比值植被指数变化率小于正常部位。小麦不同生育期,光合速率与光谱反射率的相关性不同,模拟光合速率的植被指数也不同。灌浆期,鲁原502的光合速率与光谱反射率始终呈正相关关系;在可见光范围内,对照光合速率与光谱反射率呈正相关,济麦22呈负相关;在反射率平台位置,对照光合速率与光谱反射率呈负相关,济麦22呈正相关。在小麦灌浆期,可以利用植被衰减指数进行病害程度识别及光合速率估测。该研究为利用遥感手段大面积监测小麦长势及病害发生情况提供了理论依据,也为探讨利用光谱指标无损监测的方法预测小麦条锈病发生及危害程度奠定了基础。

For real-time monitor of wheat stripe rust and large-scale recognization of crop diseases using remote sensing technology,the relations of wheat spectral reflectivity and net photosynthetic rate with disease index were studied under stripe rust stress,and the variation of photosynthetic rate was estimated with spectral vegetation indexes.The stripe rust inoculation test was conducted in field plots during the 2018—2019 wheat growth period.The varieties of Jimai 22 and Luyuan 502 with larger sowing areas were used as test materials,and Jimai 15,sensitive to stripe rust,was used as control.The photosynthetic rate and spectral reflectivity of wheat flag leaves were determined,and the disease index was investigated every 7~10 days from heading stage to milk-ripe stage.It was found that the photosynthetic rate decreased significantly with the increase of disease degree.During the flowering stage,the photosynthetic rate of Jimai 22 was higher than that of Luyuan 502.During the grain filling stage,the reflectivity in the visible spectrum range was higher at the diseased part because of lower chlorophyll content leading to lower absorption but the higher reflex of light.However,in the range of reflection platforms,the spectral reflectivity of the diseased part was much lower than that of the healthy part.The indexes related to disease stress,crop growth and yields,such as photochemical reflectance index(PRI),plant senescence reflectance index(PSRI)and ratio vegetation index(RVI)were used to reflect the variation of the disease index.Compared with the healty part,the PRI and PSRI of the diseased part were high,and the change ratio of PSRI was higher;the RVI of diseased part was lower.At different growth stages of wheat,there were different correlations between photosynthetic rate and spectral reflectivity,and the vegetation index was also different.At the grain filling stage,the correlation between photosynthetic rate and spectral reflectivity of Luyuan 502 was positive in all spectrum ranges,and that of Jimai 15 was also positive in visible spectrum range,while that of Jimai 22 was negative.However,in the range of reflectance platform,that of Jimai 15 and Jimai 22 was opposite.The PSRI could be used to recognize disease degree and estimate the photosynthetic rate in the grain filling period of wheat.These results could provide theoretical bases for monitoring wheat growth status and disease occurrence at a large scale using remote sensing method and layed foundations for estimating wheat stripe rust occurrence and degrees using lossless monitoring spectral indicators.