重金属铜和锌胁迫下的小麦冠层反射光谱特征

Wheat canopy spectral reflectance feature response to heavy metal copper and zinc stress

目前关于土壤重金属污染对作物的光谱影响仍然处于探索阶段,受植物种类和环境等因素的影响,植物重金属胁迫机理的诊断仍存在不明确的问题,作物不同生长阶段对不同重金属的耐受程度存在差异。为了探究快速监测作物受重金属污染胁迫状况,采用田间小区试验,利用光谱分析方法研究了土壤重金属不同质量分数铜(0、100、300、600、900 mg/kg)和锌(0、250、500、750、1 000 mg/kg)处理下小麦分蘖期、拔节期和抽穗期冠层光谱特征。结果表明,小麦在分蘖期和拔节期冠层光谱在可见光(350~760 nm)波段内反射率总体随着铜、锌污染浓度的增加而升高,而在近红外(760~900 nm)波段内反射率随铜、锌处理浓度的增加而降低;分蘖期不同浓度铜、锌处理下,小麦冠层光谱出现红边蓝移和红谷蓝移现象;分蘖期铜处理在600、900 mg/kg和拔节期铜处理在900 mg/kg下小麦红边归一化指数值(NDVI705)均低于0.2;分蘖期锌处理在750和1 000 mg/kg下小麦红边归一化指数值(NDVI705)均低于0.2;该试验中引起小麦受到胁迫作用冠层光谱响应的铜临界浓度介于300与600 mg/kg之间,而锌临界浓度介于500与700 mg/kg之间。

With the rapid development of economy and modern industrial and agriculture, more and more heavy metals such as cadmium, copper and zinc come into environment. Heavy metals are not only polluting soil, water and air, but also affecting crops growth and the yield, and affecting food security and human health by food chain. It was reported that heavy metal contamination of arable land in China has reached 20 million hm-2, accounting for the country＇s total cultivated area of 1/6. Therefore, many researchers pay more attention to the heavy metal pollution problems increasingly. At present, researchers usually use chemical and biological methods to test the pollution extent of different heavy metals. Those methods are time consuming and even cause the second environmental pollution. Using spectral analysis to monitor the heavy metals stress on crops is an innovative approach. However, the effect of heavy metal pollution on crops spectrum is still in the exploration stage. Because of the effect of different factors such as plants and environment, the diagnosis of heavy metal stress mechanism on plant is still unclear. The crop tolerance at different growth stages are different from heavy metals, therefor, to explore the critical concentration of different heavy metals stress on crops at the different growth stages has certain practical significance. In order to monitor the crop stress of heavy metal pollution rapidly, under open field plot conditions and using canopy spectral analysis, the canopy spectral features of wheat at different stages of tillering, jointing and heading were studied at the different treatments of Cu（0, 100, 300, 600 and 900 mg/kg） and Zn（0, 250, 500, 750 and 1 000 mg/kg）, according to the national soil quality standard（GB15618-1995） of China. The experiment was conducted in the experimental field of Qingdao Academy of Agricultural Sciences in Chengyang District of Qingdao City, in October 2014 to June 2015. The total area of the test plot was 180 m-2, and the test soil type is Shajiang black soil, with the p H value of 6.85, the organic matter content of 22.6 g/kg, nitrogen content of 94.6 mg/kg, available phosphorus content of 77.5 mg/kg, the available potassium content of 113 mg/kg, copper content of 28.1 mg/kg and zinc content of 73 mg/kg. The experiment was conducted by traditional management. The results indicated that at different concentration treatments of copper（Cu） and zinc（Zn）, the canopy spectral reflectance in the visible band（350-760 nm） increased obviously with the concentration treatments increasing of Cu and Zn at the tillering and jointing stages of wheat, however, the canopy spectral reflectance of near infrared band（760-900nm） reduced with the increasing concentration of Cu and Zn treatment levels. Wheat canopy spectral reflectance appeared red edge position and red valley position shifting toward short wavelength called ＂blue shift＂ at tillering stage of wheat under the different concentration treatments of Cu and Zn. At the tillering stage of wheat, copper treatments of 600 and 900 mg/kg and at the jointing stage copper treatment of 900 mg/kg, the red edge normalized index value（NDVI705） were less than 0.2. At the tillering stage, zinc treatments of 750 and 1 000 mg/kg, the red edge normalized index value（NDVI705） was less than 0.2. This research also indicated that the wheat canopy spectral features response obviously to the threshold values concentration treatment level of Cu were between 300 and 600 mg/kg, and Zn were between 500 g and 750 mg/kg.