不同浓度镉胁迫下水稻冠层光谱特征及其预测评价

以南粳44和两优培九两个水稻品种为材料,通过盆栽试验,研究了不同浓度镉胁迫下水稻冠层光谱特征及植株各器官镉含量间的定量关系。结果表明,两水稻品种整株、茎、叶和穗各器官镉含量均随着镉胁迫处理浓度的增加而加大,且茎中含量最高;不同浓度镉污染胁迫下的水稻冠层反射光谱曲线在可见光红光波段也存在差异,随着镉处理浓度增大,光谱曲线反射值降低,去除包络线后归一化深度加大,红边位置在两个品种中有不同程度的红移。通过构建植被指数NDV(Ix)与水稻器官中镉含量的多种关系模型,比较了模型预测的显著性,分别构建了适用于两个水稻品种各器官的镉胁迫遥感监测的预测模型,南粳44分别为y整株=86.207x2-56.633x+9.7361,y茎=157.65x2-101.89x+17.317,y叶=21.619x2-14.192x+2.5283以及y穗=4.7011x2-1.4549x+0.1628;两优培九分别为y整株=41.495x2-29.34x+5.1829,y茎=53.364x2-36.778x+6.3612,y叶=22.981x2-15.768x+2.7588,y穗=36.347x2-25.477x+4.4473。进而说明,地面高光谱遥感对水稻重金属镉污染及其胁迫水平有较好的响应,可通过水稻冠层光谱的差异性分析,实现水稻镉污染的快速、无损伤探测。

Rice Canopy Spectral Characteristics and Its Forecast Evaluation Under Cadmium Stress

Relationships between rice canopy spectral characteristics and the concentration of cadmium(Cd) in each part of rice plants under different treatments of Cd levels were investigated quantificationally through pot experiments using Nanjing 44 and Liangyoupeijiu as materials.The results were as follows.The Cd contents in whole plants,stems,leaves and spikes of both rice cultivars conformably increased with the Cd stress level,among which the content of Cd in stems was always the highest.Besides,significant differences were found in the wavelength band of red light of canopy reflectance spectra curves taken under various stress levels.As Cd stress level increased,the strength of spectral reflectance reduced,the normalized value of reflectance after removing envelopes curved downward,and the red edge positions showed apparent `red-shift’ phenomena of varying degrees in these two cultivars.Mutiple relationship models were built for NVDI(x) and Cd content in rice plant organs,the significances of their prediction were compared,and eventually the prediction models for each part of the studied cultivars were formulated for use of Cd stress remote-sensing monitoring,i.e.,for Nanjing 44,ywhole-plant=86.207x2-56.633x+9.736 1,ystem=157.65x2-101.89x+17.317,yleaf=21.619x2-14.192x+2.528 3,and yspike=4.701 1x2-1.454 9x+0.162 8,while for Liangyoupeijiu,ywhole-plant=41.495x2-29.34x+5.182 9,ystem=53.364x2-36.778x+6.361 2,yleaf=22.981x2-15.768x+2.758 8,and yspike=36.347x2-25.477x+4.447 3.Given these results,we conclude that field hyperspectral remote sensing is capable of responding fairly well to Cd stress of rice plants and also to the stress levels,enabling a method of fast and undamaging probe of rice Cd pollution through difference analysis of rice canopy spectra.