Study On Response Of Spectral Characteristics And Rice Growth Of The Rice Under Different Concentrations Of Lead Pollution Stress

It is very meaningful for the healthy diet security of human beings to use Remote sensing technology to identify and monitor the heavy metal pollution of corps. This paper inspects the typical rice field in Yanbian state and estimates the underlying ecological hazard of the local rice soil. And it takes lead, which is the uppermost heavy metal pollution source in the local region, as the object of study,to do the pot experiment of rice in the garden house of Yanbian University with7different concentration of lead pollution. After analyzing the correlation of spectral characteristics change, chlorophyll content changes, the output of rice in the whole growth period of rice, it gains the related the response relationship. Its conclusions are as followings:(1) The main heavy metal pollution condition in the research area.The paper evaluates the soil environment quality in the research area in the method of geological accumulation index and potential ecological harm index based in the heavy metal content limit evaluation standard of Soil Environmental Quality Standards (GB15618-1995)It turns out that Pb pollution is relatively serious, which reaches strong medium pollution-pollution levels, and the pollution level of As and Cd reaches light to medium inferior to Pb, while Cr、Cu、Zn are almost unpolluted. Based in geological accumulation index method the sequence of soil environmental pollution levels range from serious to slight is:Pb>As=Cd>Cr=Cu=Zn. In terms of the single ecological hazard index of heavy metals, the main potential ecological harm heavy metals are Pb and Cd and both of them reaches medium ecological damage, while other4kinds are slight ecological damage and their potential ecological damage sequence is Pb>Cd>As>Cu>Zn>Cr.The result of Ri value reaching126.74shows the study area is in the slight ecological damage. The conclusion is that lead is the most serious heavy metal pollution source.(2)Analyze rice leaf spectral characteristic variation law and determine the best monitoring band under the different lead pollution stresses.The study extracts the new spectral feature parameters, and the spectral reflectance of the "green mountain" and "red valley" in spectral curve has been through the0.05significance test, when discrepancy significances of the bands520-580nm,680-720nm and750-800nmare all above90%.The results shows that Pb makes spectral reflectance characteristic of rice changed520-800nm band and its rangeability and Pb content are positive correlation, especially the very obvious change in630-720nm band. Only Da,Db,Dc of spectral characteristic parameters has higher correlation with Pb content in rice, and their Multiple correlation coefficient are respectively R2Da=0.721,R2Db=0.522,R2Dc=0.369,among them the highest is Da. So the response of rice spectral feature parameters in520-800nm band to Pb content can be the effective means for estimating Pb pollution.(3) Distribution characteristics of soil lead levels in rice and chlorophyll content change rule under the different lead pollution stresses.With the increase of Pb concentration, Pb content is also increasing in rice stem and roots, and it is up to the highest under the concentration of1300mg/kg. This conclusion states low concentration of Pb can promote the normal growth of rice, for example, cauline leaf nitrate reduce activity, soluble sugar content and chlorophyll content all have different degrees of increase, but if the absorptive Pb concentration is too much, Pb will begin to restrain the growth of rice, even seriously hinder normal physiological activities of rice with the average symptom of yellowing and chlorine of rice leaves.That Low concentration of Pb pollution (Pb content<1300mg/kg) makes Chlorophyll SPAD values increase, while high concentration of Pb (Pb content<1300mg/kg) leads to the decrease of chlorophyll content in seedling stage states Pb pollution make destructive effect of chloroplasts in rice leaf significantly increasing. In the early time of stem tillering, chlorophyll content has been also increasing at first with the more obvious tendency than in seedling stage states, but when Pb concentration reaches900mg/kg, it starts to drop. The above discussion shows the increase of Pb concentration will badly damage chloroplast in rice leaf and the correlation of Pb pollution is more outstanding in the early time of stem tillering than in seedling stage.(4) Change law of rice growth under the different lead pollution stresses.In terms of plant height, the increase of Pb concentration under the different soil Pb pollution in soil leads to the plant height of rice decline in turn.The plant height starts to change after three weeks of transplant and the height of the plant vary from15%to20%till CK is mid2800mg/kg. For rice plants underground part, with the increase of Pb concentration, rice root length will be shorter. The research made by Zhou Yong found that in the splitting millet period low concentration of Pb had no adverse effect on the growth of rice in acid purple soil and when its concentration reached around1000mg/kg,it just had inhibitory effect on plant height and tillering, however, when its concentration reached3000mg/kg, rice growth significantly reduced. This phenomenon is similar to this study results, besides it also found that cumulative quantity of Pb increased in rice organs as the concentration of Pb in soil increased, and its regularities of distribution is:Root> leaf> stem. In the aspect of adventitious roots, with the increase of Pb concentration, rice root length will be also shorter, but the number of adventitious roots in the basement is increasing. In booting stage, when soil Pb pollution is respectively in the concentration of300mg/kg>800mg/kg、1300mg/kg、1800mg/kg、2300mg/kg、2800mg/kg, rice underground internode length is1.0cm,2.1cm,2.7cm,3.0cm,3.4cm,4.0cm,4.3cm. In the aspect of fruiting, with the increase of Pb concentration in soil, rice plants of single stem total grains and seed setting rate fell, the rate of shell and BiGu rate rise. Especially when the Pb concentration in soil is more than1300mg/kg, the average setting rate of rice plants falls fast. Among them, the rate of decline is the most obvious by6.9%when soil Pb concentration in the condition of1300mg/kg. Production is the most obvious by11.8%when soil Pb concentration in the condition of800mg/kg.