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以黄萎病胁迫下棉花叶片为试验材料,分析感染病害棉叶叶绿素(Chl)含量和氮素含量(LNC)与光谱红边参数间的关系,建立病害棉叶Chl含量和LNC的光谱红边参数诊断模型。结果表明:(1)随着病情加重,棉叶Chla、Chlb、Chla+b和LNC逐渐减小,其中Chla下降最快,Chlb下降最慢。(2)黄萎病叶片光谱反射率在可见光区(400~700nm),近红外光区(700~1300nm)和短波红外光区(1300~2500nm)呈现逐渐上升趋势,在520~680nm间达极显著(P<0.01);光谱吸收率在可见光区和短波红外光区呈现逐渐下降的趋势,达极显著(P<0.01),在近红外光区呈现先升后降的趋势。(3)病害棉叶红边位置(REP)、红边振动幅(Dr)、红谷位置(Lo)、红边深度(Depth672)和红边面积(Area672)的值均减小,红边宽度(Lwidth)的值增加,且Area672减小的幅度最大,Dr减小的幅度最小,Lwidth增加的幅度较大。(4)病害棉叶Chla含量、Chlb含量、Chla+b含量和LNC均与红边参数REP、Lo、Depth672和Area672呈极显著正相关,与Lwidth呈极显著负相关,与Dr未达显著相关。(5)利用红边参数建立的棉叶Chl含量和LNC的诊断模型均达极显著(P<0.01),其中以Area672为自变量建立的病害棉叶Chla、Chla+b和LNC的诊断模型和Lo为自变量建立的Chlb诊断模型的精度最高,能很好的诊断病害棉叶Chl含量和LNC。
The relationship between chlorophyll (Chl) content and nitrogen content (LNC) and spectral red edge parameters of infected cotton leaves was analyzed using cotton leaves under the stress of Verticillium dahliae. The relationship between Chl content and red edge Parameter diagnosis model. The results showed that: (1) Chla, Chlb, Chla + b and LNC decreased with the aggravation of disease, of which Chla decreased the fastest and Chlb decreased the slowest. (2) Spectral reflectance of Verticillium wilt leaves showed a gradual upward trend in the visible (400 ~ 700nm), near infrared (700 ~ 1300nm) and shortwave infrared (1300 ~ 2500nm) (P <0.01). The spectral absorptivity tended to decrease in the visible and shortwave infrared regions (P <0.01), and then increased in the near infrared region and then decreased in the near infrared region. (3) The values of REP, RH, Lo, Depth672 and Area672 of cotton leaf decreased, red edge width (Lwidth) increases, and Area672 decreases the most, Dr decreases the least, Lwidth increases more. (4) The Chla content, Chlb content, Chla + b content and LNC of cotton leaf had extremely significant positive correlation with red edge parameters REP, Lo, Depth672 and Area672, but significant negative correlation with Lwidth and not significantly correlated with Dr . (5) The diagnosis model of Chl content and LNC in cotton leaves established by using red edge parameters were all significant (P <0.01), and the diagnosis model of Chla, Chla + b and LNC in cotton leaves with Area672 as independent variable and The Chlb diagnostic model established by Lo for the independent variables has the highest precision and can well diagnose the Chl content and LNC of the diseased cotton leaves.