Correlation between Canopy Spectral Vegetation Index and Leaf Stomatal Conductance in Rapeseed (Brassica napus L.)

It plays a very important role for improving water use efficiency of crops and predicting crop yield and quality to monitor leaf stomatal conductance with real time, non-destructively and quantitatively by using canopy spectral characteristics. In the paper, the spectral reflectance, leaf stomatal conductance, LAI (leaf area index), leaf fresh and dry biomass of two rapeseed varieties were determined in a field experiment by split-plot design with the main plot of N levels and the subsidiary plot of culti- vars, 3 replications, and plot area of 4.3 m by 7.0 m in 2007–2008. The changes in leaf stomatal conductance and the correlation between leaf stomatal conductance and spectral vegetation index were analyzed based on the vegetation index combined with spectral reflectance in all kinds of bands. The estimating models for spectral vegetation index of leaf stomatal conductance were established according to the relationship between spectral vegetation index and leaf stomatal conductance. The results showed that there were two peaks in changes carve of leaf stomatal conductance, and one peak in the changes curve of LAI, leaf fresh and dry biomass in the whole growth period. There existed significantly positive correlation between spectral vegetation index and leaf stomatal conductance or canopy leaf stomatal conductance before flowering, and the spectral vegetation index better fitted into canopy average stomatal conductance than into leaf stomatal conductance. The quantitative relationships between spectral vegeta- tion index and canopy leaf stomatal conductance laid the foundation for rapid and non-destructive stomatal conductance estimates in a large area of rapes in future.