Analysis of the Reflectance Spectral Characteristics of the Greenhouse Cucumber under Different Water and Nitrogen Conditions

The correlation of the cucumber reflectance spectrum characteristics under different water and nitrogen conditions were studied. The results indicate that the spectral reflectance rate of greenhouse cucumber leaves decreases in the visible light band, while increasing in the near-infrared band with the rise of water and nitrogen supply levels. In the picking period, the red trough reflectance rate of cucumber is negatively correlated with the leaf photosynthesis rate under high water condition (W₁) while having a positive correlation with the latter under a low water condition (W₂). Spectral indices such as WI₁ /NDVI (675, 1050) have an extremely evident correlation with such indices as leaf water potential. The analysis indicate that reflectance spectral technology can be used to monitor the water and nitrogen supply levels of plants in greenhouse and forecast the leaf photosynthesis rate and water shortage.