Hyperspectral Analysis and Electrolyte Leakage Inversion of Creeping Bentgrass under Salt Stress
XIAO Guo-zeng1, 2, WU Xue-lian3, TENG Ke1, CHAO Yue-hui1, LI Wei-tao4, HAN Lie-bao1, 2*
1. Institute of Turfgrass Science, Beijing Forestry University, Beijing 100083, China 2. The College of Horticulture and Garden, Yangtze University, Jingzhou 4340252, China 3. The College of Economics & Management, Huazhong Agriculture University, Wuhan 430070, China 4. Geography Information and Tourism College, Chuzhou University, Chuzhou 239000, China
Abstract：Leaf electrolyte leakage is an important index of the plant cell permeability which plays an important role in the study of turfgrass salt stress. Traditional methods of measuring leaf electrolyte leakage have many disadvantages such as time-consuming, destroying the plants and being unable to monitor salt stress in large area. The aim of this study is to build a hyperspectral inversion model for leaf electrolyte leakage of creeping bentgrass under different salt concentration stresses thus to promote the application of the hyperspectral techniques in turfgrass salt stress monitoring. Creeping bentgrass was used in this study, and it was grown in water for two weeks before salt treatments. Leaves were collected at 7, 14 and 21 d under 0(CK), 100 and 200 mmol·L-1 NaCl respectively. The spectral values were gathered using Unispec-SC Spectral Analysis System (PP SYSTEMS，USA)before collecting grass leaves. Leaf electrolyte leakage was measured with electrical conductivity method. The relation and differences between salt treatments and spectral reflectance values were analyzed with EXCEL. Normalized difference vegetation index (NDVI) and difference vegetation index (DVI) were calculated using the spectral reflectance values. The first-order differential was calculated with difference method. The trilateral parameters of the blue, green and red rays were calculated at the meantime. The correlation analysis of the Leaf electrolyte leakage, spectral reflectance value, DVI and trilateral parameters was achieved by using EXCEL and Matlab software. Electrolyte leakage inversion model of the calibration set consisted of 48 high correlational samples, was built using unary linear regression, multivariate linear regression and partial least-squares regression methods. The prediction set inspection inversion model was established using the other 24 samples. The results showed that there is a positive correlation between salt stresses and 450～700 nm wave band. The leaf electrolyte leakage was positively associated with 450～732 nm band region at 0.01. The green edge amplitude and area of green edge were correlated with the foliar electrolyte leakage positively. Models based on partial least squares regression could inversion the foliar electrolyte leakage optimally. The calibration R2 reached to 0.681, and the validation R2 reached to 0.758. The calibration RMSE was 7.124, and the validation RMSE reached to 7.079. The inversion model made it possible to detect creeping bentgrass leaf electrolyte leakage under salt stress rapidly. This study also provided theoretical reference for monitoring the damage of other creeping bentgrass related plant species resulted by salt stress.
Key words：Hyperspectral;Salt stress;Turfgrass;Creeping bentgrass;Electrolyte leakage;Inversion model
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