New Normalized Difference Reflectance Indices for Estimation of Soil Drought Influence on Pea and Wheat

Abstract

Soil drought is an important problem in plant cultivation. Remote sensing using reflectance indices (RIs) can detect early changes in plants caused by soil drought. The development of new RIs which are sensitive to these changes is an important applied task. Previously, we revealed 46 normalized difference RIs based on a spectral region of visible light which were sensitive to the action of a short-term water shortage on pea plants under controlled conditions (Remote Sens. 2021, 13, 962). In the current work, we tested the efficiency of these RIs for revealing changes in pea and wheat plants induced by the soil drought under the conditions of both a vegetation room and open ground. RI (613, 605) and RI (670, 432) based on 613 and 605 nm wavelengths and on 670 and 432 nm wavelengths, respectively, were effective for revealing the action of the soil drought on investigated objects. Particularly, RI (613, 605) and RI (670, 432) which were measured in plant canopy, were significantly increased by the strong soil drought. The correlations between these indices and relative water content in plants were strong. Revealed effects were observed in both pea and wheat plants, at the plant cultivation under controlled and open-ground conditions, and using different angles of measurement. Thus, RI (613, 605) and RI (670, 432) seem to be effective tools for the remote sensing of plant changes under soil drought.

Modified Photochemical Reflectance Indices as New Tool for Revealing Influence of Drought and Heat on Pea and Wheat Plants

“…Analysis of influence of the soil drought on PRI(λ,570) measured in the canopy of plants included two variants of experiments: (i) wheat and pea plants were cultivated under conditions of a vegetation room and (ii) wheat plants were cultivated under open-ground conditions [ 65 ].…”

“…We used the spectra of reflected light and photosynthetic parameters, which were measured in experiments for our previous work [ 65 ]; only unpublished data were used.…”

“…Thus, we hypothesized that using the modified photochemical reflectance indices [ 50 ] can be more effective for revealing photosynthetic changes under action of stressors (drought and heat) than using typical PRI(531,570); to evaluate this hypothesis was the main objective of the current work. For the solution of this task, we analyzed our unpublished results of experiments described in works [ 59 ] and [ 65 ], which were devoted to the analysis of reflectance indices in spatially-fixed leaves under short-term water shortage and heat stress and the same analysis in plant canopies under the prolonged soil drought. Wheat and pea were used as suitable model plants because the reflectance of these objects was investigated in our previous works [ 43 , 44 , 49 , 50 , 59 , 60 , 65 ]; the investigations simplified the current analysis.…”

“…For the solution of this task, we analyzed our unpublished results of experiments described in works [ 59 ] and [ 65 ], which were devoted to the analysis of reflectance indices in spatially-fixed leaves under short-term water shortage and heat stress and the same analysis in plant canopies under the prolonged soil drought. Wheat and pea were used as suitable model plants because the reflectance of these objects was investigated in our previous works [ 43 , 44 , 49 , 50 , 59 , 60 , 65 ]; the investigations simplified the current analysis. Additionally, both pea and wheat are important agricultural crops that can be strongly affected by drought and heat [ 1 , 2 , 3 ].…”

Traits contributing to salinity tolerance in rice genotypes from the Mekong Delta

“…In our study, under both NaCl treatments, SPAD (Appendix ) was most negatively correlated to Cl − concentration and closely associated with tolerant avoiders. PRI also indicates photosynthetic stress, particularly in response to Cl − content in the leaf (Sukhova et al., 2023). The determination of ion content is destructive and time consuming.…”