Salinity stress effects on transpiration and plant growth under different salinity soil levels based on thermal infrared remote (TIR) technique

Abstract

Soil salinization is a serious land degradation issue in Northwest China and significantly threatens food security; thus, a comprehensive understanding of plant response to salinity stress is desirable. The objective was to detect the effect of salinity stress on alfalfa transpiration rate and plant growth under four salinity levels. The thermal infrared remote (TIR) technique was used to acquire the canopy temperature of plants exposed to four salinities (no salinity, S0; slight salinity, S3; moderate salinity, S5; and severe salinity, S7), while transpiration was evaluated based on the three temperature (3 T) model. Results indicated that the 3 T model and TIR technique successfully simulated transpiration with a high coefficient determination of R2 above 0.8. The general pattern is that canopy temperature values correspond well with salinity values. With the increase of soil salinity for the treatment of S3, S5, and S7, the canopy temperature increased by 0.88 °C, 0.98 °C, and 1.19 °C, respectively. Moreover, the growth of alfalfa was inhibited, resulting in a corresponding decrease in leaf area index by 19.3%, 31.2%, and 54.2%, respectively. Transpiration reduced by 1.2%, 6.7%, and 20.0%, correspondingly, because of stunted growth and less canopy cover. Salinity stress on agricultural crops was extremely negative; the higher the soil salinity was, the lower the canopy cover, so salinity reduced the growth rate and resulted in reduced plants growing due to osmotic effects. Where salt accumulation occurs in a horizontally nonuniform way, transpiration may be presented by spatial heterogeneity; however, there remains limited research on this issue. This research will provide a scientific basis for ecological construction programs.