Effects of drought on stomatai resistance, surface resistance and leaf temperature in four common bean genotypes (Phaseolus vulgaris L.)

Stomatai resistance (rL), surface resistance (rs) and leaf temperature (TL) are important physiological variables for the understanding of the interaction between the soil, plant, and atmosphere. These variables are used to study the response of plants to abiotic stress conditions, such as drought and high temperature, in addition to micrometeorological variables such as évapotranspiration (ET). The goal of this research was to measure the n_, rs and TL of four genotypes of common bean (Phaseolus vulgaris L.) under drought and non-drought conditions in a greenhouse environment. Three drought-tolerant genotypes were studied, BAT 477, SER 16 and SER 21, and one drought susceptible genotype, Morales. Three water regimes were used: full water supply (FWS) using 80% of the water required for soil saturation (WS) during the complete growing season; Stress 1 (S1) with 50% of WS before flowering and 60% of WS after flowering; and Stress 2 (S2) with 20% of WS before flowering and 40% of WS after flowering. Measurements were taken throughout the day at different stages of growth. The results show that there were differences in the rL, rs and TL between genotypes and between water levels, especially during the afternoon. The major differences were found between treatments S1 and S2 during reproductive development. The rL, rs and TL responded directly to the substrate water status and the rate of change was influenced by hour of the day. TL showed a linear relationship with air temperature, and the slope increased with water stress and had a polynomial relationship with η_.