Stomatal Movement in Response to Root Zone Temperature in Purple Heart (Tradescantia pallida)

The effects of root temperatures (25, 35 and 45°C) and temperature duration (30, 60 and 90 min) on net photosynthesis rate, stomatal conductance and transpiration rate in Tradescantia pallida were investigated. The experiment was conducted under controlled conditions with factorial arrangement based on a completely randomized design (CRD) and four replications. Result showed that, net photosynthesis rate was not significantly different between plants treated with 25 and 35°C. However, aperture area and width increased at 35°C and declined sharply at 45 °C as compared with that at 25 °C. Net photosynthesis rate and stomata1 conductance of plants treated with 45°C decreased to 76 and 68%, respectively, as compared with those at 35°C. Stomatal aperture area of plants treated with 35°C was 27% and 320% higher than those treated with 25 and 45°C, respectively. Stomatal resistance of plants treated with high temperature (45°C) were higher (174%) than those treated with 35°C. In 35 °C, aperture area of plants after 30 min was 61% and 45% higher than those after 60 and 90 min exposure, respectively. The results revealed that, a heat shock of roots at 45°C could lead to a significant decrease in stomatal conductance (by 81%) and transpiration rate (by 60%) as compared with those at 35°C.  Overall, the results suggest that the root temperature affects leaf gas exchange and stomatal behavior and has to be taken into account in plant production system, in particular, hydroponics.