Evaluation of the effects of increasing temperature on the transpiration rate and canopy conductance of soybean by using the sap flow method

Abstract

This study aimed to investigate the effects of increasing temperature on the transpiration rate and canopy conductance of soybean grown in temperature gradient chambers under drought and wet conditions. The heat balance method was used to measure the transpiration rate from sap flow; additionally, canopy conductance was continuously estimated from the transpiration rate and vapor pressure deficit (VPD). An increase of 3℃ in temperature resulted in an increased transpiration rate but decreased canopy conductance. Further, the differences in canopy conductance observed at high and low temperature treatments were more remarkable during the morning than around noon. This suggested that there was concomitant increase in VPD with increasing temperature when solar radiation was low during the morning. Although the transpiration rate and canopy conductance decreased during drought conditions, the overall tendency of the response to the changes in temperature and VPD was similar to those in the well-watered condition. The partial correlation coefficients between canopy conductance and VPD were negative when the temperature effect was held constant. However, those between canopy conductance and temperature showed opposite trends in the two years of study-negative in 2011 but positive in 2012. These results suggest that the decrease of canopy conductance in a high temperature treatment is more likely caused by increasing VPD than by increasing temperature itself.

Multiple Effects of CO <SUB>2</SUB> Concentration and Humidity on Leaf Gas Exchanges of Sweet Pepper in the Morning and Afternoon

“…2-a). This can be attributed to the lower GS level in the afternoon than in the morning, similar to that frequently observed in various crops such as rice (Yoshimoto et al, 2005), corn (Yasutake et al, 2006), soybean (Nakano et al, 2015), and pear (orchard) (Morandi et al, 2014). Similar to the observations in the morning (Fig.…”

Variation in canopy conductance of Cunninghamia lanceolata forest and its response to environmental factors after an extreme rainfall event

“…The strong sunlight in the afternoon causes a reduction in stomatal behaviour. This variation pattern was consistent with previous studies' results on the daytime variation of g c , such as temperate Japanese cypress forest after wetness ended (Jiao et al, 2021), Eucalyptus crebra and Callitris glaucophylla forests (Whitley et al, 2009) and Eucalyptus globulus trees (Quentin et al, 2011) in arid Australia, experimental farm under drought and wet conditions in Japan (Nakano et al, 2015). When the temperature increased, the increase of the vapour pressure in the lower stomatal cavity was greater than that of the air vapour pressure, thus the increase of the VPD made the water escape in the leaves of plants and strengthened the transpiration rate (Wu et al, 2022).…”

UAV-based thermal imaging in the assessment of water status of soybean plants

“…On this date, the lowest difference in temperature (0.2°C) was observed among treatments, most likely due to VPD (0.30 kPa), which was the lowest among all evaluations (Figure 8). Once again, our data confirm the relationship between the transpiration of soybean plants and VPD (Seversike et al 2013;Devi, Taliercio, and Sinclair 2015) and between the transpiration of soybean plants and stomatal conductance (Wilson and Bunce 1997;Nakano et al 2015). Thus, it must be emphasized that small VPD (0.30 kPa) may have resulted in a wide stomatal opening and consequently leaf cooling in all treatments.…”

“…In soybean plants, transpiration is regulated by VPD (Seversike et al 2013;Devi, Taliercio, and Sinclair 2015). Thus, an increase in VPD leads to a decrease in stomatal conductance (Wilson and Bunce 1997;Nakano et al 2015) in order to prevent excessive transpiration. In this way, plants grown under appropriate water availability (e.g.…”