Stomatal and leaf hydraulic conductivity responses to changing light and CO₂ conditions in Phaseolus vulgaris

Extreme conditions brought up by climate change have a negative impact on plant photosynthesis. However, characterizing and exploiting extant genetic variation in plants for structure and function could lead to the assembly of genotypes adapted to extreme environments. This could be accomplished by combining suitable structures and adaptive mechanisms. We selected two common bean genotypes from the Andean (Calima) and the Mesoamerican (Jamapa) gene pools and analyzed their leaf structural characteristics, leaf hydraulics, and stomatal responses to transient light and CO₂. We used the patterns of stomatal conductance to water vapor (g_sw) to track the time for stomatal stability between the two genotypes. Our results indicated contrasting leaf structures and differences in potential leaf hydraulic conductivity (Ks) and the flow rate of water in the leaf. We also found faster stomatal responses to light and CO2 for smaller stomata. Our data also indicate that leaf structural traits in the two genotypes were constructed in coordination to support efficient physiological processes. We analyzed the dynamics of water loss, and our results agree with the differences seen in stomata density and the speed to stomata response indicating that Jamapa retains more residual water than Calima. These results showed far-reaching consequences of leaf structure and hydraulics on photosynthetic gas exchange responses under global warming conditions.