Abstract
Common bean is a plant species cultivated around the globe. The objective of this study was to demonstrate how the physiological parameters associated with transpiration, photosynthesis and ethylene production vary in common bean plants under different periods without irrigation. Three experiments were carried out to assess leaf water potential, stomatal conductance, transpiration, carbon assimilation, and ethylene production as a function of different irrigation intervals. A fourth experiment with exogenous application of abscisic acid (ABA) in plants with daily irrigation was also carried out. In all experiments there was a reduction in stomatal conductance at the very early period without irrigation, which consequently influenced transpiration and carbon assimilation. It was also verified that the exogenous application of ABA caused a reduction on ethylene production in common bean plants. The relationship between increased ABA production and the reduction of ethylene production is discussed.
Highlights
A large amount of world’s common bean production is made under conditions susceptible to water deficit along the crop life cycle
Ramalho et al (2013) demonstrated this fact by exposing three different bean varieties to atmosphere with enhanced CO2 concentration during the light period of the day, which led the plants to maintain a maximum carbon assimilation rate (Amax), indicating that the increase of the CO2 concentration in the atmosphere exceeded the low conductance and that the reduction in photosynthesis during this period was only due to stomatal closure and not due to biochemical inhibition processes
Experiment I represented a period of no irrigation for maximum of 6 days for both vegetative and reproductive phases of the crop
Summary
A large amount of world’s common bean production is made under conditions susceptible to water deficit along the crop life cycle. In a study on the in vivo photosynthetic parameters characterization, Pimentel et al (2011) concluded that at 25 °C, the BRS-Pérola cultivar of common bean plants at the phenological stage R5 and in optimal water conditions presented a maximum carbon assimilation rate (Amax) of 20 μmol[CO2] m-2 s-1 at an atmospheric concentration of carbon dioxide equal to 380 μmol[CO2] mol-1of air, and was saturated at the rate of 25 μmol[CO2] m-2 s-1 at an atmospheric concentration of carbon dioxide between 600 and 800 μmol[CO2] mol-1 of air, with a maximum stomatal conductance (gs) of 0.4 mol[H2O] m-2 s-1. Ramalho et al (2013) demonstrated this fact by exposing three different bean varieties to atmosphere with enhanced CO2 concentration during the light period of the day, which led the plants to maintain Amax, indicating that the increase of the CO2 concentration in the atmosphere exceeded the low conductance and that the reduction in photosynthesis during this period was only due to stomatal closure and not due to biochemical inhibition processes.
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