Photosynthetic pigments and gas exchange in castor bean under conditions of above the optimal temperature and high CO2

Abstract

The castor bean plant, a Euphorbiaceae oil seed C₃-metabolism rustic and drought-resistant plant, is cultivated in a wide range of environments due to its good adaptive capacity. However, given the current environmental changes, many biochemical and physiological impacts may affect the productivity of important crops, such as castor bean. This work aimed to evaluate the impacts of the castor bean gas exchange in response to high temperature and increased CO₂concentration.Our experiment was conducted in a phytotron located at Embrapa Algodão in 2010. We adopted a completely randomized design, with four treatments in a factorial combination of two temperatures (30/20 and 37/30°C) and two CO₂ levels (400 and 800 mmol L^-1); four replications were performed, obtained in five surveys over the growth cycle, for a total of 80 sample units. An infrared gas analyzer (IRGA - Infra Red Gas Analyzer) was used for the quantification of the photosynthetic rate, stomatal conductance and transpiration. An increase in the atmospheric CO₂ concentration and temperature negatively affected the physiology of the castor bean plants, decreasing the net rate of photosynthesis, transpiration and stomatal conductance.