Abstract
Temperature is one of the main environmental factors involved in global warming and has been found to have a direct effect on plants. However, few studies have investigated the effect of higher temperature on tropical crops. We therefore performed an experiment with a tropical crop of Habanero pepper (Capsicum Chinense Jacq.). Three growth chambers were used, each with 30 Habanero pepper plants. Chambers were maintained at a diurnal maximum air temperature (DMT) of 30 (chamber 1), 35 (chamber 2) and 40°C (chamber 3). Each contained plants from seedling to fruiting stage. Physiological response to variation in DMT was evaluated for each stage over the course of five months. The results showed that both leaf area and dry mass of Habanero pepper plants did not exhibit significant differences in juvenile and flowering phenophases. However, in the fruiting stage, the leaf area and dry mass of plants grown at 40°C DMT were 51 and 58% lower than plants at 30°C DMT respectively. Meanwhile, an increase in diurnal air temperature raised both stomatal conductance and transpiration rate, causing an increase in temperature deficit (air temperature – leaf temperature). Thus, leaf temperature decreased by 5°C, allowing a higher CO2 assimilation rate in plants at diurnal maximum air temperature (40°C). However, in CO2 measurements when leaf temperature was set at 40°C, physiological parameters decreased due to an increase in stomatal limitation. We conclude that the thermal optimum range in a tropical crop such as Habanero pepper is between 30 and 35°C (leaf temperature, not air temperature). In this range, gas exchange through stomata is probably optimal. Also, the air temperature–leaf temperature relationship helps to explain how temperature keeps the major physiological processes of Habanero pepper healthy under experimental conditions.
Highlights
Temperature is one of the main conditions that influence plant growth and productivity
In the fruiting phenophase, the leaf area and dry mass of plants grown at 40uC diurnal maximum air temperature (DMT) were 51 and 58% lower than plants at 30uC DMT respectively (Figures 1A and 1B)
Dry mass proportion of Habanero pepper plants changed in each phenology stage
Summary
Temperature is one of the main conditions that influence plant growth and productivity. Crop yield is the end result of a chain of physiological events that begins with CO2 diffusion into the leaf air space through the stomata, leading to CO2 assimilation. This affects the accumulation of biomass and its allocation to different organs, which depends on both the net carbon balance and their programmed growth and expansion [8]. A given change in temperature has a greater effect on the leaf mass production of tropical species (some changes in the physiological mechanism of plants have been observed) [3], [6]. The optimal temperature that maximizes the photosynthetic rate increases with rising growth temperature
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