Effect of High Temperature on Photosynthesis in Beans (II. CO2 Assimilation and Metabolite Contents)

Abstract

The effect of high temperatures on CO, assimilation, metabolite content, and capacity for reducing power production in nonphotorespiratory conditions has been assessed in two different bean (Phaseolus vulgarus 1.) varieties, Blue Lake (commercially available i n the United Kingdom) and Barbucho (a noncommercially bred Chilean variety), which are known to differ in their resistance to extreme high temperatures. Barbucho maintains its photosynthetic functions for a longer period of time under extreme heat compared with Blue Lake. The CO, assimilation rate was increased by increases in temperature, with a decrease in ratio of rates at temperatures differing by 10°C. It is suggested that limitations to CO, assimilation are caused by metabolic restrictions that can be differentiated between those occurring in the range of 20 to 30°C and 30 to 35°C. It is likely that changes i n the capacity for Calvin cycle regeneration and starch synthesis affect photosynthesis in the range of 20 to 30°C. But following an increase in temperature from 30 to 35"C, the supply of reducing power becomes limiting. From analysis of adenylate concentration, transthylakoid energization, and, indirectly, NADPH/NADP+ ratio, it was concluded that the limitation in the assimilatory power was due to an oxidation of the NADPH/ NADP+ pool. In the range of 30 to 35"C, the photosystem I quantum yield increased and photosystem II maintained its value. We conclude that the reorganization of thylakoids observed at 30 to 35°C increased the excitation of photosystem I, inducing an increase in cyclic electron transport and a decrease in the supply of NADPH, limiting carbon assimilation.High temperatures affect photosynthesis by altering the excitation energy distribution by changing the structure of thylakoids (Berry and Bjorkman, 1980;Weis and Berry, 1988) and by changing the activity of the Calvin cycle and other metabolic processes such as photorespiration and product synthesis. Much of the attention has been focused on the former aspect, since thylakoids are highly sensitive to heat, whereas the restrictions imposed by high temperatures on carbon metabolism have been nearly exclusively interpreted as the effect on CO, ' Supported by a scholarship to C.P. from the Ministry of Planning of the Chilean Government.Present address: Facultad de Ciencias Agrarias y Forestales, Departamento de Producción Agrícola, Universidad de Chile, Casilla 1004, Santiago, Chile.* Corresponding author; e-mail cpasteneQabello.dic.uchi1e.cl; fax 562-678-5700.availability. The diffusion of CO, and O, and the affinity for carboxylation of the Rubisco enzyme have been proven to be affected by increasing temperatures (Hall and Keys, 1983;Jordan and Ogren, 1984; Brooks and Farquhar, 1985), but it has been argued that the stimulation of photorespiration cannot fully explain the effect of high temperature. It has been suggested that a restricted electron transport may limit RuBP supply (Berry and Bjorkman, 1980).It also has to be considered that changes in temperature induce variati...

Effects of water and temperature stresses on radiation use efficiency in a semi-arid grassland

“…For example, Andrade et al (1992) showed that the temperature from 15 to 188C during the vegetative period caused low RUE in maize. Also, high temperature (increased respiration sometimes above the rate of photosynthesis) had negative effects on crops (Pastenes and Horton 1996;Monneveux et al 2003). In a previous study, decreased precipitation as combined with high temperature showed a considerable negative effect on pasture production in southern Mongolia (Munkhtsetseg et al 2007).…”

Drought and extreme temperature tolerance for <em>Tillandsia dasyliriifolia</em>, an epiphytic bromeliad from the northern coastal dune scrubland in Yucatan, Mexico

“…Temperature regulates most of the basic aspects of cell metabolism; high temperatures denature enzymes and lower temperatures freeze tissues and damage cell membranes (Palta et al, 1993;Pastenes and Horton, 1996). Furthermore, most plants grow best when temperatures fluctuate at least a 6 to 7 ºC between day and night (Lüttge, 2004).…”

Effect of Rubisco Activase Deficiency on the Temperature Response of CO2 Assimilation Rate and Rubisco Activation State: Insights from Transgenic Tobacco with Reduced Amounts of Rubisco Activase

“…These groups suggest that Rubisco deactivation at high temperature may be a regulatory response to the limitation of one of the processes contributing to electron transport capacities. For example, at high temperature, protons can leak through the thylakoid membrane, impairing the coupling of ATP synthesis to electron transport (Pastenes and Horton, 1996;Bukhov et al, 1999Bukhov et al, , 2000. As the electron transport capacity becomes limiting, ATP/ADP ratios and the redox potential of the chloroplast decline, causing a loss of Rubisco activase activity and, in turn, a reduction in the Rubisco activation state (Zhang and Portis, 1999;Zhang et al, 2002;Sage and Kubien, 2007).…”