Photosynthetic response of wheat cultivar to long-term exposure to elevated temperature

Abstract

Wheat (Triticum aestivum L. cv. HD 2285) was grown in control (C) and heated (H) open top chambers (OTCs) for entire period of growth and development till maturity. The mean maximum temperature of the entire period was 3 ºC higher in H-compared to C-OTCs. Net photosynthetic rate (P N ) measured at different temperature (20−40 ºC) of C-and H-grown plants showed greater sensitivity to high temperature in H-plants. P N measured at respective growth temperature was lower in H-compared to C-plants. The CO 2 and irradiance response curves of photosynthesis also showed lesser response in H-compared to C-plants. The initial slope of P N versus internal CO 2 concentration (P N /C i ) curve was lower in H-than C-plants indicating ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) limitation. In irradiance response curve, the plateau was lower in H-compared to C-plants which is interpreted as RuBPCO limitation. RuBPCO content in the leaves of C-and H-plants, however, was not significantly different. Ribulose-1,5-bisphosphate carboxylase (RuBPC) initial activity was lower in H-plants, whereas activity of fully activated enzyme was not affected, indicating a decrease in activation state of the enzyme. This was further substantiated by the observed decrease in RuBPCO activase activity in H-compared to C-plants. RuBPCO activase was thus sensitive even to moderate heat stress. The decrease in P N under moderate heat stress was mainly due to a decrease in activation state of RuBPCO catalysed by RuBPCO activase.Additional key words: CO 2 and irradiance response curves; internal CO 2 concentration; ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBPCO) content and activation state; RuBPCO activase.

Climate Impacts on Agriculture: Implications for Crop Production

“…Optimum temperature ranges for photosynthetic rate in wheat is 20 to 30ºC (Kobza and Edwards, 1987) and is 10ºC higher than the optimum temperature (15ºC) for grain yield and single grain growth rate (Chowdhury and Wardlaw, 1978). Pushpalatha et al (2008) observed that rubisco activity decreased in wheat plants with a reduction in the photosynthetic rate when wheat plants were exposed to high temperatures. Increases of temperature above 25 to 35ºC, common during grain fi lling of wheat, will shorten the grain fi lling period and reduce wheat yields.…”

Heat Stress in Wheat during Reproductive and Grain-Filling Phases

“…1). Note: Data taken from Al-Khatib and Paulsen (1984); Amani et al (1996); Anjum et al (2008); Anwar et al (2007); Asseng et al (2010); Barnabás et al (2008); Blum et al (2001); Calderini et al (1999); Ferris et al (1998);Fischer (1980Fischer ( , 1985; Fokar et al (1998); Gibson and Paulsen (1999); Guedira et al (2002); Pushpalatha et al (2008);Rahman et al (1977); Samra and Singh (2005); Shewry (2009); Spiertz et al (2006); Nicolas (1994, 1995a, b); Stone et al (1995); van Herwaarden et al (1998);Wardlaw (1994); Wollenweber et al (2003); Yang et al (2002); Zhao et al (2007Zhao et al ( , 2008. Wheeler et al, 1996a,b).…”

The chlorophyll a fluorescence as an indicator of the temperature stress in the leaves of Prunus persica

“…Photosystem I (PSI) is stimulated by heat (as measured by the rate of P700 + reduction) due to greater reduction of the plastoquinone (PQ) pool by ferredoxin (Fd) at high temperatures (Tóth et al, 2007). In contrast, photosystem II (PSII), particularly the oxygen-evolving complex (OEC), is deactivated even at slightly elevated temperatures (Yamane et al, 1998), demonstrating that this process is especially sensitive to temperature stress (Pushpalatha et al, 2008).…”