Photosynthetic response of wheat cultivar to long-term exposure to elevated temperature |
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Authors: | P Pushpalatha P Sharma-Natu M C Ghildiyal |
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Institution: | (1) Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi, 110012, India |
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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 °C higher in H-compared to C-OTCs. Net photosynthetic
rate (P
N) measured at different temperature (20–40 °C) 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 CO2 and irradiance response curves of photosynthesis also showed lesser response in H-compared to C-plants. The initial slope
of P
N
versus internal CO2 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. |
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Keywords: | Additional" target="_blank">Additional CO2 and irradiance response curves internal CO2 concentration ribulose-1 5-bisphosphate carboxylase/oxygenase (RuBPCO) content and activation state RuBPCO activase |
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