Response of photosynthetic apparatus to moderate high temperature in contrasting wheat cultivars at different oxygen concentrations
Authors: Stasik, Oleg; Jones, Hamlyn G.
Source: Journal of Experimental Botany, Volume 58, Number 8, 24 June 2007 , pp. 2133-2143(11)
Publisher: Oxford University Press
Abstract:The photosynthetic responses to moderately high temperatures (38 C, imposed at 21% or 2% O2 in air and 1500 mol m2 s1) were compared in wheat (Triticum aestivum L.) cultivars grown in northern regions of Ukraine and expected to be relatively sensitive to high temperatures (North cultivars) and in cultivars grown in southern regions and expected to be relatively heat-tolerant (South cultivars). Heating intact leaves in 21% O2 for 1 h decreased CO2 assimilation by c. 63% in North cultivars and only c. 32% in South cultivars, with a decrease in PSII activity being observed in only one of the North cultivars. Carboxylation efficiency was decreased by about 2.7-fold in North cultivars with no significant effect in South cultivars. The maximum rates of carboxylation by Rubisco in vivo, Vcmax, estimated from Farquhar's model, increased more than 2-fold in South cultivars and remained unchanged in North cultivars while the maximum rate of RuBP regeneration, Jmax, decreased by 53% and 21% in North and South cultivars, respectively. Where the heat treatment was imposed in 2% O2 this increased (as compared with treatment at 21% O2) the inhibitory effect on CO2 assimilation in tolerant cultivars, but decreased it in sensitive ones. The results suggested that differences in tolerance of moderately high temperatures in wheat relate to the stability of the Rubisco function and to RuBP regeneration activity rather than to the effects on PSII activity or stomatal control.
Document Type: Research article
Publication date: 2007-06-24
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