JXB Advance Access originally published online on May 8, 2007
Journal of Experimental Botany 2007 58(8):2133-2143; doi:10.1093/jxb/erm067
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Response of photosynthetic apparatus to moderate high temperature in contrasting wheat cultivars at different oxygen concentrations
1Institute of Plant Physiology and Genetics, National Academy of Sciences of Ukraine, 31/17 Vasylkivska St., Kyiv 03022, Ukraine
2Plant Research Unit, Division of Environmental and Applied Biology, University of Dundee at SCRI, Invergowrie, Dundee DD2 5DA, Scotland, UK
* To whom correspondence should be addressed. E-mail: h.g.jones{at}dundee.ac.uk
The photosynthetic responses to moderately high temperatures (38 °C, imposed at 21% or 2% O2 in air and 1500 µmol 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.
Key words: Heat-tolerance, high temperature, photosynthetic limitation, photosystem II, Triticum aestivum L
Received 27 October 2006; Revised 13 February 2007 Accepted 7 March 2007