PLANT PHYSIOLOGY , Vol 101, Issue 1 245-250, Copyright © 1993 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Low-Temperature Effects on Photosynthesis and Correlation with Freezing Tolerance in Spring and Winter Cultivars of Wheat and Rye
G. Oquist, V. M. Hurry and NPA. Huner
Department of Plant Sciences, University of Western Ontario, London, Canada N6A 5B7 (V.M.H., N.P.A.H.)
Winter cultivars of rye (Secale cereale L., cv Musketeer) and wheat
(Triticum aestivum L. cvs Kharkov and Monopol), but not a spring cultivar
of wheat (Glenlea), grown at cold-hardening temperatures showed, at high
irradiances, a higher proportion of oxidized to reduced primary, stable
quinone receptor (QA) than did the same cultivars grown under nonhardening
conditions. In addition, there was a positive correlation between the
effects of low-growth temperature on this increased proportion of oxidized
QA, and a concomitant increase in the capacity for photosynthesis, and
LT50, the temperature at which 50% of the seedlings are killed, in
cultivars showing different freezing tolerances. This suggests that
low-temperature modulation of the photosynthetic apparatus may be an
important factor during the induction of freezing resistance in cereals.
Finally, the control of photosystem II photochemistry by nonphotochemical
quenching of excitation energy was identical for nonhardened and
cold-hardened winter rye. However, examination of measuring temperature
effects per se revealed that, irrespective of growth temperature,
nonphotochemical quenching exerted a stronger control on photosystem II
photochemistry at 10[deg] C rather than at 20[deg] C.
