Effect of long-term photoinhibition on growth and photosynthesis of cold-hardened spring and winter wheat

✍ Scribed by Vaughan M. Hurry; Marianna Krol; Gunnar Öquist; Norman P. A. Huner

• Publisher: Springer-Verlag
• Year: 1992
• Tongue: English
• Weight: 841 KB
• Volume: 188
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00192804

✦ Synopsis

The effect of repeated exposure to high light (1200 lamol" m-2.s-1 photosynthetic photon flux density, PPFD) at 5 ~ C was examined in attached leaves of cold-grown spring (cv. Katepwa) and winter (cv. Kharkov) wheat (Triticum aestivum L.) over an eight-week period. Under these conditions, Kharkov winter wheat exhibited a daily reduction of 24% in Fv/FM (the ratio of variable to maximal fluorescence in the dark-adapted state), in contrast to 41% for cold-grown Katepwa spring wheat. Both cultivars were able to recover from this daily suppression of Fv/Fu such that the leaves exhibited an average morning Fv/FM of 0.651• Fluorescence measurements made under steady-state conditions as a function of irradiance from 60 to 2000 gmol-m-2. sindicated that the yield of photosystem II (PSII) electron transport under light-saturating conditions was the same for photoinhibited and control cold-grown plants, regardless of cultivar. Repeated daily exposure to high light at low temperature did not increase resistance to short-term photoinhibition, although zeaxanthin levels increased by three-to fourfold. In addition, both cultivars increased the rate of dry-matter accumulation, relative to control plants maintained at 5 ~ C and 250 ~tmol 9 m -2 9 s -t PPFD (10% and 28% for Katepwa and Kharkov, respectively), despite exhibiting suppressed Fv/FM and reduced photon yields for 02 evolution following daily high-light treatments. Thus, al-