THE IN VIVO TOLERANCE OF PHOTOSYNTHETIC MEMBRANES TO HIGH AND LOW TEMPERATURES IN CULTIVATED AND WILD WHEATS OF THE TRITICUM AND AEGILOPS GENERA

摘要

Chlorophyll fluorometry was used to determine the in vivo tolerance of the photochemical function of photosynthesis to high and low temperatures in leaves of five durum wheat varieties (Triticum turgidum ssp. durum), one wild Triticum ( I: turgidum ssp. dicoccoides) and accessions of six Aegilops species (Ae. longissima, Ae. geniculata, Ae. speltoides, Ae. umbellulata, Ae. triuncialis, Ae. neglecta). All the Aegilops genotypes examined were more sensitive to chilling stress than durum wheat whereas the score of I: dicoccoides was intermediate. A strong variability for heat tolerance was observed between the durum wheat varieties, with the threshold temperature for photosystem-II denaturation (in plants grown at ca. 25 degrees C in a greenhouse) ranging from ca. 35 degrees C (in the variety Durelle) to almost 41 degrees C (in Cham-l). The heat tolerance of the wild wheats was between these extremes. When the heat tolerance of the photosynthetic membranes of cultivated and wild wheats was plotted as a function of their chilling tolerance, a negative linear correlation was obtained, with the notable exception of the Cham-l variety of durum wheat which was robust to both heat stress and chilling stress. Qualitatively similar results were obtained with plants grown in the field during the summer season. The relatively poor adaptation of the photosynthetic membranes of Aegilops to unfavorable temperature conditions raises questions about the usefulness of this genus for improving temperature-stress tolerance of photosynthesis in wheat.