PLANT PHYSIOLOGY , Vol 108, Issue 1 191-197, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Lipid Composition and Protein Dynamics in Thylakoids of Two Wheat Cultivars Differently Sensitive to Drought
M. F. Quartacci, C. Pinzino, CLM. Sgherri and F. Navari-Izzo
Istituto di Chimica Agraria, Universita di Pisa, 56124 Pisa, Italy (M.F.Q, C.L.M.S., F.N.-I.)
Two wheat (Triticum durum Desf.) cultivars with different sensitivities to
drought were either grown under regular irrigation or subjected to water
deficit by withholding water for 14 d. Water-stressed plants of both
cultivars underwent similar decreases in leaf water potential, but the
drought-tolerant cultivar showed higher relative water content and turgor.
Neither osmotic nor elastic adjustment mechanisms appeared to be active
under the conditions described here. Thylakoids isolated from the stressed,
drought-tolerant wheat showed an increase in lipid-to-protein ratio, in
comparison with the control, whereas this ratio remained unchanged in the
sensitive wheat. In both cultivars, water deficit determined different
rearrangements in the composition of the thylakoid individual polar lipids,
but their unsaturation level remained unaffected with the exception of
monogalactosyldiacylglycerol. In the drought-sensitive cultivar, an
accumulation of free fatty acids together with a reduction in polar lipid
amount was observed. Electron paramagnetic resonance measurements of
spin-labeled proteins of stressed plants from the sensitive cv Adamello
showed a higher spin label rotational correlation time together with lower
sulphydryl group and mobile proteic portion levels, in comparison with the
control. In the tolerant cv Ofanto, the first two parameters changed to a
lesser extent following water depletion, and the mobile proteic portion was
not altered.
