Persistence of photosynthetic components and photochemical efficiency in ears of water stressed wheat (Triticum aestivum)

MARTINEZ, DANA; LUQUEZ VIRGINIA M.C.; BÁRTOLI CARLOS; GUIAMÉT JUAN J.

PHYSIOLOGIA PLANTARUM

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2003 vol. 119 p. 519 - 525

0031-9317

Ear photosynthesis may be an important source of C for graingrowth in water-stressed plants of cereals. The main objectivesof this work were to determine the stability of the photosyntheticapparatus and the photochemical efficiency of earsin plants subjected to post-anthesis drought. Plants of wheat(Triticum aestivum L. cv. Granero INTA) were grown in potsunder a rain shelter and subjected to water stress (soil waterpotential around - 0.6 to - 0.8 MPa) starting 4 days afteranthesis. Post-anthesis drought substantially accelerated theloss of chlorophyll, Rubisco and the light-harvesting complexof photosystem II (LHCII) in the flag leaf, but the degradationof these photosynthetic components was much lessaffected by water deficit in awns and ear bracts. Quantumyield of PSII (FPSII) decreased in leaves of water-stressedplants. In contrast, ear bracts had a higher FPSII than leaves,and FPSII of ear bracts did not decrease at all in response todrought. Removing the grains immediately before fluorescencemeasurements (less than 30 min) slightly reduced FPSII, indicatingthat CO2 supplied by grain respiration may contributeto the high photochemical efficiency of ears in droughtedplants. However, other factors may be involved in maintaininghigh FPSII, since even in the absence of grains FPSII remainedmuch higher in ear bracts than in the flag leaf. The relativestability of ear photosynthetic components and their relativelyhigh photochemical efficiency may help to maintain ear photosynthesisduring the grain filling period in droughted plants.