ABNORMALITIES IN THE MALE DEVELOPMENTAL PROGRAM OF WINTER-WHEAT INDUCED BY CLIMATIC STRESS AT MEIOSIS

From the onset of meiosis, wheat plants, cv Moulin and Pernel, were su bjected to climatic stress for 7 days in a growth chamber. The stress conditions (11 mu mol.m(-2).s(-1) photosynthetic photon flux density, 1.5/8 degrees C night/day, 12.5 h photoperiod) were chosen so that the stress affected the grain set in a similar way to low radiation, poss ibly associated with chilling in the field. Control plants received 20 3 mu mol.m(-2).s(-1) photosynthetic photon flux density, 15/18 degrees C temperatures and 16 h photoperiod. In stressed plants, the grain se t was reduced due to poor fertilization, as shown by the absence of de velopment of endosperms from the embryo sacs. Male development was aff ected: anthers were frequently small, curved or shrivelled, and did no t dehisce. Pollen release was limited and the pollen load on the stigm a was low. Pollen viability (fluorochromatic reaction) was altered, bu t pollen grains were normally trinuclear at anthesis. Female fertility was unaffected. Both varieties showed the same alterations.