Résumé
Temperature is one of the main factors affecting the sexual reproductive success of plants. Both Pollen Grain Germination (PGG) and Pollen Tube Growth (PTG) play a crucial role on the progamic phase that elapses from pollination to fertilization. We have studied the effects of four temperature regimes (constant 10°C, 20°C, 30°C and field conditions) in PGG and PTG in Citrus. 'Fortunr' mandarin (CItrus clementina x C. tangerina) was used as female recipient. Two adult trees of 'FOrtune' cultivated in containers were placed under each temperature regime and pollinated with three donor genotypes grown under field conditions: Clemenules clementine (C. clementina), Pineapple sweet orange (C. sinensis) and one Papeda spedies (C. ichangensis). Ten sampes per expetimental condition were collected every day during 10 consecutive days starting the day after pollination for histological studies. PGG and PTG were monitored on 13 cross sections along the pistil. This method allowed finding the distance travelled by pollen tubes every day from the surface of the stigma. Unexpectedly we observed both PGG and PTG at 10°C. This result seems to disagree with previous research in citrus which concluded that PGG in vitro does not occur at 10°C. The results also show clear differences in the kinetics of the PTG and their dependence on temperature and genotype. At 10°C Papeda and CLemenules pollen tubes reached the ovary seven days after pollination, while Pineapple pollen tubes only reached half of the style. (Texte intégral)