Temperatures during flower bud development affect pollen germination, self-incompatibility reaction and early fruit development of clementine (Citrus clementina Hort. ex Tan.)

One of the key environmental factors affecting plant reproductive systems is temperature. Characterising such effects is especially relevant for some commercially important genera such as Citrus. In this genus, failure of fertilisation results in parthenocarpic fruit development and seedlessness, which is a much-prized character. Here, we characterise the effects of temperature on flower and ovary development, and on pollen-pistil interactions in Comune' clementine (Citrus clementina Hort. ex Tan.). We examine flower bud development, invitro pollen germination and pollen-pistil interaction at different temperatures (15, 20, 25 or 30 degrees C). These temperatures span the range from cold' to hot' weather during the flowering season in many citrus-growing regions. Temperature had a strong effect on flower and ovary development, pollen germination, and pollen tube growth kinetics. In particular, parthenocarpic fruit development (indicated by juice vesicle growth) was initiated early if flowers were exposed to warmer temperatures during anthesis. Exposure to different temperatures during flower bud development also alters expression of the self-incompatibility reaction. This affects the point in the pistil at which pollen tube growth is arrested and confirms the role of sub- and supra-optimal temperatures in determining the numbers of pollen tubes reaching the ovary.