OVULE ABORTION IN WHITE CLOVER (TRIFOLIUM-REPENS L)

Plants of white clover (Trifolium repens L.) cv. Olwen were grown in a n open glasshouse maintained at a mean temperature of 20 degrees C and ovule growth and seed production measured. Differences in the rate of growth of ovules within ovaries were observed as early as 2 days afte r pollination. Ovules reached a maximum size after 8 days with the sma llest only half the size of the largest. After 8 days, the smallest ov ules became flaccid and shrivelled. Ovule position within the ovary ha d little effect on the frequency of seed set and although there was an apparently higher probability that central ovules produced a seed tha n those nearer the peduncle or style this was not statistically signif icant. Inflorescence position and floret position on the inflorescence had a significant effect on the number of seeds per floret and seed w eight; the first formed inflorescences and the first florets to be pol linated on each inflorescence had more seeds per floret and heavier se eds and fewer florets with no seed than later pollinated florets. Ther e were also differences between florets within the same whorl. The rol e of a number of factors which may influence floret site utilisation a re discussed.