ONTOGENY AND SULFUR FERTILITY AFFECT LEAF SULFUR IN SHORT-DAY ONIONS

Five short-day onion (Allium cepa L.) cultivars grow?l with high (4.0 meg S/liter) and low (0.1 meg S/liter) S fertility were evaluated for ontogenetic changes in leaf S concentration and the association betwee n leaf S concentration and final bulb pungency as reflected by pyruvat e formation. Cultivars differed in leaf S concentration at each of eig ht sampling dates during growth and development, but the pattern of le af S accumulation among cultivars was similar. Leaf S concentration in creased during early plant development while in a nonbulbing photoperi od, but decreased as bulbing progressed to maturity with high and low S fertility. The decline in leaf S concentration during bulbing was mo re severe with low than with high S fertility. Leaves that were left t o dry on the mature bulb lost most of their S, especially with 0.1 meg S/liter, a result that could have implications in final bulb flavor i ntensity. Correlations generally were poor between leaf and final bulb S concentration or pungency.