SEED YIELD IN CARAWAY (CARUM-CARVI) .2. ROLE OF ASSIMILATE AVAILABILITY

Assimilate availability may determine seed yield of caraway during three periods: (i) before flowering it may determine dry matter allocation to flowers and thereby the number of ovaries; (ii) during flowering it may determine seed set; and (iii) after flowering it may determine seed filling. From 1990 to 1992 in the vicinity of Wageningen, field experiments were performed in which growth, assimilate storage and partitioning, and the effects of shading during various growth stages on seed set and filling, were studied to determine the importance of these three phases. Dry matter production before flowering was correlated with dry mass of flowers, but there was no relationship between the dry mass of flowers and seed yield. Assimilate availability after flowering only slightly affected seed yield, but during flowering it had a strong effect. Shading 50% (during c. 3 weeks of flowering only) reduced yield by 30% whereas 50% shading (after flowering for > 1 month) reduced yield by only 6%. In addition, the main flowering period of biennial caraway over a number of years was estimated and the daily amount of photosynthetically active radiation (PAR) for that period calculated. There was a dose linear relationship between light intensity during flowering and yield. The possibilities for yield improvement using these results are discussed.