The Effect of Post-veneralization Temperature on Seedstalk Elongation and Flowering in Carrots1

Abstract

Abstract Seedstalk height of carrot ( Daucus carota L.) was reduced as the post-vernalization temperature increased from 15/21° to 27/32°C (night/day) with no significant effect on flowering and seed formation. Seedstalks of ‘Royal Chantenay ’ carrot were most affected by the high temperatures and ‘Scarlet Nantes’ were the least affected while ‘Danvers 126’ was intermediate. Few plants had macroscopic seedstalk development 6 weeks after vernalization although the temperature during this period had a permanent influence on ultimate seedstalk height. Carrots grown at 27/32° during the initial 6 weeks following vernalization and then transferred to the optimum 15/21° grew no taller than plants held at 27/32°. Vernalization temperatures of 0°, 5°, and 10° for 10 weeks did not affect the percentage of plants flowered, time of bolting, or rate of seedstalk elongation. Ultimate seedstalk height was reduced only in ‘Royal Chantenay’ vernalized at 10°. Flowering was decreased by post-vernalization temperatures of 27/32° and 2l/27°C when carrots were stored only 5 weeks at 5° but not, after storage for 10 weeks or more. Increasing the vernalization time to 10 weeks hastened the rate of bolting in all three cultivars and increased ultimate seedstalk height in only ‘Royal Chantenay’ and ‘Danvers 126.’ Temperature during the first year of root growth, foliage removal from mature roots prior to storage, and photoperiod following vernalization did not affect seedstalk elongation or flowering.