ALTERATION OF SEEDSTALK DEVELOPMENT, SEED YIELD, AND SEED QUALITY IN CARROT BY VARYING TEMPERATURE DURING SEED GROWTH AND DEVELOPMENT

The effect of temperature on seedstalk development, seed yield and qua lity in carrot (Daucus carota L.) was investigated in growth chambers at constant day/night temperatures of 33/28, 28/23, 25/20, 23/18, 20/1 5, and 17/12 degrees C. Days to flowering, seedstalk height, number of umbels, and seed yield decreased linearly with increasing temperature from 17/12 to 33/28 degrees C. Continuous high temperature (33/28 deg rees C) had a detrimental effect on germination as measured by a stand ard germination test and an accelerated aging test. Optimum germinatio n of the progeny occurred at 20/15 degrees C; how ever, germination ra te tvas faster when seeds matured at 23/15 degrees C. Seeds that devel oped at 33/28 degrees C produced seedlings with the lowest vigor, whil e those which developed at 20/15 degrees C produced seedlings with the highest vigor. Brief exposure of plants to 33/28 degrees C during ant hesis or early seed development was as detrimental to seed yield as co ntinuous exposure to 33/28 degrees C. Exposure to high temperature (33 /28 degrees C) during late seed development had less effect on seed yi eld, and seed (quality was improved. Progeny vigor was reduced greatly , seed development at continuous high temperature (33/28 degrees C), b ut was unaffected by brief exposure to 33/28 degrees C at anthesis, ea rly, or late in seed development. These results suggest that high (33/ 28 degrees C) day/night temperatures during pollination, fertilization , or early stages of seed development can greatly reduce carrot seed y ield and seed quality.