TEMPERATURE AFFECTS PLANT GROWTH AND SULFUR UTILIZATION IN ONION (Allium cepa)

Abstract

`Willamette Sweet' onions were grown at 10, 17, 24 and 31 C in controlled environment chambers to determine the effect of temperature on plant growth and sulfur utilization in non- and bulb-inducing photoperiods. Plants were first grown for 11 weeks at a 10 hour (non-bulbing) photoperiod and then for 4 weeks at a 16 hour (bulbing) photoperiod. Plants were fertilized weekly 200 ppm 20-20-20 soluble fertilizer containing 7 percent sulfur. Plants had greatest and least growth at 24 and 10 C, respectively in the 10 hour photoperiod while bulb maturation was greatest at 30 C in the 16 hour photoperiod. Leaf sulfur concentration increased linearly in plants grown from 10 to 30 C in the 10 hour photoperiod. Bulb sulfur concentration in plants grown at 30 C was twice that of plants grown at 20 or 15 C in the 16 hour photoperiod.