INHIBITION OF GROWTH OF CALADIUM BY HIGH TEMPERATURE

Abstract

Caladium × hortulanum Birdsey `Candidum' tubers were exposed to 26, 38, 43 and 48C for 1, 2 and 3 days. Tubers were then forced in a glass-glazed greenhouse. Tubers exposed to 48C for 1 and 2 days required significantly longer to emerge than all other temperature treatments, while tubers exposed to 48C for 3 days failed to emerge. After 4 weeks of growth, exposure of tubers to 43C for 2 and 3 days and 48C for all time periods resulted in plants with reduced shoot fresh weights and fewer leaves with a width greater than 15 cm. After roots developed to the edge of the pot and shoots emerged (10 days after potting), potted tubers were exposed to 43C for 0, 4, 8, 12, 16, 20 and 24 hours per day for 1, 3 and 5 days. Potted tubers exposed to 43C for 8 or more hours per day for 3 days and 12 hours or more for 5 days were significantly delayed in emergence. Only 33% of potted tubers exposed to 43C for 24 hours per day for 5 days emerged. Exposure to 43C for 1 and 3 days resulted in increased shoot fresh weights for exposures up to 12 hours per day. As the exposure time per day increased, shoot fresh weights decreased. Exposure of potted tubers to 43C for 16 hours or more per day for 3 days reduced plant height and the number of leaves with a width greater than 15cm. Regardless of the number of hours of exposure per day, potted tubers exposed to 43C for 5 days had reduced shoot fresh weights and fewer leaves with a width greater than 15cm as compared to unexposed potted tubers. As the number of hours of exposure per day increased, shoot fresh weight and the number of leaves with a width greater than 15cm decreased.