IDENTIFICATION OF COLD-TOLERANCE BY CHANGING OF DIFFERENCE IN LEAF-AIR TEMPERATURE OF CUCURBITA PEPO L.

Abstract

To accurately and briefly identify cold-tolerance of Cucurbita pepo L. varieties, change of difference in leaf-air temperature of seedlings of different Cucurbita pepo L. varieties and cold injure indexes, antioxidase activity and MDA content were examined under the condition of low temperature at 5°C in the artificial cabinet. The results showed: change of difference in leaf-air temperature included five stages: the variety protection reaction stage, the physiology and biochemistry reaction stage, the low temperature adaptability stage, the potential release stage and the death stage. Different varieties possessed different reaction degrees and duration of time in every stage, compared with variety 'y-16', the variety protection reaction stage of variety dy was shorter and just 0.62h; but its reaction in the physiology and biochemistry stage was intense and the highest difference in leaf-air temperature was +0.9°C, duration of time was 21.6h. Additionally, its adaptability to low temperature was long (130h, ie.5.4d), the highest difference in leaf-air temperature was -1.5°C. The time when varieties commence to release potential can be used as identification of variety cold tolerance. Varieties' cold tolerance reflected by difference in leaf-air temperature was consistent with identification of cold injure indexes and antioxidase activity. Therefore, difference in leaf-air temperature can be utilized as identification index for cold tolerance of Cucurbita pepo L.