Screening for cold-resistant tomato under radiation mutagenesis and observation of the submicroscopic structure

Abstract

Tomato is a cold-sensitive crop that is vulnerable to chilling injury. To screen for chilling resistance in tomato mutants, seeds were irradiated with different doses of 60Co-γ and then evaluated according to the five stages of the chilling injury index. Moreover, physiological indexes and observation of the submicroscopic structure by electron microscopy were used to examine cold resistance in the mutants. The physiological index results showed much higher cold resistance in the mutants compared to wild type. The cellular structures of the cold-resistant mutants were more complete than in wild-type plants after chilling treatment. The chloroplasts of the mutants were close to the cell periphery; the double membrane structure of the chloroplast was intact, and well-developed granal stacks were interconnected by stroma. Compared to wild-type plants, the stomatal density of cold-resistant mutants increased considerably, though the stomatal size showed no obvious changes.