Seasonal changes in frost hardiness in cloudberry (Rubus chamaemorus) in relation to carbohydrate content with special reference to sucrose

Abstract

Monthly determinations of frost hardiness of cloudberry (Rubus chamaemorus L.) buds and rhizomes were done from October 1978 to October 1979. For buds LT50 (lethal temperature for 50% of the plant material) was calculated from the percentage of bud breaking and for rhizomes from visual estimations of the degree of coloring by triphenyltetrazolium chloride. The frost hardiness varied from—11.5°C in November to—4°C in May to July for buds and from—16°C in January to—3°C in June— July for rhizomes. Dehardening started in February while the plants were still covered with snow. In connection with the determinations of frost hardiness, carbohydrate analyses were done. There was a good correlation between the degree of frost hardiness and the amount of soluble carbohydrates determined with anthrone. Sucrose, determined by gas chromatography, seemed to be the sugar contributing most in this correlation.