Freezing injury of Japanese chestnut (Castanea crenata Sieb. et Zucc.) in relation to changes in twig water content and xylem pressure from winter to early spring

摘要

In order to elucidate the cause of freezing injury of Japanese chestnut (Castanea crenata Sieb. et Zucc.), investigations were carried out with emphasis on the ascent of water in the xylem tissue from winter to early spring. From mid-January to mid-April, the water content of twigs was hogher and the freezing tolerance of buds waas lower as the tree was younger.Xylem pressure was measured with manometers connected directly to the most recent shoots of 3-year-old trees or to the trunks of one-year-old seedlings. At first, negative pressure was observed in the xylem pressure. And then, positive pressure accompanied with increase in the twig water content and the vessel water was observed. In case such ascent of water occurred during January through March, severe freezing injury was caused.On the contrary, trees without such increase in the water content did not suffer freezing injury. Each tree differs largely in its time to begin absorbing water through the roots. There differences might reflect the genetic divergence of the rootstocks.