Low Temperature Hardiness of Populus maximowiczii and Selection of Resistant Clones

1986

6 Abb., 3 Tab., 3 Lit. Ang.

Unselbständiges Werk

6974

200014150

In order to select hardy clone in the spring and in the fall, artificial freezing test were done in different growing stage. Low temperature treatment was done in a freezing box following natural temperature changesat outdoor condition near testing days. Change of temperature was controlled a utomatically by a programing system from 5 p.m. to the next morning at 9 a.m. Desired minimum temperature was varied and set out from 24 to 4 a.m. according to the object of experiment. After treatment, cuttings were planted in water in a green house for two months. Judging the injury of cuttings was scored on a 1(normal) - 3(dead) basis. 1. Frost hardiness in the spring. 30 clones of 10-year-old were treated in 3 bud developing stages. In budbreak stage in mid April, almost of all clones survived without injury at -15C treatment. At leafexpandingstage in late April, wide variation was found among clone at -8, -13 and -15C treatment, but all clones died at -16C and survived at -2C. At leaf emergence stage in early May, -8C treatment showed also wide variation among clones. As a result, 5 resistant clones showing significant difference at 5% level were selected among 30 tested clones. 2. Frost hardiness in the fall. Highly significant correlatin or r = 0.707 was found between growth cesation and frost hardiness in the fall. Adult tree of 10-year-old was more hardiness than 1- year-old rooted cuttings of the same clone. Selection was done using 88 clones under the treatment at -5, -10, -15 and -20C from early October to early November. In early October, all clones were died at -15C treatment, and in early November, all clones were survived at -20C treatment. But, in the case at -5, -10, -15C treatment according to different dormant stage, wide variation of resistance was found and 11 frost hardy clones in the fall were selected. In winter, early February, immersed cuttings in liquid nitrogen were survived.