VARIATION OF GROWTH RHYTHM AMONG FAMILIES AND CORRELATION BETWEEN GROWTH RHYTHM AND GROWTH-RATE IN BETULA-PENDULA ROTH

Growth rhythm, including growth initiation, growth cessation, growth p eriod, and growth rate for Betula pendula were observed on two full-si b trials of reciprocal recurrent selection and polycross. The results indicate that most of the characters of growth rhythm show significant differences among families and mating patterns. The variations of the characters of growth rhythm are more strongly under genetic control t han those of growth rate. The correlations between most characters of growth rhythm and growth rate are highly significant.