Time-course analyses of abscisic acid level and the expression of genes involved in abscisic acid biosynthesis in the leaves of <Emphasis Type="Italic">Betula platyphylla</Emphasis>
(1) Key Laboratory of Forest Tree Genetic Improvement and Biotechnology (Ministry of Education), Northeast Forestry University, 26 Hexing Road, Harbin, 150040, People’s Republic of China;