Structure and development of sieve cells in the secondary phloem of Larix decidua Mill. as related to function

摘要: Only one or two layers of sieve cells the previous year's phloem in lateral branches Larix decidua persist as fully mature cells. Immature cambial derivatives that have not completed differentiation may also over-winter. Periclinal cell divisions vascular cambium were first observed by mid-April. During short period greatest activity (mid-April to mid-May), early is laid down. Late formed over a much longer period, from mid-May late September. Microautoradiography revealed only are involved translocation 14C assimilates June. The fine structure actively translocating described. impact on long-distance transport discussed.