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LEAF DEVELOPMENT, PHOTOSYNTHESIS, AND C 14 DISTRIBUTION IN POPULUS DELTOIDES SEEDLINGS
Author(s) -
Larson Philip R.,
Gordon John C.
Publication year - 1969
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1969.tb09760.x
Subject(s) - photosynthesis , biology , seedling , respiration , botany , apex (geometry) , photosynthetic capacity , horticulture
Rates of net photosynthesis and dark respiration and distribution of C 14 from selected leaves were determined for young cottonwood ( Populus deltoides ) trees at different stages of development. Four series of five trees—one series for each of four treated leaf positions—were included in the study. Maximum C 14 export occurred when a leaf had just attained maximum size. Lower stem leaves reached maturity quickly and began exporting photosynthate when demands of the young seedling were high. Leaves at higher stem positions matured more slowly, but senescence was also delayed so their effective export life was prolonged. Translocation from a newly exporting leaf was primarily upward to developing leaves and the apex. As a leaf at any one position aged, the translocation pattern gradually shifted from upward to bi‐directional and finally to a predominantly downward direction. Photosynthate translocated downward was incorporated into stem wood and roots. Maximum photosynthetic efficiency coincided with the downward shift of C 14 export. Thereafter, net photosynthesis began to decline, at first slowly and then more rapidly. The patterns of photosynthesis, respiration, and C 14 export associated with leaf age all varied according to leaf position on the stem.