Allocation of current photosynthate and changes in tissue dry weight within northern red oak seedlings: individual leaf and flush carbon contribution during episodic growth

Relatively little is known about the changing carbon allocation patterns in species with episodic growth cycles such as northern red oak (Quercus rubra L.). To examine such changing allocation and growth patterns, northern red oak plants were grown from seed in controlled environment chambers through four cycles of growth. 14CO2 was supplied to leaves of the first, second, or third flushes at different Quercus morphological index growth stages within each flush, and the distribution of 14C within the plant was analyzed. Carbon allocation from source leaves of the first and second flush was primarily upward during the subsequent cycle of shoot growth and downward during lag and bud growth stages. All leaves within a flush did not respond the same. Upper leaves allocated most 14C-photosynthate upward during leaf and shoot growth while lower leaves supplied more 14C to lower stem and roots. During the third and fourth flushes, differential allocation from leaves within a flush resulted in essentially equal upward and downward carbon allocation. Growth and allometric relationships reflected these changes in carbon allocation.