Distribution and metabolism of current photosynthate by single-flush northern red oak seedlings

Abstract

Carbon distribution and metabolism by northern red oak seedlings (Quercus rubra L.) were followed for 72 h after a 30-min photosynthetic exposure to (14)CO(2). Approximately 50% of the assimilated carbon was lost during this time, presumably through respiration. Most of the (14)C recovered in the plant remained in the source leaf. Most of the exported (14)C was found in stems and especially roots. Position of the source leaf did not affect distribution of translocated (14)C; however, upper source leaves retained slightly more (14)C than lower source leaves. Most (14)C in all tissues was found initially in sugars. Labeled carbon in this fraction decreased rapidly and increased in other chemical fractions, particularly residue (structural carbohydrates and lignin). More (14)C was incorporated into residue than into any other chemical fraction, indicating continued growth by each of the tissues during the lag stage of seedling development. Labeled carbon increased in proteins for 6 to 12 h after treatment, then remained essentially constant for the remainder of the transport period, indicating both rapid incorporation of the pulsed (14)C into, and slow turnover of, the labeled protein components. In source leaves, (14)C incorporated into starch in the light was lost during the dark period, a typical diurnal storage pattern. In stems, (14)C in starch increased for 12 h, then decreased during the dark period, and then increased during the rest of the transport period. This pattern indicates that stems have both diurnal and long-term storage pools of starch. In roots, (14)C in starch increased rapidly for 12 h, then remained constant for the rest of the transport period, indicating primarily long-term storage in this tissue. Peak (14)C in amino acids in taproot preceded that in stem tissue, indicating recycling of (14)C from the roots to the shoot in amino acids.

Ontogeny affects response of northern red oak seedlings to elevated CO2 and water stress: I. Carbon assimilation and biomass production

“…The physiology and growth of northern red oak seedlings have been characterized for low-stress, controlled-environment conditions (Hanson et al, 1987Dickson, Isebrands & Tomlinson, 1990 ;Isebrands, Tomlinson & Dickson, 1994). Interactive effects of multiple environmental factors on physiology and growth of northern red oak are the subject of this paper whose objectives were to : (1) evaluate how elevated atmospheric CO # and water deficit, two potentially interactive environmental stressors associated with climate change, modify processes of C assimilation and biomass accumulation, and (2) to characterize the effect of ontogenic changes in C source-sink relations on C assimilation response to environmental stress.…”

Storage, mobilization and interrelations of starch, sugars, protein and fat in the ray storage tissue of poplar trees

“…Whether such differences in distribution must be attributed mainly to differences in sink strength of the individual site, to the relative proximity to source leaves, or even to differences in the amount of parenchyma cells, cannot be decided yet. Detailed studies on carbon and nitrogen allocation in red oak seedlings (Dickson et al 1990), I-year-old poplar 'trees' , and 8-year-old pine trees (Hansen and Beck 1990) cannot yet answer this important question.…”

Carbon allocation and morphology of cherrybark oak seedlings and sprouts under three light regimes

“…Slight accumulations of 14 C in these tissues probably reflects retransport of 14 C-assimilates from root tissues rather than direct transport from source leaves (Dickson et al, 1990). Isebrands and Nelson (1983) also found low levels of 14 C in unlabeled branch tissues in Populus clones and, therefore, were not "parasitic" on the rest of the plant.…”