Abstract
Light (about 3,000 foot-candles) neither increased nor decreased the sink strength of young, rapidly expanding leaves of Phaseolus vulgaris L. cv. Black Valentine, as measured by the comparative rates of import of 14C-labeled photosynthates by sink leaves in the light versus dark in short term experiments. Although irradiated sink leaves accumulated more 14C activity, the difference was fully accounted for by photosynthetic reabsorption of respiratory CO2 derived from substrates translocated to the sink leaves.
Maximum sink strength was attained when the sink leaf reached 7 to 8 cm2 in area (9 to 10% of its fully expanded size). Thereafter sink strength declined rapidly and asymptotically to a near zero value at about 45% final area. During this period, however, the rapid decline in translocation was offset by a rapid rise in the photosynthetic rate of the sink leaf, maintaining a near constant relative rate of dry weight increase until the sink leaf had expanded to about 17% of its final area. Although the increasing photosynthetic capacity was associated with a decreasing import capacity, suggesting that the rate of translocation to the sink leaf was controlled by the developing capacity of the sink leaf for photosynthesis, it was not possible to vary the total (true) translocation rate to the sink leaf by varying the photosynthetic rate of the sink leaf in short term light-dark experiments. Despite a high ratio of source to sink in these experiments, no evidence accrued that translocation into young bean leaves was ever sink-limited.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Fellows R. J., Geiger D. R. Structural and Physiological Changes in Sugar Beet Leaves during Sink to Source Conversion. Plant Physiol. 1974 Dec;54(6):877–885. doi: 10.1104/pp.54.6.877. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Giaquinta R. Source and sink leaf metabolism in relation to Phloem translocation: carbon partitioning and enzymology. Plant Physiol. 1978 Mar;61(3):380–385. doi: 10.1104/pp.61.3.380. [DOI] [PMC free article] [PubMed] [Google Scholar]
- VAN SLYKE D. D., PLAZIN J., WEISIGER J. R. Reagents for the Van Slyke-Folch wet carbon combustion. J Biol Chem. 1951 Jul;191(1):299–304. [PubMed] [Google Scholar]