Import of ¹⁴C‐Photosynthate by Developing Leaves of Sugarcane

Abstract

AhstractSink-to-source transition was studied in developing sugarcane (Saccharum interspecific variety L62-96) leaves. Fully-expanded, mature sugarcane leaves were fed 14C02 for 20 minutes, incorporating about 617 Bq. After five hours the leaves of each plant were cut into 1-cm-length segments that were weighed and then placed in scintillation cocktail for counting. All leaves younger than the leaf fed I4CO2 imported labeled photoassimilate. Three to four leaves had both importing and non-importing regions within the blade and a distinct transition region between them. A transition region was observed in leaves which had expanded to between 30 and 90 % of final blade length. Radioactivity per gram fresh weight was calculated as a measure of sink strength. Sink strength was greatest in the youngest leaf and declined with leaf age. The results of this study indicate that 1) import of photosynthate by developing sugarcane leaves occurs over a longer span of developmental ages than in dicotyledonous leaves and 2) the actual tissue region undergoing transition within such a leaf can be resolved as narrow zone between the importing and non-importing regions.

Phloem Transport of Resources

“…In contrast to eudicot leaves, the transition from sink-to-source function of grass leaves is protracted, with the laminae and sheath intercalary meristems continuing to be active during leaf emergence. For instance, for sugarcane, phloem import of photoassimilates into ensheathed portions of developing leaves continues until they have reached 90% of their final size (Robinson-Beers et al 1990). In developing maize leaves, the switch to a phloem loading function is accompanied by an absence of PD connectivity of basipetally differentiating metaphloem SE/CCs complexes with adjacent phloem parenchyma.…”

“…Elongation of each internode and a significant rate of resource unloading from the phloem commences once the leaf subtended at its upper node reaches full expansion (Moore & Maretzki 1996) and begins to export photoassimilates (Robinson-Beers et al 1990). Cell elongation occurs acropetally above the cell division zone of the intercalary meristem located immediately above the basal node of each internode (Moore 1987).…”

Modification of a Specific Class of Plasmodesmata and Loss of Sucrose Export Ability in the sucrose export defective1 Maize Mutant

“…Plasmodesmata apparently transport substances selectively based on the size, charge, and structure of the transport molecule . Furthermore, plasmodesmal structure, composition, and regulation may differ in different cells and tissues (Robinson-Beers et al, 1990;Epel, 1994;Waigmann and Zambryski, 1995).…”

“…Methods of feeding, autoradiography, and scintillation counting were modified from those used in a previous study on sugarcane (Robinson-Beers et al, 1990). Each leaf was clamped into a water-cooled aluminum leaf chamber.…”

Radiosynthesis of 6’-Deoxy-6’[18F]Fluorosucrose via Automated Synthesis and Its Utility to Study In Vivo Sucrose Transport in Maize (Zea mays) Leaves

“…Radiotracers have been used in plant science for more than 60 years, and there is a growing body of work and interest in using in vivo radiotracer imaging studies to trace sugar dynamics in plants [ 13 – 19 ]. A number of radioactive isotopes, both long-lived (e.g., 14 C) and short-lived (e.g., 11 C), have been used to study sugar transport and distribution in plants [ 15 , 20 – 24 ].…”