Carbohydrate Fractions of Lemon Peel

Postphloem, Nonvascular Transfer in Citrus

“…Although substantial dilution of sieve tube sucrose can be assumed to arise from other phloem cells as well as xylem, values may still reflect gross differences in levels of vascular bundle sugars. These vary, but sugar content in that portion of the segment epidermis immediately Position along transport path monosaccharide levels are common in grapefruit [28,30] (30). Generally similar translocation profiles were observed over the length of individual fruit segments (Fig.…”

“…Timing of radiolabel arrival appeared to account for some variation along stem to stylar length, but not major differences in inward, radial transfer. Sugar levels in the juice sacs were similar throughout the entire segment length, as is typical for grapefruit at this stage of development (30).…”

“…SA), but increased levels of '4C-hexoses were detected in the sink structures rather than en route. Grapefruit often store hexoses as they near full expansion (30) and no clear relationship was evident in Figure S between the percentages of '4C-hexoses found in the postphloem path and the efficiency of '4C-assimilate transfer.…”

“…7E). Both also dropped dramatically near the completion of fruit development (sugar accumulation generally continues slowly after juice sac expansion [30]). Differences between rates of water and C entry were evident, however, particularly when rising respiratory losses were included in calculations of total C demand relative to water inflow (not shown).…”

“…This up-hill gradient was evident for a longer portion of fruit development than was that of sucrose alone. The extent of hexose production during final phases of juice sac expansion often varies considerably under field conditions (30), resulting in total sugar gradients persisting for variable periods.…”