Hartt C E
Physiology and Biochemistry Department, Experiment Station Hawaiian Sugar Planters' Association, Honolulu, Hawaii 96822.
Plant Physiol. 1967 Mar;42(3):338-46. doi: 10.1104/pp.42.3.338.
Low moisture supply, controlled by 3 methods (adding NaCl to a complete nutrient solution, allowing a cut stalk to wilt, or withholding irrigation in the field), decreased the velocity and percentage rate of translocation of (14)C-photosynthate. The surplus sucrose not used in growth moved more slowly in the phloem and was stored in the stalk.Low moisture supply depressed translocation of (14)C-photosynthate more severely than it curtailed formation of (14)C-photosynthate in the same leaf: therefore, the effect of moisture supply upon translocation was primary.Low moisture supply retarded profile development in the stem, and a loss in moisture gradient was associated with a steepened slope of the profile. These results indicate a flow mechanism of translocation rather than diffusion.Results reported now and previously point to the operation of a slow pressure-flow mechanism particularly during the night but also during the day; superimposed upon this general mass transport is the more rapid process of phototranslocation which is independent of sugar gradients and which can cause the accumulation of sucrose at the storage-sink.During ripening, storage of sucrose in the stalk may be increased by withholding water because less sucrose is hydrolyzed in transit, less is used in growth, and the slowly moving sucrose has more time for transfer from the phloem to the storage parenchyma.
通过三种方法（向完全营养液中添加氯化钠、让切断的茎枯萎或在田间停止灌溉）控制低水分供应，降低了¹⁴C光合产物的转运速度和转运百分率。未用于生长的多余蔗糖在韧皮部中移动得更慢，并储存在茎中。低水分供应对¹⁴C光合产物转运的抑制作用比对同一叶片中¹⁴C光合产物形成的抑制作用更严重：因此，水分供应对转运的影响是主要的。低水分供应阻碍了茎中浓度梯度的形成，水分梯度的降低与浓度梯度曲线斜率的变陡有关。这些结果表明转运是一种流动机制而非扩散机制。现在和以前报道的结果表明，特别是在夜间但白天也存在一种缓慢的压力流机制；在这种一般的物质运输之上叠加着更快速的光转运过程，光转运独立于糖梯度，并且会导致蔗糖在储存库中积累。在成熟过程中，通过停止供水可能会增加茎中蔗糖的储存量，因为运输过程中水解的蔗糖减少，用于生长的蔗糖减少，并且移动缓慢的蔗糖有更多时间从韧皮部转移到储存薄壁细胞中。
