Translocation of Assimilates and Phosphate in Detached Bean Leaves

Abstract

¹⁴C-assimilates were accumulated by the veins in the blades and transported basipetally into the petioles of detached leaves of Red Kidney bean (Phaseolus vulgaris L.). Neither process was greatly affected by mild moisture stress, age of fully enlarged leaves, or period in the dark prior to exposure to ¹⁴CO₂. However, both vein loading and transport into petioles were greatly reduced by oxygen deficiency. The basipetal transport of ³²PO₄ also did not appear to be greatly reduced by 6 or 8 days of darkness prior to the application of phosphate-³²P, followed by a transport period of 1 day in the dark. Endothall at 5 × 10⁻³ m was effective in stopping basipetal flow of ³²P. It is considered that transport in leaves may be powered by forces in the plasmodesmata of the cell walls between the border parenchyma and phloem.