Phloem unloading in the potato tuber. Pathways and sites of ATPase

摘要: Potential pathways for sucrose unloading in the potato tuber were examined by light and electron microscopy. Abundant plasmodesmata connected sieve elements with surrounding parenchyma also companion cells. Plasmodesmata rarer, however, between cells elements. These observations suggest that may leave enter storage directly via symplast transport through cell not be a prerequisite unloading. Plasmodesmata, grouped together primary pit fields, abundant cells, isolated separated enzymically, showed considerable variation plasmodesmatal distribution on different faces of single cell. Deposition starch was found to occur cortex while an endodermis Casparian strip present external phloem, suggesting assimilates initially cortical entirely symplastic pathway. The possible involvement ATPase process cytochemically, using lead-salt precipitation method. By contrast previous findings phloem no evidence activity unique element-companion complex. favour view is passive process.