Figure 5

A proposed model for salt accumulation in bladder cells. Monosaccharides are transported from mesophyll cells to bladder cells by the GLUTs, and enter the TCA cycles for producing ATP. Hemoglobin (HB) helps with oxygen diffusion in stalk and bladder cells, and the oxygen is used for oxidative phosphorylation, which produces ATP. Vacuolar ATPase (V-ATPase) and plasma membrane H⁺ ATPase generate the proton gradients and membrane potential that are necessary for Na⁺ and Cl⁻ transport from the leaf to bladder cells, and then from the cytoplasm to the vacuole of bladder cells via Na⁺/H⁺ exchanger and chloride transporters, respectively. The ratio of cell sizes drawn in the diagram does not reflect the actual ratios. Stalk cells are represented in dashed lines because no transcriptome data are currently available for this type of cells.