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Abscisic acid (ABA) caused a 7-8-fold increase in volume flow in excised bean root systems and this was coupled with an increase in (42)K, (36)Cl and (24)Na flux into the xylem. The transport of (42)K and (36)Cl increased by a factor larger than the stimulation of volume flow, resulting in an increase in the concentration of those ions in the xylem exudate. Carbonyclcyanide-m-chlorophenyl hydrazone, on the other hand, eliminated ABA-stimulated (42)K transport and caused a further inhibition of (42)K flux, thus providing additional support for the proposition that ABA stimulation may involve an energised process of ion transport. ABA also increased the accumulation of (24)Na and (36)Cl in bean root tissue, but not that of (42)K.

(6,7,16,18,21). In a recent paper, Outlaw et al., (18) presented a qualitative description of phosphate distribution within Vicia faba leaves, and showed, by x-ray microanalysis, that phosphorus is more abundant in guard and epidermal cells than mesophyll cells.Histological staining and microsurgical separation of cell types, followed by enzyme specific assay, showed that phosphorus was present predominantly as Pi. In earlier work, low phosphorus contents of mesophyll cells of Atriplex (28) and Puccinellia (27)

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