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In lymphocytes, the Na+/H+ antiport can be stimulated by 12-O-tetradecanoylphorbol 13-acetate (TPA) and by osmotic shrinking. Since TPA acts by stimulating protein kinase C, we undertook experiments to determine if protein phosphorylation also underlies the osmotic stimulation of the antiport. We found that at least one of the membrane polypeptides labeled in cells treated with TPA is also phosphorylated by hypertonic shrinking. In both instances phosphorylation is alkali labile and associated with serine and threonine residues. We tested the possibility that shrinking activates phospholipase C, thereby stimulating protein kinase C through release of diacylglycerol. No decrease in phosphatidylinositol 4,5-bisphosphate levels was detected in hypertonically treated cells. Moreover, the concentrations of inositol phosphates, including inositol trisphosphate, were not altered in shrunken cells. Thus, shrinking does not appear to activate phospholipase C. Whereas TPA induced intracellular redistribution of soluble protein kinase C, no such effect was detected in osmotically activated cells. It was concluded that osmotic stimulation of the Na+/H+ antiport is associated with activation of protein phosphorylation by a kinase that is similar, but not identical to protein kinase C. Experiments in Na+-free or amiloride-containing media indicate that phosphorylation is not a consequence of activation of the antiport.

The Osseo is an early, puick maturing variety with a distinct upright compact habit of growth. Yields are comparable to Waseca and Red Warba with an exceptionally high per cent composed of tubers above 2I/4''in diameter. Tubers are white, smooth, round, blocky and uniform in size. It should prove useful wherever an extra whrly white variety is desired.

Summary: A three-year study was conducted to determine the effects on Red Pontiac potatoes of simulated hail damage applied at three stages of growth. Both total yields and yields of U.S. #1 size tubers decreased, progressively as the degree of hail damage increased from 25% to 100% defoliation. Twenty-five per cent hail damage reduced total yields by 10% whereas 100% defoliation reduced yields 56% on the average. Stage of growth when hail damage occurred also affected yield reduction. Damage applied when 50% of the plants were past full bloom caused more serious yield reductions than hail damage to plants in full bloom or plants beginning to flower. Lowest yields occurred when 50% of the plants were past full bloom stage and when completely defoliated, and least yield reduction occurred when plants at 50% bloom were only 25% defoliated. Specific gravity of tubers was decreased only by the most severe hail damage applied to the oldest potato vines.As the degree of damage from simulated hail was increased the percentages of smaller sized tubers increased and the percentages of larger sized tubers decreased. Thus, hail damage not only decreased total yields but decreased the percentages of potatoes of U.S. #1 size. The results of this study show that the Red Pontiac potato variety has a tremendous capacity to recover from hail damage. When 50% of the plants were in bloom, simulated hail damage to the extent of 25% defoliation did not significantly affect yields and 50% defoliation at this stage caused only slight yield reduction. However, either more complete defoliation at this stage or only partial defoliation at later stages of growth prevented the plants from producing normal yields.