MEIRI, A., Institute of Soils and Water, Agricultural Research Organization, Bet Dagan, Israel
PLAUT, Z., Institute of Soils and Water, Agricultural Research Organization, Bet Dagan, Israel
SHIMSHI, D., Institute of Soils and Water, Agricultural Research Organization, Bet Dagan, Israel

The existence of water potential gradients in flowering shoots and leaves of roses (Rosa sp., cv. Baccara) and along flag leaves of wheat (Triticum aestivum L.) were studied by means of the Scholander pressure chamber. In roses grown in greenhouse, the water potential measured in transpiring shoots was higher than in leaves detached from these shoots, whereas the potential differences between leaf and shoot after equilibration in the dark were small or negligible. A progressive decrease in water potential was found upon repeated measurement on the same organ; this decline was steeper in leaves than in shoots. Extrapolating this decline to excision time resulted in water potential values which, in transpiring shoots, were 3 to 5 bars higher than in leaves. Detopping the flower bud did not alter this pattern, indicating that the highest water potential in the shoot was in the stem. In field‐grown wheat, the water potential measured in a whole flag leaf was about 6 bars higher than that measured in the apical one‐third of the leaf, and this difference disappeared after equilibrating the detached leaf for 1 h in the dark. These potential differences indicate the presence of resistances along the water path in the organ. The results obtained by the pressure chamber represent the highest water potential in the organ, rather than the average water potential. Copyright © 1975, Wiley Blackwell. All rights reserved