LEVITT, J., Division of Soils and Water, Volcani Center, Bet Dagan, Israel
ZAKEN, R.B., Division of Soils and Water, Volcani Center, Bet Dagan, Israel

A link was sought between small water stresses and the larger metabolic changes that accompany them. A simple infiltration weight method of measuring percentage intercellular space is described and its errors evaluated. It yielded values for leaves (16–35%) similar to those recorded elsewhere by the pycnometer method. The percentage of intercellular space decreased to 0–50% of the value in turgid leaves with a simultaneous loss of turgor only in the sunflower leaves. Turgor remained constant in the orange leaves. Similar results were obtained with the pycnometer method. Measurements revealed that the total or most of the decrease in the volume of sunflower leaves on loss of turgor was due to a decrease in area: the smaller decrease in the volume of orange leaves was entirely due to a decrease in thickness. It is suggested that the sclerophyll nature of the orange leaves is an adaptation to prevent a secondary O2‐deficit stress on exposure to a water stress. Copyright © 1975, Wiley Blackwell. All rights reserved