Relationship between Relative Turgidity and Diffusion Pressure Deficit in Leaves

Abstract

A PRACTICAL field-method for measuring water deficits in plants has been described¹ in which the water content of samples of leaf disks is measured and compared with that of parallel samples rendered fully turgid by floating on water. The field-water content expressed as a percentage of the turgid water content was called the ‘relative turgidity’. This technique and mode of expression have proved successful in studying the ecology of a variety of plants in Uganda², Israel³, the United States⁴ and Australia⁵. It is, however, difficult to assess the full significance of relative turgidity values without a knowledge of their equivalence in terms of ‘diffusion pressure deficit’. For example, 80 per cent relative turgidity in different species might mean quite different degrees of ‘water stress’ expressed as the diffusion pressure deficit of the leaves.