Validation of relative water content for studying plant water relations in crambe

Abstract

The study of the adaptation of crambe ( Crambe abyssinica Hochst. ex R.E. Fries), a potential new oil seed crop, to arid lands agriculture requires the evaluation of techniques for studying plant-water relationships specifically for crambe. One such technique, relative water content (RWC),wwas studied to determine the effect of time of floating on the kinetics of rehydration and dry weight loss of leaf discs and the influence of physiological leaf age and stage of plant development at different levels of water stress on the RWC and the kinetics of rehydration of crambe leaf tissue. The objective of this study was to calibrate the RWC technique as a means of measuring the internal water balance of crambe. Four greenhouse experiments were conducted using the cultivar, Meyer, as the experimental plant material and water stress treatments ranging from 0 to −1.0 MPa soil water potential in pot culture. Leaf discs of crambe plants subjected to different levels of water stress, stages of development and leaf age completed Phase I of rehydration in 4 h. No loss in dry weight resulting from floating time up to 5 h was detected under the experimental conditions used. Leaf age, stage of plant development and level of water stress affected rate of rehydration of leaf discs in Phase I. Both rate of water uptake and quantity of water absorbed increased as leaf age and water stress increased. Leaf discs from plants in the vegetative stage absorbed more water at higher rates and had higher RWCs than those from plants in the reproductive stage. Relative water content was found to be suitable for studying plant water status in crambe, but care must be taken to use leaves of similar age from plants of comparable stage of development.