The Relationship Between Plant Water Potential and Transpiration Rate in Young Cabbage Plants Growing in Wet Soil

Water potentials in the plant stem were monitored together withtranspiration rates in young cabbage plants growing in potsof soil and subjected to cyclic transpirational demands. Whenthe soil was very wet plant water potential was approximatelyproportional to transpiration rate. At lower soil water contentswater potentials remained almost constant despite considerablechanges in transpiration rate. When the transpiration rate washigh, water potentials in plants were lower in wet soil thanin soil having a slightly lower moisture content. It is arguedthat the results can best be explained in terms of root conductivityincreasing as the plant becomes more water stressed when thegradient between soil and plant water potentials steepens. Key words: Cabbage, Stem water potential, Transpiration rate