Bound water in durum wheat under drought stress
Rascio, A. | Plantani, C. | Di Fonzo, N. | Wittmer, G.
To study drought stress effects on bound water, adsorption isotherms and pressure-volume curves were constructed for two durum wheat (Triticum durum Desf.) cultivars: Capeiti 8 (drought tolerant) and Creso (drought sensitive). Plants were grown under well-watered and water-stressed conditions in a controlled environment Differential enthalpy (deltaH) was calculated through van't Hoff analysis of adsorption isotherms at 5 and 20 degrees C, which allowed us to determine the strength of water binding. deltaH reached the most negative values st approximately 0.06 gram H2O/gram dry weight and then increased rapidly for well-watered plants (until 0.10 gram H2O/gram dry weight) or more slowly for drought-stressed plants (until 0.15 - 0.20 gram H2O/gram dry weight). Bound water values from pressure-volume curves were greater for water-stressed (0.17 gram H2O/gram dry weight) then for well-watered plants (0.09 gram H2O/gram dry weight). They may be estimates of leaf moisture content where deltaH reaches the less negative values and hence some free water appears. With respect to the well-watered plants, tightly bound water tended to be less bound during drought, and more free water was observed in cv Creso compared to cv Capeiti 8 at moisture contents > 0.10 gram H2O/gram dry weight.
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