Effect of excess Cu on the photosynthetic apparatus of runner bean leaves treated at two different growth stages |
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Authors: | Waldemar Maksymiec Ryszard Russa Teresa Urbanik-Sypniewska Tadeusz Baszyski |
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Institution: | Istituto Sperimentale per la Cerealicoltura, S.S. 16 Km. 675, I-71100 Foggia, Italy |
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Abstract: | Variations in water binding strength, water relations and the accumulation of solutes during water stress of three durum wheat ( Triticum durum Desf.) cultivars are reported and discussed. Water binding strength was determined by constructing adsorption isotherms at 5 and 20°C and by calculating the differential enthalpy (ΔH) after van't Hoff. Reducing sugars, proline, K+ and Cl? were the major contributors to osmotic adjustment. Solutes, such as quaternary ammonium compounds, and non-reducing sugars contributed to osmotic potential at full turgor, but did not increase in proportion to water stress. Genotypic differences have been observed for K+ accumulation capability, the water-stressed leaves of cv. Capeiti 8 showing the largest increase. The same cultivar demonstrated the most negative ΔH values, indicative of strongly bound water, and the highest integrated enthalpy (ΔHinf) values for leaf moisture below 0.1 g H2O per g dry weight, i.e. in the isotherm region where water was presumably chemisorbed to the charged groups of macromolecules. The accumulation of ions (Cl?, K+) and proline was concurrent with an increase in the binding-strength of tightly and weakly bound water, respectively. |
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Keywords: | Adsorption isotherms bound water durum wheat osmotic adjustment Triticum durum water stress |
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