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Physiological and biochemical changes in leaves of interspecific Prunus rootstock (GF677) exposed to different external K, Ca, and Na supply

Ahlem Zrig1, Hatem benMohamed, Sarra Oueled Ali, Taieb Tounekti1, Maria Serranoc, Daniel Valero and Habib Khemira1

Physiological and biochemical changes of interspecific hybrid almond rootstock GF677 exposed to different external K+, Ca2+ and Na+ were investigated in this study. Plants were grown either with a complete nutrient solution containing 10 mM K+ and Ca2+ without or with 75 mM NaCl and 75 mM NaCl alone. Growth, gas exchange, leaf pigments, free polyamine, proline, total sugar contents, total polyphenols as well as total antioxidant activities were determined. A significant reduction of biomass was detected in GF677 in response to additional KCl and CaCl2 in the culture medium. Nevertheless, the best results in terms of photosynthetic rate, photosynthetic pigment concentrations and mineral nutrition (limitation of Na+ accumulation and maintenance of Ca2+ and K+ leaf content) were obtained in response to the combined Ca2+ + NaCl or K+ + NaCl treatment. However, the most important was the fact that the addition of K+ under salinity increased the chlorophyll content, the Chla and Cha/Chlb ratio. Such increment was more pronounced compared to that induced by Ca2+ addition in saline medium. Furthermore, our results showed that the exogenous supply of K+ under saline conditions increase the petunidin-3-glucoside leaf content. The high accumulation of this component is considered as a more important source of antioxidants than others components. Interestingly, the results showed a significant accumulation of Putriscine, proline and sugar under K+ + NaCl treatment in GF677. The addition of Ca2+ or K+ alone or with NaCl enhanced the polyphenols accumulations in leaves of GF677 compared to unstressed plants.