Control of hyperhydricity of Pistacia khinjuk stocks in vitro shoots.

Hyperhydricity is the most extensive physiological disorder during in vitro propagation. This disturbance can induce anatomical, morphological and physiological problems that cause serious damage. The factors that cause hyperhydricity are the composition of nutrient media and cultures conditions. To reduce the hyperhydricity of Pistacia khinjuk, ammonium nitrate (NHNO), calcium chloride (CaCl·2HO), cytokinins of meta-topolin (mT) and 6-benzylaminopurine (BAP) at different concentrations were investigated in Murashige and Skoog (MS) medium. The lowest percentage of hyperhydricity (34.30%) were obtained from the medium containing 1650 mg/L NHNO, 110 mg/L CaCl·2HO and1 mg/L mT; the highest percentage of hyperhydricity (68.42%) were obtained from the medium containing 206.25 mg/L NHNO, 440 mg/L CaCl·2HO and 0.5 mg/L BAP. The maximum average number of shoots per explant (2.45), average shoots length (18.47 mm) and proliferation rate (85%) were obtained from the medium containing 1650 mg/L NH4NO3, 110 mg/L CaCl2·2H2O of MS and 1 mg/L mT. In addition, when soluble protein (2.12 mg/g) and total chlorophyll a, b (0.96 mg/g) value of normal (non-hyperhydric) shoots were higher than hyperhydric shoots, carotenoid (11.75 µg /g) and water content (78.70%) value of normal shoots were lower than hyperhydric shoots. This study concludes that the hyperhydricity percentage of in vitro P. khinjuk shoots was reduced (12.8%) on modified MS medium with NHNO, CaCl·2HO and mT according to standard MS medium.