The use of drought-tolerant rootstocks is one of the available solutions for the cultivation of pear in semi-arid areas. In order to achieve drought-tolerant rootstocks, seeds of Pyrus syriaca, and Pyrus salicifolia species as well as Pyrus communis cv. Spadona, Khoj no. 1 and Khoj no. 2 were cultivated in the field conditions. This research was carried out as a factorial experiment with two factors of pear species (in five levels) and water stress (in two levels of control and drought stress) based on a randomized complete block design. In drought treatment, the irrigation time was considered based on 80% of allowed water depletion. In control blocks, normal irrigation was performed. The experiment began in July and continued to late September. In stress conditions, P. communis cv. Spadona and Khoj no. 1 had the highest seedling height and stem diameter and P. salicifolia and P. communis cv. Khoj no. 2 had the lowest of the rate of these traits. The lowest increase in electrolyte leakage (EL) and the highest proline content were in P. communis cv. Khoj no. 2 and P. salicifolia and the highest EL and the lowest proline were observed in P. communis cv. Spadonain under drought stress conditions. The most and the least relative water content (RWC) were belonged to P. communis cv. Khoj no. 2 and Spadona, respectively, in stress conditions. According to the studied traits, P. salicifolia and P. communis cv. Khoj no. 2 populations were more tolerant to drought stress.

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An optimum culture medium for micropropagation of pomegranate, cvs. 'Malase Yazdi' and 'Shirine Shahvar' is defined and protocols have been developed for in vitro shoot proliferation and rooting of the cultivars. Axillary buds of young shoots were used as explants. The shoots were multiplied in vitro on Murashige and Skoog (MS) supplemented with 0, 1.5, 2, and 2.5 mg.l −1 of N6benzyladenine (BA). The micropropagated/cloned shoots were rooted on MS and half strength (1/2) of MS containing indole-3-butyric acid (IBA) at three concentrations (0, 0.5, and 1 mg.l −1 ) and 0.5 mg.l −1 naphthalene acetic acid (NAA). The cultivar 'Malase Yazdi' multiplied better than 'Shirine Shahvar'. In both cultivars, the maximum shoot number with maximum shoot height was produced on medium with 2 mg.l −1 BA. Control medium free from plant growth regulator also supported shoot multiplication. The cultured shoots exhibited the greatest number of leaves on a medium containing 2.5 mg.l −1 BA. The cloned shoots of 'Malase Yazdi' rooted the best on half-strength MS medium with 0.5 mg.l −1 IBA while shoots of 'Shirine Shahvar', rooted on 1 mg.l −1 IBA and 0.5 mg.l −1 NAA in half MS medium. This method can be used to quickly propagate and conservation of these two pomegranate cultivars for future prospects.

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Non-exchangeable K release can greatly influence soil K fertility. This study was carried out to study the release of non-exchangeable K from 22 surface and subsurface soils of southern Iran using successive extraction with 10 mmol/l of CaCl₂ and oxalic acid in a period of 2−1368 h at 25 ± 1°C. Alfisols, Aridisols, Entisols, Inceptisols, Mollisols, and Histosols were among the studied soil orders. Illite, smectite, chlorite, vermiculite, kaolinite and palygorskite clay minerals were identified. The amount of non-exchangeable K varied from 95 to 506 mg/kg. Results showed that CaCl₂ and oxalic acid released 60 and 55% of non-exchangeable K from soils, respectively. The discontinuity in slope was found when the cumulative amount of released K was plotted versus time, supporting the multi-reactive nature of K exchange sites. The cumulative K release in soils ranged from 87 to 300 mg/kg for CaCl₂ and 78 to 300 mg/kg for oxalic acid which was well described by simplified Elovich and power function equations. The b constant of simplified Elovich as an index of non-exchangeable K release rate was in the range of 10 to 36 mg/kg for CaCl₂ and 11 to 36 mg/kg for oxalic acid. The highest b constant was measured in Inceptisols and Alfisols, while the lowest values were found in Entisols and Histosols. In conclusion, the K release pattern was similar for both extractants and affected by clay content and type, and soil depth.