Physiological and Morphological Responses of Almond Cultivars under In Vitro Drought Stress

In this study, physiological and morphological responses of five almond cultivars to drought stress were investigated under in vitro conditions. Plantlets from five commercial almond cultivars (Supernova’, ‘Tuono’, ‘Sahand’, ‘Ferragnes ’ and ‘Shahroud 21’] were established in MS medium containing 0.5 mg per liter BAP and then subcultured  in MS proliferation medium containing 1 mg per liter BAP. Plantlets were exposed to four different levels of polyethylene glycol containing 0, 2, 4 and 6 percent, respectively, which is equivalent to 0, -0.14,-0.36 and -0.66 bar of water potential as drought stress levels during four weeks. This study was carried out as a two-factor factorial experiment in a completely randomized design with three replications, each consisting of two jars, each contained two explants. At the end of the stress period, physiological indicators of stress, including leaf relative water content (RWC), proline content and ion leakage of leaves and morphological indicators, including plantlet height and number of developed leaves, were measured. The results showed that drought stress increased ion leakage and proline content, while it reduced the RWC, plantlet height and number of developed leaves. According to these results, ‘Supernova’ and ‘Tuono’ were less affected by drought stress compared to other cultivars, while ‘Shahroud 21’ and ‘Ferragnes’ were more affected than others. ‘Sahand’ also showed an intermediate performance compared to other cultivars.