Exogenous auxin improves root morphology and restores growth of grafted cucumber seedlings

The aim of this study was to investigate the effects of exogenously applied auxin over the rootstock cuttings on root morphology parameters and stand establishment rate of salt-stressed cutting grafted cucumber seedlings. For that purpose, before grafting, the cut ends of the rootstocks were soaked for few seconds into auxin solution (indole-3-acetic acid (IAA) or indole-3- butyric acid (IBA))at different concentrations and afterwards were grafted by the root pruned splice grafting (RPSG) method. Ten days after grafting, the grafted seedlings were transplanted into individual pots where two different levels of salt-stress (0 and 50 mM) were established. Root morphology parameters, as well as dry matter of the root system and the whole plants were successively analysed to randomly selected plants. Exogenous auxins improved root morphology parameters and restored root growth under salinity conditions. The best results were obtained through the application of IBA, which promoted a better rootstock - scion relationship, presumably due to faster development of phloem and xylem tubes, and the promotion of a vigorous root system which increases plant's absorbing capabilities for water and nutrients under adverse soil conditions.