Salt tolerance differences mechanisms of grafting combinations between two Handroanthus species

To explore the changes in salt tolerance and the response mechanisms of grafted Handroanthus spp., Four types of grafting treatments were conducted using H. impetiginosus and H. chrysanthus, including reciprocal grafts and self-grafts (controls). Using 0.5% NaCl solution for salt stress, after 21 days of stress treatment, the salt tolerance of each grafted combination was observed and analyzed,, and the changes in cell membrane integrity, content of osmotic adjustment substances, antioxidant enzyme activities, and the balance of sodium and potassium ions under salt stress were observed and analyzed. The aim is to reveal the physiological characteristics of salt-tolerant rootstock grafting to improve the salt tolerance of Handroanthus spp.The results indicated that both forward and reverse grafting unions of the two Handroanthus species enhanced salt tolerance, with significantly greater salt tolerance in grafted plants using the more salt-tolerant H. impetiginosus as the rootstock. Under salt stress conditions, the physiological and biochemical responses of grafted Handroanthus spp. revealed the important role of rootstock-scion interaction in improving their salt tolerance The salt-tolerant mechanisms involved maintaining the integrity of cell membranes in leaves and roots, reducing the accumulation of malondialdehyde, increasing the content of free proline and the activity of superoxide dismutase, intercepting excess sodium ions in the roots, and promoting the upward transport of potassium ions to the leaves, thereby maintaining the ionic homeostasis within the grafted plants.