Differential responses of ‘Muscat Hamburg’ and ‘Balıkçı Siyahı’ grapevines to boric acid application under salinity stress: mitigation versus toxicity

Abstract

This study was conducted during the 2023–2024 vegetation period in an unheated plastic greenhouse at the Ordu University research site. In this study, agricultural perlite was used as a trial medium for soilless cultivation, and the effectiveness of boric acid in reducing the effects of salt stress was investigated on ‘Balıkçı Siyahı (Vitis labrusca)’ and ‘Muscat Hamburg (Vitis vinifera)’ grape varieties. Within the scope of the experiment, shoot, root, and physiological parameters, including chlorophyll content, ion leakage, and cell membrane damage rate, were comprehensively evaluated. Salt stress significantly suppressed growth parameters, particularly shoot length, shoot diameter, and fresh shoot weight. Conversely, root-related morphological characteristics, including root dry weight and number, were stimulated under salt stress, demonstrating a defense mechanism to optimize water uptake and restrict the translocation of toxic ions. Overall, ‘Balıkçı Siyahı’ exhibited superior salt tolerance compared to the ‘Muscat Hamburg’ variety. The application of boric acid notably improved plant growth and physiological stability under saline and non-saline conditions. Among the boric acid concentrations, the 1 mM dose provided optimal physiological protection for the tolerant variety, effectively reducing ion leakage and preserving the chlorophyll content. However, under saline conditions, a high boron concentration (2 mM) was found to cause significant toxicity in the more salt-sensitive ‘Muscat Hamburg’ variety. Therefore, to alleviate salt stress, the use of a 1 mM boric acid concentration and cultivation of the ‘Balıkçı Siyahı’ grape variety are particularly recommended.