Response of African Basil (Ocimum gratissimum L.) to Salt Stress under Tropical Conditions in the Republic of Benin: Growth, Ions and Organic Solutes Accumulation

Aims: This research aims at evaluating the effect of salt stress on plant growth, Na+, K+, proline and soluble sugars contents in leaves and roots of local cultivar of African basil in Republic of Benin. Study Design: The experiment was laid out in a Completely Randomized Design (CRD) having five treatments and three replications. Place and duration of Study: The experiment was carried out in screening house under natural conditions at the Center of Agricultural Research of Agonkanmey, Commune of Abomey-Calavi, Republic of Benin from January to February, 2020. Methodology: Five salt concentrations (0, 30, 60, 90 and 120 mM) were used to irrigate three weeks old plants for two weeks. After two weeks, plant growth, sodium (Na) and potassium (K), proline, and soluble sugars contents of leaves and roots were determined. Results: Salt stress induced a significant reduction (p = .05) in shoot growth from 60 mM NaCl but had no impact on the number of leaves and shoot water content. Root growth was significantly reduced (p = .05) already at 30 mM NaCl. Leaf and roots Na+, proline and soluble sugars contents significantly increased (p = .05) under salt stress whereas K+ content decreased significantly (p = .05) only in root. Conclusion: Salt stress reduces the growth of African basil plants due mainly to Na+ ion toxicity. The ionic selectivity ratio (K+/Na+) rather than the K+ ion content plays an important role in the response of basil plants to salt stress, while both proline and soluble sugars accumulation may contribute to osmotic adjustment.