The current study was undertaken to evaluate the responses of okra to salinity and to study the beneficial effects of silicon and gibberellic acid on yield and ionic attributes of okra under salinity stress. For this purpose, a pot experiment was conducted at the Horticultural Farm of the Department of Horticulture, The University of Haripur, Pakistan. Seeds of the okra cultivar ‘Sabz Pari’ were sown in pots. The experiment was established in a complete randomized design with factorial layout and included a total of 14 treatments deriving from the combination of two factors: two salinity levels and seven treatments with silicon or gibberellic acid. Okra seeds were pretreated with either 0, 50, 75 or 100 mg/L of gibberellic acid and then planted into pots. After germination plants were subjected to 0 mmol (control) or 50 mmol salinity; silicon (in the form of potassium silicate) was applied to plants exogenously at the rate of 2 mmol, 3 mmol, or 4 mmol. The following parameters were measured: number of days to flowering, pod length, pod weight, number of pods per plant and pod yield per plant, and the contents of Na+, Cl-, K+, and proline in the leaves. The results revealed that under 50 mmol NaCl salinity okra plants treated with 100 mg/L of GA3 had the shortest time to flowering (48.3 days) and the lowest Na+ ion content (14.9 mg/L) and Cl- ion content (9.8 mg/L), while in these plants we measured an increased pod weight (18.9 g), pod length (14.6 cm), number of pod per plant (22.6), pod yield per plant (1225 g), K+ ion and proline contents (18.9 mg/g and 28.8 µmol/g, respectively). Hence, this study allowed to conclude that the highest salinity level reduced the yield and altered the ionic status of okra plants, whereas GA3 and Si lowered the toxic effects of salinity and 100 mg/L GA3 along with 4 mmol silicon can be used in order to reduce salinity toxic effects.
Keywords: Na+, Cl-, proline, pods, okra pods