Evaluating potential of borage (<i>Borago officinalis</i> L.) in bioremediation of saline soil

Abstract

Bioremediation is an efficient, economical and environmentally acceptable strategy used for coping with the salinization of agricultural soils. In this study, borage has been proposed as possible candidate for bioremediation of Na⁺ and Cl⁻. In this order, the borage (Borago officinalis L.) seeds were sown under four levels of salinity (non-saline as control, 5, 10 and 15 dSm^-1). Bioremediation and production potentials of borage were evaluated at three growth stages: seedling or early growth, vegetative and flowering stages. This study has been conducted using factorial experiment in randomized complete block design with three replications. The saline ions accumulation in company with changes in growth and chemical composition of borage was studied. The results indicated that the contents of Na⁺ and Cl⁻ in plants increased as salinity levels of growth medium were enhanced. The noticeable contents of Na⁺ and Cl⁻ (9.096 and 5.665%, respectively) were accumulated in borage aerial parts at the highest level of salinity (EC of 15 dSm^-1), whereas minimum values, 2.029 and 1.520%, occurred at non-saline condition. Although, borage growth decreased with increasing salinity, its survival/or noticeable growth indicated that this plant could tolerate salinity up to EC of 15 dSm^-1. The salinity had a significant effect on the total phenol, alkaloids and tannins and their contents increased with increasing salinity. In contrast, mucilage content and swelling index significantly decreased with increasing salinity. Therefore, borage had noticeable quality and quantity yield up to salinity level of 15 dSm^-1 and could cumulatively remove considerable amounts of salt from the soil. In addition, if borage can be cultivated as an inter-crop all year round at saline soil with EC up to 15 dSm^-1, it can remedy saline soil in respect to Na⁺ and Cl⁻.

Keywords: Borago officinalis L., bioremediation, growth stage, salinity, salt tolerance