Response of sesame seedlings to different concentrations of humic acids or calcium nitrate at germination and early growth

Abstract

This study was conducted in order to evaluate the response of sesame seeds (Sesamum indicum L.) to organic or mineral fertilization. The effects of two fertilizers, which were calcium nitrate and humic acids were studied separately at germination and early seedlings growth. Different concentrations of humic acids (HA0: 0, HA1: 500, HA2: 1000 and HA3: 2000 mg L–1) or calcium nitrate (CaN0: 0, CaN1: 50, CaN2: 100 and CaN3: 200 mg L–1) were applied distinctly to the growth media. The experimental design was accomplished in a completely randomized block design with three replications. Germination measurements, seedlings length, fresh seedling weight, total chlorophylls and carotenoids, total soluble proteins and sugars were determined. Results showed that humic acids applied at 1000 mg L-1 or calcium nitrate applied at 100 mg L-1 reduced the mean germination time (3.5 and 3.61 days) and had the highest germination index (GI) and the highest coefficient of velocity (CV). The longest seedling was obtained at the concentrations HA2 and CaN2 (+22%). Total chlorophyll and carotenoids were significantly higher in seedlings receiving the HA2 and CaN2 and these treatments increased total soluble proteins content by 32%. Higher concentrations of humic acids or calcium nitrate HA3 and CaN3 delayed germination and enhanced proline and total soluble sugars, respectively, by 42% and 46%, compared to control. These preliminary results indicated that the use of fertilizers should be optimized and they can be transformed at high level to an abiotic stress menacing plant productivity. On the other hand, suitable concentrations of fertilizers can be used in the future as a remedy to improve growth under abiotic stress.