Physiological effects of pre-sowing seed treatment with gibberellic acid on Nigella sativa L

Apre-sowing treatment was applied to black cumin (Nigella sativa L.) seeds, which were surface-sterilized and soaked for 5, 10 or 15 h in 10–6, 10–5, or 10–4M aqueous solution of gibberellic acid (GA). The potted plants were then analysed at 50, 70 and 90 days after sowing for leaf chlorophyll (Chl) content, stomatal conductance (gs), carbonic anhydrase (CA) activity, nitrate reductase (NR) activity, total protein content, net photosynthetic rate (PN), capsule number and seed yield at harvest (130 days after sowing). All these parameters were found to be appreciably enhanced by the hormone treatment. The most prominent results were obtained with 10–5M GA following a pre-sowing treatment for 10 h, in which case the values for PN, CAand NR activity, and seed yield were elevated by 44, 40, 30 and 40% respectively over the control at the 70 day stage.