Effects of melatonin on flowering, seed yield and seed quality of onion under salt stress

Abstract

The effects of melatonin on flowering, seed yield and seed quality of onion (Allium cepa L.) under salt stress conditions were investigated. Onion bulbs were incubated for 24 hr before planting in 1, 2, 4 and 8 μM melatonin solutions. Salt stress was imposed on the plants four times after planting by an irrigation programme using 100 mM, 200 mM and 400 mM NaCl. The data recorded were: number of leaves, leaf length, number of flowers, flower stalk length, main flower stalk length (from bulb neck to flower structure), expected number of seeds, 1000-seed weight, seed creation percentage, number of seeds per bulb, germination rate, initial count value, germination peak day, germination index, germination peak value, average daily germination, germination value and average germination day. At 400 mM salinity stress, no flowering was observed even though green leaves formed from the bulbs. At 200 mM salinity, only 8 μM melatonin solution provided flowering of the plants. As a result of testing to determine seed quality, seeds obtained from plants grown under 100 mM salt stress with supplementation of 2, 4 and 8 μM melatonin gave similar results, although at 200 mM salinity, a dose of 8 μM melatonin gave significantly highest values. When all the results are evaluated together, it can be suggested that an application of 8 μM melatonin may preserve the seed yield and seed quality of onion under salt stress condition.</p