Effects of salinity on plant growth and development of onion (Allium cepa L.)

This research was carried out in Çanakkale Onsekiz Mart University Agricultural Faculty's laboratory and greenhouse between 2003-2004 with Texas Early Grano 502 PRR onion cultivar. The objective of this study was to determine the effects of different NaCl concentrations (0, 1.5* 3.0, 4.5, 6.0 ve 7.5 mmhos/cm) on onion at seed, seedling and bulb stages. In laboratory seed tests, germination speed (%), germination rate (%)* germination ratio (%) and radicula length (mm) were measured. Onion seedling and bulbs which were planted in plastic pots placed in greenhouse. In seedlings* plant length (cm), neck length (mm), neck diameter (mm), leaf length (cm), number of leaves, plant weight (g), root weight (g), root length (cm), onion length (mm), and onion diameter (mm) were determined. In onion bulbs, bulb weight (g), bulb diameter (mm), bulb length (mm), shape, brightness, outher peel number (number), inner peel width, bulb firmness, soluble solid content (%)* pH, citric acid (%), vitamin C (mg/100g), and pyruvic acid (mol/1) changes were investigated. The results of the present research showed that morphological, physiological and biochemical features on onion seeds, seedlings ahd bulbs chanced according to applied amount of salt. Germination speed (%), germination rate (%) germination ratio (%) and radicula length (mm) of seeds decreased with increasing concentrations. In overall, onions seedling and bulbs were affected negatively from the salt treatments in terms of morphologic, physiologic and biochemical features. It was also observed that the intensity of the effect increased with the increasing levels of salt concentration. With salt treatments, bulbs became hollow and their weight (g), diameter (mm), length (mm), outher and inner peel numbers (number), inner peel width decreased. Furthermore, salt treatments caused decreases in pH and vitamin C (mg/100g) content in bulbs, and increases in soluble solid matter (%) and pyruvic acid (mol/1) contents. Key Words: Onion, salinity* germination, growth and development, biochemical change. II