Seed germination, seedling growth and seedling development associated physiochemical changes in Salicornia brachiata (Roxb.) under salinity and osmotic stress

Abstract

Salicornia brachiata (Roxb.) exhibits seed germination and grows luxuriantly under extremely saline conditions. We hereby report seed germination potential, seedling growth and seedling development associated physiochemical changes in S. brachiata. Seawater above 75 % strength, NaCl above 400 mM and PEG above 20 % reduced seed germination by 50 % in S. brachiata. Germination energy, coefficient of velocity of germination, relative salt injury, and different germination indexes decreased with stress strength. NaCl at 1000 mM and PEG at 40 % completely inhibited seed germination in S. brachiata. In recovery studies, 100 % seeds germinated once the inhibitory stress was removed. S. brachiata exhibited a significantly higher seed vigor index under 75 % strength of seawater and 200 mM NaCl. Malondialdehyde accumulation during seedling development was in accordance with the accumulation of reactive oxygen species (ROS). Sugar, free amino acid, and proline contents varied with seedling development and type of stress. Higher accumulation of polyphenols and flavonoids during seedling development helped to reduce the ROS accumulation. Accumulation of inorganic ions varied and S. brachiata maintained the ratio of K+/Na+ once the seedling is established. S. brachiata exhibited comparatively higher activity of the studied cell wall hydrolases, which helped to maintain hydration and elasticity of cell wall during seed germination and seedling development. Differentially higher activity of superoxide dismutase, guaiacol peroxidase and glutathione oxidase during seedling development under stress conditions helped to reduce the ROS accumulation. The results indicated that among stress solutions of similar osmolarity, maximum inhibition was observed in the seawater and it was followed by NaCl and PEG at seed germination stage.