A Study on the Accumulation of Proline- An Osmoprotectant Amino Acid under Salt Stress in Some Native Rice Cultivars of North Kerala, India

Salinity is a major yield reducing factor in coastal as well as arid irrigated rice production systems. Salt induced abiotic stress is an acute problem, interrupting the metabolic processes of plants, resulting in reduced growth and productivity. Proline is an amino acid which increases in plants under abiotic stress. Salinity stress affects the metabolism of plants leading to severe crop damage and loss of productivity. Oxidative stress is one consequence of salinity that may be responsible for much of the damage. We inspected the immediate accumulation of proline in salinity induced stress in seven native rice (Oryza sativa L.) cultivars. Among the seven, five namely Orthadian, Chovvarian, Kuttusan, Kuthiru and Orkazhama were collected from a saline rice tract of the region and two namely Kunhutty and Veliyan from a non-saline rice tract of the region. The plants were subjected to different levels of salt stress ranging from 0 to 200 mM of NaCl and the concentration of proline in the leaf samples was inspected. Results showed that proline concentration increased in all the cultivars studied in relation to increase in salt stress and it was progressive along with increase in stress. This property was shown by all the cultivars irrespective of the fact whether they evolved in a saline habitat or a non-saline habitat. However, proline accumulation was higher in the cultivars collected from the saline tract when compared to the cultivars collected from the non-saline tract.