Effect of salinity on plant growth,photosynthetic pigments and proline content in leaves of watermelon seedlings

To lay a foundation for further studying and clarifying the physiological mechanism of watermelon plant under salinity,the growth and physiological changes of watermelon seedlings in response to salinity were explored.The effects of different concentration NaCl stress on plant growth,photosynthetic pigments content,relative membrane permeability and proline content in leaves of watermelon(Citrullus lanatus M.)seedlings grown hydroponically were studied.The results showed that lower concentration(25 and 50 mmol·L-1)NaCl treatments improved watermelon seedlings growth while higher concentration(75,100 and 150 mmol·L-1)NaCl stresses obviously inhibited its growth;with increasing NaCl concentration,relative membrane permeability increased significantly,however,photosynthetic pigments and proline content in leaves showed clear regularity that increased at lower concentration and decreased at higher concentration,and reached the highest value at 75 mmol·L-1 NaCl for photosynthetic pigments content,at 50 mmol·L-1 NaCl for proline content.The research revealed that lower concentration salinity contributed to growth rather than caused stress-induced damage;on the contrary,higher concentration salinity significantly inhibited plant growth,destroyed the structure of cell membrane and influenced the normal metabolism of photosynthetic pigments and proline in watermelon seedlings.