Effect of Salt and Water Stress on the Proline and Total Chlorophyll Content and Nutrients Uptake on Two Sweet Potato Cultivars Grown on Soilless Culture

Soil salinity is one of the important characteristics of arid and semi-arid regions in the world. Salinity and water stress affect plant growth and development. Sweet potato (Ipomoea batatas L.) is a crop with economical importance in the world. Sweet potato is an efficient and low production cost crop that is grown during almost the whole year. However, it is sensitive to water and saline stress, situations that generate yield reduction and loss in the quality of the tuber root. An experiment was performed to determine the yield, proline and total chlorophyll content, and N, Mg and Na uptake in plants from two sweet potato cultivars ('Huambachero' and 'Untacip') grown under three (2.0, 3.0 and 3.5 dS/m) salt and two water (watering each 2 and 4 days respectively) stress levels during summer-fall conditions in La Molina, Lima, Peru. The salt and watering levels were controlled by the use of the soilless culture technique. The plants were grown in quarry sand and watered with a nutrient solution containing a N, P and K concentration (mg/L) 125-20-200. The increase of the salt levels decreased the yield in both cultivars. Under water stress conditions, the yield decreased in 'Untacip', while no increase was observed of the tuber root fresh weight in 'Huambachero'. In 'Untacip' leaves, the total chlorophyll content increased significantly when the salinity increased, but it decreased when the plants were grown under water stress conditions. The proline content increased significantly under salt and water stress conditions in leaves and tuber roots of both cultivars. The increase of the salinity induced less N uptake in 'Untacip' when plants were watered each 4 days. Water and salt stress induced less Mg uptake in leaves of both cultivars. The Na uptake increased when the plants were grown under both stress conditions. Proline accumulation is a common metabolic response of higher plants to water deficits and salinity. Salinity and water stress decrease plant growth by affecting N and Mg uptake required for cell growth and chlorophyll synthesis. According to the results, under stress conditions, 'Untacip' was more tolerant than 'Huambachero'.