Tuesday, November 14, 2006

Non-structural Carbohydrate Composition in Woody Plants as Indicator of Salinity Tolerance.

Ursula K. Schuch, University of Arizona, Plant Sciences Department, Tucson, AZ 85719, Husein A. Ajwa, USDA-ARS, UC Davis c/o USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905, and Dean A. Martens, USDA-ARS Southwest Watershed Research Center, 2000 E. Allen Road, Tucson, AZ 85719.

Salinity is limiting growth and productivity of many plant species.  The objectives of this study were to determine how carbohydrate composition of salt sensitive and salt tolerant woody perennials were affected by increasing salinity in the root zone and whether changes in carbohydrate composition could potentially be used as a rapid screening tool to determine the salinity tolerance of different plant species.  Acacia stenophylla, a salt tolerant species, and Chilopsis linearis, a salt sensitive species were grown in sand culture and were irrigated with solutions 0.6, 2.5, 5.0 or 10.0 dS/m.  Dry weights and non-cellulose carbohydrates (NCC) and cellulose carbohydrates (CC) fractions of shoots were determined after 16 weeks.  Subsequently, the salt tolerant species Cercidium floridum and Eremophila maculata and salt sensitive species Chilopsis linearis and Tecoma stans were treated as described before and NCC concentrations in leaf tissue were determined after 5 and 12 weeks.  Increasing salinity had no effect on dry weight and combined NCC and CC shoot tissue concentrations of A. stenophylla after 16 weeks of treatments.  Dry weight of C. linearis decreased with increasing salinity.  Increased concentrations of arabinose, rhamnose, galactose, xylose, and total carbohydrates were found with treatments of 2.5 dS/m or greater, but glucose concentration was unaffected.  The two species differed in the percentage of CC and NCC of total carbohydrates.  In leaf tissue, increasing salinity treatments caused increased levels of NCC rhamnose and NCC xylose in C. linearis and T. stans within 5 weeks, but no changes in the salt tolerant species.  Total NCC concentrations and percentage of individual NCC's in leaf or shoot tissue responded to salinity stress and have potential as a screening tool to determine the relative susceptibility of plant species during early stages of growth.