Changes in cell wall carbohydrates composition of leaves and shoots from Lotus tenuis under saline stress

MARIA ELENA VAGO; JORGE ZAVALA; MARINA CIANCIA

Buenos Aires

Simposio; International Symposium of Forage Breeding; 2015

Changes in cell wall carbohydrates composition of leaves and shoots from Lotus tenuis under saline stressMaría Elena Vago1, Jorge Zavala2, Marina Ciancia3,4¹Facultad de Ciencias Agrarias, Universidad Católica Argentina, Freire 183, 1425 CABA, Argentina. ²Cátedra de Bioquímica, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, 1417 CABA, Argentina. 3Cátedra de Química de Biomoléculas, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453, 1417 CABA, Argentina. 4CIHIDECAR-CONICET, Ciudad Universitaria, Pabellón 2, 1428 CABA, Argentina.Forage legumes are key components on cattle diets based on natural grasslands in the Flooding Pampa (Argentina). Lotus tenuis is highly nutritious and the predominant legume in this area due to its ability to grow under stresses of waterlogging and salinity. Part of salt stress resistance of plants depends on their cell walls whose biochemical characteristics define their quality and digestibility as forage. The aim of this work was to study the differences on the cell wall carbohydrates due to saline stress. A tolerant salt stress line was grown on loam/perlite under greenhouse conditions. Two saline treatments were used: dose 1, watered with 75 mM NaCl, and dose 2, with 150 mM NaCl. Dried and milled samples of leaves and shoots were analyzed for neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin. Also, they were sequentially extracted with organic solvents, and the residues were extracted twice with hot water, obtaining two extracts and a residue.The whole water soluble material represented 15.1-18.6 % of samples from plants grown in saline conditions and 12.1-13.5% for those from control. The amount of carbohydrates in shoots almost doubled the one in leaves. They contained high amounts of amylose and soluble pectic material, highly digestible components. The most evident difference between leaves and shoots was the presence of high quantities of rhamnose in leaves which suggests the presence of rhamnogalacturonan-I, but were not affected by salt treatments. Extracts from leaves and shoots showed major amounts of arabinose and galactose, which should derive from pectin structures or arabinogalactan proteins. The amount of galactose decreased with the increase of added salt, while arabinose increased, suggesting important differences in the side chains of those polymers. The residues contain most of the cell wall material. A decrease in NDF and ADF was found for the salt treated samples. The amount of hemicellulose and cellulose was lower in leaves in agreement with the carbohydrate determinations. These results begin to reveal some evidences about changes in cell walls from leaves and shoots of Lotus tenuis grown under saline stress that could affect its potential voluntary intake and digestibility. Corresponding author: María Elena Vagomevago@uca.edu.ar