Activities of fructan- metabolizing enzymes in barley stems subjected to terminal drought stress

Barley crop grown in semiarid areas may experience water deficit especially during grain filling that makes them more dependent on stem water-soluble carbohydrates (WSC). Fructans are the most important reserved carbohydrates. A pot experiment was undertaken at Shahid Chamran university in the duration of 2010-2011 growing seasons to investigate the accumulation and loss of WSC and the activity of fructan-metabolizing enzymes under water stress in four barley (Hordeum vulgare L.) cultivars namely Nimruz, Jonub, Nosrat and Torkaman. Cultivars were different in WSC-related traits such as WSC concentration (WSCc) at anthesis, maximum WSCc and rate of WSC accumulation in ten-day period after anthesis. Water withholding elevated WSC remobilisation efficiency. The activity of sucrose:sucrose 1-fructosyl transferase (1-SST; EC 2.4.1.99) harmonized the rate of WSCc increase in cultivars. The change in fructan 1-exohydrolase (1-FEH; EC 3.2.1.80) activity on the fifteenth day postanthesis was along with the change in stem reserve remobilisation. Considering acid invertase (EC 3.2.1.26) activity, a significant difference was observed between cultivars on the fifteenth day post anthesis under water-stressed conditions. Cultivars showed different manners in use of current photosynthesis and stem reserves that could be an important reason in different decreases in grain weight affected by water stress.