IMPROVED PERFORMANCE OF TRANSGENIC FRUCTAN-ACCUMULATING TOBACCO UNDERDROUGHT STRESS

Fructans are polyfructose molecules produced by approximately 15% of t he flowering plant species. It is possible that, in addition to being a storage carbohydrate, fructans have other physiological roles. Owing to their solubility they may help plants survive periods of osmotic s tress induced by drought or cold. To investigate the possible function al significance of fructans, use was made of transgenic tobacco (Nicot iana tabacum) plants that accumulate bacterial fructans and hence poss ess an extra sink for carbohydrate. Biomass production was analyzed du ring drought stress with the use of lines differing only in the presen ce of fructans. Fructan-producing tobacco plants performed significant ly better under polyethyleneglycol-mediated drought stress than wild-t ype tobacco. The growth rate of the transgenic plants was significantl y higher (+55%), as were fresh weight (+33%) and dry weight (+59%) yie lds. The difference in weight was observed in all organs and was parti cularly pronounced in roots. Under unstressed control conditions the p resence of fructans had no significant effect on growth rate and yield . Under all conditions the total nonstructural carbohydrate content wa s higher in the transgenic plants. We conclude that the introduction o f fructans in this non-fructan-producing species mediates enhanced res istance to drought stress.