Growth, photosynthate partitioning and fructan accumulation in plants of Vernonia herbacea (Vell.) Rusby under two nitrogen levels

the effect of two nitrogen concentrations on fructan accumulation and plant growth was analysed in plants of vernonia herbacea during a year period. plants of this species accumulate inulin-type fructans in the underground reserve organs (rhizophores). the plants were cultivated in glasshouse conditions and received weekly nutrient solutions containing 1.3 mmol.l-1 no3- (n-limited) or 10.7 mmol.l-1 no3- (n-sufficient). plants treated with n-sufficient solution presented an increase in total growth with higher biomass, more but smaller leaves resulting in higher total leaf area, higher net assimilation rate, specific leaf mass and higher biomass allocation to aerial organs. in addition, these plants presented higher contents of reducing sugars and lower fructan contents. in contrast, n-limited plants showed reduced total growth with lower biomass, higher biomass allocation to underground organs and higher fructan contents. therefore, although n-limited plants presented a higher fructan concentration, the amount of fructan produced per plant was similar in both n treatments.