Morphological plasticity of sunflower in response to light availability and carbohydrate accumulation with especial attention paid to fructans

GARCÍA LEONELA ANALÍA; MARTINEZ-NOËL G.; GIORGI M. E; TOGNETTI J. A; DOSIO, GUILLERMO A.A.

Rosario

Simposio; XXXIV REUNIÓN DE LA SOCIEDAD ARGENTINA DE FISIOLOGÍA VEGETAL; 2023

SOCIEDAD ARGENTINA DE FISIOLOGÍA VEGETAL

Changes in plant structure may define plant capacity to synthesize and accumulate soluble carbohydrates that will ultimately contribute to grain filling in sunflower, via actual photosynthesis or previously stored reserves. The present work is aimed at studying the relationship between light-driven changes in organ size and sugar accumulation in this species, with special attention to fructans formation. We performed three field experiments with three sunflower genotypes under contrasting irradiance or capitulum removal treatments. We analyzed growth parameters and the dynamics of production and distribution of soluble carbohydrates in plant organs.Increasing light availability from shaded to control treatment induced a moderate enhancement of storing organs volume and an increase in soluble carbohydrates concentration. In contrast, when light availability increased from control to thinned treatment a strong growth promotion with no increase in sugar concentration was observed.Carbohydrates analysis of capitulum tissue at the highest light availability revealed, for the first time in this species, the presence of inulin-type fructans. The amount of each member of the series appeared to decline starting from isokestose, being DP = 15 the longest fructan detected. Results suggest that, in sunflower, fructans could be synthesized only when sucrose availability exceeds a high threshold. The dilution of sucrose under usual field growing conditions would prevent the induction of fructan metabolism.Given the relationship between fructans and tolerance to abiotic stresses including drought, the present finding opens a new perspective for breeding and management of this crop.Both light and carbohydrates per se affected the plastic growth response of organs, which was independent from genetic background and may directly impact on plant capacity to store sucrose, ultimately conditioning crop yield under stress.