Impact of high temperature on sucrose translocation, sugar content and inulin yield in Cichorium intybus L. var. sativum

Abstract

Cichorium intybus is a biennal species storing inulin in taproot during the first year and flowering after vernalization. Heat impact on sugar distribution and inulin yield remains poorly documented. Plants were cultivated under ambient or high (ambient+5 °C) temperature for 27 weeks. Plants were monthly harvested and morphological parameters, bolting rate, sugar translocation, soluble sugars and inulin content were determined. Heat reduced shoot and root growth and unexpectedly induced precocious bolting. It increased fructose contents in roots and leaves, increased root myo-inositol and reduced leaf sucrose content. At harvest, inulin content was higher in heat-treated than in control roots but total amount of inulin produced per plant was lower. Heat inhibited sugar translocation from leaves to secondary roots. Total soluble sugar content was lower in leaves but higher in roots of bolted plants compared to non-bolted ones. Bolting induced an increase in the mean degree of polymerization of inulin and root lignification. High temperatures impaired inulin production as a result of root growth inhibition and reduced sugar translocation from the leaves to the roots. Heat induced precocious bolting on non-vernalized plants. Bolting reinforced root growth inhibition and thus inulin yield decrease.