Background and Aims Flooding stress is known to affect root growth and sugar metabolism in plants, but data are crucially missing for Cichorium intybus which stores inulin in its tap root.
The aim of the present study was to quantify the impact of recurrent episodes of flooding stress on plant growth, water status, photosynthesis and sugar metabolism in relation to inulin synthesis and accumulation in roots of this species.
Methods Plants were cultured for 25 weeks under controlled environmental conditions on a sand substrate in columns saturated with nutrient solution for periods of 2-3 weeks (starting on week 12) alternating with 7 days non-flooding periods. Plant growth, water status, photosynthesis-related parameters and sugar concentration and metabolism were monitored at
regular intervals up to the end of the treatment.
Key Results Flooding increased the number of leaves but reduced net photosynthesis in relation to stomatal closure and decrease in PSII efficiency. The roots of flooded plants are shorter and larger than those of controls but fresh and dry weight were similar in the two situations. Reducing sugars and organic acids accumulated in the leaves while glucose, fructose, sucrose and 1-kestotriose accumulated in the roots. Sucrose synthase (EC 184.108.40.206) and invertase (EC 220.127.116.11) activities increased in both organs while sucrose-phosphate- synthase activity (EC 18.104.22.168) remained unaffected by flooding. Inulin synthesis was delayed in flooded roots and its mean degree of polymerization (DP) was reduced as a consequence of
fructan:fructan 1-fructosyltransferase (1-FFT, EC 22.214.171.124) inhibition.
Conclusions Cichorium intybus is able to cope with intermittent episodes of flooding and modify organ shape without any effect on final weight. Quantity of inulin produced per plant remained unaffected but the quality of inulin (mean DP) decreased as a consequence of flooding.