Impact des hautes températures chez la chicorée à inuline (Cichorium intybus L. var sativum) : induction florale, teneurs en sucres et en hormones

Root chicory (Cichorium intybus L. var sativum) is a biennial plant that stores inulin in its taproot during the first growing season and flowers after vernalization. This plant is cultivated as a source of inulin principally in Western Europe where increases in summer temperatures are expected as a consequence of climate changes. Our aim was to study the impact of heat on growth, physiology and yield of root chicory. We found that heat reduced growth and yield and that heat induced bolting and flowering independently of vernalization. We observed that high temperatures impaired inulin production as a result of root growth inhibition even if it increased photosynthesis. Our results suggested that heat reduced sugar translocation from the leaves to the roots. Bolting reinforced root growth inhibition and thus inulin yield decreases. High temperatures induced bolting and flowering but paradoxically, we also confirmed that high temperatures may have a de-vernalization effect by suppressing flowering in vernalized plants. We found that heat increased FLC-LIKE1 (CiFL1) expression, a gene previously shown to be repressed by vernalization in chicory. Our results suggested that the control of flowering by temperature is complex in root chicory and that CiFL1 could be involved in its regulation. We also found that hormonal profile was affected by vernalization and high temperatures and that high temperatures affected the development of reproductive structures and decreased flower fertility. To conclude, this study showed that chicory is relatively resistant to heat even if growth and yield were affected and that heat had contrasting effects on flowering induction: it induced bolting and flowering in non-vernalized plants, whereas it induced de-vernalization and suppressed flowering of vernalized plants.