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Caractérisation physiologique de la réponse à la sècheresse de la Lavande et du Lavandin : impact de la culture inter-rang

Abstract : French Lavender and Lavandin crops are subject to severe dieback, resulting from the interaction between Stolbur's disease and increasingly intense and frequent droughts. Improving the resistance of Lavender plantations is a challenge to safeguard this sector with a strong economic, tourist and social impact on its territory. A project involving partners from research and the Lavender sector aims to increase crop resistance through new practices. Within this framework, the objectives of the thesis were i) to identify physiological indicators of the state of stress, and in particular a physiological threshold of non-recovery, following severe droughts in Lavender and Lavandin and ii) to evaluate the effect of the agro-ecological practice of inter-row cultivation on the response of Lavandin to summer drought. In addition, a study on climate forecasting focused on production departments revealed an increase in summer and autumn temperatures and a decrease in autumn rainfall on the near horizon (2021-2050), confirming the interest of our work for the sector. To continuously monitor the physiological condition of the plants during a drought, PépiPIAF-type dendrometers, which measure variations in stem diameter, were used on these species. Two indices related to the intensity of the drought and the damage caused were thus identified: percentage loss of diameter (PLD) and loss of rehydration capacity (PLRC). Plants did not recover from a drought (PLRC = 100%) when the PLD had reached a maximum value of about 21%. These results mean that the inability to recover occurs when the elastic water storage are empty, thus demonstrating their importance during intense droughts. During dehydration, acoustic measurements and electrolyte leakage showed that this inability was associated with significant cell damage and not a high level of embolism. These two indices developed under controlled conditions also made it possible to diagnose the stress state of lavandins in the field. Dendrometers on lavandins revealed water stress exerted by an inter-crop vegetation cover during the growing season and summer drought. The water stress was earlier with this cover but the intensity of the drought was identical to that with bare soil. In addition to the importance of this work in fundamental research, in particular on the mechanisms of plant mortality, these results open perspectives on the anticipation of mortality in Lavender plantations, and even on the management of irrigation of these crops, for a reasoned control of the hydric stress necessary for the production of essential oils but harmful to the plants according to its intensity and the period.
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Lia Lamacque. Caractérisation physiologique de la réponse à la sècheresse de la Lavande et du Lavandin : impact de la culture inter-rang. Biologie végétale. Université Clermont Auvergne, 2020. Français. ⟨NNT : 2020CLFAC012⟩. ⟨tel-02985392⟩

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