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As all perennial plants, fruit trees must cope with multiple environmental stresses during their life. The current progressive increase in air temperature makes fruit trees particularly fragile because of their long life during which they might accumulate stresses and the long duration of the selection process to search for more adapted materials. The progressive temperature increase directly impacts the tree phenology, especially their flowering time which results from the regulation of dormancy duration. The ongoing changes endanger the flower quality and the synchronicity of flowering among varieties that is necessary for cross-pollination. Moreover, during summer, despite the irrigation of most orchards, trees must face periods of soil water deficit and/or high temperatures during which the regulation of stomatal closure may impact the tree water use efficiency. Fruit development also depends on the climatic conditions during formation and maturation whereas floral induction occurs for the next season. In this talk, we will briefly review the threats for fruit production and the physiological mechanisms possibly involved that would deserve deep investigations for provid ing a more comprehensive knowledge of fruit tree temperature perception and responses. This knowledge is indeed crucial to draw strategies for the creation of new plant material better adapted to future climatic conditions.

International audience; In apple, carbon source/sink relationships are assumed to affect fruit growth and floral induction and consequently tree flowering potential. Nevertheless, the effect of local variation of carbon source/sink relationships and distances within trees on these processes remains unclear. This study aimed at investigating the effect of distances between leaves, fruits and meristems on fruit size and floral induction. Experiments were performed on adult trees of the ‘Golden’ cultivar from 2015 until 2017 in the south of France. Thirteen treatments with different kinds of local leaf or fruit removal were set up in mid-June on trees previously managed to be either in low or high crop loads. Mean fruit weight and floral induction rate were evaluated in the different parts of the tree including defructified and defoliated parts.The floral induction rate was reduced on parts of the tree that were defoliated, whatever the defoliation treatment and, therefore, the distance to remaining leaves. Moreover, no impact of defoliations on floral induction was observed on not-defoliated parts of the trees. Both together, these results show a major impact of local source/sink conditions on floral induction. Fruit weight was reduced on the parts of the trees that were defoliated when leaf removal was performed on one side of the Y-Shape trees or on half of the branches. This decrease was also observed but to a lesser extent on defoliated shoots when leaf removal was performed randomly on half the shoots. This suggests that carbon fluxes came from the neighboring shoots to sustain fruit growth of non-leafy shoots. Fruit weight increased for trees subjected to fruit removal treatments, probably due to a flux of carbon from the parts of trees without fruits. This study confirms that source-sink relationships have a great impact on floral induction and fruit growth. Moreover it gives new knowledge on the scale of plant organization at which source-sink relationships affect these processes. These experiments will be used to calibrate a functional structural model built to simulate floral induction variability within trees.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Haploidization in onion (Allium cepa L.) using immature flower buds simulates zygotic embryogenesis with no fecundation. In order to know the involvement of polyamines (PAs) in this process, we determined the concentration of endogenous PAs in flower buds and experimented the addition of various combinations of PA molecules in the medium. At the inoculation stage, high levels of free and conjugated spermidine and low putrescine + hydroxyputrescine/spermidine + spermine ratio characterized the highest responsive varieties. During in vitro culture, high levels of putrescine and its derivatives characterized the lowest responsive varieties, whereas high levels of spermidine and spermine characterized responsive varieties. The putrescine + hydroxyputrescine + homospermidine/spermidine + spermine ratio remained low in responsive varieties. The addition of spermidine or spermine (2 x 10(-3) M) to the culture medium improved significantly the embryo production. Our results suggest that the arginine decarboxylase pathway is involved in PA biosynthesis during the in vitro culture of flower buds. Our study showed that specific ratios of PAs are required for successful gynogenesis in onion

Trois types de taille en vert du verticille sont pratiqués sur deux cultivars de cerisier de vigueur différentes (Burlat et Napoléon) : pincement très court et très précoce (13 avril 1992), taille à 4 noeuds et taille à 8 noeuds, ce derniers tous les 15 jours du 8 mai au 14 août 1992. Le pincement précoce et les tailles courtes provoquent une modification de l'évolution des bourgeons de la base : d'une destinée florale ils deviennent végétatifs. Plus la taille en vert est précoce plus le pourcentage de rameaux qui repoussent est élevé, plus les rameaux sont longs et florifères. Nous supposons que ceci est dû au délai nécessaire aux méristèmes des bourgeons axillaires pour qu'ils accomplissent leur initiation florale

Etude sur la production d’éthylène chez le sapin de douglas (Pseudostuga menziesii) suite à une annelation d’écorce et à un trempage racinaire. (Etude préliminaire à l'induction florale)

Induction florale chez les conifères : étude des interactions entre activité racinaire, croissance aérienne et initiation florale chez Pseudotsuga menziesii. Aspects morphologiques, rôle possible de certains régulateurs de croissance

Etude des cytokinines chez Pseudotsuga menziesii Mirb.

Premières contributions à l'étude des floraisons secondaires chez le poirier. Analyse histologique. Facteurs eco-physiologiques. Facteurs génétiques.

I- L'induction florale chez les arbres fruitiers[br/] Différenciation des bourgeons floraux du Prunier[br/] Période d'induction florale chez la variété Williams[br/] II- La régularité des productions annuelles[br/] a) contrôle de l'abondance de la floraison[br/] b) contrôle du taux de fructification[br/] III- Conclusion[br/]