S13 - Session O2 - Effect of different aluminium supplies during vegetative phase and sepal blueing in hydrangea inflorescence

Authors: Hanaé Roman *, Vincent Guerin, Lydie Huché-Thélier, Béra Ley-Ngardigal, Elise Herbommez, Thomas Eveleens, Nathalie Leduc

In Hydrangea macrophylla , the quality of the flowering plant depends both on its architecture and the color of the inflorescences. Indeed, the presence of delphinidin in the sepals allows a pink coloration, or blue one if aluminum (Al) is also present in the substrate. Nevertheless, the relation between quantities of Al supplies and sepal blueness is unclear. Within the framework of the MATCH project, which aims to reduce crop inputs, one of our objective is to reduce Al supplies, in light with Al toxicity for the environment. Traditionally, Al is added at the end of the vegetative phase, until a foliar concentration of 400mg Al/kg DM (dry mass) (Leuween et al., 2003). This threshold, experimentally defined, must allow to obtain a deep blue stain of sepals. Nevertheless, growers observe that the number of necessary Al supplies varies according to varieties. To optimize the amount of Al applied, trials are conducted by reducing the quantities of Al applied at the end of the vegetative phase. So, different amounts of Al (as in production=100%, 50% and 0) were applied during the outdoors vegetative phase to three hydrangeas varieties with a gradient of blueing capacity. Mineral element, including Al, quantifications in different organs were performed during vegetative and flowering phases to characterize Al content and its effect on plant mineral nutrition. The inflorescence color was objectively characterized with a spectrocolorimeter. In addition, plant phenotyping was carried out at flowering to compare the quality of the plants obtained with different Al supplies. First results will be presented on both the visual quality of the plants and the evolution of Al and other mineral contents in the organs in relation to the plant growth and the color of the inflorescences.