variations in root mineral uptake of young Acer pseudoplatanus, L. (Acéracées) according to long and short term nutritional history. Application of woody plants cultivated in soilless culture

In the case of ornamentals woody plants culture leading in containers, is it necessary to supply fertilizer continuously or can we achieve the same aerial development with a fractional supply? This fertilization perspective assumes that the root system could develop a short term capacitive functioning to ensure a continuous nutrition of the aerial system whatever its mineral uptake variations. This hypothesis was tested in young sycamore tree (Acer pseudoplatanus L., Aceraceae) which is known for its ornamental qualities. After a botanical description, its behaviour in soilless culture conditions was studied. Its aerial vegetative development is characterised by a strong fluctuation with two distinct growth waves separated by a reduced growth period. Its root mineral uptake varies strongly at the weekly and seasonal scales. Nitrate and Potassium are the main elements absorbed. At the seasonal scale, their both uptakes are strongly coupled but the ratio Nitrate/Potassium absorbed goes up from 2 in spring to 7 in autumn. Then, the hypothesis has been demonstrated with a study of mineral uptake ability of root system after aerial system cutting (stumps). Isolated root system shows a strong ability for nitrate uptake. For example, the young sycamore can absorb nitrate before the spring bud burst, and such absorption represent 5 to 40% of the total nitrogen content in plant at this time. However, the root system nitrogen uptake ability shows strong variations in relation with the old and recent nutritional story of plant. Finally, the hypothesis was tested from an agronomic point of view with a culture in horticultural conditions. The results have shown that a weekly fertilizer supply does not induce any change in aerial system development compared to a daily supply if the cumulated fertilizer quantities supplied each week are equal. The integration of the short term root system capacitive functioning at the whole plant scale is discussed and some research perspectives are presented.