Spatial feature of the path from the chilling receptor to the bud endodormancy release: experimental contribution in peach tree
Résumé
Not many studies have been carried out that aimed at knowing the spatial features of the transduction of external signals that influence bud endodormancy release in woody perennials: which structures are able to perceive the signals? Which buds are targets (at the endodormancy release level) of the transduction process borne in a given receptive structure? Some of these studies concerned temperature at rather large scales; they generally could not afford definite conclusions at the bud endodormancy level. Very few studies were at smaller scale: they used warm baths or active substance application on single buds. Surprisingly, though temperature is undoubtedly the main natural factor driving the bud endodormancy release, to our knowledge, no work addressed the effect of temperature per se. We carried out experiments which consisted in selective chilling of some nodal groups of buds on shoots of 'Redhaven' peach tree under full endodormancy. A device (temperature conditioned localized air jets) was designed in order to provide an as sharp as possible temperature gap between given chilled buds and the 'non-chilled' rest of the tree structure (the adjacent axis tissue included). During 2 experimental seasons we tried different chilling doses. The chilled vegetative buds broke or did not, depending on the chilling dose; most of the broken buds got long shoots. Neither the chilled nor the non-chilled floral buds bloomed. We can conclude (i) the nodal group of buds, or a part of it, is a receptor of the chilling signal, sufficient for initiating a process that releases the endodormancy of its vegetative bud; (ii) the transduction process that is initiated in a given nodal buds group does not reach any other bud. Different aspects of the results are discussed and prospects for further experiments on the topic are given.