Original article Hormonal changes throughout maturation and ageing in Pinus pinea Ana Elisa Valdés a , Belén Fernández a, *, María Luz Centeno b a Unidad de Fisiología Vegetal, Departamento de Biología de Organismos y Sistemas, Universidad de Oviedo, c/Catedrático Rodrigo Uría, s/n. 33071 Oviedo, Asturias, Spain b Departamento de Biología Vegetal, Facultad de Ciencias Biológicas yAmbientales, Universidad de León, Campus de Vegazana, León, Spain Received 30 September 2003; accepted 13 February 2004 Abstract Phytohormones, which are responsible for certain age-related changes in plants, play a major role throughout maturation and ageing. Previous results dealing with this topic allowed us to describe an ageing and vigour index in Pinus radiata based on a ratio between different forms of cytokinins (Cks). The aim of the present study was to extend the studies on the changes in the hormonal status throughout maturation and ageing to Stone pine (Pinus pinea L.). With this aim in mind, a number of Cks were analysed in addition to indole-3-acetic acid (IAA) and abscisic acid (ABA) in terminal buds, axillary buds and in the apical portion of needles collected from trees at different stages of development. The results showed an increasing pattern in the levels of various Cks similar to that found in previous studies on P. radiata. Although the maintenance of the same ratio as an ageing and vigour index was not ratified, these results seem to point to Cks as major hormones throughout maturation and related processes in conifers. The distribution of hormones between the two parts of the needle is also discussed. © 2004 Elsevier SAS. All rights reserved. Keywords: Abscisic acid; Cytokinins; Indole-3-acetic acid; Maturation; Pinus pinea; Stone pine 1. Introduction Efforts to accomplish rapid propagation of woody plants have met with limited success as their vegetative propagation becomes increasingly difficult with age, due to the loss of morphogenic competencies throughout maturation [14,28]. The effects of tree maturation have been a major obstacle in the deployment of selected clones. While cuttings from juve- nile trees are able to root easily, once the tree has reached its flowering capacity, serial grafts are necessary to recover rooting abilities [16]. However, since it is not possible to visually detect whether a grafted scion is able to root, at- tempts at rooting imply time-consuming work as well as economic losses. Little is known about maturation and ageing in a physi- ological sense. More data about these processes could be useful in the search for a maturation index for both an early selection of genotypes and evaluation of reinvigoration alter- natives, making forestry programs more profitable. A num- ber of maturation indices have been reported, that take into account pH patterns [1], morphological traits [19,20], or various biochemical compounds and plant hormones [9,17]. For instance, there is genetic evidence that abscisic and indole-3-acetic acids (ABA and IAA, respectively) may in- teract to regulate root growth and rooting potential, which is directly associated with juvenility [31]. Furthermore, cytoki- nins (Cks), which are hormones extensively involved in plant development and in the transition from vegetative to repro- ductive phase [24], participate with auxins in developmental processes controlling each other’s abundance [31]. In a pre- vious study, Valdés et al. [33] described an ageing and vigour index in the ratio of N6–isopentenyladenine (iP)-type to zeatin (Z)-type Cks in both axillary and terminal buds of the coniferous species Pinus radiata. This index showed a de- creasing pattern throughout tree maturation due to decreas- ing levels of iP-type as well as increasing amounts of Z-type Cks. This finding was inverted in the reverse process of reinvigoration, an increase in iP-type Cks and a drop in Z-type Cks levels being observed parallel to the recovery of certain juvenile traits, in both terminal [35] and axillary buds Abbreviations: ABA, abscisic acid; Cks, cytokinins; DHZ, dihydrozea- tin; DHZR, dihydrozeatin riboside; IAA, indole-3-acetic acid; iP, N 6 - isopentenyladenine; iPR, N 6 -isopentenyladenosine; J1, 1-year-old trees; J4, 4-year-old trees; OO, 35-year-old trees; Y, 15-year-old trees; YO, 22-year- old trees; Z, zeatin; ZR, zeatin riboside. * Corresponding author. E-mail address: bmfernan@uniovi.es (B. Fernández). Plant Physiology and Biochemistry 42 (2004) 335–340 www.elsevier.com/locate/plaphy © 2004 Elsevier SAS. All rights reserved. doi:10.1016/j.plaphy.2004.02.004