title: Maximum Growth Potential and Periods of Resource Limitation in Apple Tree.
abstract: Knowledge of seasonal maximum potential growth rates are important for assessing periods of resource limitations in fruit tree species. In this study we assessed the periods of resource limitation for vegetative (current year stems, and woody biomass) and reproductive (fruit) organs of a major agricultural crop: the apple tree. This was done by comparing relative growth rates (RGRs) of individual organs in trees with reduced competition for resources to trees grown under standard field conditions. Special attention was dedicated to disentangling patterns and values of maximum potential growth for each organ type. The period of resource limitation for vegetative growth was much longer than in another fruit tree species (peach): from late May until harvest. Two periods of resource limitation were highlighted for fruit: from the beginning of the season until mid-June, and about 1 month prior to harvest. By investigating the variability in individual organs growth we identified substantial differences in RGRs among different shoot categories (proleptic and epicormic) and within each group of monitored organs. Qualitatively different and more accurate values of growth rates for vegetative organs, compared to the use of the simple compartmental means, were estimated. Detailed, source-sink based tree growth models, commonly in need of fine parameter tuning, are expected to benefit from the results produced by these analyses.
authors.affiliation: Forests and Biogeochemical Cycles, Department of Sustainable Agro-Ecosystems and Bioresources, Centro Ricerca e Innovazione - Fondazione Edmund MachSan Michele all'Adige, Italy; Faculty of Science and Technology, Free University of Bolzano-BozenBolzano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Reyes
authors.affiliation: Department of Plant Science, University of California at Davis, Davis CA, USA.
authors.forename: Theodore
authors.initials: T
authors.lastname: DeJong
authors.affiliation: Department of Computational Biology, Centro Ricerca e Innovazione - Fondazione Edmund Mach San Michele all'Adige, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Franceschi
authors.affiliation: Faculty of Science and Technology, Free University of Bolzano-Bozen Bolzano, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Tagliavini
authors.affiliation: Forests and Biogeochemical Cycles, Department of Sustainable Agro-Ecosystems and Bioresources, Centro Ricerca e Innovazione - Fondazione Edmund Mach San Michele all'Adige, Italy.
authors.forename: Damiano
authors.initials: D
authors.lastname: Gianelle
keywords: carbon allocation; fruit growth; maximum potential growth; relative growth rate; shoot growth; source/sink; tree growth; vegetative growth