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  • Author or Editor: Loïc Pagès x
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Leaf emergence was studied on main and first-order shoots of peach and nectarine [Prunus persica (L.) Batsch.] trees belonging to nine standard cultivars, during their first growing season. The number of emerged leaves was recorded on main shoots (originating from the grafted buds) and on first-order shoots (inserted directly on main shoots). Similarly shaped leaf emergence curves were observed on main and first-order shoots for all the cultivars. Leaf emergence rate decreased gradually as the number of leaves increased. The number of emerged leaves could be modeled as a monomolecular function of accumulated thermal units. Significant differences were found between cultivars in a multiple analysis of variance of the model parameters, for main and first-order shoots. The ranking of the cultivars was similar for both types of shoots. Leaf emergence rate was lower on first-order shoots than on main shoots. Differentiating between shoot types is necessary for a reliable comparison of genotypes.

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Genotypic variations in the length-diameter relationship of branches among peach and nectarine [Prunus persica (L.) Batsch.] cultivars were investigated. The length and basal diameter of all undamaged first-order shoots from 1-year-old trees of 14 cultivars and one accession were measured. Statistical analysis of the allometric relationship between length and basal diameter of shoots provided evidence of genotypic differences for that relationship, although the diameter of very short shoots did not differ between genotypes. A gradient existed from `Armking' with thin shoots (9 mm in diameter for 85.5-cm-long shoots) to `Flavorcrest' with thick shoots (16.4 mm in diameter for 85.5-cm-long shoots). Early selection for shoot thickness should be possible in breeding programs. The likely consequences of observed shoot thickness variations on the mechanical and hydraulic properties of shoots are discussed.

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