Growth parameters of 'Golden Delicious' apple trees (Malus × domestica Borkh)
High yield and high quality of tree fruit result from appropriate orchard design and management practices. This requires an accurate knowledge of vegetative growth, branching, and flowering processes of fruit trees. Tree development knowledge is the fundamental information necessary to build functional-structural tree models, which have various applications in agriculture. To build such models, information is needed on the distributions of growth parameters, not merely means as are often reported. The objective of this study was to quantitatively analyze shoot development and examine the correlations between fruit quality and light distribution in apple trees. This study was conducted in 2014, on 'Golden Delicious'/G.16 apple trees grown at the Purdue Meigs Research Farm. Measurements of shoot development were taken to determine the shoot growth rates, the frequency of leaf and stem length distribution, as well as the branching characteristics of two-year-old branches. The light distribution in tree canopies was measured and fruit quality was analyzed to determine correlations between them. Results showed a heterologous growth pattern of different types of shoots in trees. Vegetative spurs had the largest leaves, reaching a length of 90 mm, while flowering spurs had the smallest ones, which were about 40 mm. Most vegetative spurs and bourse shoots were less than 5 cm in length. For terminal shoots, however, the lengths were evenly distributed between 5 and 16 cm. The highest branching frequency was found in the middle section of two-year-old shoots, while more reproductive laterals were found in the distal portion as opposed to the basal or middle portions of shoots. Light intensity was a good predictor of soluble solid concentration and skin background color, but was poorly correlated with individual fruit weight, firmness and starch pattern index. The data collected in this study are being incorporated into a model of apple tree growth in collaboration with colleagues in the Department of Computer Graphics Technology at Purdue University.
HIRST, Purdue University.
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