title: Effect of location in the canopy on the colour development of three apple cultivars during growth.
abstract: BACKGROUND
  Homogeneity in appearance is one of the quality aspects asked for in the supply chain. Decreasing the biological variation in batches of harvested apples (cultivars Braeburn, Fuji and Gala) becomes increasingly important. Skin colour is one of the aspects that determine both optimal harvest and stage of development. Skin colour is affected by location in the canopy. The rules of development of biological variation are now established and will be used on skin colour data.
  
  
  RESULTS
  The Minolta colour aspects a*, b* and L* measured before commercial harvest change in a sigmoidal fashion and can be analysed including the biological variation, with a logistic model in indexed nonlinear regression, obtaining explained parts of above 90%. The mechanism of colour change is not affected by state of development or location in the canopy. The location in the canopy affects the intensity of both red and green colouring compounds. The variation in colouration is not affected by the location in the canopy.
  
  
  CONCLUSIONS
  The red-coloured apple cultivar (Gala) depends more on the location in the canopy than the less-coloured cultivars (Fuji and Braeburn). The colour development in Fuji apples is considerably slower, with a much larger variation in stage of development. The location in the canopy affects all aspects of biological variation (biological shift factor and asymptotic starting level of colouration) for all three colour aspects L*, a* and b*, but only the mean value, not the standard deviation. The biological shift factors per colour aspects are linearly related. Once induced, variation remains constant during development.
authors.affiliation: Faculty of Agriculture, University of Maribor, Maribor, Slovenia.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Unuk
authors.forename: L M M Pol
authors.initials: LM
authors.lastname: Tijskens
authors.forename: Blaž
authors.initials: B
authors.lastname: Germšek
authors.forename: Peter
authors.initials: P
authors.lastname: Zadravec
authors.forename: Andrej
authors.initials: A
authors.lastname: Vogrin
authors.forename: Janez
authors.initials: J
authors.lastname: Hribar
authors.forename: Marjan
authors.initials: M
authors.lastname: Simčič
authors.forename: Stanislav
authors.initials: S
authors.lastname: Tojnko
mesh_terms: D003116:Color; D004777:Environment; D005638:Fruit / Q000254:growth & development*; D016015:Logistic Models; D027845:Malus / Q000254:growth & development*; D010860:Pigments, Biological; D018515:Plant Leaves; D013045:Species Specificity; D014197:Trees
chemical_list: D010860:Pigments, Biological