2.4 Measurement of density and diameter of lenticels in apple skin
The density of lenticels on skin of apples sampled at 90, 115 and 140 DAFB was measured by counting the number of lenticels within a 1 cm2 lattice of transparent plastic film laying over the sunlight-exposed surface of the fruit. The number of lenticels in 30 lattices was averaged for each cultivar, with one lattice per fruit. The diameter of lenticels was measured at a magnification of 400× under an Olympus light microscope provided with a light filter. A thin layer of peel at the juncture between the shoulder and body of apple fruit was mounted in a drop of water on a slide, and the diameter of each lenticel [(length+width)/2] was measured with an ocular micrometer. The diameters of 40 lenticels were averaged for each cultivar.