Chlorophyll a / b ratio in green tissues from 39B3 mutant and wild type cultivar of Citrus clementina. Chlorophyll a and b content was measured in young and old leaves and fruit peel exocarp from wild type clementine cultivar (Wt) and 39B3 mutant (39B3). Measurements were also taken from exocarps of a normal wild type clementine tree showing fruit colour delay (Wt-d) due to altered environmental conditions. The relative content of chlorophyll a to chlorophyll b is represented as the Ca/Cb ratio. Data are average of 3 (exocarp) or 5 (leaves) independent determinations and error bars show standard deviation.