Simplification of the enhancement of visibility of leaf veins in longan using digital mammography

The leaf blades in the canopies of higher plants play an important role in intercepting light energy, CO₂ assimilation and water transpiration. They are, therefore, critical for plant growth and development in the overall plant life cycle. The leaf vein network is important for the distribution of water (the xylem route) and for sugar transport (the phloem route). In this study, apical shoots with 3-5 fully-expanded leaves from 3-year-old longan (Dimoparpus longan L. 'Puang-thong') trees at Lopburi Province, Thailand were collected. The apical shoots (20 cm in length) were dipped into 4% KI (w/v) under either controlled temperature at 40.2 to 41.9^οC (KI-40) or at room temperature (KI-RT). Control shoots were dipped in water. Shoots were then kept overnight before being examined by digital mammography. In the KI-40 treatment, leaf vein networks with high resolution were observed. Minor leaf veins were able to be distinguished in the KI-40 but not in the KI-RT treatment. A histogram distribution in the KI-40 leaves clearly showed the intensity enhancement (intensity 118.67) when compared with KI-RT leaves (intensity 65.45). In addition, the minor vein length in the KI-40 leaves was shown to be higher in the zone close to the leaf margin, compared with the zone adjacent to the mid rib (the main leaf vein). The KI-40 treatment showed that it is possible to explore some leaf vein characteristics, as a result of the improved contrast resolution, when using digital mammography.