Morphological characterization of leaves at different crown positions of tangerine genotypes

The leaf anatomy has been shown as an important tool to understand the interaction between this organ and its microclimate but this topic is still unclear for citrus plants. The objective of this study was to analyze the leaf structure of Ponkan, Fremont and Thomas tangerine and Murcott tangor. Fully expanded leaves were collected collected, from the 2nd and 3rd nodes of plagiotropic branches facing West, at three crown heights (lower, middle and upper). The leaves were fixed in 70% ethanol and embedded in historesin and sectioned in a semi-automatic microtome. The sections were stained with toluidine blue; images were captured under a light microscope coupled and analyzed to measure leaf tissue thickness. The Fremont tangerine leaves had greater epidermis thickness on the adaxial and abaxial surfaces and secretory cavity diameter as well as a shorter distance between secretory cavities, whereas the Murcott leaves had greater palisade and spongy parenchyma thickness. Thus, Fremont and Murcott are potential varieties for xeric conditions, as they are able to reduce transpiration and make optimal use of high incident radiation. The microclimates created by plant architecture may affect the leaf anatomy of the Ponkan, Fremont and Thomas and Murcott trees, allowing anatomical plasticity.