Physiological changes during heartwood formation young Eucalyptus bosistoana trees 

 -  IAWA Journal, p.1-13, 2018 .
<br/><br/> Eucalyptus bosistoana F.Muell. is valued for its naturally durable heartwood. As part of an E. bosistoana breeding programme, we have tested the hypothesis that there is a prolonged transition from sapwood to heartwood in young trees, resulting in a wide transition zone. This needs to be considered when assessing trees for heartwood quantity and quality. Heartwood formation was investigated in radial profiles in cores from bark to bark of 6-year-old trees with conventional and confocal microscopy, and with a range of different staining techniques that visualised the physiological changes taking place in the parenchyma cells. Using immunolabelling with antibodies against histone proteins and ?-tubulin, histochemical staining using potassium iodide (I3-KI)and fluorescence emission spectral scanning, we demonstrated that in heartwood nuclei, microtubules, reserve materials (starch)and vacuoles were absent. The observations revealed that 6-year-old E. bosistoana trees contained heartwood. The loss of wáter conductivity by tyloses formation and the death of the parenchyma cells occurred in close proximity resulting in a transition zone of ~1 cm. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>AMYLOPLASTS<br/>CONFOCAL MICROSCOPY<br/>EXTRACTIVES<br/>JUVENILE COREWOOD<br/>NUCLEI<br/>PARENCHYMA CELLS<br/>RAY CELLS<br/>TYLOSES<br/>WOOD