Contribution to the fine anatomy and histochemistry of birdseye sugar maple
2003
Rioux, D. | Yamada, T. | Simard, M. | Lessard, G. | Rheault, F.J. | Blouin, D.
Light and transmission electron microscope observations of birdseye tissues in sugar maple revealed the following features in the xylem: inclined axial elements, vessels smaller and shorter than the ones found in adjacent normal xylem, occasional gaps between xylem cells, abnormal thickenings of vessel secondary walls, and absence of multi seriate rays. Histochemical and cytochemical tests also indicated that birdseye xylem was less lignified than adjacent normal xylem. When this figure appeared in more than five consecutive growth rings, collapsed and hypertrophied cells were observed at the beginning of rings. These abnormal cells seemed to show that cambial initials were injured at the start of the growing season. The injury apparently occurred following a pressure exerted on a group of fibres present in the inner bark, very close to the cambium. After forming these unusual cells, the cambium resumed production of more typical elements. In birdseye tissues, the phloem layer was reduced and rays showed many anomalies. These anatomical changes may have induced poor translocation of nutrients to the cambium, eventually leading to abnormal differentiation of xylem derivatives. High levels of ethylene may have stimulated phellogen activities that could have generated a pressure toward the cambium. Future studies on birdseye formation are also suggested.
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