Anatomy and Ultrastructure of Pith Fleck-Like Tissues in Some Rosaceae Tree Species

Abstract

Unusual xylem tissues were found in Amelanchier laevis, Prunus pensylvanica, P. virginiana, Sorbus americana and S. aucuparia. These zones of abnormal xylem were composed of hypertrophied cells and bands that apparently comprised collapsed cells. The hypertrophied cells appeared to occupy gaps that began to form in the cambial zone. Histochemical tests indicated that the bands were highly lignified and impermeable to an aqueous solution of KMnO4, as revealed by fluorescence. Transmission electron microscope examination disclosed clearly that the bands were composed of collapsed cells and showed that the hypertrophied cells had thicker walls which contained, at times, additional layers. Although the cause of this tissue formation is unknown, its anatomy is quite similar to pith fleck tissues reported by others as being caused by cambium mining insects.

Contribution to the fine anatomy and histochemistry of birdseye sugar maple

“…This response has been reported after cambium injury in Acer saccharum and other hardwood species, for instance following damage induced by cambium miner insects (Gregory and Wallner 1979;Krishnamurthy et al 1986;Rioux 1994). Following injuries made by these insects, the resulting abnormal tissues, called pith flecks, are composed of collapsed cambial cells or their immediate xylem derivatives that completely surround hypertrophied cells; the latter usually originate from ray cells that swell and divide to eventually fill the hole produced by larvae.…”

A suberized perimedullary reaction zone in Populus balsamifera novel for compartmentalization in trees

“…In addition to supporting that concept, it has been reported that keeping wood sections under water saturation prevents wood degradation by fungi already present in the wood, while decreasing the water content during drying, but naturally not below a critical level, triggered the attack of the wood and the growth of these microorganisms (Boddy 1992). Even if suberin, or the waxes associated with it, is probably the most ideally suited substance to limit air diffusion within the tissue and at the same time is a polymer that is particularly resistant to pathogen attack, it should be stressed that nonpolymeric phenols and lignin have also been reported to increase wall impermeability to different substances (Läuchli 1976;Eastman et al 1988b;Rioux 1994). In 1994, all the suberized defensive structures of P. balsamifera, as described in the present paper and in Rioux and Ouellette (1991a), appeared more rapidly when the inoculum contained a large number of O. ulmi cells, particularly rich in hyphae, in comparison with the less concentrated inoculum that was essentially composed of conidia that likely had been dispersed by the sap movement and then might have only poorly germinated in this nonhost tree.…”