Tylosoids in latiferous canals of Toxicodendron vernicifluum.
This study aims to investigate the ontogeny, anatomy and ultrastructure of the tylosoids in the laticiferous canals of T. vernicifluum (lacquer tree), samples were processed for light microscopy and TEM. Results showed that the tylosoids in the lumina of laticiferous canals originated from epithelia through periclinal division. Laticiferous canal invasions varied seasonally, at the beginning of traditional tapping season of raw lacquer, the quinone conglomerations dissolved, laticiferous canal function was renewed and epithelia secreted raw lacquer; at the end of the traditional raw lacquer-tapping season, tylosoids formed and blocked the laticiferous canals by quinone conglomerations until the next raw lacquer-tapping season. The irreversible invasion was mainly distributed in the nonfunctional phloem region near the periderm. These results suggested that the seasonal changes of tylosoids might provide insights into the defense mechanism of laticiferous canals against the invasion of other substances when cavity pressure decreases at the end of the tapping season of raw lacquer.