Abstract
The feeding activity of Eriosoma lanigerum alters the stem vascular system of Malus domestica to such an extent that it may prioritize the water flow to its galls, as postulated by the “gall constriction” hypothesis. Accordingly, such feeding activity on host plant stems causes an asymmetrical cecidogenetic field relative to the aphid’s location along the stem axis, whose symptoms may be evaluated through the influence on the differentiation of xylem cells. From the anatomical perspective, we investigate the secondary xylem aspects of the galls on the M. domestica stem regions regarding the position of the aphid colonies in the radial axis. We also investigate aspects of the differentiation of xylem cells in the axial axis: below the gall, in the gall, and above the gall, to test the “gall constriction” hypothesis. In the M. domestica – E. lanigerum system, the similarity of the vessel elements in the portions above and below the gall contradicts the “gall constriction” hypothesis, however the over-differentiation of parenchyma cells and redifferentiation of abnormal vessel elements may have promoted a higher water supply to the gall than to the non-galled stem portions, functioning as a compensatory mechanism for the maintenance of the water status in gall developmental site.
Keywords:
apple trees; secondary xylem; vessel elements; wooly-apple-aphid
Full Article: https://www.scielo.br/j/abb/a/wRVmX6M9kxKGsCWZmVVPYsb/?format=html&lang=en