Dm. Joel et D. Losnergoshen, THE ATTACHMENT ORGAN OF THE PARASITIC ANGIOSPERMS OROBANCHE CUMANA AND O-AEGYPTIACA AND ITS DEVELOPMENT, Canadian journal of botany, 72(5), 1994, pp. 564-574
Some species of Orobanche are parasitic weeds attacking the roots of v
arious crops and causing extensive damage. The development of the youn
g parasite was investigated using light and electron microscopy. Germi
nating O. aegyptiaca and O. cumana form a short root, with no root cap
, which is covered by a thin cuticle. As soon as the root reaches a ho
st, elongation stops, the apex expands, and peripheral cells become pa
pillate. The extended apex becomes the young attachment organ. The out
er papillar surface of the extended apex bears wall protuberances that
are encircled with a thick cuticular belt and covered with a thin cut
icle. These protuberances secrete a carbohydrate that accumulates in a
subcuticular space and is released to the surface, forming a thin adh
esive layer that binds the parasite to its host. Bacteria are commonly
found in the secretion pool, on the papillae, and in the outer cell w
alls. The event of attachment of the young parasite to host surface si
gnals a shift from the independent to parasitic phase. This change als
o includes a shift from the accumulation of lipids to the accumulation
of starch.