PJB-2011-228
THE MORPHOLOGY AND ANATOMY OF THE HAUSTORIA OF THE HOLOPARASITIC ANGIOSPERM CUSCUTA CAMPESTRIS
LAN HONG1,2,*, HAO SHEN2,*, HUA CHEN2,3,†, LING LI1, XIAOYING HU2, XINLAN XU2, WANHUI YE2 AND ZHANGMING WANG2
Abstract
The morphology and anatomy of the haustoria of the holoparasitic angiosperm Cuscuta campestris parasitizing itself and different tissues of Mikania micrantha were studied under scanning electron microscope, confocal laser scanning electron microscope and light microscope. C. campestris has a low stomatal density on the stem and there is a nonfunctional conical protuberance with a unique elliptic pore at the apex, which has not been reported before and we call it pseudo-haustorium. The pseudo-haustorium originates from the cortical parenchyma just external to the pericycle. Its initial cells divide anticlinally and periclinally, and then develop into an endophyte primordium, which consists of file cells and meristematic cells. When C. campestris infects host stem, petiole, leaf lamina and itself, it prefers host stem and has the least choice for leaf lamina. The development of the haustoria invading different tissues reveals that the haustorium in the leaf lamina region without veins is initially flat and its search hyphae does not differentiate into xylem and phloem hyphae, which differs from the haustoria with the annular vessel and phloem hyphae in host stem, petiole and its own stem. These indicate that the haustoria might differentiate vascular tissues only when their search hyphae come in with the contact the vascular tissues of the host or itself.
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