숙주식물에 침입한 기생피자식물 새삼(Cuscuta japonica Choisy) 흡기(吸器)의 발달과 미세구조

Abstract

The development and ultrastructure of the endophyte in the parasitic angiosperm Cuscuta japonica Choisy growing within the host plant Impatiens balsamina L. was studied with light and electron microscopy. The endophyte consisted of mainly vacuolated parenchymatous axial cells and elongate peripheral cells. The peripheral cells had large nuclei and a dense cytoplasm including abundant cellular organelles. It was suggested that the elongate peripheral cells are metabolically very active. These cells were transformed into the filamentous hyphal cells which were separated each other and independently penetrated into the host tissues. Cytologically the hyphal cells growing within the host parenchyma were similar to that of the peripheral cells. Especially the hyphal cells contained various plastid types including well-developed thylakoids, starch grains, crystals. The hyphal cells reached the host xylem were differentiated into the water-conducting elements, xylary hyphae, by thickening of the secondary walls. The hyphal cells reached the host phloem were differentiated into the nutrient-conducting elements, phloic hyphae. The phloic hyphae possessed a thin layer of peripheral cytoplasm showing a typical feature of sieve-tube member such as the parallel arrays of smooth endoplasmic reticulum, mitochondria, and plastids with the fine starch granules. The structural features of the endophytic cells were compared with those of the other parasitic plants and were discussed in view of the translocation of materials from host to parasite.