構成臺灣水韮球莖維管組織之細胞

Components of Vascular Tissue In The Corm of Isoetes Taiwanensis

臺灣水韮球莖內之維管組織、由管胞、篩胞和薄壁細胞三種細胞所組成。由形成層產生的維管組織排列特殊，靭皮區和木質區交互而排。形成層最初產生者為靭皮區細胞。靭皮區內只具篩胞，而木質區內則多為薄壁細胞，只有少數管胞滲雜其間。篩域均勻地分佈於篩胞之徑線切面和橫切面之細胞壁上，篩胞內常可看到一道（偶有二道）管狀細絃（命名為篩絃）由兩切線縱切面壁貫串細胞腔。

Three cell types, tracheid, sieve cell and parenchyma are recognized in the vascular tissue of the corm of Isoetes taiwanensis Devol. The cambium gives rise to several layers of phloem cells, alternating with several layers of xylem cells. The earliest cambial derivatives are phloem cells. Phloem is composed of sieve cells only with sieve areas uniformly distributed on both radial and transverse walls, whereas xylem consists of mainly the parenchyma and small amount of tracheids scattering among parenchyma. One, occasionally two tubular bridges (termed sieve trabeculae) lying radially across the cell lumen of sieve cell are recognized.