Anatomical Studies On Vegetative Organs Of 9 Species Of Cycads

Applying multidisciplinary theory such as plant anatomy, plant morphology, plant physiology, plant ecology etc, this research have studied on anatomical structure of a part of their root, stem, pinnae and rachis in C. taiwaniana, C. hainanensis, C. parvulus, C. diannanensis, C. simplicipinna, C. elonga, Macrozamia longispina, Dioon edule and Bowenia aserrulata, which can provide specific basis for phylogenetic classification and phylogenetic development of Cycadaceae, and it was vital significant to reveal the unity between structure and their biotope. The results show as follows:The structure of the roots, stems, pinnaes and rachises of Cycadaceae is significantly different from Zamiaceae. There is also difference on the structures of 3 genus of Zamiaceae. The structure and configuration is relatively consistent in 6 pecies of Cycadaceae, but each species has its own structure characteristic.In this analysis, the number of the growth rings is different in the stems of C. taiwaniana, C. hainanensis and C. elonga, because of cycads' age. Secondary xylem of each growth ring is inside and secondary phloem is outside, these two rings are separated by some parenchymatous cells. This unique vascular tissue structure is distinctive from other plants, which is the result of phylogenetic development and adapting to the long-term adverse environment.As the structure of the pinnaes, palisade and spongy tissues are found in the structure of the rachises of the 9 species of cycads, which is an advent appearance that cycads adapt to the environment. The vascular bundle is schizogenetic and arranged by typical " (?) " shape in numerous species of Cycadaceae; while C. elonga possesses schizogenetic bundle and conjoint bundle as well, and its vascular bundles arrangement is reverse "(?)". But the arrangement of vascular bundles are reverse "(?)", "(?)" and arc in M. longispina, Dioon edule and B. aserrulata respectively. The author has discussed the process of the structure changing with the vascular splitting and hyperplasia, and found that there is a similarity in C. taiwaniana, C. parvulus, C. diannanensis and C. simplicipinna, but C. hainanensis has the difference slightly, M. longispina and Dioon edule have obvious difference from the above species. C. elonga is between the other species of Cycadaceae and the 2 species of Zamiaceae, but much similar to the latter even more. As far as the arrangement, type and splitting way...