J Integr Plant Biol. ›› 1964, Vol. 12 ›› Issue (1): -.

• Research Articles •    

Studies on the Morphological Differentiation of Excised Stems of Mentha arvensis L. I. The Effect of Colchicine upon the Excised Stem Tips

C. L. Lee, Y. S. Hu and S. J. Liu   

Abstract: The excised stem tips of Mentha arvensis L. which had been cultured in vitro with various concentrations of colchicine manifested a series of changes of the internal structures. If 0.1% of colchicine was added into the culture medium as soon as the excised stem tips were explanted, the formation of the adventitious roots normally found at the base of the excised stem tips was completely inhibited. Nevertheless the internode between the fifth and the sixth node showed tremendous bulging. Five days after the excised stem tips being cultured in vitro, various aqueous concentrations of colchicine were added, as soon as some of the adventitious roots had been established at the base. The distal ends of the already grown adventitious roots, after 24 hours of treatment, showed spindle-shaped swellings and the roots ceased to elongate. Longitudinal sections of the tumefacient part exhibited remarkable increment in size of the cortical and stelar cells. Furthermore, the nuclei of these cells were irregularly aggregated. By this time the layers of the root-cap showed reduction in number and its cells were considerably modified. The internode between the fourth and the fifth or the fifth and the sixth node apparently tumefied concomitantly with the various changes in the internal structures. The activities of the apical meristem had been greatly reduced and no further extention in length could be discerned. After the excised stem tip was treated with colchicine within one week, the lowest node was cut and transplanted into a new tube with medium devoid of colchicine. Five days after such treatment, the newly formed adventitious roots were visible near the cut surface at the base. These roots, in general, appeared similar to normal ones and were capable of growing continously. Although most of the apexes displayed no growth activities, one or both axillary buds at the fifth or sixth node promptly elongated; these were never being tumefied. Results from a series of aseptic cultures substantiated with certainty the finding that the excised stem tips treated with various concentrations of colchicine could not effectively form polyploidy with regularity in the meristematic cells. However, colchicine caused abnormal growth in various tissues, and especially induced different degrees of tumefaction. Descriptions of the anatomical and cytological changes of the excised stem tips treated with colchicine were also presented.

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