J Integr Plant Biol. ›› 1963, Vol. 11 ›› Issue (3): -.

• Research Articles •    

Studies on the Embryos of Pinus koraiensis Grown in Vitro III. Morphological Differentiation of the Root During Germination

C. L. Lee and Chang Hsin-ying   

Abstract: Root development of the intact or excised embryos of Pinus koraiensis Sieb. et Zucc., exhibited discrepant morphological differentiation under experimental condition. That development of the root enclosed in intact megagametophyte grown in the sterile culture medium without sugar, although it showed more rapid elongation, essentially resembled that of the soil-grown seedlings. However, morphological variations existed in the root growth of the excised embryo after one week’s culture. It manifested particularly in the development of the coleorhiza-like structure. As the root elongated, it first appeared as a reddish mass covering the root cap. Gradually this tissue mass became loosened and separated from the root cap. Finally it was torn and pushed aside by the elongated root. In the further growth of excised embryos, seven to eight layers of loose tissue which arose from the subepidermal cells were developed around the root tip. Later, the surface layer assumed the appearance of rhizoids and was subsequently shed. During further extention of the first root, zonation of the root apex became inconspicuous. The meristem became reduced in extent; only a layer of initial cells existed between the root cap and the hypocotyl. Meanwhile the root cap became reduced to only a few cell layers, some of which eventually degenerated. After six weeks in culture, the meristematic tissues of some of the root apexes eventually became parenchymatous and maturation of short tracheids extended up to 100–200 μ from the apex. Ultimately root ceased to elongate and became senile.

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