Histology an Organesis in Canot Calus Tissue Cultured in Vitro

[摘要] The carrot callus tissues are cultured on the following three kinds of medium, i. e., the standard medium, "the root-forming medium" and "the embryo-forming medium", after the subculturing of different periods from isolation. The histological observations of these calli are undertaken by the ordinary paraffin method. The friable callus tissues within one year and more after isolation are composed of the tissue particles. These tissue particles have its characteristic organization according to the nutrient medium. The stock callue tissues cultured on the standard medium are composed of the tissue particles of the surface-growing type, in which the parenchyma containing the groups of tracheid-like element is covered with the growing zone of proliferating cells on the surface. While the nodular callus tissues cultured on "the root-forming medium" - standard medium. excluding 2, 4-dichlorophenoxy acetic acid - are constituted from the minute tissue particles which are homologus to the "meristematic nodules" of Gautheret. These "meristematic nodules" unite each other with the loose parenchyma on their surfaces and build up the larger tissue nodule of several millimeters in diameter. During the course of the repeated subcultures over three years, the gradual chages in the components of the stock callus tissue are observed. In these changes, the following two features are distinctly noticeable; first, the degeneration of the tissue particle into fragments and second, the increase in the proportion of the giant free cell in the cell population of the callus tissue. When the callus tissue within one year after isolation are cultured on "root-forming medium", the root primordia differentiate endogeneously from the cambial layer located uuder the outer loose parenchyma of the "meristematic nodule". From this observation, the significance of the organization of the tissue particles for the differention of the roots in carrot tissue is suggested. When the callus tissues being until about one year after isolation are cultured on "the embryo-forming medium", the adventive embryos are found to be generated from the few embryonic cells that are clearly distinguished by size and stainability from the other kinds of cell. The embryonic cells are always situated either on the outermost layer of the tissue particles or in free state.

[学科分类] 农业科学（综合）