On the Relation between the Georeaction and its Reaction Time

1) Under the condition in which the direction of gravity acting upon a plant axis is turned by keeping it horizontally, the reaction time required for presenting the histological dissmilarity between the upper side and the lower of the axis has been studied. 2) In the case of the hypocotyl of a jute, Corchorus capsulasis L., during the process of 8 hrs. after the horizontal treatment the upper cortex becomes thicker than the lower one and the differentiation of phloem fibrous cells is more accelerated at the upper side than the lower, so that the difference in the shape and structure of the fibrous cone is brought about between both sides ; in 16-20 hrs., the number of fibrous bundles constituting the upper fibrous cone increases by one as compared with that constituting the lower, and thereafter with a lapse of time, the formation of the fibrous bundles lags behind markedly at the lower side in contrast with the upper side where the formation of them is accelerated more and more. In the xylem, during 4 hrs. after the horizontal treatment, there are differentiated about 3 layers of cells from the cambium at both sides and the upper ones expand their walls remarkably. The several layers of cells occupying the middle of the xylem which have been made before the treatment, elongate radially by this time and as the extent of thier elongation is larger at the upper side than the lower. more growth in thickness is seen at the upper side ; But the lignification of cell-walls is more accelerated at the lower side than the upper. Within 24 hrs., while there are differentiated no more than 3-4 layers of cells at the lower side, and their lignification becomes higher at that side than at the upper side, 5-8 layers of cells are differentiated by the cambium at the upper side and they begina radial elongation from the deeper ones and thus the thiu-walled wood part which is clearly recognizable as a reaction tissue,is formed. 3) In less than 24 hrs., cells of the lower cortex of the hypocotyl of a caster bean plant Ricinus communis, become larger than the upper ones; in 35-50 hrs., striking differences of histological structures are seen between the upper side and the lower of the xylem, namely the cells of the upper side, like those of a vertical axis, are polygonal and combined closely with one another and their walis are thinner in marked contrast with the lower side in which the cells become larger and are elliptical, showing intercellular spaces among them, their walls being thicker. The respective walls of xylem and phloem fibrous cells, of both the upper and lower side begin to lignify and form the cellulose thick layers at the inner side of each cell of the upper side, but the cells of the lower side do not yet form those layers with the lapse of 80 hrs., In four days,the pith cells of the upper side elongate radially, but the lower ones retain the round shape. 4) From the above, it may be seen that the transversal polarity is generated in the plant axis in a comparatively short time, followed by the appearance of differences between the upper and the lower sides of the axis, when it maintains its horizontal position with gravity acting upon it in the transversal direction