Abstract
As is reported in the previous part of this paper, all parts of root surface of rice plants can adsorbe more ferreous compounds from media, when metabolic activities of roots have dropped as the plant growth advanced. The largest amount of the coatings is therefore found about the period of heading. However it was found somewhat differently circumstanced with that per 100mg dried roots and per unit area of root surface. This fact was shown in earlier periods of growth. In the experiments of which is reported here, a positive correlation between them was proved. The amounts per unit surface area is theoretically to be called the adsorption power of ferreous compounds of roots. The adsorption power is announced in this papar as the ferreous coating formation, the amounts per unit root weight being included. In these experiments, it was first experimentally examined whether the ferreous coating formation was depended upon root activity or not. Next it was also tested whether the ferreous coating formation was related to the absorption of bases e.g. the cation-exchange capacity of roots or not. Ferric ions in media are to be exchanged by other cations on root surface and thus the adsorption of them occurs to be followed by their absorption, as well as other cations are absorbed. The absorbed ferric ions are assimilated in plant body and the surplus of them being adsorbed on the surface may be formed into ferreous coatings, accompanied with their adsorption combinations. Such adsorption may readily happen because of the lower lyotropic character of ferric ions. As far as this hypothesis may be true, the ferreous coating formation is surely related to the cation-exchange capacity of rice roots. From these experiments, the following main results were obtained. 1) Among roots which grew in all kinds of media containing ferreous compounds, it was observed that young parts of roots and young roots themselves were never stained by ferreous compounds. Moreover the parts of roots placed under oxidizing conditions such as the basal parts of roots were also scarecely stained (Tab.1). 2) Roots which emerged later were always less remarkably stained than those which appeared earlier (Tab.2 & Fig.1). 3) Plants of which the tops were untouched had roots less discoloured by ferreous compounds than those of which the aboveground parts were entirely cut off (Tab.2 & Fig.2 A & B). 4) Plants of which the underground parts were aerated during the experimental course had roots less stained, as compared with those not aerated and those of which the leaves were cut one third when each leaf emerged normally (Tab.2 & Fig.3 A & B). From these results it was assured that young roots and young parts of roots produced less ferreous coatings on their surfaces. The cation-exchange capacity of roots were estimated by the percolation method. Amounts of ferreous coatings were determined in parallel by the o-Phenanthrolin method, six varieties of different resistabilities against soil reduction being used. 5) The cation-exchange capacity per total roots weight and per 1OOg roots were rather highly correlated respectively with the amounts of ferreous coatings per total root weights (Tab.3 & Fig. 4 A, B & C). From this fact the amounts of ferreous coatings may suggest the intensity of absorption of bases from media
