Studies on the Ferreous Coating Formation in Roots of Rice Plants : (V) Ferreous coating formation in plants grown under abnormal conditions

Abstract

As is previously reported, we have made clear that; (1) Ferreous coating formation (F. C. F.) in roots of rice plants proceeded parallely with nutrients absorption (N, P, and K) and production of the whole dry weigtht, (2) F. C. F. was closely correlated with the oxidation and sorption of Fe⁺⁺ in media by roots, (3) Ferreous coating was mainly made with Fe⁺⁺ oxidized and sorbed by roots and (4) The okidation and sorption of Fe⁺⁺ were also influenced by Fe⁺⁺ concentration in media. So far as it was concerned, physiological activities conducted by plant from the begining to a certain period of the growth may be proportionally recorded by F. C. F. measured at that period. This paper dealt with how F. C. F. is affected when plants are grown under abnormal conditions. Experiments are consisted of those mentioned below; (A) Effects of defoliation, (B) the same of leaf-blast infection, (C) the same of different soil temperatures, (D) the same of soils artificially deoxidized and (E) the same of nutrient deficiencies upon F. C. F., Fe⁺⁺ oxidation and sorption in roots. F. C. F. in roots were washed away by 0.5 N-HCl and then colorimetrically determined by O-phenanthroline method. Fe⁺⁺ oxidation and sorption by roots were estimated by determining concentration of Fe⁺⁺ remained in FeSO₄ solution, in which roots to be tested were soaked for 24 hrs. In addition, Fe⁺⁺ concentrations in soils were also colorimetrically measured in filtrates, after soils were shaken with 1M CH₃COONa solution. Main results obtained are as follows: (A) According to the grades of defoliation, F. C. F. in roots were either increased or decreased against non-defoliated (Fig. 1). The same resulted in Fe⁺⁺ oxidation and sorption by roots (Fig. 2). In testing these physiological changes (Fig. 3), a temporaly rise of activities was found in defoliated plots. (B) When plants were infected by leafblast, F. C. F. in roots was also increased (Fig. 4). (C) The higher the soil temperature, the more F. C. F. in roots and Fe⁺⁺ in soils were produced (Fig. 5). From this fact, F. C. F. in roots may be determined by amounts of Fe⁺⁺ in soils. But as illustrated in Fig. 6, when Fe⁺⁺ oxidation and sorption were measured, the higher temperature plot indicated higher physiological activities in contrast to the lower temperature and then activities decreased up to nearly equal values. From these it is clear that not only Fe⁺⁺ amounts in soils but also the temperature affected F. C. F. in roots. (D) In artificially deoxidized soils, F. C. F. in roots of two varieties were similarly increased, notwithstanding the reduced plant growth (Fig. 7). (E) Nutrient deficiencies such as -N and -P made Fe⁺⁺ oxidation and sorption in roots more active, but -K plot less active against complete nutrients plot (Fig. 8). This fact was obtained by using 30 days old seedling, but it was quite reverse when younger plants were used (Fig. 9). When abnormal conditions as mentioned above were given to plants, certain kinds of physiological activation or retardation may occur in infected or damaged parts, from where those effects may reach other parts, for instance, from top to roots. These facts were already recognized by some workers, just as activated or inactivated respiration in roots due to defoliation and others. From our results we can make an assumption again that such physiological changes happened in top or roots due to treatments may be recorded in the form of ferreous coating.