Abstract
It has been experimentally confirmed that the availability of potash for plant growth is diminished with an excess of soluble iron salts, while this undesirable effects of the latter should be removed by an adequate addition of the former. These actions depend upon not only direct effects of respective element, but mutual action or the antagonism between the elements. The authors have carried out an investigation with taro plants, Colocasia esculenta SCHOTT, which are considered to be one of the "potash-favor plants." Cosequences of the investigation are summarised as the following : 1) The antagonistic effects of K_2O to Fe_2O_3 are recognizable in the increment of growth of taro plants which are measured, by size and weight of leaf-blades, petioles and roots. The effects are less significant in earlier stage of the growth, but they are more evident in later period. 2) The antagonistic effects of K_2O display not only to Fe_2O_3 for the plant growth, but to CaO, and they doubtlessly take place to MgO. They are estimated by the ratio-values as Fe_2O_3 : K_2O, CaO : K_2O and (Fe_2O_3+CaO) : K_2O which are determined among ash ingredients, in reference to the growth of plant organs. 3) They are, also, estimated by the similar way with regard to eletrically dialysable bases of dried matter of the plant organs. It is considered that a part of the bases which are totally found among ash ingredients, is in active state from physiological view point, being movable, dialysable and transformable. While the other part of those should be in stable or fixed forms, building tissues of the plant body or settling as physiologically inactive materials. The dialysable bases are, generally, less than the non-dialysable ingredients, with a few exception of K_2O. K_2O, Fe_2O_3 and CaO are dialysed to both electrodes, showing, in general, negatively charged bases<positively charged bases by weight. These dialysable bases should be in dissociated state or ions which may be simple inorganic and so-called complex organic ions. 4) The antagonistic relationships are evidently displayed between K_2O and Fe_2O_3,CaO or Fe_2O_3+CaO in dialysable forms. Fe_2O_3 remains, particularly, in non-dialysable state to greater extent, in consequence of the antagonistic action of K_2O. 5) The antagonistic effects of K_2O to Fe_2O_3 and CaO are obvious, too, by sugars and starch which are products of the assimilation. The effects to sugars are significant in such vegetative organs as leaf-blades and petioles, while those to starch are revealed in root-tubers which are the reserve or reproductive organ. Because, the sugars are not principal reserve materials of the taro plants but are intermediate products to become higher molecular carbohydrates after polymerisation. The starch, however, is the stable reserve material in root-tubers. 6) pH of pressed juices of different plant parts have been measured by the method using quinhydron electrodes. There is found no relationship between pH values and the antagonistic effects, and also, between those and carbohydrates. 7) Specific electro-conductivity of the pressed juices prepared from the same samples to 6,have been determined after Kohlrausch's method. It has no mutual relation to the antagonistic effects of K_2O, merely showing noticiable difference between plots with and without K_2O. Degree of the specific electro-conductivity of juice is in order as leaf-blades<root-tubers<petioles.
