Studies on the pithiess of radish. VI

Abstract

The present studies are designed to elucidate the effect of soil and fertilizer on the pithy tissue formation.i) The effect of the exchangeable base supply on the growth and the pithy tissue formation.In this experiment, quarternary diluvial clay loam had about 13m.e. of exchange capacity and about 2.5m. e, of exchangeable base. The value for exchangeable base supply was obtained by subtracting the exchangeable base from exchange capacity. The rates of base supply were, namely, 75, 42. 5, 37.5, 32.5, and 17.5 per cent of the value as obtained above. The rate of root growth increased and the degree of pithiness decreased in proportion to the amount of cation supply, but in the case of a high rate of magnesium in total exchangeable cation, the thickening growth of roots is inversely related to the amount of magnesium supply and the occurrence of pithy tissue is relatively prevented. However, it is necessary for us to establish more successful methods.ii) The effect of soil conditioner, polyvinyl alcohol (PVA), on the growth and the pithy tissue formation.The rate of PVA application in the soil ranges from 0 to 1.6 per cent (w/w). The clay loam soil treated with PVA forms completely stable aggregates at the rate of 0.8 per cent. The relationships between the growth or the degree of pithiness and the rate of aggregate formation or the rate of PVA application are as follows:Positive correlation{Rate of PVA application or of aggregates formation versus root growth and degree of pithinessNegative correlation{Rete of PVA application or of aggregates formation versus leaf weight, T/R ratio, and root lengthFrom these relationships, the occurrence of pithy tissue may be ascribed to the fact that the accumu-lation of assimilates or nutritives into the fresh root lags behind the abrupt thickening growth.iii) The effect of three element supply during the period of rapid thickening growth on the pithiness.The concentration of elements in the nutrient solution of cultural plot was as follows.Nitrogen 126ppm. Phosphorus 62ppm. and Potassium 117ppm.In the treatment plots the concentration of one of the three elements was doubled.In the plot given double amount of nitrogen, the plant growth was checked. It may be suggest that there was a toxic effect of ammonium sulfate added to double the amount of nitrogen. With regard to the degree of pithiness there was no significant difference among the four test plots.iv) The effect of foliage spray of urea on the growth and the pithy tissue formation.Urea was contained in foliage spray solution at the rate of one per cent. Treatment is recommended to be made after the unfolding of four leaves. The urea spray tended to increase the root growth, but the degree of pithiness became slightly lower. There was, therefore, no significant difference with regard to the latter character between the control plot and the urea spray one.