Ecological Studies of Rice Plants Grown Early or Late in the Season : I. Occurrence of black-and dark-brown colored roots in early-planted rice on ill-drained boggy paddy-fields. : II. Observation of the coloring symptom in the roots of early-planted rice plants from certain localities in Chiba Prefecture.

Abstract

Rice plants, of two varieties, cultured early in the season-transplanted May 3- in comparison with those raised in an ordinary season-transplanted June 20- were studied in retard to the coloring phenomenon in their roots on ill-drained boggy, soils. Accumulation of starch in the basal parts of their leaf-sheaths and culms and Eh₆ and temperature of the soil in relation to the phenomenon were examined. I. In both of the cases compared, coloring of the roots became conspicuous at the stage of tillering climax when the starch contents in the culm-and leaf-sheath-bases began to decrease. Especially dark-brown colored roots were found highest in number at the time little after the early panicle-formation-stage of the plant, showing no clear differences between the early and ordinary cultures, while the occurrence of the black colored roots which reached the maximum of number about at the heading-stage were more frequent in the early culture plants. The phenomenon seemed not to be affected by the soil temperature, but was assumed to be related to some physiological conditions of the plant connected to lower Eh₆ of the soil. II. Results obtained by various kinds of soil from many places in Cihba Prefecture tested, indicated almost similar relations as above mentioned.