SOME PHOTOPERIODIC AND TEMPERATURE RESPONSES OF THE RADISH

Abstract

Radishes (Raphanus sativus) were grown from the seedling stage in lots illuminated with natural daylight for (a) about 15 hrs. per day and (b) for 7.5 hrs. per day, at 25[degree] and 15.5[degree] C. At 25[degree] (but not at 15.5[degree]) significant differences in extent of thickening of the hypoeotyls were found between long and short daylight periods; at 25[degree] there were fewer thickened hypocotyls under short-day conditions, the hypocotyls tended to be recumbent, and the foliage was larger at 4.30 p. m. Microchemical tests showed a little fructose and much glucose in the hypocotyls; those of plants grown at high temp. and long day showed an abundance of small starch grains, starch storage being unusual in this sp.