Some physiological characters of long- and short-day plants

Abstract

The plants used in the present studies are the followings. Long-day plants (LP) : oat, pea, white clover, spinach etc. Short-day plants (SP) : soy bean, tobacco, chrysanthemum, morning glory etc.
The decrease in the total nitrogen content of the new grown-up leaves of SP during the night is greater than that of LP. This fact indicates that the transport of nitrogen compounds in SP are accelerated in the dark. The elongation of the leaves of SP in the dark is greater than that in the light; but in LP its difference is non pronounced, or rather in some cases the elongation in the light is greater, In SP, however, the elongation of the leaves is accelerated even in the light, when the mature leaves are covered with tin-foil. From these facts it seems probable that, one of the causes of the accelerated elongation of the leaves of SP is that the translocation of nutrient substances from the mature leaves is promoted in the dark.
To observe the effects of β-indoleacetic acid on the elongation of the leaves in dark, the basal portion of the cuttings is dipped in the solution of indoleacetic acid. The elongation of the leaves of SP is accelerated markedly by the growth substance; but in the case of LP there is few effects of it.
The daily variation of reduced ascorbic acid content in the new grown-up leaves is similar both in the case of LP and SP. It increases during the day and decreases during the night. The ratio of reduced ascorbic acid content in young growing leaves to that in the new grown-up ones is greater in the plants growing vigorously, but when SP have been induced photoperiodically the ratio becomes smaller. One would think that there would be some relations between the shifting in the ratio and the photoperiodic induction in flowering.