STUDIES ON THE PHYSIOLOGY OF DEVELOPMENT IN CROPS. 4. STUDIES ON PHYTOPERIODICAL CONTROL FOR TUBER FORMATION IN SWEET POTATO

The cuttings and apical portion of stein in sweet potato were growlh under artificial light and specific photoperied and temperature. Though the plant growth was poor under insufficient light intensity of artificial light, the tuber formations were induced at long light period (16L+8D) and not induced at short light period (8L+16D) and low temperature of darkparied. The determinative factor for tuber formation of sweet potato seems to be a stimulation which has intimate relationship with specific photoperiod and temperature and no direct relation with the growth of plant body and light intensity. The root pattern of inductive state for tubers and non-inductive state were different distinctly, the former were silky and slender, the latter were branchy, and stout appearence. This different root pattern must be due also to the specific photoperiod and temperature and may have any relationship with the stimulation for tuber formation from the point of auxin physiology etc.

1. 발아시부터 단일, 암기저온 조건하에서는 괴근은 전연 형성되지 않고, 장일조건에서만 괴근이 형성됨. 따라서 장일조건이 고구마괴근 형성에 대한 유도조건 내지 촉진조건임을 알 수 있다. 2. 본실험은 시종 약전광(300W 전구 사용)으로 재배하였기 때문에 동화작용이나 생장이 특히 미약한 상태에서도 괴근이 유도되었다. 따라서 괴근형성에는 동화물질이나 생장보다도 장일조건이 직접적결요인을 이루는 1종자극을 성립하는 것으로 보인다. 3. 장기조건과 단일조건하의 근계가 서로 특이한 상태를 나타냈고 그것은 단일과 장일조건이 이룬 자극과 관계하는 것으로 보인다. 4. 고구마괴근이 장일조건에 유되되는 사실의 생태학적 의의를 고찰함.