Yukindo Tsuno

Studies on Yield Forcast in Main Crops : III. Growth of rice plant in relation to its photosynthetic activity

Photosynthetic activity, nitrogen contents, carbohydrate accumulation etc. were studied in rice plants, using variety, Norin 37, grown on a field with different levels of fertilizer application and planting density. The results were as follows. 1) Throughout all of the growing stage, highly positive correlation was observed between total nitrogen content of leaves and photosynthetic activity (Fig. 2). 2) Also an intimate correlation existed between the weight of leaves per plant and photosynthetic activity expect during the growth stages prior to the ear-initiation (Fig. 3). 3) During the ripening stages, associated with the carbohydrate translocation to the ear, nitrogen in the vegetative parts of plant was declined, which in turn caused the decreased photosynthetic activity of the leaves. Consequently nitrogen absorption from the soil during the period after heading was considered to be beneficial for maintaining the photosynthetic activity relatively at a higher level throughout the ripening period.