Relationship between Growth and Nitrogen Accumulation for Vegetative Cotton and Soybean Plants

Abstract

Experiments were conducted to determine whether the nitrogen absorption function of the roots is directly related to the photosynthate supplying function of the leaves under steady-state conditions during vegetative growth phase of cotton (Gossypium hirsutum L) and soybean (Glycine max [L.] Merrill) plants. A direct relationship between these two functions would imply a balanced interdependence and contradict the views that growth of all plant parts is dependent on carbohydrate supplied by the leaves and that nitrogen uptake is dependent only on existing root and soil characteristics. Plants were grown under both artificial light in CERs and natural light in air-conditioned greenhouses, at three thermoperiods, and with three levels of nutrient supply. The data show that RGR_R and RARN_P were not significantly different within thermoperiod or nutrient supply and agree with those obtained in a previous experiment with tobacco (Nicotiana tabacum L.) The results suggest that plant growth models should be based on the balanced interdependence of the nitrogen absorption and photosynthate supplying functions