SOME ASPECTS OF THE RELATION BETWEEN NECTAR SECRETION AND NITROGEN, PHOSPHORUS, AND POTASSIUM NUTRITION

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Abstract
The influence of mineral nutrition on nectar secretion both per se and in relation to certain aspects of growth and development was studied in snapdragon and red clover plants growing in sand culture. Snapdragon was grown at two levels each of nitrogen, phosphorus, and potassium, red clover at three levels each of phosphorus and potassium. The volume of nectar and weight of nectar sugar secreted per inflorescence were affected by the supply of each of the elements studied. Secretion in snapdragon was favoured by the lower levels of nitrogen, phosphorus, and potassium. Secretion in red clover was best at the low and intermediate levels of phosphorus and at the intermediate level of potassium. Although a high concentration of phosphorus or potassium in the mineral supply reduced secretion in both species, the threshold concentration for this inhibitory effect was higher in red clover than in snapdragon. High concentrations of potassium consistently reduced the sugar concentration of the nectar in both species. Flower number as well as quantity of secretion per inflorescence varied with nutritional treatment. For maximal production of nectar by the plant, the following conditions of fertility would appear desirable: A level of nitrogen low enough to avoid excessive vegetative growth, a level of phosphorus sufficient to promote good flowering, and a level of potassium which is neither low enough to limit growth severely nor high enough to reduce flower production.