THE INFLUENCE OF CALCIUM AND MAGNESIUM SUPPLY ON NECTAR PRODUCTION IN RED CLOVER AND SNAPDRAGON

Abstract

The effect on nectar production of factorial combinations of three levels each of calcium and magnesium, comprising a ninefold variation in concentration, was studied in red clover and snapdragon. Plants were grown in sand and the essential elements supplied by daily sub-irrigation. Nectar secretion in red clover was comparatively sensitive to the availability of calcium and magnesium, the best factorial combination (intermediate calcium and high magnesium) producing almost twice as much nectar per unit of inflorescence weight as the poorest (low calcium and low magnesium). Nectar production was not correlated with vegetative growth or flower production. Inter-treatment variation was less extreme in snapdragon. In one crop the combination of high calcium and high magnesium, which supported the best growth and flower production, also gave the best nectar yield; in another crop the lowest level of calcium, sub-optimal for growth, produced the most nectar. The effects of nutrition on secretion were not related to the influence of pH, which was constant, or to the content of calcium, magnesium, nitrogen, phosphorus, or potassium in the red clover or snapdragon shoots.