Response of seedlings of soybean, sunflower and sorghum to added mineral nutrients

Abstract

The capacity of seed of soybean, sunflower and sorghum to sustain early growth was studied by growing seedlings from germination to day 15 at 25¦C in growth cabinets in either aerated nutrient solution, aerated deionised water or rolled cotton towelling wetted with deionised water. Growth was markedly better in the nutrient solution and significant differences in growth and in content of nitrogen, phosphorus and potassium were observed 7-11 days after imbibition. By day 15 the dry weights of soybean, sunflower and sorghum seedlings grown in rolled towelling were only 38, 20 and 36%, respectively, of those grown in nutrient solution. Growth in deionised water was very poor and most seedlings were beginning to die by day 15. This was associated with a leakage of potassium from the seedlings to the growing medium, an effect consistent with impaired membrane permeability due to calcium deficiency. The marked effect of added mineral nutrients on the early growth of seedlings indicates that vigour tests which seek to measure the growth potential of a seed batch should be conducted under conditions providing adequate nutrition rather than in inert media. The growth of seedlings in aerated nutrient solution at optimum temperature for about 15 days can be taken as quantitative measures of potential growth and seed vigour. A comparison of growth of seedlings in aerated nutrient solution and an inert medium can be taken as a measure of the nutrient status of a seed lot.