A Bioassay to Determine the Limiting Minerals for Seeds from Nutrient- Deprived Senecio Vulgaris Plants

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Abstract
(1) The aims of this experiment were to determine which nutrient elements are most limiting to growth in newly-germinated seedlings of Senecio vulgaris dependent on their seed reserves, and how seedling nutrient-requirements are affected by the nutrient status of the parent plants. (2) Seeds were collected from plants which had been grown on a range of concentrations of Hoagland''s full nutrient solution (20-100%). Seeds were also collected from plants growing the field. (3) The seedlings were grown for three weeks in seven nutrient solutions, each of which had one macro-nutrient missing. These solutions lacked respectively nitrogen, phosphorus, potassium, calcium, magnesium, iron or sulphur. A control solution (containing a full nutrient supply) was also set up. (4) The final mean dry weight of the seedlings in each treatment was taken as a measure of their ability to rely on their internal supplies of each specific nutrient in the initial stages of growth. (5) Overall, the parental nutrient treatments had no significant effect on the seedling mineral requirements. (6) The most limiting elements in the seeds from the glasshouse parents were calcium and nitrogen and the least limiting were sulphur and iron. Phosphorus, potassium and magnesium were intermediate. Without nitrogen a seedling attained a dry weight of only three to five times that of the embryo; without sulphur it attained twenty-two to thirty-nine times the embryo weight. (7) Seedlings of the field-grown parents differed from those of the glasshouse parents in being generally larger and notably less limited by calcium and phosphorus. (8) The results indicate that the seedlings are more dependent on an external supply of certain mineral nutrients than others in the initial stages of growth. The balance of nutrients stored in the seeds of Senecio vulgaris is not related in any simple way to the apparent nutrient requirements of the seedlings.