Mineral Nutrition of Drosera erythrorhiza Lindl. With Special Reference to Its Tuberous Habit

The seasonal cycle of uptake and partitioning of nitrogen, phosphorus, potassium, magnesium, sodium, calcium and zinc by Drosera erythrorhiza was studied in natural habitat near Perth, W.A. All elements except calcium were mobilized from germinating parent tubers with more than 80% efficiency. The leaf rosette served as the major repository for minerals obtained from the parent tuber and rooting medium. Efficiency of carry-over from vegetative parts to the new season's tubers was 88% for phosphorus, 79% for nitrogen, 71 % for dry matter, 63% for magnesium, 56% for potassium, but only 25-39 % for calcium, sodium and zinc. Pot culture studies showed insects to be an effective source of nitrogen and phosphorus, and eluate of ash particularly a source of potassium. Habitat soil enriched with whole ash produced tubers especially rich in nitrogen, phosphorus, magnesium and calcium, elevated levels of phosphorus being attributed particularly to the ash. Growth on full mineral culture solution or distilled water produced tubers with low levels of minerals. Tuber composition varied greatly between habitats, especially in relation to phosphorus, nitrogen and zinc. The relationship between phosphorus levels in tubers and recent fire history of a habitat was examined.