| Abstract: | The effect of phosphate concentration in flowing solution cultureat a range between 0.04 and 32 mmol m–3 P on the growthof perennial ryegrass was studied in two experiments, each lastingabout 45 d after sowing. Phosphorus contents of seedlings wereaffected by the concentration in solution within about 5 d fromgermination, and dry weight differences were first observedat about 6 d after this. The rate of uptake of phosphate byseedlings was affected by the concentration in solution beforethe root fresh weight or root/emdash shoot ratio had changed.Young plants (less than 4 weeks old) were more sensitive tophosphate concentration in solution than older ones. In conditionsof high rate of growth, older plants required a solution concentrationbetween 0.1 and 0.4 mmol m–3 P to achieve maximum potentialgrowth rate, whereas for plants of similar age but less dryweight, 0.04 mmol m–3 P was adequate. Towards the endof the experimental period, plants growing at a nominal solutionconcentration of 0.04 mmol m–3 P were able to obtain phosphatefrom a solution of about 0.01 mmol m–3P. Phosphate toxicity was not observed, nor were there visual symptoms(other than reduced growth) of phosphate deficiency in plantswhose growth was limited by phosphate concentration in solution. Key words: Lolium perenne, Phosphate uptake |
