Nutrient inflows into apple roots. I. 32P-orthophosphate uptake from solution by M.9 rootstocks and Worcester Pearmain seedlings |
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Authors: | K K S BHAT |
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Institution: | East Mailing Research Station, East Mailing, Maidstone, Kent ME19 6BJ |
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Abstract: | Abstract. The rates of uptake of 32P-labelled orthophosphate by whole root systems of young apple trees (M.9 rootslocks and Worcester Pearmain seedlings) were measured in solution culture. Using a solution depletion technique, the 32P-phosphate uptake rates per unit length, surface area or fresh weight of roots were determined as a function of 32P-phosphate concentration in solution at the root surface over the range 0.25–10 mmol m?3. The effect of P concentration within various plant parts on the relation between uptake rate and external P concentration was studied using plants differing in internal P levels. The apparent minimutn P concentration below which P uptake ceased was of the order of 0.25–0.50 mmol m?3. Fluxes, inflows and unit absorption rates increased approximately proportionately with solution concentration up to 10mmolm?3. Except perhaps in the case of the low-P M.9 plant, there was no evidence of a diminishing returns type of relationship over the range of solution concentrations examined. The threshold P concentration in solution above which uptake rates cease to increase thus appears to be higher for apples than for other species. At any given P concentration, fluxes, inflows and unit absorption rates were higher for M.9 than for Worcester and for low-P plants than for high-P plants. The difference between plants of different P status was more marked for M.9 and seems to be more closely related to shoot P levels than to root P. |
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Keywords: | Malus domestica Rosaceae apple M 9 rootstock Worcester Pearmain P uptake root demand coefficient |
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