Differences between Natural Populations of Trifolium repens L. in Response to Mineral Nutrients

The response to phosphate of samples of natural local populationsof T. repens, collected from soils of different phosphate contents,was determined over a wide range of phosphate levels in sandculture. A marked correlation (r = +0.96) was found betweenresponse of populations to phosphate at low phosphate levelsand the amount of phosphate in the native soil of the population;populations from soils high in phosphate showed larger reductionsin growth at low phosphate levels than did those from soilslow in phosphate. It is concluded that response to phosphateis one aspect of the physiological adaptation of the naturalpopulations to particular soil conditions. Populations alsodiffered in response to very high levels of phosphate, and inthe range of phosphate levels tolerated; the possible adaptivesignificance of this is discussed in relation to the phosphatebuffering effects of the native soils. Populations tolerantof low phosphate levels had higher concentrations of phosphorusin the shoot material, and a higher uptake of phosphorus perunit weight of roots, than did intolerant populations. The differencesbetween populations in response to phosphate are therefore believedto be due to difference in uptake rather than to differencein metabolic requirement of phosphate.