EFFECTS OF PRETREATMENT WITH PHOSPHATE IN NATURAL POPULATIONS OF AGROSTIS CAPILLARIS L.

SUMMARY Clones of six populations of Agrostis capillaris L., collected from contrasting soils, were grown in sand culture for 6 months supplied with either 1 or 40 mg P dm −3 with weekly applied solutions (low and high P‐pretreatments. Plants from the low P‐pretreatment were extremely P‐deficient. Individual unrooted tillers of the pretreated plants were subseqently grown in sand culture for 10 weeks with main treatments of 1 and 40 mg P dm −3 . High P‐pretreated plants produced higher yields than low P‐pretreated plants in the 1 mg P dm −3 treatment, demonstrating a distinct P ‘carry‐over’ effect. Plants of populations from nutrient‐deficient sites were not slower growing or less responsive to P than those from more fertile sites, and plants of the very acidic soil populations were particularly vigorous. However the populations from colliery spoil appeared to be more efficient at utilizing P when P supply was low. There were no differences between P‐pretreatments in yield at 40 mg P dm −3 but, depending on population, low P‐pretreated plants accumulated between 5 and 55% more P in expanded leaf material than plants of the high P‐pretreatment. This indicates that the increases in rates of P uptake and translocation induced by P‐deficiency, frequently reported in short‐term investigations, may persist for several weeks. The relationship between initial and final P‐status of shoots was examined using genetic variability within populations as the basis of correlations. No simple linear relationship between these variables existed and possible reasons for this are discussed. The greatest increase in P concentration in shoots at 40 mg P dm −3 as a consequence of low P‐pretreatment occurred in a population from colliery spoil and it is suggested that this, together with a high efficiency of utilization of P, may be part of an adaptive physiological strategy.