Phosphorus allocation and utilization in three grass species with contrasting response to N and P supply

Abstract

SIJMM.ARYThe growth of the grass Brachypodium pinnatum (L,) Beauv. in Dutch nutrient-poor chalk grasslands increases with enhanced nitrogen supply, whereas other grass species also require an enhanced phosphorus supply for a similar response (e,g, Dactylis glomerata L.), or are competitively suppressed at any increase in nutrient supply (e.g. Briza media L.). We investigated whether this interspecific variation in response to N and P supply is caused by differences in P productivity (PP), i.e. the instantaneous rate of biomass production per unit of P present in the plant. We hypothesized that FP is highest in Brachypodium pinnatum, in contrast to N productivity which is known to be the highest m Dactylis glomerata. Phosphorus productivity and its components were studied using a growth analysis with four exponential P addition rates of 0-03, 0-06. 0'09 and 0-11/0-1 5 mg P mg"^ P d"'.Although Brachypodium pinnatum allocated more P to its leaf blades, it had a lower P productivity at high N and low P supply than did Dactylis glomerata. This was associated with a higher productivity per unit leaf P Ln Dactylis glomerata. Across all species and treatments, leaf PP showed a distinct negative correlation with P concentration per leaf area, regardless whether the variation in area-based leaf P concentration was caused by variation in leaf thickness, leaf tissue mass density or mass-based P concentration. A possible explanation for this would be a positive correlation between leaf chlorophyll concentration and P concentration, leading at high concentrations to shading within the leaf and to a low photosynthetic rate per unit leaf P. We conclude that a high pp is determined by the ability of a plant to distribute its P over a large leaf area, rather than by greater allocation of P to the leaves. Interspecific relationships for P productivity are similar to those known for N productivity.

Phosphorus nutrition‐mediated effects of arbuscular mycorrhiza on leaf morphology and carbon allocation in perennial ryegrass

“…LMA was twofold lower under high P supply in comparison with P-deficient conditions. High LMA is often associated with P deficiency because of high concentrations of nonstructural compounds (Rao et al, 1989;Ryser et al, 1997;de Groot et al, 2001). Variation in leaf thickness has been reported in response to changes in light intensity and nutrient availability (Witkowski & Lamont, 1991;Meziane & Shipley, 1999), but its functional determination as related to changes in environmental conditions is still unclear.…”

“…Leaf morphological changes affect nutrient distribution per unit of leaf area, which, in turn, affects the productivity of nutrients allocated to leaves (Poorter & Evans, 1998). Ryser et al (1997) reported a close relationship between productivity of leaf P and the ability to distribute it over a large leaf area. Our results indicate that AMF colonization would affect such relationships through the improvement of the P status of the plants.…”

The nutritional control of root development

“…In a comparison of a fast-growing species (Dactylis glomerata) and a slow-growing species (Brachypodium pinnatum) that co-occur in many nutrient-poor calcareous grasslands, it was found that only the former developed thicker roots when grown under conditions of high N or P (Ryser et al, 1997).…”

Time-dependent, species-specific effects of N:P stoichiometry on grassland plant growth

“…In search of an explanation for these field observations, a number of greenhouse experiments have been carried out to investigate the morphological and physiological responses of grassland plants to varying balances of N and P (Shaver and Melillo 1984;Ryser et al 1997;Güsewell 2005a;Macek and Rejmankova 2007). Short-term experiments show that adding N, leading to high N:P supply ratios, increases plant biomass, whereas adding P, leading to low N:P supply ratios, does not promote plant growth (Güsewell 2005c;Güsewell et al 2003).…”