Nutrient Stoichiometry in Pinguicula Vulgaris: Nutrient Availability, Plant Size, and Reproductive Status

Abstract

Current understanding of the extent, causes for, and consequences of variation in nutrient composition in plants is limited. Important questions to be addressed include to what extent nutrients covary, how flexible nutrient ratios are within a population or species, how reproduction influences nutrient ratios, and how much the ratios of nutrients to mass and nutrients to each other change through ontogeny. This information is needed to assess the physiological and ecological consequences of plant nutrient composition and to what extent plants function as balanced systems in acquisition and allocation of resources. We studied the variation in nutrient stoichiometry (i.e., the ratio between contents of different nutrients within a plant) in relation to three factors: (1) environmental availability of nitrogen, (2) plant size, and (3) reproductive status. We investigated these questions in 11 populations of the carnivorous plant Pinguicula vulgaris in northern Scandinavia. Dry mass and N and P content were measured for reproductive and vegetative portions of flowering individuals and for winter buds corresponding to four reproductive states: control reproductive individuals, experimentally vegetative individuals (from which flower buds were removed), adult vegetative individuals, and individuals below the threshold size for reproduction. [N], [P], and to a lesser extent, N and P content were positively related to soil N, but not to prey capture. Nutrient stoichiometry was also size dependent; in general, small plants were relatively enriched in N and relatively depleted in P compared to larger plants. Reproductive status affected not only size, but also nutrient stoichiometry of the resulting winter bud. Winter buds derived from reproductive individuals had a higher [N] and lower [P] than those of the different types of nonreproductive individuals. Our findings indicate that studies of nutrient stoichiometry in plants must go beyond links between environmental and plant nutrient concentrations to consider internal processes such as growth and reproduction.

Strong relationship between elemental stoichiometry and metabolome in plants

“…3). These decreasing N/P ratios during the growing season also have been found in other terrestrial plants (20,21) and in animals (22,23). Moreover, under these favorable conditions for growth, the assimilated C is allocated more to growth and energy supply (more primary metabolism) than to antistress or defensive mechanisms (less secondary metabolism).…”

From Elements to Function: Toward Unifying Ecological Stoichiometry and Trait-Based Ecology

“…Interestingly, organisms' size and growth rate are usually negatively correlated (Table 1), which implies that, based on the growth rate hypothesis, smaller heterotrophic organisms might generally have lower N:P ratios (Figure 2). These explicit connections between body size, ontogeny, and N:P stoichiometry have been well documented (Elser et al, 1996;Gillooly et al, 2005;Méndez and Karlsson, 2005;Meunier et al, 2016a). Further, larger cells have higher biomass-specific storage capacity due to smaller surface/volume ratios and higher minimum cellular metabolic requirement that selectively allows them to provide them with a competitive advantage over smaller cells under higher resource concentrations (Figure 3; Irwin et al, 2006).…”

Stem, root, and older leaf N:P ratios are more responsive indicators of soil nutrient availability than new foliage

“…A number of studies link relative growth rate to seasonality and show that foliar N:P ratio can be lower during periods of active growth (Me´ndez andKarlsson 2005, Rivas-Ubach et al 2012), probably due to RNA demand for P (Sterner and Elser 2002). Shifts in foliar N:P with season could influence storage and thus stem N:P, but the sensitivity of this response relative to foliage, and as a function of stem age and type (twig vs. branch), remains to be determined.…”