Interspecific differences in maternal support in herbaceous plants: CNP contents in seeds varies to match expected nutrient limitation of seedlings
Abstrakt
Maternal care is one of the key fitness parameters in all organisms. In plants, maternal care takes the form of seeds production.
Although seed mass is the most studied proxy for this maternal provision due to its correlation with the overall amount of nutrients, this proxy does not take into account seed nutrient contents and the proportions of light-dependent resources (C) and soil-dependent resources (N and P), which can strongly affect seedling establishment and survival. We tested the hypothesis that seed nutrient contents is fine-tuned to the expected conditions of seed germination, namely, that seeds of plants from light-limited conditions will have proportionally more carbon than those of plants that are not light-limited and vice versa.
We used a phylogenetically informed comparative approach with 510 central European herbaceous species to examine relationships between proportions of N, P and nonstructural C, and the environment in which their seedlings typically germinate. We showed that, in spite of the strong phylogenetic signal in nutrient contents, proportions of N and nonstructural C vary according to our hypothesis, i.e. seeds are primarily provided with nutrients expected to be limiting in a given environment.
Namely, the proportion of nonstructural C in seeds was higher in species from nutrient-rich habitats. This enables seedlings to develop independent resource-acquiring organs quickly.
We demonstrated that seed nutrient contents depends on seed mass; namely, the proportion of P out of the total seed mass was higher in small seeds, and the proportion of unusable structural C was higher in large seeds. Our results suggest that seed nutrient content is under selection driven by both seed mass and the environment in which seedlings are likely to germinate.
It means that seed nutrient content is a seed trait of clear ecological relevance and hence deserves much closer attention.