upzl's blog

Stoichiometric relations in plants, with emphasis on C:N:P, are reviewed. Both theoretically and empirically it is found for whole plants as well as for different tissues that nitrogen concentrations increase slower than phosphorus concentrations. A lack of data prevents the establishment of relations between nitrogen and other elements. Optimal element ratios where elements are simultaneously limiting growth can be established. There is a considerable variability around these optimal ratios in observed values. Conclusions about the ecological significance of stoichiometric relations based on these observations may therefore be biased. The significance of this variability remains to be established.

Light gradients are ubiquitous in nature, so all plants are exposed to some degree of shade during their lifetime. The minimum light required for survival, shade tolerance, is a crucial life-history trait that plays a major role in plant community dynamics. There is consensus on the suites of traits that influence shade tolerance, but debate over the relative importance of traits maximizing photosynthetic carbon gain in low light versus those minimizing losses. Shade tolerance is influenced by plant ontogeny and by numerous biotic and abiotic factors. Although phenotypic plasticity tends to be low in shade-tolerant species (e.g., scant elongation in low light), plasticity for certain traits, particularly for morphological features optimizing light capture, can be high. Understanding differential competitive potentials among co-occurring species mediated by shade tolerance is critical to predict ecosystem responses to global change drivers such as elevated CO₂, climate change and the spread of invasive species.

Source: http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.39.110707.173506