Intra-individual variation in Galium odoratum is affected by experimental drought and shading

Plant Phenotypes as Distributions: Johannsen's Beans Revisited

AbstractIn the early twentieth century, Wilhelm Johannsen's breeding experiments on pure lines of beans provided empirical support for his groundbreaking distinction between phenotype and genotype, the foundation stone of classical genetics. In contrast with the controversial history of the genotype concept, the notion of phenotype has remained essentially unrevised since then. The application of the Johannsenian concept of phenotype to modularly built, nonunitary plants, however, needs reexamination. In the first part of this article it is shown that Johannsen's appealing solution for dealing with the multiplicity of nonidentical organs produced by plant individuals (representing individual plant phenotypes by arithmetic means), which has persisted to this day, reflected his intellectual commitment to nineteenth-century typological thinking. Revisitation of Johannsen's results using current statistical tools upholds his major conclusion about the nature of heredity but at the same time falsifies two important ancillary conclusions of his experiments-namely, the alleged homogeneity of pure lines (genotypes) regarding seed weight variability and the lack of transgenerational effects of within-line (within-genotype) seed weight variation. The canonical notion of individual plant phenotypes as arithmetic means should therefore be superseded by a concept of phenotype as a dual property, consisting of central tendency and variability components of organ trait distribution. Phenotype duality offers a unifying framework applicable to all nonunitary organisms.

Plant subindividual functional diversity and carbon cycling

Plant subindividual trait variation is a neglected level of functional diversity that contributes to the variation of phenotypes and ecological communities. Disregarding the role of subindividual functional diversity (SFD) in nature may lead to incorrect understanding of spatial and temporal scales of relationships between trait diversity, ecosystem function, and carbon cycling.

Within-individual leaf trait variation increases with phenotypic integration in a subtropical tree diversity experiment

Covariation of plant functional traits, that is, phenotypic integration, might constrain their variability. This was observed for inter- and intraspecific variation, but there is no evidence of a relationship between phenotypic integration and the functional variation within single plants (within-individual trait variation; WTV), which could be key to understand the extent of WTV in contexts like plant-plant interactions. We studied the relationship between WTV and phenotypic integration in c. 500 trees of 21 species in planted forest patches varying in species richness in subtropical China. Using visible and near-infrared spectroscopy (Vis-NIRS), we measured nine leaf morphological and chemical traits. For each tree, we assessed metrics of single and multitrait variation to assess WTV, and we used plant trait network properties based on trait correlations to quantify phenotypic integration. Against expectations, strong phenotypic integration within a tree led to greater variation across leaves. Not only this was true for single traits, but also the dispersion in a tree's multitrait hypervolume was positively associated with tree's phenotypic integration. Surprisingly, we only detected weak influence of the surrounding tree-species diversity on these relationships. Our study suggests that integrated phenotypes allow the variability of leaf phenotypes within the organism and supports that phenotypic integration prevents maladaptive variation.