Premise of research.

Cotyledons have important functions in early seedling stage and have important effects on later stages, but we know little about the relationships among developmental stability, canalization and phenotypic plasticity in cotyledons.

Methodology.

We conducted a field experiment with five herbaceous species, by subjecting them to contrasting light conditions and burial depths and measuring their cotyledon size and fluctuating asymmetry (random deviation from perfect bilateral symmetry, indicating developmental stability or instability), coefficient of variation and plasticity of cotyledon size, to investigate the relationships among cotyledon developmental stability, canalization and plasticity in response to shading and deep burial.

Pivotal results.  

Pharbitis purpurea, Convolvulus arvensis and Carpesium abrotanoides had increased cotyledon size in response to shading at both burial depths; Abutilon theophrasti showed reduced cotyledon size in response to shading vs. full light at shallow depth, but greater cotyledon size in response to both shading and deep burial. Shading increased cotyledon fluctuating asymmetry of P. purpurea and C. abrotanoides, while deep burial decreased it. Cotyledon fluctuating asymmetry had positive correlations with coefficient of variation and plasticity in response to shade in shading, with little correlation between coefficient of variation and plasticity.

Conclusions.  

Results suggested A. theophrasti may have greater tolerance for multiple stresses than the other species, and deep burial may improve shade tolerance of cotyledons through moderate level of stress selection. Both developmental instability and decreased canalization may indicate the state of faster growth. Developmental instability can facilitate more-active response to shading in cotyledon, while the relationship between canalization and plasticity should be more complex.