The morphology of Chenopodium album seed germination

Taxonomic description.  While on the the mature Chenopodium album plant, the seeds (ovary) are superior and borne horizontally.  The sepals are attached at one point and wrap around the seed.  The seeds are enclosed by a membranous pericarp that is easily removed.  Embryos wrap around the seed and overlap to form the beak.  A small beak is formed by the embryo on one side, with the micropyle visible at the base.  The seed is ovate, with convex sides and acute, keeled margins.  the testa has faint radial striations but is otherwise smooth.   Seeds range from 1.1-1.5 mm in diameter.   Morphology is not uniform, variation is arises from several factors affecting seeds.  The majority of the seed are black and shiny, a small amount brown, light brown or red. {Williams, 1963; Flora of Pakistan; Indianjournals.com)

C. album seeds produced by parent plants consists of individuals with potentially different germinability-dormancy capacities, seed heteroblasty.  This heterogeneous seed rain is the blueprint for seedling recruitment timing and pattern (as modulated by local environmental conditions).  Seedling emergence, recruitment, is the single most critical event in the weeds' subsequent assembly in agricultural plant communities, hence fitness.  Some of the inherent variation in C. album seed heteroblasty may be associated with external seed morphology. 

MORPHOLOGICAL HETEROGENEITY WITHIN A LOCAL POPULATION

SEED COLOR

These three pictures are of the same mature C. album seed, but each photographed in a different light level (high to lower, left to right).  The seed within this surrounding tissue is black and shiny (see below). The different colors in different light intensities may indicate this seed tissue layer acts as a light lens, changing the spectra absorbed and reflected in different light regimes.  This light diffusion is a consequence of this surrounding tissue layer, seen in closer detail in the table below.

Above:  Black seed with surrounding tissue	Above:  Black seed with surrounding tissue; center of seed with tissue removed revealing shiny black seed interior

IMMATURE (RED) SEED

Apparently immature red seeds as this one usually germinate in our controlled environment cabinets in ideal conditions

SEPALS ATTACHED TO SEED

SEED COVERING TISSUE

Above:  Smooth half (upper left), tissue layer half (lower, right)	Above:  tissue layer Below:  close-up of tissue layer and floral remnant	Above:  side view of seed with intact tissue layer Below:  close-up of tissue layer

SEED PORTAL

Above:  Smooth seed with portal	Above:  Seed portal close-up

SEED INTERIOR, CROSS-SECTION

Above:  Cross-section of seed interior; portal is in lower right of seed	Above:  Close-up of seed interior cross-section; portal is in lower right of seed

References Cited

Williams, J.T. 1963. Journal of Ecology 51:711-725.

Flora of Pakistan, vol.204. www.eFlora.org.

Indianjournals.com.

   Nate Looker, Agronomy Department, Iowa State University

The seed photographs on these pages were taken by Nate Looker, Lindsey Altenhofen and Jack Dekker.  Nate Looker's photography and micrography was done at the Iowa State University Microscope Facility, Bessey Hall, to document the apparent variation in seed color and morphology.  This photographic study was conducted as part of his Freshman Honors Mentor Program project in the spring, 2009.  Lindsey Altenhofen's contributions were part of her Freshman Mentor Program project, and her BS/MS degree program, all with common lambsquarters from 2007-2010.  The taxonomic descriptions of common lambsquarters were part of Lindsey Smith's Freshman Mentor Program project done in 2010.

©jdekker-2011