Seeds and Seedlings - Seed Testing - page 22

CLASSIfICATIon of EMbryoS (boTH AnGIoSPErMS And GyMnoSPErMS)
Martin (1946) classiied embryos into three types as basal , peripheral , or axile , depending on their posi-
tion within the seed. Figure 2.10 shows the main groupings and several subdivisions within each group.
Many monocotyledonous seeds have basal embryo arrangements in which embryos are relatively small and
restricted to the lower half of the seed or are laterally positioned. Embryos of many dicotyledonous species
are peripherally positioned in the seed and the embryo is large and often curved. For other dicotyledonous
species, particularly those with large cotyledons serving as nutritive tissue, the embryo ills the entire seed.
Gymnosperm seeds typically have an axile embryo arrangement and the embryo is centrally arranged.
As germination begins, the embryo receives nourishment from food storage tissue as it develops into a
new plant. Usually, it is the root that emerges from the seed irst, except in aquatic species where the shoot
is usually the irst structure to emerge.
Basal
Embryo located near basal end of seed. Rudimentary embryos also fall into
this category.
Representative families: Cyperaceae, Poaceae, Apiaceae, Ranunculaceae,
Magnoliaceae, and Papaveraceae.
Axile
Embryo located near the center of the mid-section of seed. Embryo may be
lat, bent, curved, spatulate, or straight, and may or may not extend from
basal to distal end of seed.
Representative families: Pinaceae.
Peripheral
Embryo surrounds (in part) inner area of nutritive storage tissue. The curved
embryo lies near the seedcoat.
Representative families: Amaranthaceae, Caryophyllaceae, Chenopodia-
ceae, and Polygonaceae.
Entire
Embryo ills the entire seed with cotyledons as the nutritive tissue and a
pronounced radicle or embryonic axis.
Representative families: Cucurbitaceae, Brassicaceae, Fabaceae, and Astera-
ceae.
Figure 2.10. Embryo types.