Comparison of Gymnosperms, Angiosperms, and SLVPs

megaspores in Selaginella (SLVP)

released from megasporangium

microspores in Selaginella (SLVP)

released from microsporangium

mega/female GP³ in Selaginella

free living, surrounded by megaspore wall; archegonia, smaller than GPs of other SLVPs

micro/male GP in Selaginella

free living, antheridium; multiple sperm cells, smaller than GPs of other SLVPs

sperm and fertilization in Selaginella

flagellated, dependent on water

egg cell in Selaginella

in archegonium of megaGP

embryo development of Selaginella

no ovule, within 1n GP inside megaspore wall

nutritive tissue in Selaginella

GP provides nutrients to growing embryo via placenta tissue

seed and fruit in Selaginella

no seed, no fruit

megaspores in Gymnosperms (Conifer-type)

retained in nucellus (megasporangium) of SP³

microspores in Gymnosperms (Conifer-type)

retained in microsporangium of GP

mega/female GP³ in Gymnosperms (Conifer-type)

not free-living — in ovule of SP, archegonia, highly reduced (~2000 cells)

micro/male GP in Gymnosperms (Conifer-type)

not free living; pollen (male GP) develops in microsporangia, pollen NOT microspore is released. no antheridia (mature GP=6 cells), 2 sperm cells, extremely reduced.

sperm and fertilization of Gymnosperms (Conifer-type)

not flagellated, independent of water; entire microGP (pollen) transferred to megaGP; 2nd sperm dies, no function

egg cell of Gymnosperms (Conifer-type)

in archegonium of megaGP

embryo development in Gymnosperms (Conifer-type)

within ovule, within megaGP (1n endosperm)

nutritive tissue in Gymnosperms (Conifer-type)

entire GP (endosperm) functions as food store for embryo

seed/fruit in Gymnosperms (Conifer-type)

seed consists of: embryo (2n), endosperm (1n), seed coat (2n)⁴ — derived from integuments, no ovary and no fruit (naked seed)

megaspores of angiosperms

same as Gymnosperms

microspores of angiosperms

same as gymnosperms

mega/female GP³ of angiosperms

not free-living, in ovule of SP; no archegonia, reduced to 7 cells (8 nuclei)

micro/male GP of angiosperms

same as gymnosperms, but mature GP = 3 cells, not 6.

sperm/fertilization of angiosperms

not flagellated, independent of water; entire microGP (pollen) is transferred to megaGP

double fertilization: second sperm forms 3n endosperm (w/ 2 polar nuclei)

egg cell of angiosperms

in embryo sac = megaGP

embryo development in angiosperms

within ovule, within 3n endosperm; no GP

nutritive tissue in angiosperms

endosperm = triploid; may be substituted by food stored in cotyledons

seed/fruit in angiosperms

seed consists of embryo (2n), endosperm (3n), seed coat (2n)⁴, derived from integuments, seed surrounded by fruit from ovary