Gymnosperm Review Flashcards

Flashcards about Gymnosperms

Gymnosperm

Gymnosperm refers to plants with 'naked seeds,' meaning the seeds are not enclosed in ovaries.

Pine Tree Sporophyte

A mature pine tree is the 2n sporophyte and has both male 2n 'pollen cones' and female 2n 'ovulate cones'.

Male Cones

Small, soft, and transient cones that produce pollen in coniferous trees.

Male Gametophyte Production

Each 2n male pollen cone contains many 2n microsporangia holding 2n microsporocytes (cells) that undergo meiosis to produce n microspores.

Pollen Grain Development

Each n microspore grows (by mitosis) into a n pollen grain and contains the n male gametophyte (which will later produce sperm via highly reduced antheridium—literally 1 cell!).

Ovulate Cone Scales

Each 'scale' of a 2n ovulate cone contains two 2n ovules, each with an outer protective 2n integument and a micropyle opening (where a pollen grain will enter).

Female Gametophyte Production

Each 2n ovule has a 2n megasporangium with a 2n megasporocyte cell that produces a n megaspore by meiosis.

Megaspore Development

The n megaspore in the ovule develops into a n female gametophyte with an n archegonium that produces an n egg by mitosis. The female gametophyte will never leave the sporophyte (~few 100 cells!)

Pollination

Occurs when wind carries an n pollen grain to a female cone, entering an ovule’s micropyle opening, where the pollen grain’s male n gametophyte grows a pollen tube delivering haploid sperm.

Pollen Grain Function

Pollen grains disperse and protect sperm, and eliminate the need for water

Fertilization (Gymnosperms)

Occurs inside the female ovule, where an n sperm in the pollen tube reaches the n egg produced by the n female gametophyte creating a 2n zygote that grows into a new 2n sporophyte embryo.

Seed Formation

The whole ovule becomes a seed.

Seed Components

Protective seed coat (2n) from the ovule integument ; a 2n sporophyte embryo ; n food reserves (derived from the gametophyte).

Flowers

Modified leaves made of four rings, with reproductive structures (stamens and carpels)

Fruits

Mature ovaries that help disperse seeds