How Plants Colonized Land

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The diploid embryo is retained within the tissue of the female gametophyte. Nutrients are transferred from parent to embryo through placental transfer cells.

Land plants are called embryophytes because of the dependency of the embryo on the parent.

Slide 8

Land Plants Life Cycle

Gametophyte

(n)

Gamete from

another plant

n

n

Mitosis

Gamete

FERTILIZATION

MEIOSIS

Mitosis

Spore

n

n

2n

Zygote

Mitosis

Sporophyte

(2n)

Alternation of generations = Derived traits of land plants

Slide 9

Derived Traits of Land Plants Multicellular Dependent Embryos

Embryo

Maternal tissue

Wall ingrowths

Placental transfer cell

(outlined in blue)

Embryo (LM) and placental transfer cell (TEM)

of Marchantia (a liverwort)

2 µm

10 µm

Slide 10

Walled Spores Produced in Sporangia

The sporophyte produces spores in organs called sporangia.

Diploid cells called sporocytes undergo meiosis to generate haploid spores.

Spore walls contain sporopollenin, which protects against dessication making them resistant to harsh environments.

Slide 11

Derived Traits of Land Plants: Walled Spores Produced in Sporangia:

Spores

Sporangium

Sporophyte 2n

Longitudinal section of

Sphagnum sporangium (LM)

Gametophyte n

Sporophytes and sporangia of Sphagnum (a moss)

Slide 12

Multicellular Gametangia

Gametes are produced within ‘sex organs’ called gametangia.

Female gametangia, called archegonia, produce eggs and are the site of fertilization.

Male gametangia, called antheridia, are the site of sperm production and release.

Slide 13

Derived Traits of Land Plants: Multicellular Gametangia - ‘sex organs’

Female gametophyte

Male

gametophyte

Antheridium

with sperm

Archegonium

with egg

Archegonia and Antheridia of Marchantia (a liverwort)

Slide 14

Apical Meristems

Apical meristems are growth regions at plant tips, allowing plants to sustain continual growth in their length.

Cells from the apical meristems differentiate into various tissues.

Slide 15

Apical Meristems - Allow for Growth in Length throughout Plant’s Lifetime.