Lab

• Pine Lifecycle

• Lilly Lifecycle

Dates for plant group origins:

• Mosses 475• Ferns 420• Gymnosperms 360• Angiosperms 160

The Pine Life cycle Fig. 30.9

Gnetum

Ephedra

Ovulate cones

Welwitschia

PHYLUM GNETOPHYTA

PHYLUM CYCADOPHYTA PHYLUM GINKGOPHYTA

Cycas revoluta

Douglas fir

Pacific yew

Common juniper

Wollemia pine

Bristlecone pine Sequoia

PHYLUM CONIFEROPHYTA

Gnetophytes• 3 genera: Welwitschia, Ephedra, Gnetum• Mostly dioecious• Have more Similarities to angiosperms:

– Have vessel elements,– Lack archegonia (except Ephedra) – Two sperm nuclei in pollen. Fertilizes two eggs in

some groups. Analogous to double fertilization n angiosperms

• Morphologically diverse group, grouped by genetic comparisons

• Common ancestral pool long gone, a few remote descendents remaining.

Gingko biloba

• Dioecious, heterosporous

• Dichotomous venation

• Deciduous

Cycads

• Leaves look like palms, ferns

• Makes cones

• Dioecious, herterosporous

• Pollen tube produces sperm inside !!

Pollen (Staminate) Cone: • Produced yearly• Short lived- die after

releasing pollen• Different species release pollen

at different times to avoid hybridization• The male cone has the microsporangia on scale-like

sporophylls .– (n) microspores from by meiosis– They develop into pollen grains– Produces millions of pollen grains per branch

• Carried by wind- random mating

Pollen • are the male gametophytes

– just 4 cells ! – generative cell forms the pollen tube– Pine pollen have wing cells to keep them afloat

in air

• are covered with a tough sporopollenin.• are carried away by wind or animals until

pollination occurs.• pollen grain will elongate a tube into the

ovule and deliver sperm (nuclei) into the female gametophyte via pollen tube

• No longer need film of water to fertilize

Ovulate cone• very small and fleshy when young

• Forms the “Pine Cone” with seeds– often matures over 2-3 years

• form on branch tips to catch pollen

• 2 megasporangia form on each scale or sporophyll– Megasporangia form 2 ovules – They become the 2 mature

seeds per scale in the pine cone

Ovule• Forms inside female (ovulate) cone• Megasporangia on sporophylls under go

meiosis – one surviving (n) megaspore.• Megaspore grows inside by mitosis

integuments (2n) to become female gametophyte– With 3 archegonia and eggs (pine).

• Zygote develops into embryo, inside nutritive female gametophyte tissue.

• Embryo goes dormant, integuments harden and ovule now becomes a seed

Pine ovule

Pine Megasporangia : ovulate cone

Pine Ovule; female gametophyte & Archegonia

Pine Microsporangia & pollen

Staminate Ovulate

Pine pollen & pollen tube

Angiosperms

• Flowers – attract pollinators

• Ovary = Fruit

• Ovules ( inside)=seeds

The flower

• Sepals• Petals• Stamens (male)

– Anther - pollen– Filament

• Carpel (female)– Stigma– Style– Ovary– Ovule-eggs

Figure 30.13 Flower-pollinator relationships

A flower pollinated by honeybees.This honeybee is harvesting pollen and Nectar (a sugary solution secreted by flower glands) from a Scottish broom flower. The flower has a tripping Mechanism that arches the stamens over the bee and dusts it with pollen, some of which will rub off onto the stigma of the next flower the bee visits.

(a) A flower pollinated by nocturnal animals. Some angiosperms, such as this cactus, depend mainly on nocturnal pollinators, including bats. Common adaptations of such plants include large, light-colored, highly fragrant flowers that nighttime pollinators can locate.

(c)A flower pollinated by hummingbirds. The long, thin beak and tongue of this rufous hummingbird enable the animalto probe flowers that secrete nectar deep within floral tubes. Before the hummer leaves, anthers will dust its beak and head feathers with pollen. Many flowers that are pollinated by birds are red or pink, colors to which bird eyes are especially sensitive.

(b)

The life cycle of an angiosperm

Nucleus ofdevelopingendosperm

(3n)

Zygote (2n)

FERTILIZATION

Embryo (2n)

Endosperm(foodsupply) (3n)

Seed coat (2n)

Seed

Germinatingseed

Pollentube

Sperm

Stigma

Pollengrains

Pollentube

Style

Dischargedsperm nuclei (n)

Eggnucleus (n)

Mature flower onsporophyte plant(2n)

Key

Haploid (n)

Diploid (2n)

Anther

Ovule withmegasporangium (2n)

Male gametophyte(in pollen grain)

Microspore (n)

MEIOSIS

Microsporangium

Microsporocytes (2n)

MEIOSIS

Generative cell

Tube cell

Survivingmegaspore(n)

Ovary

Megasporangium(n)

Female gametophyte(embryo sac)

Antipodal cellsPolar nucleiSynergidsEgg (n)

Pollentube

Sperm(n)

Gametophyte growth

Angiosperm seed formation

Flower cross section # 52

• Ovules

• Pistil

• Anthers

• Petals

• Sepals

• Germinating pollen

Lilly Anther