Chapter 29 and 30: Plants

Objectives

-Understand that land plants evolved from green algae

-Mosses and other nonvascular plants have life cycles dominated by gametophytes

-Ferns and other seedless vascular plants were the first plants to grow tall

-Seeds and pollen grains are the key to success for land plants

-Gymnosperms bear “naked” seeds (cones)

-Reproductive adaptations of angiosperms include flowers and fruit

Morphological and Molecular data suggests land plants evolved from green algae (Charophytes)

Morphological1. Rossete shaped cellulose synthesizing

proteins in plasma membrane2. Peroxisome enzymes that help minimize loss

of organic products of metabolism from photorespiration

3. Flagellated sperm4. Formation of a phragmoplast during cell

division

Genetic Sampling also indicates similarities

1. Alternation of Generations-Has a multicelluar haploid and

diploid organisms-Plants are called embryophtes

due to the embryonic activity in the female gametophyte

- Analogous to mammals

2. Production of protective spores

3. Multicellular Gametangia (1n)

Adaptations or derived characteristics that allowed plants to move to land.

4. Use of an Apical meristem for elongation

Current Understanding of plant evolution

Bryophyte refers to all Nonvascular plants

-Gametophytes are longer and larger then Sporophyte

Horwort

Liverwort

Mosses

Seedless Vascular Plants-Sporophyte dominant-Contain Xylem, which brings water and minerals up from the roots

** Allows for strength in stem = growing tall -Contain Phloem for transport of organic compounds

Leaves divided into1. Microphylls (smalll)2. Megaphylls (large extensive leaves)

Sporophylls-Modified leaves that contain Sporangia-Homospores = one type of spore-Heterospore = male (microspore)and female spore (megaspore)

Seedless Vascular Plants

The importance and evolutionary significance

of seeds as a derived characteristic

1. 2n Embryo with its food supply

2. Means the embryo can survive away from mother plant

3. Analogous to a detachable woman’s womb

4. Dispersed in a variety of ways

5. Contributions to human society

Hunter/Gatherer

to

Settlers using agriculture

Immergence of Seed plants

1. Reduced Gametophyte stage –Allows for protection of the gametophytes within the sporangia of the sporophyte = great success in seeded plants

2. Contain heterospores (Male and Female)

3. Seeds have advantages over spores (More protection, Food source, Can remain dormant longer, Stored food can help in germination)

Development of seeds and pollination

1. Female (Megasporangium) is covered by a thin layer called integument

2. Megasporangium undergoes Meiosis and produces a Megaspore

3. Pollen is produced in a mircospore

4. Pollen doesn’t need water to swim in like Flagellated sperm of seedless plants (Wind or hitch hike)

1. Female Gametophyte grows

2. Male Gametophyte is in the pollen grain

3. Pollination occurs (Pollen (1n) enters through an opening of the integument and fertilizes the egg

4. After fertilization the integument turnes into the seed coat

5. Embryo or new sporophyte begins to form

Gymnosperms

- Naked seeds (No Fruit)

-Four Gymnosperm Phyla

1. Ginkgophyta

2. Coniferophyta

3. Cycadophyta

4. Gnetophyta

Conifers have both pollen and ovulate cones

Microspores produce pollen grains that contain the gametophyte

Pollination occurs when pollen attaches to the Megaspore and germinates forming a pollen tube (digests its way through the Megasporangium)

While pollen tube extends the Megaspore undergoes meiosis

Usually takes about a year from pollination to seed and only one embryo usually survies

Carpel produces megaspores

Angiosperms are flowering plants

Stamen produce microspores which turn in to pollen

Fruits

-Fruits are the ovary with the fertilized seed inside

-Protect and aid in dispersion

Double fertilization produces endosperm or nutrients

-Possible reason is to synchronize development of food sources and seed

4 megaspores are formed with one surviving

Some flowers self pollinate while most have mechanisms to cross pollinate

Magnoliids

Basil Angiosperms

EudicotsMonocots