Ch. 35 Plants

Background of Plants Multicellular Euks Photosynthetic autotrophs Cell walls are made of cellulose Excess carbs are stored as starch

Alternation of generations Sporophyte generation - all cells are diploid Gametophyte generation- all cells are haploid - Split into divisions, not phyla - Thought to have evolved from the green algae Chlorophyta *-phyte = plant

Classification: 4 major groups 1) Bryophytes- The mosses. NO VASCULAR TISSUE. Must live in moist environments to aid in diffusion of water up plant.

Classification: 4 major groups *Tracheophytes- Plants that have xylem and phloem (transport vessels = Vascular Tissue) 2) Seedless Vascular Plants- The ferns. Have vascular tissue, but no seeds (uses spores only). Considered ancient.

Classification: 4 major groups 3) Gymnosperms- Cone (conifer) plants. Can live in very dry habitats because of modifications to reduce water loss (waxy cuticles)

Classification: 4 major groups 4) Angiosperms- Flowering plants. Most diverse and plentiful of all the plants. Split into the monocots and dicots.

How Plants Moved to Land: Cell walls- Allows for better support of plant Roots and root hairs- Better absorption of water from soil Stomata- Open and close to allow gas exchange. Can be in stomatal crypts (holes) Sporopollenin- Coats spores and pollen to protect it from the environment. C4 and CAM plants

Plant Reproduction (non-flowering plants) Alternation of Generations - Monoploid and diploid life cycles alternate - Gametophye (n) produces gametes by mitosis - Sporophyte (2n) produces monoploid spores by meiosis

Plant Reproduction: Bryophytes (mosses) Gametophyte generation is dominant. Starts its life as a protonema and then individual gametophytes arise. Gametophytes will develop either archegonia (produces egg) and antheridia (produces sperm). Gametes meet and form the sporophyte that gets its nutrients from the gametophyte. On the top of the sporophyte forms a sporangia which contains spores.

Plant Reproduction: Seedless vascular plants (ferns) Sporophyte is dominant part of life and is separate from the gametophyte. Gametophyte develops as a heart-shaped plant on the ground. Archegonia and Antheridia can be found on the underside. Water is needed for the sperm to meet the egg, but after this occurs, a zygote will form and the sporophyte will sprout. These sporophytes will contain sori (clusters of sporangia) that will burst and release spores to start cycle again.

Seedless vascular plants-

Plant Structure and Growth Plants have a great deal of “plasticity”- they can adapt well to their environment because they are not able to move if the habitat changes.

Three Plant Organs- Roots, Stems, Leaves 1) Roots- anchors, absorbs nutrients/water, and storage of goods. Adventitious roots- Roots with an abnormal origin (sometimes above the ground) Most absorption is close to the root tip because there are many roots hairs located there (increase surface area)

Roots cont. Eudicots have taproots (main vertical root) with some lateral roots attached Monocots have fibrous roots *Know the structure of both the Eudicot and Monocot root All lateral roots originate from the pericycle

Stems 2) Stems- Support and transport of goods Alternation between nodes (where the leaf is attached) and internodes (the space between the leaves) Axillary bud- Could develop into a lateral shoot (branch) Terminal bud- at the top of the plant and the tips of the branches *Know the picture below Leaves originate from the leaf primordia * Know the structure of both the Eudicot and Monocot stem

Leaf Eudicot- Multi-branched veins Monocot- Parallel veins 3) Leaf- Main photosynthetic organ of the plant. Contain the blade and petiole (stalk), although some plants lack the petiole (grass) Eudicot- Multi-branched veins Monocot- Parallel veins *Know the picture below Stomata- Gas exchange Guard Cells- Open and close the stomata Mesophyll- Palisade (main site of photosynthesis) and spongy

Bundle Sheath Cells- Protect the vascular tissue Cuticle - Waxy coating to prevent water loss  

Leaf: Stomata What causes the stomates to OPEN? Lots of water Depletion of CO2 will also open the stomates. Increase in potassium ions Active transport of H+ ions out of the guard cells

Leaf: Stomata What causes the stomata to CLOSE? Lack of water High temperatures- Stimulates cellular respiration in the leaf Abscisic acid- Chemical that signals the guard cells to close

Dermal tissue- Outer protective covering Three Tissue Systems- Dermal, Vascular, and Ground- All of these can be found throughout the plant Dermal tissue- Outer protective covering Non-woody plants- Epidermis Woody plants- Periderm 2. Vascular tissue- Long distance transport - Vascular tissue is collectively known as the stele but can referred to as the vascular cylinder or vascular bundle - Xylem- Carries water up the plant - Phloem- Carries sugars down the plant

Plant Tissue - Pith - Cortex 3) Ground Tissue- Storage, photosynthesis, and support of plant - Pith - Cortex

Differentiated Plant Cells (see end of chapter notes for pictures of all of these) 1. Parenchyma cells- Typical plant cell. Most metabolic processes take place here (photosynthesis). Totipotent. 2. Collenchyma- In strands or cylinders. Supports young parts of the plant shoot. Flexible. (ie- Celery strands) 3. Sclerenchyma- Thick secondary cell wall made of lignin. Rigid. Found in parts of the plant that are no longer growing. (ie- Seed coats, nutshells, the grainy parts of a pear)

Water conducting cells of the xylem DEAD at maturity and have pits in them that connects the cell to their neighboring cell - Tracheids - Long and thin - Vessel Elements- Short and wide.

Sugar conducting cells of the phloem Alive at maturity (but lack organelles) - Associated with a companion cell next to it that houses the organelles needed Sieve tube members make up the sieve tubes with sieve plates between them. (Sieve = sugar!)

Plant Growth The lifespan of a plant varies. - Annuals- Live only 1 year - Biennials- Live 2 years - Perennials - Live indefinitely Meristems- Perpetually embryonic

Meristems

Plant Growth Apical meristems- Primary growth (root tips and stem tips) and compose the primary plant body (this is the whole plant in herbaceous plants) Lateral Meristem- Site of secondary growth which will give girth (width) to the woody plants

Plant Growth The vascular cambium is the lateral meristem, and it is only one cell layer thick. The vascular cambium will lay down the following every year: A layer of secondary xylem (wood of the tree) to the interior of itself A layer of secondary phloem (bark) to the exterior of itself

Plant Growth Lateral meristems- only found in woody plants.