The Wonderful World of Plants

The Basics

What is a plant? Multicellular eukaryotes Cell walls made of cellulose Develop from multicellular embryos Contain Vascular Tissues (Xylem and Phloem) Xylem: Vascular Tissue Moves Water Upward Phloem: Vascular Tissue Moves Nutrients Both up and down Do photosynthesis to get energy (autotrophs) Examples: trees, moss, roses

Plant Cell Important Parts Chloroplast: Carry Out photosynthesis Chlorophyll: Green pigment Cell Wall: made of Cellulose

Chlorophyll and Wavelengths Two types of Chlorophyll absorbs different wavelengths of light. Both absorb blue and red light the best

All plants are eukaryotic autotrophs 6H20 + 6CO2 → C6H12O6 + 602 This reaction takes place in the chloroplast with the help of a photosynthetic pigment such as chlorophyll.

Root Cross Section Responsible for uptake of water The first root that comes from a plant is called the radicle. A root's four major functions are 1) absorption of water and inorganic nutrients 2) anchoring of the plant body to the ground, and supporting it, 3) storageof food and nutrients, 4)vegetative reproduction and competition with other plants.

Stomata and Gas Exchange  The gas exchange that occurs when stomata are open facilitates photosynthesis Photosynthesis is the process by which plants convert sunlight into usable energy. During photosynthesis, carbon dioxide is taken in from the atmosphere through the stomata and oxygen is released as a waste product. Certain factors can affect the rate of photosynthesis Three factors can limit the speed of photosynthesis: light intensity, carbon dioxide concentration and temperature. Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide.

Parts of a Seed The embryo can be distinguished from the other major parts of a seed based on component parts and function. It consists of the epicotyl, hypocotyl, radicle, and one or two cotyledons. It is the one which develops into a plant with an upward growing shoot and a downward growing root system

The Life Cycle of Plants

Life Cycle of Plants Plants have an alternation of generations. The diploid (2N) phase is the sporophyte. The sporophyte makes spores. The haploid (1N) phase is the gametophyte. The gametophyte makes gametes.

For mosses, the gametophyte is the dominant form.

For ferns, gymnosperms, and angiosperms, the sporophyte is the dominant form.

The Divisions of Plants

Plant Divisions Plants are divided into groups based on: 1. Whether or not they have vascular conducting tissues. Xylem – moves water from the roots up to the leaves Phloem – moves sugars made in the leaves down to the roots. 2. Whether or not they make seeds. 3. Whether or not they have flowers. The four groups are: 1. bryophytes (mosses) 2. seedless vascular plants (ferns) 3. gymnosperms (cone bearers) 4. angiosperms (flowering plants)

Bryophytes Examples include mosses and liverworts.

Characteristics of Bryophytes Bryophytes do not have special tissues to conduct food and water. They rely on osmosis to move water around their bodies. Because of this, they don’t get very tall. They rely on water to be able to reproduce because the sperm swim through water to the eggs.

Moss sporophyte and gametophyte

Seedless Vascular Plants Ferns are vascular which means they have xylem and phloem. Xylem and phloem allow these plants to grow taller than mosses. Ferns are seedless plants. They make spores.

Ferns

Ferns reproduce with spores

Horsetails and club mosses are close relatives of ferns

The Seed Plants Gymnosperms and Angiosperms

Gymnosperms Have vascular tissue. Make seeds. Do not have flowers, but do have cones. The 1N gametophyte stage is enclosed entirely within the 2N sporophyte structure.

Gymnosperm cones…male and female. Which is which?

Gymnosperms include conifers and ginkgoes

Angiosperms Have vascular tissue. Make seeds. Do have flowers. The 1N gametophyte stage is pretty much enclosed entirely within the 2N sporophyte structure.

Angiosperms include any flowering plant…tulips, cherry trees, zinnias

Flower Structure and Seed Dispersal

Angiosperms Flowers contain ovaries which protect the egg. Somehow, sperm needs to get to the egg. Once the egg is fertilized, it turns into a seed. Somehow the seeds need to be dispersed – spread away from the parents. Seeds are dispersed by fruit, sticking to the fur of animals, or spread by the wind.

Flower Structure

Seed dispersal

Angiosperms can be Further Divided

Angiosperms can be divided into Monocots and Dicots Single cotyledon Two cotyledons Parallel leaf veins Branched leaf veins Flower petals in 3’s Flower petals in 4’s or 5’s Roots are fibrous One big tap root

Leaf Vein Patterns Monocot Leaves: Veins are parallel Dicot Leaves: Veins are branched Dicot leaf

Flowers Monocot Flower Dicot Flower

Roots Monocot-roots are fibrous Dicot-one big tap root

Plant Behavior

Plants can maintain homeostasis.

Phototropism Phototropism is the movement of plants towards light.

Gravitropism/Geotropism Roots move down and shoots grow up in the dark in response to gravity.

These plants were situated in various positions, but the shoots continued to move against gravity.

Thigmotropism Thigmotropism is a plant’s response to touch. This plant responds to a stationary object by wrapping its stem around it to anchor itself.

This plant responds to touch by wilting This plant responds to touch by wilting. What advantage may this be to the plant?

Photoperiodism - Some plants respond to the amount of daylight – Poinsettia turn red and flower in response to shorter days

Some plants “eat” animals Considered both Autotrophic and Heterotrophic Monkey cup A.K.A. Tropical pitcher plant

Sundews – insects are attracted to surface and get stuck on mucus

Venus Fly Trap