Plants

Chapter 9

Plants Plants range from microscopic to huge

redwood tress. Like bacteria, some plants grow in extreme

conditions like ice bound polar regions, and hot deserts.

All plants need water, but some need to be completely submerged in either salt or fresh water.

Plant cells Plant cells are different from animal and bacterial

cells. They are more complex because they need special

organelles to survive. They have a nuclei and contain numerous

chromosomes. And they also have cell walls, made of cellulose, that allow for protection and also aid in structure of the plant.

Plants also contain chloroplasts that contain chlorophyll, a green pigment that allows photosynthesis to occur.

Many plants cells also have a large central vacuole that is needed to store water, and other pigments besides chlorophyll.

Origin of Plants Plants are said to evolve

from green algae that lived in the sea.

Algae use pigments like chlorophyll to go through photosynthesis as well as other pigments like carotenoids and xanthophylls.

Fossils of early plants from 420 mill years ago show a common ancestry to green algae.

Land Plants It makes sense for plants to end up on land b/c there

is more opportunity for them to get sunlight and CO2 for photosynthesis.

One structure that helps plants stay hydrated is called the cuticle.

It covers the stems and leaves and is a waxy substance that doesn’t allow water to exit the cells of the plants.

Plants also, adapted to land in the reproductive aspect. They evolved a water proof seed that allowed better reproduction development on land.

Classification of Plants Plants can be vascular or nonvascular. Vascular plants have things called xylem and

phloem that act almost like veins and arteries. They carry water and nutrients up and down the plant as needed.

Non –vascular plants do not have these but use other methods to transport water and nutrients throughout the plant.

H.W. pg 247 ques 1-4

Sec 9-2 Nonvascular seedless plants Nonvascular plants are usually just a few cells thick

and only 2-5cm high. They do not have all of the structures that a large vascular plant might have.

Instead of roots they have rhizoids, or threadlike structures that anchor them in the ground.

They also do not have flowers that produce seeds, they use what are called spores.

They usually grow in damp places so that surrounding water can diffuse directly through their cell membranes.

Nonvascular seedless plants Mosses are one type .

They have green leaf like growths around a central stalk, and many celled rhizoids.

Sometimes they have caps on their stalks that hold their spores.

Mosses grow on tree trunks, rocks, and the ground, usually in damp areas.

Nonvascular seedless plants Liverworts are nonvascular plants that have

one celled rhizoids, and were thought to have medicinal properties that helped in curing liver diseases.

Hornworts look like spikes, but only have one chloroplast per cell. Their spores look like the horns of cattle.

Liverworts & hornworts

Nonvascular seedless plants Good things about these types of plants is that

they can last without a lot of water for a good period of time.

They can grow in thin soil and their spores get carried by the wind so they can reproduce.

They are considered pioneer species because they are usually the first to grow in an undisturbed environment.

Vascular seedless plants Vascular seedless plants don’t use seeds

either, they use spores, but they do have xylem and phloem to carry water and nutrients throughout the plant.

These types of plants grow a lot larger than nonvascular plants because of the vascular tissue. They get more water and more nutrients.

Vascular seedless plants Ferns are the largest

of this group and have stems, leaves called fronds and roots.

There are thousands of fern species on earth and they carry their spores on the underside of their fronds.

Vascular seedless plants Club mosses are more

closely related to ferns than to mosses.

They have vascular tissue and have needle like leaves.

They have spores at the end of their stems in structures that resemble pine cones.

Vascular seedless plants When these vascular seedless plants die they

decay and become compressed in the ground to form Peat.

Peat is a material that is the beginning stages of coal, and we can use it to get energy. Peat is used highly in places like Ireland, that have swampy boggy areas.

If Peat is left alone, after many, many years of compaction it will become coal.

H.W. pg 253 ques.1-4

Sec 9-3 Seed plants Seed plants are the largest category of plant

on earth. Every tree, vegetable, and fruit is a seed plant.

They have leaves, stems, roots, and vascular tissue.

The leaves of a seed plant is were photosynthesis takes place. There will be more chloroplasts in the leaves of a seed plant then anywhere else.

Leaf structure

Leaves have different layers. The upper and lower parts are called the epidermis, which cover and protect the leaf, the upper one is covered by a waxy cuticle.

The epidermis has small opening called stomata, to allow water, CO2 and O to enter and leave the cell.

These stomata each have 2 guard cells that open and close them.

Leaf structure Below the epidermis is the palisade layer.

This layer has tightly packed cells that contain many chloroplasts for photosynthesis.

Below the palisade layer is the spongy layer, which contains vascular tissue and air spaces.

Stems The trunk of a tree is really the stem of the

tree. Stems are located above ground and support the branches and leaves above it.

Materials like water, and nutrients make their way from the ground through the stem, to the leaves and vice versa through vascular tissue in the stem, leaves and roots.

Plant stems can be herbaceous, soft and green, or woody, like large trees and shrubs.

Roots Roots of a seed plant are the largest part of

the plant. They allow for absorption of water and other

nutrients from the ground through their vascular tissue.

They also act as anchor into the ground. And they store food as well. Carrots beets and potatoes are all plant roots.

Vascular tissue Xylem moves materials from the roots up to

the rest of the plant and to the leaves so photosynthesis can occur.

Phloem carries material from the leaves down to the rest of the plant, like sugar made in the leaves during photosynthesis.

Seed plant classification Gymnosperms- are plants that produce seeds

that are not protected by a fruit. They have no flowers, and their leaves are

needle like. Conifers, cycads, ginkgoes, and gnetophytes

are the 4 major types of gymnosperms. Conifers are pine trees, firs, spruces,

redwoods. They all produce male and female cones that are the plants reproductive structures.

Angiosperms These plants have flowers and have a fruit

that contains seeds. They include all flowers like roses and fruits like apple, strawberries etc…

Angiosperms are divided into 2 groups: monocots and dicots.

Monocots Vs. dicots Have one cotyledon, apart of a seed that

stores food. Dicots have 2.

Monocots have slender leaves and have flower parts in multiples of 3.

Dicots have wider leaves and flowers parts in multiplesof4 or 5.

H.W. pg 270 ques. 1-15