Unit 15: PlantsChapters 20-22

Chapter 20: Plant Diversity

 20.1 Origins of Plant Life

Plant life began in the water and became adapted to land.

Green Algae (Domain Eukarya, Kingdom Protista) and Plants (Domain Eukarya, Kingdom Plantae) share many characteristics:

○ photosynthetic eukaryotes

○ contain chlorophyll—green pigment that captures energy from sunlight during photosynthesis

○ use starch as a storage product

○ have cell walls with cellulose (all plants and most green algae)

○ are multicellular

○ reproduction involving sperm and egg

○ Green algae are not currently classified with plants since algae do not have roots, stems or leaves, and most species are aquatic.

Plants have 4 major adaptations that allow them to live on land.

1. Retaining moisture (prevent desiccation)○ cuticle—clear waxy, waterproof layer ○ that helps hold in moisture○ stomata—holes in the cuticle

surrounded by special cells allowing the stomata to close to prevent water loss or to open to exchange gases with the air (bring in CO2 and release O2 and water vapor).2. Transporting resources

○ vascular system—a collection of specialized tissues that bring water and mineral nutrients up from the roots and transport sugars to where they are used or stored

○ vascular system allows the plants to grow taller ○ nonvascular plants must remain small because water

moves by osmosis

Plants have 4 major adaptations that allow them to live on land.

3. Growing upright○ tall plants compete better for light○ lignin—hardens the cell wall of

some tissues to provide support, such as in wood

4. Reproducing on land○ pollen grain—contains a cell that will form

sperm; structure of the pollen allows it to be carried by wind or animals and not require water

○ seed—storage device for a plant embryo; the seed coat protects the embryo from drying out

20.2 Classification of Plants

○ The Plant Cell: Review

○ Are plants autotrophic or heterotrophic?

○ Are plants prokaryotic or eukaryotic?

○ Are plants multicellular or unicellular?

○ Plant cell walls are made of….

cellulose

autotrophic (plants are producers and they make their own food via photosynthesis; have chloroplasts)

multicellular

eukaryotic (eukaryotes have a nucleus just like we do and YOU are Eukaryotic)

1 2

3

4

5

6

7

nucleus rough ER

central vacuole

chloroplast

cell wall

mitochondria

Golgi

20.2 Classification of PlantsNonvascular Plants (3 phyla) • do not have a system for

transporting water and other nutrients within their body• nonvascular plants are small

and lack vascular tissue (xylem and phloem); therefore cannot develop stems, roots, and leaves

• includes mosses (bryophytes), liverworts, and hornworts

Vascular Plants (6 phyla) • contain structures with vascular

tissue (roots, stems and leaves)• vascular plants (also known as

tracheophytes) are composed of:• tissue (roots, stems, leaves)• each plant part – tissue, root,

stem, leaf - has a specific role in keeping the plant alive through photosynthesis

• Include club • mosses, ferns,

gymnosperns, & angiosperms

Plants are divided into two major groups:Nonvascular Plant - mossSphagnum moss is commonly used by humans. It does not decay when it dies and thick deposits of this are known as peat. Peat has many uses:○ can be burned as fuel○ absorb water, so often used to

make soil more productive○ antibacterial properties (which

prevents decay)○ serves as carbon reservoirs in the

carbon cycle

Question: If nonvascular plants don’t have roots or stems, why do we find most of them near water?

Answer: they don’t have the structures to transport water so in order to get water they have to be near it to “absorb” it directly; it moves cell to cell by osmosis

Vascular Plants

contain vascular tissue (xylem and phloem – discussed later)○There are two types of vascular plants:

- seedless plants - seeded plants

Vascular

Seedless Plants

Seeded Plants

Gymnosperms

Angiosperms

○Plants with seeds can be grouped into two additional categories:○ gymnosperms and

angiosperms

Vascular Plants○ Advantages of conducting

tissue ○ transportation of water

and sugar within a plant○ development of true roots,

stems, and leaves○ grow taller (gaining more

sunlight) and deeper (gaining more water)

○ store sugars for future use○ don’t rely on osmosis and

diffusion

Seedless Vascular Plants:spore – haploid asexual

reproductive cell that divides by mitosis into a multicellular haploid organism

Spores have thickened walls that prevent the cells from drying out

Photograph below shows spores growing in clusters called sori on the back of the fern

Examples: ferns, club mosses, horsetails, and whisk ferns

http://en.wikipedia.org/wiki/Image:Lycopodium_plant.jpg

Horsetail ↓

whisk fern ↑

fern ↓

sori

Seeded Vascular Plants:○ seed - adaptation to terrestrial life composed

of a plant embryo, stored food and a protective coat

○ advantages of seeds ○ seeds allow reproduction without free-

standing water○ seeds protect and nourish a plant’s embryo.

Types of seeded vascular plants

○ Gymnosperms○Produce cones○Conifers, cycads, ginkgoes, and

gnetophytes○ Angiosperms

○Fruits or flowers○The angiosperms are classified as

either monocots or dicots.

an adultperson!(Giant Sequoias, Yosemite NP)

Types of seeded vascular plants:

○ Gymnosperms○ seed plants whose seeds are not

enclosed in fruit○ the cone is the reproductive

structure; ○ contains pollen in males and ovules

(eggs) in females○ Examples: conifers (pine, fir, cedar

cypress), cycads, ginkgoes, and gnetoph ytes

ovulate cone - from a pine tree (female)

staminate cone - from a pine tree (male)

Types of seeded vascular plants:

○ Angiosperms○ seed plants that have seeds enclosed in

some type of fruit○ the flower contains the reproductive

structures○ Examples: monocots and dicots

Types of seeded vascular plants:

○Angiosperms○seed plants that have seeds

enclosed in some type of fruit○the flower contains the

reproductive structures○Examples: monocots and dicots

Angiosperms are categorized by seed type:Monocots:

○ one cotyledon—food source for baby plant before it has true leaves for photosynthesis

○ veins in leaf parallel○ vascular bundles in complex arrangement

(scattered)○ fibrous root system ○ floral parts in multiples of three○ Ex) grasses, corn, wheat, tulips, lilies

• Dicots:○ two cotyledons ○ leaf veins netlike○ vascular bundles arranged in ring ○ taproot usually present ○ floral parts in four or five○ Ex) most deciduous trees,

roses, daisies, peanuts

Angiosperms are categorized by seed type:

Angiosperms

Angiosperm are also categorized by stem type and lifespan:

○ stem type: woody or herbaceous○ lifespan:

○ annual (life cycle in one year), ex. petunias and pansies

○ biennial (life cycle in two years)○ex. carrots

○ perennial (lives more than 2 years) ○ex. trees and shrubs

Chapter 21: Plant Structure and

Function

21.1 Plant Cells and Tissues○ Organ - group of tissues working together to

perform a common function○ Tissue - group of cells working together for a

common purpose○ Plants have three main organs—leaves, stems,

and roots.○ These three organs are made up of three

tissue systems — dermal, ground, and vascular.

○ These three tissue types are made up of three basic cell types — parenchyma, collenchyma, and sclerenchyma.

 3 basic plant cell types:

○ parenchyma – found throughout the plant and store starch, oils, and water; also house chloroplasts in the leaves; makes up most of fruits, stems, and roots

○ sclerenchyma — strongest of these cell types that have a second cell wall hardened by lignin; provide support; cells are dead at maturity and make up wood, nut shells, seed coats

○ collenchyma – found in younger tissues of leaves and roots; provide support while the plant grows.

3 tissue systems in plants:

○ dermal tissue system – covers the plant; epidermal (outer) layer of cells of plants.○ ground tissue system – specialized for photosynthesis in leaves and for storage and support in stems and roots.

○ vascular tissue system – internal system of tubes and vessels that transports water, mineral nutrients, and organic compounds to all parts of the plant.

2 types of vascular tissue: xylem and phloem

○ xylem – transports water and minerals UP from the roots to the shoots (memory trick—remember “wxyz”…water carried by the xylem (xy sounds like a z))

○ phloem – transports sugar (food) from where it’s made (leaves) or stored (cells in leaves or roots) to where it’s needed (remember phloem (ph sounds like an f) transports food).

xylem phloem

Leaves (photosynthesis)

roots

Wate

r +

m

inera

ls

Ph

ood

(s

ug

ar)

↑

↑

↑↑

21.2 & 21.3 The Vascular System and Stems & Roots

StemsFunction: support, storage, and transport

Storage:○ stems can store food and water (ex. cacti,

potatoes, ginger)

Support:○ stems can be woody or herbaceous○ stems support leaves, flowers, and fruits

21.2 & 21.3 The Vascular System and Stems & Roots

Transport:

xylem – transports water and minerals up from the roots to the shoots

○ forces responsible for the movement of fluids through xylem are transpiration, cohesion, adhesion, and absorption.

○ What process is the main force for the movement of fluids through xylem?transpiration

21.2 & 21.3 The Vascular System and Stems & Roots

Transport:

Xylem

See Figure 2.2 p. 622 and watch Animated Biology--Movement Through A Plant: What process is the main force for the movement of fluids through xylem? transpiration

http://tinyurl.com/msun9zk

21.2 & 21.3 The Vascular System and Stems & Roots

○ phloem – transports sugar (food) from where it’s made (leaves) or stored (cells in leaves or roots) to where it’s needed

○ The transport of sugar down the plant requires energy. Plants pump sugar from a source into the phloem. The change in the concentration causes water to follow sugars into the phloem, increasing the pressure and pushing the sugars through the phloem into a sink.

RootsFunction- support the plant, absorb water and nutrients, transport water and nutrients to the stem, and store nutrients

Roots are either fibrous or form a taproot.

Main parts of the root:○ vascular cylinder (or stele)

is in the center; contains the xylem and phloem

○ root hairs—tiny projections of epidermal cells on the roots that increase the surface area which increases absorption of water; microscopic

○ root cap—protects the growing tip

○ meristem—where the new cells are produced (aka zone of cell division)

RootsRemember that nitrogen fixation happens near the roots where bacteria live. (Nitrogen fixation is when nitrogen in the atmosphere is converted by bacteria into nitrogen compounds like ammonia, nitrates and nitrites.)Nitrogen is important for making nucleic acids, proteins, and chlorophyll.

21.4 LeavesLeaves absorb light and carry out photosynthesis. 

LeavesFunction - site of sunlight absorption and photosynthesis

○ flat structure increases surface area

Leaf Characteristics:○ composed of blade

and petiole

blade

petiole

Leaf characteristics continued:

Leaf Characteristics:○ simple or compound (based on how many leaves/

leaflets are coming off of the main branch)

Simple leaves

Leaf characteristics continued:

○ venation- types of veins – parallel or net-like (palmate or pinnate)○ Palmate - veins meet/touch at the base of the

leaf○ Pinnate - veins attach to one large vein that

is throughout leaf○ Parallel - veins run parallel to one another

down the length of the leaf (like a blade of grass)

Leaf with parallel veins

Leaf Tissues (layers of the leaf):

○ cuticle – clear, waxy layer that protects leaf from drying out (desiccation); secreted by the epidermis

○ epidermis – outer layers of leaf, made of dermal tissue

○ mesophyll – layer of ground tissue in the leaf in between the epidermal layers, surrounds the vascular tissues (xylem and phloem) and is divided into two layers:○ palisade layer – rectangular cells below the upper

epidermis that capture the majority of sunlight; where the majority of photosynthesis occurs; ground tissue

○ spongy layer – loosely packed cells with air spaces that connect to the stomata; where some photosynthesis occurs; ground tissue

Leaf Tissues (layers of the leaf):

○ stoma(ta) – site of transpiration and gas exchange; holes in the upper and lower surfaces of leaves; surrounded by guard cells

○ guard cells - control water loss by closing a plant’s stomata when water is scarce

guard cells

stomata

Cross-section of a Leaf

Ch. 22: Plant Growth, Reproduction, and ResponsePlants reproduce either sexually or asexually and hormones help regulate their growth, development, and response to their environment.

22.1 Plant Life Cycles Plant life cycles alternate between producing spores and gametes; this is known as alternation of generations.

• gamete - a haploid (unpaired chromosome) reproductive cell that unites with another haploid reproductive cell to form a diploid zygote (fused cell)

• gametophyte - haploid structure that makes gametes; microscopic in most plants

• sporophyte - diploid structure that makes spores; most plants

Sporevs.

Seed

Spores:● nonvascular plants-

–water needed for fertilization

– reproduces with spores

● vascular seedless plants– water needed

for fertilization– reproduces with

spores

Seeds:● vascular seeded plants

– gymnosperms- cones– angiosperms

■ make pollen and ovules (ovaries)

■ oncee fertilized, the ovules produce fruit

■ fruit houses/protects seeds

22.2 Reproduction in Flowering Plants (Angiosperms)

Reproduction of flowering plants takes place within flowers.Flowers have four layers—sepals, petals, stamens, and pistils.

• sepals- modified leaves that are the outermost structures that protect the developing flower; often green but can be brightly colored.• petals- modified leaves that are the innermost structures that are colorful to attract pollinators

22.2 Reproduction in Flowering Plants (Angiosperms)

• stamen- male reproductive structure– anthers produce pollen

• pollen grains contain sperm– filaments holds anthers up to make accessible to wind or

pollinators• pistil- female reproductive structure; made of one or more carpels that have three parts:

– stigma- top of the style, sticky so pollen sticks– style- tube that leads from the stigma to the ovary– ovary- where ovules

(eggs) develop • Ovaries with ovules

become fruits with seeds after the ovule (egg) is fertilized by sperm from the pollen; See Figure 2.3 page 647.

22.2 Reproduction in Flowering Plants (Angiosperms)

pollination – when a pollen grain reaches the stigma of the same plant species

fertilization – the process of the sperm combining with the egg to form the diploid zygote and the food for the growing plant embryo that is within the seed (read p. 646 if you would like to learn about the more complex details of double fertilization in plants)

Parts of a seed

– seeds contain an embryo (baby plant), which is a new sporophyte, and a supply of stored nutrients for the embryo

– cotyledons of a seed help transfer nutrients to the embryo

– seed coat covers and protects a seed

Fruit or Veggie?• fruit - ripened ovary; contains seeds• botanically, tomatoes, peppers, squash,

olives, and cucumbers are FRUITS, not vegetables

• vegetables – edible parts of plants not involved in reproduction (leaves, stems, roots)o roots – carrots, turnips, radisheso stems – celery, bok choi, rhubarb,

garlic, broccoli, onions, potatoeso leaves – lettuce, cabbage, parsley

· other plant parts we eat:o seeds – pinto beans, peas, sunflower

seeds, corn, pepper corns, rice, pecans, coconut

o flowers – anise flowers (licorice), basil, broccoli tips