Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANTS.

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

PLANTS


• Plants are multicellular photosynthetic eukaryotes

– They share many characteristics with green algae

– However, plants evolved unique features as they colonized land

What is a plant?


PLANTLEAFperformsphotosynthesis

CUTICLEreduces waterloss; STOMATAallow gas exchange

STEMsupports plant(and may performphotosynthesis)

Surrounding watersupports the alga

ALGA

WHOLE ALGAperformsphotosynthesis;absorbs water,CO2, andminerals fromthe water

HOLDFASTanchors the alga

ROOTSanchor plant;absorb water andminerals from the soil (aidedby mycorrhizalfungi)


• Unlike algae, plants have vascular tissue

– It transports water and nutrients throughout the plant body

– It provides internal support


• Two main lineages arose early from ancestral plants

Plant diversity provides clues to the evolutionary history of the plant kingdom


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Radiation offlowering plants

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First seed plants

Early vascular plants

Origin of plants


• One lineage gave rise to bryophytes

– These are plants that lack vascular tissue

– Bryophytes include mosses, which grow in a low, spongy mat


• Vascular plants are the other ancient lineage

• Ferns and seed plants were derived from early vascular plants and contain

– xylem and phloem

– well-developed roots

– rigid stems


PARTS OF A VASCULAR PLANT


• Ferns are seedless plants whose flagellated sperm require moisture to reach the egg


• A major step in plant evolution was the appearance of seed plants

– Gymnosperms

– Angiosperms

• These vascular plants have pollen grains for transporting sperm

• They also protect their embryos in seeds


• Gymnosperms, such as pines, are called naked seed plants

– This is because their seeds do not develop inside a protective chamber

• The seeds of angiosperms, flowering plants, develop in ovaries within fruits


PLANT TISSUES


• Angiosperms, or flowering plants, are the most familiar and diverse plants

• There are two main types of angiosperms

– Monocots include orchids, bamboos, palms, lilies, grains, and other grasses

– Dicots include shrubs, ornamental plants, most trees, and many food crops

The two main groups of angiosperms are the monocots and the dicots

PLANT STRUCTURE AND FUNCTION


• Monocots and dicots differ in seed leaf number and in the structure of roots, stems, leaves, and flowers

SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS

MONOCOTS

Onecotyledon

Main veins usually parallel

Vascular bundles incomplex arrangement

Floral parts usuallyin multiples of three

Fibrousroot system

Twocotyledons

Main veins usually branched

Vascular bundles arranged in ring

Floral parts usually in multiples of four or five

Taprootusually present

DICOTS


• Root system

– Provides anchorage

– Absorbs and transports minerals and water

– Stores food

• Root hairs increase the surface area for absorption

The plant body consists of roots and shoots


• Shoot system

– Consists of stems, leaves, and flowers in angiosperms

– Stems are located above the ground and support the leaves and flowers

– Leaves are the main sites of photosynthesis in most plants


PARTS OF A FLOWERING PLANT


• The terminal bud is located at the tip of a stem – It is the growth point of the stem

• Axillary buds can give rise to branches

• In apical dominance, the terminal bud produces hormones that inhibit the growth of axillary buds

– This results in a taller plant that has greater exposure to light


• Roots and stems are adapted for a variety of functions

– Storing food

– Asexual reproduction

– Protection

• Plant breeders have improved the yields of root crops by selecting varieties, such as the sugar beet plant, with very large taproots

Many plants have modified roots and shoots


• Modified stems include

– runners, for asexual reproduction

– rhizomes, for plant growth and food storage

– tubers, for food storage in the form of starch

STRAWBERRYPLANT

POTATOPLANT

IRISPLANT

Runner

TuberTaproot

Rhizome

Rhizome

Root


• Modified leaves include tendrils and spines– Tendrils help plants to climb

– Spines may protect the plant from plant-eating animals


NUTRITION


ELEMENTS NEEDED IN PLANT NUTRITION



GROWTH REGULATION


• Light is central to the life of a plant

• Photosynthesis is the most important chemical process on Earth

– It provides food for virtually all organisms

• Plant cells convert light into chemical signals that affect a plant’s life cycle

Life in the Sun


• Light can influence the architecture of a plant– Plants that get adequate light are often

bushy, with deep green leaves

– Without enough light, plants become tall and spindly with small pale leaves

• Too much sunlight can damage a plant

– Chloroplasts and carotenoids help to prevent such damage


• Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water

AN OVERVIEW OF PHOTOSYNTHESIS

Carbondioxide

Water Glucose Oxygengas

PHOTOSYNTHESIS


• Plants, some protists, and some bacteria are photosynthetic autotrophs

– They are the ultimate producers of food consumed by virtually all organisms

Autotrophs are the producers of the biosphere


• On land, plants such as oak trees and cacti are the predominant producers


• In aquatic environments, algae and photosynthetic bacteria are the main food producers


• In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts

• A chloroplast contains:

– stroma, a fluid

– grana, stacks of thylakoids

• The thylakoids contain chlorophyll

– Chlorophyll is the green pigment that captures light for photosynthesis

Photosynthesis occurs in chloroplasts


• The location and structure of chloroplasts

LEAF CROSS SECTION MESOPHYLL CELL

LEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outermembrane

Innermembrane

ThylakoidcompartmentThylakoidStroma

Granum

StromaGrana


Are plants useful

to man?


How are plants useful to man?

List the ways you use plants everyday.


We eat plants for breakfast,

lunch and dinner.

What plants have you

eaten today?


We use plants to make our clothing.


We use plants to make medicines.


We use plants to build furniture

and buildings.


Plants are useful in

cleaning the air

we breathe.


Man is very dependent on plants.

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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PLANTS.

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