Botany

SAT II Review

Things to know that we’ve already covered…

• Plant cell structure (Chapter 4)• Photosynthesis (Chapter 7)• Angiosperm reproduction and double

fertilization (31.9-31.15)

2 major divisions of land plants

I. Non vascular plants

II. Vascular plants

I. Non vascular plants(bryophytes)

• No vascular tissue• Small, inhabiting shady, moist areas• Include mosses, liverworts, hornworts

II. Vascular Plants

Have vascular tissue - tubelike, elongatedcells through which water (xylem) and sugars (phloem) are transported. Has true roots, stems and leaves.

Grow in a variety of environments-why?

2 major divisions of VASCULAR plants

I. Seedless plants

II. Seed plants

I. Seedless plants

Must have a moist environment in which to grow.

Includes Club Mosses- LycophytaHorsetails/Sphenophyta,Ferns/Pterophyta

All reproduce by forming spores.

Let’s move on to the other division of vascular plants…

Reproduce by seeds. A seed is an embryo with a food supply (endosperm) enclosed in a tough, protective coat.

II. Seed plants

2 major divisions of VASCULAR SEED plants

I. Gymnosperms

II. Angiosperms

I. Gymnosperms

• Most are conifers (cone-bearing trees)• Seeds are formed in cones• Plants contain some “female” cones that make spores

and some “male” cones that make pollen

Anthophyta = Flowering Plants

Seeds are protected within flowers and develop inside fruit.

This is the most successful group of plants.Why?

II. Angiosperms

2 major divisions of VASCULAR PROTECTED SEED/FLOWERING plants.

I. Monocots

II. Dicots

Angiosperms:Divided into two classes, based on the number of seed leaves (cotyledons) within the seed.

Monocots: (non-wood)grasses, lilies, palms

Dicots:Shrubs, trees, herbs and flowers.

Dicot and monocot stems

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SummaryPLANTS

Monocot Dicot

Protected Seeds Unprotected Seeds

Seeded Plants Seedless Plants

Vascular Non-Vascular

KingdomPlantae

Angiosperms Gymnosperms

Chapter 31

Plant structure, reproduction, and development

Body plant – roots, stems, and leaves

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General Tissue types

• Dermal tissue – outer protective covering

• Vascular tissue – xylem and phloem

• Ground tissue – between epidermis and vascular

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Vascular tissue

• Xylem – Conducts water and minerals upward in the plant– Dead at maturity – do not consume water

• Phloem– Carries sugars that have been produced in the

leaves and/or stems.– Barely alive – require ATP from companion cells to

assist in transport

Transporting water up the xylem (Chapter 32)

• Root pressure• Capillary action• Transpiration-cohesion

theory – Water evaporates from

the leaf surface– Water molecules are

connected to each other by hydrogen bonds

– Water is pulled up the xylem from the root

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Transporting sugar through the phloem (Chapter 32)

• Sucrose is pumped into phloem cells at the source

• Water enters from the adjacent xylem cells via osmosis

• The sugar solution is forced down the phloem cells under pressure.

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Leaf structure

• Mesophyll is between epidermis layers– Palisade layer is more ordered to maximize

photosynthesis– Spongy layer is

more diffuse, leaving space for gas movement

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Stomata

• Pores in the leaf surface

• Regulated by guard cells

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Growth

• Primary growth– Apical meristem on root and shoot extend the

vertical length of the plant

Growth• Secondary growth

– Lateral meristems increase the girth of woody plants

– Vascular cambium • One cell thick, between

primary xylem and phloem

• Produces new secondary xylem (inside) and phloem (outside) each year

• Growth is not continuous throughout the year, creating rings

Growth

• Secondary growth– Cork cambium

• Forms cork (bark), which replaces the epidermis (from original shoot)

• Forms protective covering for root and shoot

Reproduction - Alternation of generations

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Alternation of generations

• Sporophyte – Main body of the angiosperm plant

• Immature male gametophyte = pollen grain• Mature male gametophyte = pollen tube• Female gametophyte = egg sac

– Enclosed in the ovule– the ovule is a section of the ovary

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Double fertilization

• The pollen tube enters the ovule

• One nucleus fertilizes the center two nuclei

• Results in triploid (3n) endosperm nucleus

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Asexual reproduction – Vegetative propagation

• Tubers (like potatoes) – underground storage equipped with buds on the surface

• Runners (like strawberries) – horizontal stems that can give rise to new roots and shoots

• Bulbs – underground buds (contains several buds that can be new plants)

• Grafting – two young plants are joined

Chapter 33

Plant hormones and behaviors

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One group of hormones stimulates growth and development

• Auxin – origin: apical meristem of the shoots– Stimulates cell elongation in stems– Retards cell elongation in roots.

• Gibberellins – origin: buds and leaves– Breaks dormancy in buds by stimulating mitosis– Stimulates mitosis in developing leaves

• Cytokinins – origin: roots– Works with auxins to stimulate cell division– Delay aging (used on freshly cut flowers)

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The other group stimulates aging and death or dormancy

• Abscisic acid (inhibitors) – Retards growth– Causes dormancy in seeds

• Ethylene– Causes fruit ripening– May work along with auxin to retard elongation of

root cells– Causes leaf falling

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Phototropism

• Plants bend toward light – auxin migrates to the dark side, elongating those cells

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Gravitropism

• Response to gravity – roots grow downwards, shoots grow upwards

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Thigmotropism

• Response to touch – caused by changes in water pressure– Coiling around a support– Tree trunks grow thicker in response to winds

Photoperiodism – flowering regulated by light

• Short day plants (long night plants)– Flower in early spring or autumn (when nights are

longer)

• Long day plants– Flower in summer (when nights are shorter)

• Day neutral plants– Flowering begins when the plant has a certain

number of branches and flowers until frost

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