Introduction to Plants Plant structures, Signaling defences, Responses to the Environment

Introduction to Plants

Plant structures,

Signaling defences,

Responses to the Environment

Why are plants important?

Food Photosynthesis produces oxygen Roots prevent soil erosion Leaves absorb pollutants Take in Carbon Dioxide

Types of Plants Bryophytes – lack a true vascular

system (xylem and phloem)– Mosses

Remain small Need water to reproduce – sperm swims to

female plant to fertilize egg – grows into stalk with spore case on end

Seedless Vascular Plants Ferns

– Have xylem and phloem– Reproduce by spores instead of seeds

Seed Plants - Gymnosperms

Nonflowering seed plants– Many produce seeds in cones - conifers– “naked seeds” – have no flesh around it.

Seed Plants - Angiosperms

Flowering seed plants– Produce flowers containing male and/or

female reproductive structures

Seed Produced from union of egg and

sperm– Egg is in flower – usually deep inside– Sperm is in pollen – carried to egg during

pollination– Fertilization produces embryonic plant

within stored food and a protective coating

Pollination Wind Water Animals – bats, insects, birds,

mammals, snails, etc.

Fruits Attracts animals so seeds get

dispersed Seeds usually can pass through

animal’s digestive system to be dropped a distance away from parent plant

Structures of Angiosperms

Roots– Grow toward water– Absorb water and minerals– Transport them to stem– Store food– Anchor plant

Types of Roots Taproot system Fibrous root system

Root Tip Remember the root tip we squashed to

see the cells undergoing Mitosis?

Root cap

Zone of cell division

Zone of elongation

Zone of differentiation

Leaves You already know the structure of the

leaf:

Flower Structure

Carpel

Fertilization

Vegetative Reproduction Cuttings - houseplants Runners - strawberries Mutations – naval oranges Grafts Suckers – aspen roots

Plant Hormones Chemical messengers – made in one part of

plant and work on another (just like human hormones).

Auxins – responsible for growth at the end of stems – cut them off, and plant will send out shoots from the sides of stems. Pruning uses this info to make bushier plants.

Others include cytokinins for root growth, Giberellins for seed growth, ethylene for fruit ripening, and abscisic acid for fruit and leaf growth.

Plant Responses Phototropism gravitropism Thigmotropism hydrotropism

Dormancy in Winter Deciduous Trees

– Lose leaves in autumn – Why?– Low level of metabolism in winte– Growth is suspended until leaves grow in

spring

Evergreen trees Metabolism slows in cold weather, but

they can start up any time the temperature rises.

Lose leaves all year long, a little at a time.

Photoperiodism Plant responds to intervals of day and

night Long night plants – flower in late

summer or early fall Short night plants – flower in early to

midsummer

How long do plants live?

Monocots vs Dicots

How a Plant Grows:

Secondary Growth:

Tree trunks:

Water Transport

Fruits:Mature ovary

Growth of Seed: