Transcript Introduction to Plants

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?
Zone of
differentiation
Zone of
elongation
Zone of cell
division
Root
cap
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
Mature ovary
Fruits:
Growth of Seed: