Transcript Plant Control and Hormones

The Wonderful World of Plants
M. Merritt May 2006
The Basics
All plants are eukaryotic
autotrophs
 6H20
+ 6CO2 →
C6H12O6 + 602
 This
reaction takes
place in the
chloroplast with
the help of a
photosynthetic
pigment such as
chlorophyll.
The Life Cycle
of Plants
Life Cycle of Plants
 Plants
have an alternation of generations.
 The diploid (2N) phase is the sporophyte.
The sporophyte makes spores.
 The haploid (1N) phase is the
gametophyte.
The gametophyte makes
gametes.
The Divisions
of Plants
Plant Divisions
Plants are divided into groups based on:
1. whether or not they have vascular
conducting tissues.
Xylem – moves water from the roots up to the
leaves
Phloem – moves sugars made in the leaves
down to the roots.
2. whether or not they make seeds.
3. whether or not they have flowers.
The four groups are:
1. bryophytes (mosses)
2. seedless vascular plants (ferns)
3. gymnosperms (cone bearers)
4. angiosperms (flowering plants)
Bryophytes
 Examples
include mosses and liverworts.
Characteristics of Bryophytes
 Bryophytes
do not have special tissues to
conduct food and water.
 They rely on osmosis to move water
around their bodies. Because of this, they
don’t get very tall.
 They rely on water to be able to
reproduce because the sperm swim
through water to the eggs.
Moss sporophyte and
gametophyte
Seedless Vascular Plants
 Ferns
are vascular which means they
have xylem and phloem.
 Xylem and phloem allow plants to grow
taller than mosses.
 Ferns are seedless plants. They make
spores.
Ferns
Ferns reproduce with spores
Horsetails and club mosses are
close relatives of ferns
The Seed Plants
Gymnosperms and
Angiosperms
Gymnosperms
 Have
vascular tissue.
 Make seeds.
 Do not have flowers, but they do have
cones.
 The 1N gametophyte stage is pretty much
enclosed entirely within the 2N
sporophyte structure.
Gymnosperm cones…male
and female. Which is which?
Gymnosperms include conifers
and ginkgoes
Angiosperms
 Have
vascular tissue.
 Make seeds.
 Do have flowers.
 The 1N gametophyte stage is pretty much
enclosed entirely within the 2N
sporophyte structure.
Angiosperms include any
flowering plant…tulips, cherry
trees, zinnias
Flower Structure
and Seed
Dispersal
Angiosperms
 Flowers
contain ovaries which protect the
egg.
 Somehow, sperm needs to get to the
egg.
 Once the egg is fertilized, it turns into a
seed.
 Somehow the seeds need to be dispersed
– spread away from the parents.
Flower Structure
Seed dispersal
Angiosperms
can be Further
Divided
Angiosperms can be divided into
Monocots and Dicots
Monocots
Single cotyledon
Dicots
Two cotyledons
Parallel leaf veins
Branched leaf veins
Flower petals in 3’s
Flower petals in 4’s or
5’s
One big tap root
Roots are fibrous
Seeds
Leaf Vein Patterns
Flowers
Roots
Seed Plants
3
main organs
 Roots:
absorb water, nutrients;
anchor plant
 Stems: support and transport
system
 Leaves: photosynthetic organ;
help with gas and water
exchange
Root Growth
Cell
division
occurs in the
apical meristem
 As
new cells
develop, they
elongate and
develop into
specialized cells
Plants Do
Cool Stuff!
Plants can fertilize
themselves!
When
a male gamete from
one plant fertilizes the
female gamete of the
same plant!
Plants can maintain
homeostasis
Gas
exchange
 CO2
and O2
Water
intake/release
Tropism
Response
stimuli
Examples:
of plants to external
 Phototropism
 Gravitropism
 Thigmotropism
Tropisms
can be positive
(towards stimuli) or negative
(away from stimuli)
Phototropism
Phototropism
is the
movement of
plants towards
light
Gravitropism
Roots
move
down (in
response to
gravity) and
shoots grow
up (against
gravity)
These plants were situated in various
positions, but the shoots continued to
move against gravity.
Thigmotropism
 Thigmotropism
is
when a plant
moves in
response to
touch
 Plant may wrap
around a
surface
 Ex:
vine
This plant responds to touch by
wilting. What advantage may this
be to the plant?
Photoperiodism - Some plants
respond to the amount of
daylight – Poinsettia turn red and
flower in response to shorter days
Last cool thing: Plants make
hormones!
Hormones: chemicals that control cell
division, growth, maturation and
development
• Allow plants to RESPOND
• To day length (photoperiodism)
• To stimuli
Types of Hormones
1.Auxins:
stimulate cell
elongation in roots
2.Cytokinins: help stimulate
cell division in apical
meristem
3.Ethylene: stimulates fruits to
ripen
Some plants “eat” animals