Transcript Introduction to Plants

Introduction to Plants
Mrs. M. Rightler
Earliest Plants
 Algae
 Phytoplankton
 Lived
in the sea
Problems with life on land
Problem
 Drying Out
 Making Food
 Reproduction
Solution
 Waxy cuticle, stomata
 Formed leaves
 Develops spores &
seeds
 Gravity & Support  Bark (cork) & vessels
 Roots & vessels
 Getting water &
nutrients
Types of Plants
Avascular
– Bryophytes
– nonseed
plants
Tracheophytes
– vessels
support
for transport and
Mosses & Liverworts: The
Bryophytes
 First
land plants
 AVASCULAR = very small
 500 m.y.a.
 Must grow in moist environments
 Used for fuel (peat)
Reproduction in Bryophytes
 Mosses
have a protonema
(liverworts do not)
 Sexual reproduction
Antheridium – makes sperm
– Archaegonium – makes eggs
–
 Asexual
reproduction
Fragmentation
– Formation of gemmae
–
Tracheophytes
 Vessels
XYLEM = transports water & dissolved
minerals from roots to leaves
– PHLOEM = transports sugars from
leaves to rest of plant
–
 Spores
or seeds for reproduction
Club Mosses (Lycophyta)
 Leaves
produce spores
Strobilus = spore-bearing leaves
– Prothallus = produces antheridia &
archaegonia
–
Horsetails (Sphenophyta)
 Jointed
stems
 Reproduction similar to club moss
Ferns (Pterophyta)
 400
m.y.a.
 Dominant form = sporophyte
 Structure
Rhizome = underground stem
– Fronds = leaves
– Sori = store spores on underside of
fronds
–
Gymnosperms
 Gymno
= “naked” Sperm = “seed”
 First plants to produce seeds
No flowers
– No fruit
–
Why Make Seeds?
 Has
own food supply
 Protective coat against harsh
conditions
 Some are designed for travel to new
areas
Sporophytes produce:
 MICROSPORE
Produce male gametophyte
– Produce pollen
–
 MEGASPORE
Produce female gametophyte
– Produce ovule (makes archaegonia
with egg cells)
–
Gymnosperm Reproduction
Pollen grains carried by wind
 Land on ovule, develop pollen tube
 Sperm move through tube to fertilize egg

–
–
–
Fertilized egg = ZYGOTE
EMBRYO = young, diploid sporophyte plant
COTYLEDONS = food storage for embryo,
become first leaves
Why Pollen Instead of
Spores?
 Plant
can live in very dry areas
 Fertilization does not require water
 Pollen has protective coat and food
supply for sperm
Why Ovules Instead of
Archaegonia?
 Protective
tissues prevent drying out
 Ovule holds archaegonia and
protects eggs from elements
Minor Gymnosperm Groups
Cycadophyta (1st in Triassic Era)
 Ginkgophyta

–
–

Only one species today Ginkgo biloba
Most lived 200 m.y.a.
Gnetophyta – only three genera
–
–
–
Gnetum – house plants
Ephedra – weight loss, allergies & asthma
Welwitschia
Coniferophyta (largest
group)
Needle or scale-like leaves
 Bear seeds in woody cones
 Can live in very cold climates
 Most are evergreens
 Have wood

–
–
Made of thick-walled vessels (TRACHEIDS)
Tracheids are xylem
Angiosperms
– “flower”
Sperm – “seed”
 Extremely diverse
 All have seeds enclosed in fruit
 Angio
Cambium
 Any
growth tissue in plants
 Types of cambium
Vascular = produces xylem & phloem
– Cork = produces cork (bark)
–
Overall Structures
 Roots
 Stems
 Leaves
 Flowers
[121]
Roots [124]
 Absorb
water & nutrients
 Hold plant in place
 Root types:
Fibrous
– Tap
– Prop
– Aerial
–
Stems
[123]
 Support
leaves & flowers
 Sometimes photosynthesis
 Transport (contain xylem & phloem)
 Types
herbaceous – green & flexible
– Woody – stiff, have cork layer, usually
brown
–
Leaves
[119]
Cuticle = protection
 Stomata = gas exchange, water loss
(transpiration)
 Epidermis = protection, color
 Mesophyll

–
–
Palisade = most PHOTOSYNTHESIS
Spongy = Vascular bundles run through it
Flowers
[131]
Pistils = female reproductive structures
 Stamens = male reproductive structures
 Complete flowers

–
–

Have petals & sepals
Have male and female parts
Incomplete flowers = missing one or
more parts
Types of Angiosperms
[115]
Monocots
Dicots
mono = “one”
di = “two”
cot = “seed leaf”
cot = “seed leaf”
 Approx. 60,000
 Approx. 170,000
species
species
 Flowers = multiples  Flowers = multiples
of 3
of 4 or 5
 Leaf veins parallel  Leaf veins branching
Plant Tropisms

Tropism = plant response to external
stimulus
–
–

Positive: plant moves toward stimulus
Negative: plant moves away from stimulus
Types:
–
–
–
Phototropism = light
Gravitropism = gravity
Thigmotropism = touch
(nastic movement – direction does not matter)
Plant Hormones
Hormone – chemical produced in one
part of an organism that has an effect on
a different part of the organism
 Types

–
–
–
–
Auxins – regulate growth
Gibberellins – speeds growth, germination
Abscisic acid – dormancy, close stomata,
stress
Ethylene – ripens fruit