Introduction to Plants
Mrs. M. Rightler
Earliest Plants
Algae Phytoplankton
Lived
in the sea
Problems with life on land
Solution Waxy cuticle, stomata Formed leaves Develops spores & seeds Gravity & Support Bark (cork) & vessels Roots & vessels Getting water & nutrients Problem Drying Out Making Food Reproduction
Types of Plants
Avascular
– Bryophytes
– nonseed – vessels
plants
Tracheophytes
for transport and
support
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. Gnetum – house plants Ephedra – weight loss, allergies & asthma Welwitschia
Gnetophyta – only three genera
– – –
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
[121]
Leaves
Flowers
Roots [124]
Absorb
water & nutrients Hold plant in place Root types:
Fibrous – Tap – Prop – Aerial
–
Stems
Support
[123]
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 Phototropism = light Gravitropism = gravity Thigmotropism = touch
(nastic movement – direction does not matter)
Types:
–
–
–
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