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					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


				
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