Post on 27-Mar-2015
Introduction to Plants
Mrs. M. Rightler
Earliest Plants
AlgaePhytoplanktonLived in the sea
Problems with life on land
ProblemDrying OutMaking FoodReproduction
Gravity & SupportGetting water &
nutrients
SolutionWaxy cuticle, stomataFormed leavesDevelops spores &
seedsBark (cork) & vesselsRoots & vessels
Types of Plants
Avascular –Bryophytes–nonseed plants
Tracheophytes–vessels for transport and support
Mosses & Liverworts: The Bryophytes
First land plantsAVASCULAR = very small500 m.y.a.Must grow in moist environmentsUsed 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 plantSpores or seeds for reproduction
Club Mosses (Lycophyta)
Leaves produce spores– Strobilus = spore-bearing leaves– Prothallus = produces antheridia &
archaegonia
Horsetails (Sphenophyta)
Jointed stemsReproduction similar to club moss
Ferns (Pterophyta)
400 m.y.a.Dominant form = sporophyteStructure
– 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 supplyProtective coat against harsh
conditionsSome 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 windLand on ovule, develop pollen tubeSperm 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 areasFertilization does not require waterPollen has protective coat and food
supply for sperm
Why Ovules Instead of Archaegonia?
Protective tissues prevent drying outOvule 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 leavesBear seeds in woody conesCan live in very cold climatesMost are evergreensHave wood
– Made of thick-walled vessels (TRACHEIDS)– Tracheids are xylem
Angiosperms
Angio – “flower” Sperm – “seed”Extremely diverseAll have seeds enclosed in fruit
Cambium
Any growth tissue in plantsTypes of cambium
– Vascular = produces xylem & phloem– Cork = produces cork (bark)
Overall Structures [121]
RootsStemsLeavesFlowers
Roots [124]
Absorb water & nutrientsHold plant in placeRoot types:
– Fibrous– Tap– Prop– Aerial
Stems [123]
Support leaves & flowersSometimes photosynthesisTransport (contain xylem & phloem)Types
– herbaceous – green & flexible– Woody – stiff, have cork layer, usually
brown
Leaves [119]
Cuticle = protectionStomata = gas exchange, water loss
(transpiration)Epidermis = protection, colorMesophyll
– Palisade = most PHOTOSYNTHESIS– Spongy = Vascular bundles run through it
Flowers [131]
Pistils = female reproductive structuresStamens = male reproductive structuresComplete flowers
– Have petals & sepals– Have male and female parts
Incomplete flowers = missing one or more parts
Types of Angiosperms [115]
Monocots
mono = “one”
cot = “seed leaf”Approx. 60,000
speciesFlowers = multiples
of 3Leaf veins parallel
Dicots
di = “two”
cot = “seed leaf”Approx. 170,000
speciesFlowers = multiples
of 4 or 5Leaf 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