Kingdom Plantae How did they get onto land? How do plants respond?

Problems of plants: having to do with being sessile (Unable to Move). must protect selves must disperse must meet mate must choose a good environment must deal with competition on site must live in the same place year round (seasons) must “eat” = CO², water, light In water, algae – how are they done?? And is there a problem??

How Did the Land Plants Arise? Land plants retain derived features they share with green algae: Chlorophyll a and b. Starch as a storage product. Cellulose in cell walls.

Major structural changes in sequence Cuticle-waxy protection against drying out on land Tissue differentiation; root, leaf, stem. Stomata-to control water loss Conductive tissue-xylem and phloem Secondary growth-branches

Moss; add stomata.

Needed for land and dry conditions = stomata, mosses And all higher plants.

Moss- limited in height – no special support structures – these are club mosses – stand up better

Tracheophytes: ferns and up Add vascular tissue

Today, tree ferns tropical. In ancient times – only trees.

Xylem – has cellulose rings – like trachea of lungs; dead tissue, moves materials up Phloem – surrounding it – live tissue-move sugars downward For water and nutrient transport, xylem for support

To get really tall, organize xylem – secondary growth.

Major reproductive changes Haploid dominant to diploid dominant Development of spores (haploid) Loss of aquatic sperm – replaced by pollen, which is airborne Retention of egg on plant Development of seed (food for embryo) Development of flowers (pollen transport) Many plants both male and female.

Pine: haploid reduced to pollen grain and egg (plus some support tissue Pollen (sperm) is airborne. Addition of a seed. –food for embryo Seed is a cone not a fruit Male and female on same plant, but separate structures Oldest trees alive-Bristlecone Pine over 4900 years old Gymnosperm from Greek-”Naked Seed” Gymnosperms = pine trees

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Flowering plants = angiosperms Develop flowers = reproductive area; can be male and female or one or other Haploid part = pollen (airborne) and egg, plus surrounding material. Seed-enclosed in a fruit Flowers derived from specialized leaves. Can use insects, etc. to transfer pollen

Reproduction summary Go from aquatic sperm to aerial pollen Switch from spore (haploid) to survive bad times to seed (diploid) with stored energy to survive bad times.

How do Plants Respond? Tropism- response of a plant to a stimulus Stimulus-anything in the environment that causes a change in the behavior in the organism Some Stimuli that Plants Respond to: Touch Light Gravity Temperature Amount of water

Plant Hormones-control growth changes triggered by tropisms Ethylene Gas-stimulates fruit ripening (banana will speed up the ripening of apples) Fruit is picked before it is ripe and sprayed with ethylene gas before shipping to stores Other hormones control plant growth.

Photoperiodism Plant’s sensitivity to daily hours of light and darkness for flower production Long-day plants-need less than hours of darkness Short-day plants-want 12 or more hours of darkness to produce flowers Day-neutral plants- can flower within a range of darkness hours