Topic 9 - Plant ScienceA.S. 9.1 Plant Structure & Growth

IB Biology HL

Domain Archcaea

Domain Bacteria

Domain Eukaryota

425 mya

2 bya

488 mya

400 mya

385 mya

5 Main Groups Plants• 1) Chlorohyta (green algae):chloroplasts-usually,

unicellular, aquatic environments

• LAND PLANTS:

• 2) Bryophytes (mosses): spores, not vascular, no true

roots, need moisture

• 3) Ferns: Roots, leaves, short stems. Spores on

underside of frond.

• 4) Conifers: Roots, stems, leaves, seeds. Narrow

leaves w/waxy cuticle, seeds produced from ovules on

scales of cones

• 5) Angiosperms (flowering plants): Roots stems,

leaves, seeds. Seeds produces in ovary in flower.

3 Groups Land PlantsPlant Group Major features

Non-vascular land

plants

~488 mya

Paleozoic

Ordovician

• Less dependent on water-live on land

• No conducting tissue (so need moist environ)

• Produce spores (not seeds)

• Often grouped together as bryophytes

• Usually small and grow close to ground

• Include mosses, liverworts, and hornworts

Seedless vascular

plants

~425 mya

Paleozoic

Silurian

• Well-developed vascular tissue

• Produce spores (underside of frond-no seeds)

• Include horsetails, ferns, club mosses, and whisk ferns

(most extant specimens small—some extinct species

very large)

Seeded vascular

plants

~385 mya

Paleozoic

Devonian (Gymn)

• Most living plant species are in this group

• Seeds contain an embryo, a supply of nutrients, and a

protective outer coat

• Have extensive vascular tissue and include some of the

world’s largest and oldest organisms

non-vasc

seeds

Vasc

• Simple plants, limited size• Hold loose dirt in place• Live in moist areas• Depend on external water

transport for reproduction: motile male gamete

• No vascular tissue = movement through osmosis/diffusion

• No true roots = have rhizoids -like root hairs (absorb water, anchor plant)

• No stems• No leaves = similar structures

but only one cell thick. • Produce spores in a capsule at

end of a stalk

Non-Vascular: Bryophytes ~ 450 mya

moss

liverwort

Filicinophytes

Vascular tissue—spores on underside of frond

• Have vascular tissue: can be bigger– Xylem: H2O + minerals

– Phloem: sap (sugar, AAs, hormones...)

• Live in moist areas

• Have roots, stems and leaves (fronds)

• Motile male gametes: can occupy terrestrial environments BUT still needs water for reproduction

• Spores (no seeds) produced in sporangia, generally on the underside of the leaf

• Leaves are curled, and then uncurl as they mature

Vascular-Alternating Life Cycle Filicinophytes, or Ferns

frond

young frond

rhizome

roots

http://www.biology87.org/apbio/diversity/PlantLabPicts/statio4.jpg

http://www.biology87.org/apbio/diversity/PlantLabPicts/s

tatio6.jpg

Spermatophytes(seeded vascular plants)

Synapomorphy--seeds

2 Groups Seeded Plants

~385 mya

Paleozoic

Devonian

(Gymnosperms)

~144 mya

Mesoozoic

Cretaceous

(Angioperms)

385 mya

ORIGIN OF SEEDS (Progymnosperms) – 385 mya

ConiferophytesConifer

• Contain a well developed vascular tissue (big plants!), roots, stems (woody) and leaves• Produce male (contain pollen) and female (contain ovules) cones• Produce seeds which develop on the scales of the female cones• Gametes are not motile: does not depend on water for reproduction• Tough, needlelike leaves with thick cuticles and sunken stomata: adaptations for dry environments• NO REAL FLOWERS + NO FRUITS

e.g. pines, spruces, firs,

cypress, yews

Sequoias

National Park in California

• Flowering plants with roots, stems and leaves• Occupy all environments• Gametes are not motile (does not need water for

reproduction)• Seeds are produced – develop inside the ovaries in the

flower• Ovary develops into a fruit which aids in seed dispersal

AngiospermophytesFlowering Plants

Why are angiosperms so successful?

• Seed protected in fruit

• Fruit skin and flowers can be different colors, have

different scents, and have different nutritional values

• Can attract dispersers (reds and yellows attract birds-

others bear, primates, and so on

• Pollen easily dispersed by wind, birds, insects including

butterflies

Drawing a flower:

• Female Reproductive Organs: stigma + style + ovary = PISTIL

• Male Reproductive Organs: anther + filament = STAMEN

• Petals: attract animals

• Sepals: protection

• Two types of angiospermophytes

• Cotyledon= seed leaf

• Differences in leaves, arrangement of vascular tissue, root system and stem composition.

Monocotiledonous x Dicotiledonous

Monocotiledonous x DicotiledonousCharacteristic Mono Di

Cotyledons 1 2

Leaf Parallel veins Netlike veins

Flowers Floral organs x 3 Floral organs x4 or x5

Roots No main root Main root present

Stem Vascular tissues scattered Vascular tissue in ring

Monocotyledenous PlantsCorn and wheat, etc.

Dicotyledenous PlantsBean, etc.

9.1.1 Draw and label plan diagrams to show the distribution

of tissues in the stem and leaf of a dicotyledonous plant.

9.1.1 Draw and label plan diagrams to show the distribution

of tissues in the stem and leaf of a dicotyledonous plant.

9.1.1 Tissues in stem of dicotyledonous plant

9.1.1 Tissues in leaf of dicotyledonous plant

9.1.1 Tissues in leaf of dicotyledonous plant

9.1.2 Outline three differences between the

structures of dicotyledonous and

monocotyledonous plants.

From BioNinja.com

Upper Epidermis

•Function: Main function is water conservation (secretes cuticle to create a waxy

outer boundary)

•Distribution: On top of leaves where light intensity and heat are greatest

Palisade Mesophyll

•Function: Main photosynthetic tissue (cells contains many chloroplasts)

•Distribution: Upper half of leaf where light intensity is greatest (upper epidermal

cells are transparent)

Spongy Mesophyll

•Function: Main site of gas exchange (made of loosely packed cells with spaces)

•Distribution: Lower half of leaf, near the stomatal pores (where gases and water

are exchanged with the atmosphere)

Vascular Tissue

•Function: Transport of water (xylem) and the products of photosynthesis

(phloem)

•Distribution: Found in middle of leaf (allowing all cells optimal access)

9.1.4 Identify modifications of roots, stems, and leaves for different

functions: bulbs, stem tubers, storage roots, and tendrils.

A storage organ is a part of a plant specifically modified to store energy (e.g.

carbohydrates) or water

They are usually found underground (better protection from herbivores) and may

result from modifications to roots, stems or leaves:

Storage roots: Modified roots that store water or food (e.g. carrots)

Stem tubers: Horizontal underground stems that store carbohydrates (e.g.

potato)

Bulbs: Modified leaf bases (may be found as underground vertical shoots) that

contain layers called scales (e.g. onion)

Some plants (called succulents) have modified leaves or stems (thickened, fleshy

and wax-covered) to enable water storage (e.g. cacti)

Other plants (e.g. vines) have modifications to their leaf or stem to enable

climbing support and attachment - these are called tendrils

9.1.4 Identify modifications of roots, stems, and

leaves for different functions: bulbs, stem tubers,

storage roots, and tendrils.