Chapter 29: Plant Diversity I

Plants originated from

Green algae about 470 Million years ago

About 425 million years ago

Traits of facilitating life on land appeared

What are the three structure of plant

Reproductive structure

Photosynthetic branches

Structure that anchor the plant to the soil

What are three types of plants

• Nonvascular plants

• Seedless vascular plants

• Seed plants

What is the function of plants 

Supply oxygen, food sources and habitat for many other terrestrial organism

The closest relative of plant

Green algae called Charophytes

What are some evidence that algae is plants’ ancestor?

• multicellular, eukaryotic, photosynthetic autotrophs

• have cellulose in their cell walls and chloroplasts containing chlorophyll a and b

Morphological and Molecular evidence of Plant and green algae shared ancestor

• Cellulose-synthesizing membrane proteins are arranged in rings, rather than linear sets

• Structure of flagellated sperm

• Sequence similarities in nuclear, chloroplast, and mitochondrial DNA

Sporopollenin

• a polymer that prevents zygotes form drying out present on charophytes and plants

• Helps to resist harsh environment

Charophytes moving from ocean to land will

• Benefit:  unfiltered sunlight, more plentiful CO2 and nutrient rich soil

• Challenges: Scarcity of water and lack of structural support against gravity

Embryophytes

Plants with embryo

• dependency of the embryo on the parent

Derived Trait of Charophyte from plants

• Alternation of generation

• Walled spores produced by sporangia

• Apical meristems

Derived Trait of plant: What is alteration of generation?

The process which the life cycle of plants alternate between two generations of multicellular organism

• Gametophyte and sporophyte

Gametophyte

Multicellular haploid produces haploid gametes (sperm and egg) by Mitosis

Sporophyte

Multicellular diploid produces haploid spores by Meiosis

Spores develop into

Gametophyte

Fertilized egg develop into

Sporophytes

Diploid Embryo is retained within

The tissue of the female gametophyte

How the nutrients are transferred with embryophytes?

From parent to embryo through placenta transfer cells

Derived Trait of plant: Sporangia

Organ in the plant that produces spores

Derived Trait of plant: Apical Meristem

• Located at the tip of the root and shoot for the cell division

  • The cell divide continuously enabling elongation of roots an shoots for better resource acquisition

Derived Trait of plant: Cuticle 

Waxy covering the epidermis

Derived Trait of plant: Stomata

Specialized cell that allow for gas exchange between the outside air and the plant

Early plants lacked

True toots and leaves making absorption challanging

The fossil suggests that 420 million yeas ago

symbiotic associations with fungi (mycorrhizae) may have helped plants without roots to colonize land

when did the first plant spore appear

470 million years ago

Vascular tissue

Cells join into tube s for the transport of water and nutrients

Vascular plants

Plants with complex vascular system

Non vascular plant

Lack of an extensive transport system

Bryophytes

• name of non vascular plants such as liverworts, mosses and hornwarts

• not a monophyletic group

Seedless vascular plants

Have extensive vascular transport system but does not produce seeds

Seedless vascular plants divided into two clades

Lycophytes

Monilophytes

Lycophytes

Club mosses and their relatives

Monilophytes

Fern and their relatives

The majority of living plants are

Seed vascular plants

What is seed?

Embryo packed within a supply of nutrients inside a protective coat

What are the two group of seen plants?

• Gymnosperms

• Angiosperms

Gymnosperm

Produce seed that are enclosed (naked)

Angiosperm

• Produce seed that develop inside chambers that originate with flowers

• 90% of living plant species

Bryophytes

Nonwoody herbaceous plants

What are some examples of bryophytes?

• Liverwort

• Mosses

• Hornwort

Which cycle is dominant for bryophytes?

Haploid gametophytes are dominant in all bryophytes

Bryophytes: Protonema

mass of green, branched and one cell thick filament spore of moss

Bryophytes: How does moss develops gametophyte?

Protonema absorbs water and nutrients and form buds that develop into gametophyte

Why most of the bryophyte does not get taller?

• Lack of rigid support of tissues

• Lack of vascular tissue for long distance transport

Bryophytes: Rhizoids

Root like structure that anchor gametophyte to the substrate

• Does not absorb water or minerals

Bryophytes gametophyte: Gametangia

Produces gametes in plants, algae, ferns

Bryophytes gametophyte: Archegonia/ archegonium

Female gametangia

• Produce single non-motile egg

Bryophytes gametophyte: Antheridia

Male gametangia

• produce many motile sperms

How does the Bryophytes sperm move?

Flagellated sperm will swim to the egg through a film of water in response to chemical attraction

Bryophytes gametophyte: What happens to the fertile egg?

As an embryo it will be retained within the archegonium

Bryophytes gametophyte: Reproduction, Sexual or asexual?

• Can be produced sexually but it is limited by the water availability and the proximity of male and female gametophytes

• Asexual production is frequent

Bryophytes sporophyte

It depends on the gametophyte and are attached to them

Bryophytes sporophyte three major parts consist of 

• Foot: Absorbs nutrients from the gametophytes

• Seta (stalk): conducts nutrients to the sporangium

• Capsule: AKA sporangium which it produces spores by meiosis

How the spores re dispersed?

the peristome at the top of the capsule disperses the spores when conditions are dry

Liverwort characteristics

• The name comes from their liver shaped gametophyte

Hornwort characterisitcs

• long horn shaped sporophyte

• spores are released when horn split open

• Form symbioses with nitrogen fixing bacteria

Mosses characteristics

• Sporophyte visible to the naked eye

• photosynthetic when are young

What moss is important ecological and economically?

• It is commonly lived in moist forest and wetland

• Also inhabits extremely cold, hot and dry environment

• It rehydrates after complete desiccation

• IT HELPS TO RETAIN NITRON IN SOILS

What is PEAT?

• Decayed organic material (moss)

• It is used as source of fuel

Peatland characteristics

With low temperature, pH and oxygen level, it inhibits decay of moss and other organism

• is can preserve corpses for thousands of years

Peatland fact with Earth

• 3% of earth land is covered with peatland but it contains 1/3 of world’s soil carbon

• overharvest will cause global warming

what makes the plant to grow taller?

The vascular tissue allow plants to grow tall

What is one of the difference between bryophyte and vascular plant SPOROPHYTE?

Vascular plant sporophyte lives independently from the gametophyte from it nutrient supply where bryophyte sporophyte depend from gametophyte

Vascular plants Are characterized by:

• Life cycle with dominant sporophytes

• Transport in vascular tissue called xylem and phloem

• Well developed root and leaves

• Sporophylls: Spore bearing leaves

Seedless Vascular life cycle

• Sporophyte are larger and complex

  • Fern: Leafy part is sporophyte and the gametophyte are tiny plant growing bellow the soil surface

Vascular Tissue: Xylem

• Conducts most of the water and minerals through TRACHEIDS

• Dead at functional maturity

Vascular Tissue: Tracheids

Water conducting long tapered cell that conducts water in the plant

Vascular Tissue: Lignin

When xylem cell is at functional maturity it dies and releases complex organic polymer that are deposited in the cell wall of the plants which it makes them rigid.

Vascular Tissue: Phloem

• Arranged in tube for transport of organic materials such as sugar

  • Cells are alive at functional maturity

Function of Vascular Tissue

• Structural support

• Long distance  transport needed for the plant to grow tall

Function of Root

• Organs that anchor vascular plants into the ground and absorb water and nutrient from the soil

  • It resembles the stem tissue of earlier vascular plants

Function of Leaves

• Increase surface area for light capture

• Conduct most of the photosynthesis in plants

Type of Leaves: Microphylls

• small

• spine shaped

• single vein

• found only in lycophytes

Type of Leaves: Megaphylls

• large leaves

• highly branched vascular system

• found in all plant groups

Sporophylls

Leaves with sporangia attached

Sporophylls of angiosperm are called

Carpels and stamens

Homosporous

• Most of the seedless vascular plants

• One type of sporophyll and sporangium

  • Produce one type of spore: becomes bisexual gametophyte

Heterosporous

• All seed plants and some seedless plants

• two types of sporophylls with different sporangia

• Produces different spore types

  • either male or female spores

Megasporophylls

Megasporangia→produce large megaspores→ female gametophyte

Microsporophylls

Microsporangia→ produce small microspores→ male gametophyte

Phylum Lycophyta (lycophytes)

• seedless vascular plants clade

  • club mosses, spike mosses, quillwort

Phylum monilophyta (monilophytes)

• Seedless vascular plants clade

  • fern, horsetails, whisk fern and its relative

Lycophytes characteristics

• Grow in diverse habitat

• some have photosynthetic gametophyte

• sporophyte with both leafy upright stem and ground hugging root forming stem

• spikemoses and quillwort: heterosporous

• Clubmosses: Homosporous

• Not true mosses

Monilophytes: Fern

• Most species are homosporous and have spring like device for spore disposal

• Large megasporophylls

Monilophytes: Horsetails

• bisexual gametophyte

• have separate fertile and vegetative stem

• Horsetail sporophytes have jointed stems with rings of small leaves or branches

Monilophytes: Whisk Ferns and its family

• all are homosporous: bisexual gametophyte

• Three fused sporangia form a yellow knob on the end of each stem

Monilophytes Characteristics

• Most widespread seedless vascular plant

• Most diverse in tropic

• Most closely related with seed plant than lycophytes

When did lycophytes, horsetails, and ferns formed?

During Devonian and Carboniferous period