Plant Ancestry 1

Red Algae – phycoerythrin pigment - deep water, most are unicellular - many use alternation of generations (a multicellular diploid sporophyte and a haploid gametophyte)

Green Algae – similar ultrastructure to plantsChlorophytes (phylum name)

Unicellular – flagellatedEx: chlamydomonassee life cycle p. 567

Colonial Ex: spyrogyra and volvox

Multicellular Ex: ulva and caulerpa(see life cycle)

Green Algae – Charophyceans (phylum)- similar cellulose production mechanism- similar peroxisome enzyme- similar flagellated sperm structure- genetic similarities- similar phragmoplast formation (vesicles and cytoskeleton complex near the cell plate during mitosis)- both have sporopollenin, a polymer that prevents exposed zygotes from drying out

Stop and show PLOP

Plants 2

They are distinguished from algae becausethey are embryophytes (plants with embryos)

Land plants have: (charophyceans don’t) see p. 602-603.- Apical meristems – found at the tips of roots and shoots; a dividing region of nondifferentiated cells.- Alternation of generations - alternate between adult haploid – gametophyte and adult diploid - sporophyte

- Walled spores produced in sporangia adult sporophyte has a structure called sporangia which produces haploid spores from a diploid sporocyte. Spores are walled in sporopollenin.

- Multicellular gametangia that produce gametes. Female version: archegonia – produces

1 egg. Male version: antheridia – produces

sperm, many are flagellated

- Multicellular, dependent embryos Embryos develop inside the female parent, receives nourishment from placental transfer cells. Therefore, known as embryophytes.

Also, many plants have a waxy cuticle to prevent dessication (drying out) and pathogen infection.Many have special metabolic pathways to produce secondary compounds to deter predators,block uV light, etc.

Plant divisions 3

Nonvascular (a.k.a. Bryophytes) - No extensive transport system - Includes mosses, liverworts and hornworts

Nonvascular Plants (Bryophytes)– Mosses - Many live in moist environments (b/c no vascular tissue.- mosses and liverworts have stomata- sphagnum moss produces peat (partially decayed organic matter)- have rhizoids; long filaments of cells to anchor the moss, no role in water or mineral absorption, not made of tissue.- Life cycle – see diagram on page 607

alternation of generations(know all terms)

Vascular Plants (a.k.a. Tracheophytes)- 2 groups:

Seedless Plants - fernsSeed Plants: embryos are packaged with a supply of nutrients in a protective coat. 2 types: Gymnosperms – “Naked seed plants,” no

chambers for a seed (mostly conifers).

Angiosperms – “Flowering plants,” seeds develop in ovaries/chambers. Ovary

originates as flowers and develop into fruits.

Vascular Plants (Tracheophytes) 4 Evolved in the early Carboniforous. Most early plants (bryophytes and ferns) were limited to moist environments by swimming sperm.

All vascular plants have:1. Life cycles with a dominant (large and complex) sporophyte, gametophyte is very reduced.2. Roots that are present to anchor the plant and absorb nutrients and water.

3. Transport using vascular tissues known as xylem and phloem. xylem – conducts most water and

minerals.- includes tracheids (dead, tube-shaped cells)- cells are strengthened by lignin (protein – allows them to grow tall.)

phloem – living, sugar-conducting cells arranged in tubes - distribute sugars, amino acids, and organic products.

4.Leaves are present to increase surface area for photosynthesis.

2 main types of leaves:Microphylls – small, spine-shaped with a single veinMegaphylls – highly branched, larger

have a vascular system (p. 613)

There are also some spore-bearing leaves called sporophylls.

microphyll megaphyll

Seedless Vascular Plants 5Ferns! See fern life cycle on p. 611

(alternation of generations)

Seed Vascular Plants- Have a microscopic gametophyte (that’s so cute!) It stays inside the female sporophyte for protection.- Most plants have 2 kinds of spores (p. 620) Megasporangia produces a megaspore

which develops into female gametophyte Microsporangia produces a microspore

which develops into male gametophyte

-Have Ovules – (female) which consist of megasporangium, a megaspore and sporophyte tissue called integument.

-Have Pollen grains (male) – which develop from microspores and contain the male gametophyte protected by sporopollenin.

-Pollenation occurs when pollen is transferred to the ovule. Pollen grains land, germinate, and grow a pollen tube that delivers the male gametophyte. Most sperm are nonflagellated.

- The fertilized ovule will develop into a seed. The seed contains: embryo, food and a protective seed coating called the integument.

- The seed resists harsh environments by lying dormant.- Seeds increase dispersal rate for offspring.

Gymnosperms: “naked seeds” (not in ovary) -Many seeds are exposed on modified leaves (usually from cones). Therefore, they are known as conifers.

- Life cycle – see p. 624

Angiosperms (Phylum Anthophyta): 6“Flowering Plants”:

- Flowers are specialized for sexual reproduc.- Pollination occurs with the help of wind (like gymnosperms), insects, etc. (more directed.)

Flower Anatomy – see p. 625sepals and petals – sepal protects flowers.

- petals attract pollinators.stamens (microsporophylls) – produce

male microspores that make pollengrains containing a male gametophyte.parts: filament (stalk) and

anther (terminal sac, pollen is produced there)

.

Carpels (megasporophylls) – make megaspores that become gametophytes.

Sometimes, 1 carpel or group of carpels is called the pistil.parts: stigma – sticky tip that receives

pollen. style – leads to the ovary ovary – at base of carpel, has

one or more ovules. receptacle – attaches carpel

to stem.

Fruits – they are thick ovaries at maturity(Ex: pea pod, see p. 626)

- they protect seeds and aid in dispersal - pollination triggers a hormone change that causes the ovary walls to thicken and become pericarp.

- Fleshy pericarp: peaches, apples - Dry pericarp: nuts, beans, grains

- Fruit ripening is stimulated by the hormone ethylene.

Life Cycle of an Angiosperm – see p. 627- Most species cross pollinate (p. 627)- Double pollination occurs in most:

1. Diploid zygote is formed from one fertilized egg. The sporophyte embryo

develops with a rudimentary root and one or two seed leaves. (monocots – one, dicots – two p.631)2. Second sperm fuses with 2 nuclei in the central cell of the (polar) gametophyte. Forms an endosperm with starch and amino acids for nourishment.

- Angiosperm seed germination will begin after moisture and temperature conditions are ideal. This is triggered by hormones called gibberellins.

-Root growth and stem elongation are triggered by a hormone called auxins.

Chapter 36 – Transport in Plants – 3 Types 7See p. 765

1.Individual Cell Transport of water andsolutes.

Proton Pumps – p. 769. Buildsup a membrane potential outsideof the cell (uses ATP). Cotransportthrough chemiosmosis transports substances back into the cell.Ex: sugar (sucrose) loading from leaves K+ in guard cells (look at diagram of guard cells in book, p. 777), NO3- from root cells

Root Hairs on a root cell help to increasesurface area.

Some plants have a symbiosis with afungus to form structures calledmycorrhizae (p. 767), which are fungalHyphae that help absorb water and minerals.

2. Short Distance Transport between several cells. (water and solute transportat the tissue and organ level)3 Pathways (p. 768)1 – Can pass through each cell membrane

(through aquaporins and proteins)2 – Pass through Symplast, which is a

cytosol continuum of plasmodesmata3 – Pass through Apoplast, which is a

continuum of cell walls and extracellular spaces (very direct route)

3. Long Distance Transport (xylem and phloem)Xylem – unidirectional transport from

roots to leaves. P. 775Increases water loss because oftranspiration through stomata (90%is lost – can wilt if not replaced)

Xylem Loading – water and mineralabsorption pathway to xylem: p. 773Epidermis (via root hairs)

↓to cortex (made of ground tissue)

↓to endodermis via symplast (waxy Casparian Strip forces water to go through a membrane to prevent minerals and water from leaking out.)

↓To xylem

Xylem Transport:- At night, roots pump minerals into the xylem. This decreases the water potential inside, forcing water to diffuse in from the cortex. This generates root pressure, an upward push of xylem sap. If too much water flows in, guttation results at the leaves. - Transpiration results in an upward pull from: adhesion, cohesion, surface

tension and negative pressure at the water/air interface, negative water potential at leaves.

Phloem: transfers organic nutrients 8known as translocation.

- In angiosperms, sucrose is transferred from mesophyll cells to phloem by specialized phloem cells called seive-tube members.- Phloem sap can be up to 30% sucrose. (& some amino acids, minerals, hormones)

- Direction of transport is variable, but is always from a sugar source to a sugar sink.

Source – organ that produces sugar or breaks down starch

Sink – a net consumer or storer ofsugar (growing roots, buds,stems and fruits)

Loading of Phloem – see p. 780Mesophyll cells → symplast or apoplast → sometimes via companion cells (with ingrowth of cell walls) known as transfer cells → seive tube members of phloem.

Loading into companion cells is usuallydone through active transport via protonpump and cotransport. (This is becauseseive tube sucrose content is 2-3 timeshigher than mesophyll.)

- Unloading of phloem is usually done through diffusion at a sugar sink.

-Movement through phloem occurs through pressure flow of sugar solution (p. 781) Increased pressure builds up at the

source. Lower pressure is at the sink.This causes the xylem water to diffuseinto the phloem and move from sourceto sink and take sucrose with it(rate is about 1m/hour.)

Ch. 35 – Plant Structure, Growth and Develop.Growth:

Annuals – complete their life cyclesin 1 year or less

Biennials – live 2 years Perennials – live many years (trees,

shrubs, some grasses)

Plant tissues:Dermal (epidermis, endoderm)

- single layer of tightly packed cells to cover and protect Ex: root hairs, cuticle

Vascular (transport tissues)Ground Tissue – bulk of plant tissue is

ground tissue which is found between the dermis and vasculartissues. Mostly made of parenchyma cells. Functions inphotosynthesis, storage, support,and metabolism.

Specialized Cells:Parenchyma Cells – thin, flexible (no

secondary cell wall), most commontype, can divide for repair.Found in: photosynthetic cells, stems, roots, fruits, and usuallyhave plastids.

Collenchyma cells – grouped in strands,help support young shoots. No secondary cell wall (no lignin); therefore, they can grow.Ex: celery strings

Sclerenchyma Cells – supporting cellswith thick secondary cell walls withlignin. Cannot elongate when mature. Many are dead at maturity (lose protoplasts.)2 types:

sclereids – short and irregularshaped, like in seed coats,nut shells or pear grit.

fibers – fibers that are long, thin,and tapered like hemp or flax.

More Plant Growth:Apical Meristems – tips of roots and

buds of shoots.- Responsible for increase in length, primary growth. (lateral meristems help with secondary growth, increase in width: vascular tissue and cork cambium)

See p. 747 (bottom) for apical meristemRoot cap – for protectionZone of Division – includes root apical

meristem. New cells producedhere (mitotic division.)

Zone of Elongation – cells elongate,push tip

Zone of Maturation – cells completedifferentiation and mature.This produces epidermis, ground tissue and vascular tissue.

Tissue organization of stems and roots:(on your own) p. 750 and lab manual (p. 106)

Tissue organization of leaves see p. 751cuticleupper epidermispalisade meophyll (tighter)spongy mesophyll – spread out

(increases gas exchange)veins (xylem and phloem) covered with

bundle sheath cells for protectionlower epidermiscuticle

Plant Hormonessee p. 827