Last day- talking about fungi, covered some basic characteristics of the kingdom & started looking at some of the phyla

Phylum Glomeromycota - Glomeromycetes

Root

AM

Small group (about 160 spp. known) but important as nearly all form arbuscular mycorrhizae

About 90% of plant species form associations with glomeromycetes

- fungus supplies phosphate & other minerals plus H2O- plant supplies sugars & other organic compounds- important for growth of corn, wheat & many other plants

(a) The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus.

(b) The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards.

(c) Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open.

(d) Neurospora crassa feeds asa mold on bread and other food (SEM).

10 m

Phylum Ascomycota – Sac Fungi

Largest phylum of fungi - about 65,000 spp. described - from unicellular yeasts, to molds, to complex cup fungi, morels, etc.

- form sexual spores in saclike asci- asci contained within ascocarp which may be large structure (e.g. ‘mushroom’ of a morel)

Many ascomycetes are saprobes, others mutualists, but also many plant pathogens- about 40% of spp. form the fungal partner in a lichen, an association between fungus & photosynthetic green algae or cyanobacteria

ascus with 8 ascospores

Neurospora life cycle – an ascomycete

Asexual spores called conidia simply produced at end of hyphae- conidia may at times fuse on to hyphae of other mating strain leading to plasmogamy (etc.)

(a) Fly agaric (Amanita muscaria), acommon species in conifer forests in the northern hemisphere

(b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat

(c) Shelf fungi, important decomposers of wood

(d) Puffballs emitting spores

Phylum Basidiomycota – the Club Fungi

Another large group (~30,000 spp.), includes many large ‘mushrooms’, shelf fungi, puffballs, but also plant parasites (rusts & smuts)

Especially good at breaking down tough lignin & cellulose of wood

- usually live as dikaryotic mycelium

- occasionally produce basidiocarp (fruiting body) with club-shaped basidia

- karyogamy occurs in basidia, then meiosis produces 4 basidiospores

‘Fairy ring’ – basidiocarps produced at edge of expanding mycelium

Importance of fungi

Immensely important, usually positive but…

As decomposers, vital role in recycling nutrients

As symbionts (endomycorrhizae, ectomycorhizae, endophytes living in plant leaves, etc.) extremely important in promoting plant growth

As component of lichens, important in succession of barren habitats, as bioindicator, etc.

As plant pathogens, very damaging financially & ecologically

chestnut blightcorn smut ergots on rye

Role in producing baked goods, cheeses, alcohol, drugs & other useful chemicals is of huge economic value

The Plants - Kingdom Plantae

Plants are relative newcomers to Earth - earliest fossils ‘only’ 475 MYA

What makes a plant a plant?

- many derived traits of plants relate to move to land

Apical meristems: localized areas of cell division & growth at tips of shoots and roots, allowing increase in length

Alternation of generations, & multicellular embryos

- 2 distinct generations, haploid gametophyte produces eggs & sperm, diploid sporophyte produces asexual spores

- both generations multicellular, & sometimes independent

Fertilized egg develops within gametophyte tissue as multicellular embryo

- specialized placental transfer cells for obtaining nutrition from parent

- land plants also known as embryophytes

Walled spores produced in sporangia - multicellular organs where spores produced

Tough layer of sporopollenin (a complex polymer) coating spores & pollen, protects from dessication

Multicellular gametangia where gametes produced & protected- archegonium produces eggs- antheridium produces sperm

Where did they come from?

Presumably evolved from some sort of algae…- multicelular, eukaryotic & photosynthetic (like red, brown & some green algae)

- cell walls made of cellulose (like brown algae, green algae & dinoflagellates)

- have chloroplasts with chlorophylls a & b (like green algae, euglenids, & some dinoflagellates)

- green algae 3 for 3…

One group of green algae, the charophytes, share more:

- rosette shaped cellulose- synthesizing complexes

- peroxisome enzymes

- similar flagellated sperm

…and formation of phragmoplast in dividing cell - cytoskeletal elements, serve as scaffold for new cell plate

…and also DNA sequences support close relationship

Earliest branches off plant phylogeny are lumped as ‘bryophytes’, paraphyletic (?) group lacking complex vascular tissue

Life cycle of non- vascular plants dominated by gametophyte generation

- start as thin filaments: protonemata

- gametophores have antheridia or archegonia at tip, produce sperm or eggs

- zygote (2n) grows in archegonium, foot absorbs nutrients

- develops into sporophyte with seta & capsule

- meiosis produces haploid spores to start next generation

Liverworts – Phylum Hepatophyta – about 9,000 spp. ?- gametophytes may be leafy or thalloid

- have air pores that stay open for gas exchange

Hornworts – Phylum Anthocerophyta

- only 100 spp. - named for sporophyte shape, & ‘wort’ = herb

- early colonists of open moist soils, symbiotic w. cyanobacteria

Hornworts show important adaptations to life on land: waxy cuticle covering surface & stomata for gas exchange with guard cells to control opening

Mosses – Phylum Bryophyta

- 15,000 spp., some abundant

- ‘leafy’ structure, leaves one cell thick, absorb water & minerals

- ‘non-vascular’ plants, but may have simple water conducting cells (hydroids) in ‘stem’ & leaf midvein

- anchored in ground by delicate rhizoids

- young sporophytes green & photosynthetic, turn brown, reddish, etc. as they mature - capsule has peristome with teeth that open or close with humidity

Sphagnum bogs cover large areas in cool climate areas- important ecologically, & as carbon sink

Often, low pH, temps & O2

levels lead to slow decay…

Peat traditionally harvested as fuel (& still is), & extensive use in gardening

Eventually, plants developed more sophisticated vascular systems to transport water & food, & grew larger

The ‘seedless vascular plants’ again a paraphyletic group, defined by what they lack rather than shared derived traits- a ‘grade’, not a ‘clade’

Some fossil relatives may have lacked roots & even proper vascular tissue, though do show branching growth

Modern vascular plants do share several traits, including life cycles with dominant sporophyte:

- sperm still must swim through film of H2O to reach egg

Vascular tissue includes:Xylem – transports water & minerals- made up of tracheids & sometimes vessels- dead cells, strengthened by lignin

Phloem – carries sugars & organic compounds through living sieve cells or sieve-tube elements