Plant Diversity I (ch. 29)

life at the edge and the greening of earth

microbial mats

• prokaryotes + algae

• 1.2 billion YA

• along the edges of bodies of water

charophyte algae

ancestral to embryophytes

not true plants so they are classified as algae

moving from water to land

• benefits of terrestrial environments:

  • unfiltered light

  • no competition

  • plentiful CO2 + nutrients

• challenged of terrestrial environments

  • desiccation (drying out)

  • radiation (ultraviolet radiation)

  • support; water provides buoyancy

  • dispersal; where will the offspring go

  • gas exchange

what is a plant?

• multicellular eukaryotes

• photoautorophs

• develop from an embrya- multicellular structure nourished by the parent plant

  • embryophytes- plants in general

• sporopollenin- polymer that is protective- dispersed on land

• multicellular gametangia- eg. antheridia + archegonia localized strutucre responsible for producing sperm and egg

• apical meristems- regions of cell division at shoot + root tip where cell division occurs

non-vascular plants- mosses + liverworts

• bryophytes- plants in general

• small plants (adaptive)

  • optimization of surface area/volume ratios → water + nutrient absorption

• ground hugging

• need water to reproduce bc sperm are flagellated

• gametophyte dominant

spring tails + thripps- small! insects

• reduced water and increase in the insects can facilitate bryophyte reproduction

hepatophytes

• liver- looks like a liver wort- general word for plant

• thallus liverworts- green cornflake

• no stomata so they use pores which are unregulated

• gemmae (allows them to reproduce asexually)

• spores- 470 mya

• doctrine of signatures

  • a book w plants that were believed to aid in human health

gemma cup

bryophytes

lack true leaves / roots

stomata

early uses / economics- dry moss is rly absorbant

size of pore can be changed to regulate gas exchange + water loss

conducting tissues / tissues in true moss

cells dedicated to moving waters + sugars in phytobryophytes

• leptoids

  • moves sugars

• hydroids

  • moves water

moss life cycle

peat bogs as carbonsinks

pea bogs- wetland environments where the surface layer is full of living moss, beneath is a hydrated layer with masses of carbon from the moss that preceded them

makes up less than 1% of the earth area

life on the edge

• dominant for 100 mya

• nvp- first to make the jump ~470 mya

• limitations

  • lack of vascular tissue

tracheopohytes- vascular plants

• seedless v.p

• earliest evidence is 425 mya i,e emerged when nvp were dominant

• dominant up to 240 mya

• sporophyte stage dominant

• lignified vascular tissue

  • cells that are hollow and stacked on top of each other to make tubes

  • lignin- found in cell walls which strengthen it

  • a plant can now transport materials over longer distances

  • can also grow taller because of the structure

true leaf

flattened sctucture born on a stem that has vascular tissue

microphyll leaves

single strand of unbranched vascular tissue

megaphyll leaves

multiple strands of branched vascular tissue

lycophytes- club/ spike moss

• moss like

• microphyllous leaves

• sporangia clustered in strobili

• heterosporous

  • heterospory- the production of different types of spores

  • microspores- smaller + will form male gametophytes

  • megaspores- larger + will form female gametophytes

• homosporous

  • homospory- only 1 spore type produced

  • spore develops into a bisexual gametophyte

monilophytes

true ferns, whish ferns, + horsetails

whisk ferns

• lack leaves and true roots

• dichotomous branching (fork appearance)

• symbiotic fungi

• parasitic on decomposing fungi in the soil

• the fungus are probably getting their nutrients from plants

• non-photosynthetic + dependent on fungus activity for nutrition

horsetails

• reduced leaves- vestigial as they dont perform any function

• sporangia clustered in strobili

• cilica in the stem used to strengthen them

• silicone dioxide in stems used as an abrasive

true ferns

• megaphyll leaves have branches plumbing

  • club moss (lycophytes) is the only group that has microphyll leaves

  • all other vascular plants have megaphyll leaves

  • most ferns are homosporous

  • most spores are bisexual

  • second to flowering plants (super diverse)

• sporophyte generation is diploid

• cells begin as diploid, mesiosis occurs to produce haploid spores
  

• grow into a gametophyte

• looks like a liverwort but its not because of the tissue

• small dots are antheridia and archegonia

• this is a homosporous spore

• heart shaped

• dependance on water for reproduction

homospory vs heterospory

• sporangium (2n)- job is to produce spores (of a single type)

outcrossing + selfing

the carboniferous period

• most of the plant diversity where they were all seedless vascular plants

• during pangea

• where we can date the coal bearing period

• what is coal?

  • carbon based fossil fuel

• as they died, they created a thick organic material under the water

• pressure and heat from sediment and rock turned peat into cial