Lecture 9 Flashcards
Kingdom Plantae aka Embryophyta
290 000 extant species, most photoautotrophic, most terrestrial (some aquatic), shares a common ancestor with green algae charophytes
first photosynthesizers on land
rewarded with an expanse of terrestrial habitat - space, sunlight unfiltered by water and algae, abundant CO2, mineral-rich soil, few herbivores or pathogens
oldest terrestrial photosynthesizers
cyanobacteria
oldest terrestrial plant spores
475 MYA, in clumps of 2 or 4
4 main groups of plants
- non-vascular plants
- seedless vascular plants
- gymnosperms
- angiosperms
3 land plant shared synapomorphies with charophytic algae
- rosette-shaped cellulose-synthesizing complexes (make cellulose microfibrils of cell wall)
- structure of sperm resembles charophyte sperm (only for plants with flagellated sperm)
- presence of phragmoplast during cell division
phragmoplast
helps construct cell plate between incipient cells, which goes on to become new cell wall
Viridiplantae
some systematists put chlorophytes, charophyceans and embryophytes together
6 synapomorphies of plantae
- multicellular, dependent embryos
- alternation of generations
- sporopollenin
- adaptations for water conservation
- lignified vascular tissue for internal transport (lacking in bryophytes)
- apical meristems
placental cells
present in plant embryos so parent can provide nutrients
alternation of generations
life cycle in which haploid multicellular and diploid multicellular body forms alternate
sporopollenin
tough, stable polymer in walls of plant spores, including pollen
2 adaptations for water conservation in land plants
- waxy cuticle on epidermis acts as waterproofing
- stomata pores in the epidermis of leaves and other photosynthetic organs, changes in shape of bordering cells can close pores
lignin
a complex polymer of alcohols which strengthens vascular tissue
2 types of vascular tissue
xylem and phloem
apical meristem
undifferentiated tissue from which new cells arise, and differentiate into various tissues, including surface
epidermis and internal tissues
compartmentalization of resources in terrestrial plants
structural specialization for water and minerals in ground (roots), light and gases above ground, elongation and branching to maximize exposure
3 phyla of bryophytes
- Hepatophyta (liverworts) - 9000
- Anthocerophyta (hornworts) - 100
- Bryophyta (mosses) - 15 000
non-vascular plant aka bryophyte characteristics
not monophyletic (hornworts sister to vascular plants), lack true vascular tissue (only a few cells thick), small
bryophyte life cycle
- haploid gametophytes dominant
- separate organs for egg and sperm
- sperm swim through water film to fertilize egg in archegonium (need to live in moist places)
- zygote and sporophyte retained and nourished by gametophyte, release thousands of asexually produced haploid spores
archegonium
produces a single egg
antheridium
produces many flagellated sperm
sphagnum moss
forms extensive deposits of undecayed organic material called peat (muskeg), inhibit bacterial activity, peatlands act as carbon reservoirs stabilizing atmospheric CO2 levels, peat used as fuel, harvested for soil conditioner
