Chapter 29 - Plant Diversity I Flashcards
What is the likely common ancestor of all land plants?
Green algae that is still a mystery
- chlorophytes (aquatic)
- charophyta (sister to all land plants
What are the 5 key traits of land plants?
1) alternation of generations and protected embryos
2) multicellular, dependent embryos
3) walled spores produced in sporangia
4) multicellular gametangia
- archaegonia = female
- antherida = male
5) apical meristems
- are localized regions of cell division
- at the tips of roots and shoots
How do plants deal with limited water availability?
- a waxy cuticle on exposed surfaces helps prevent water loss as does the exchange of gases through the stomata
- tracheids are specialized for water and mineral transport
Charophytes
- rings of cellulose-synthesizing proteins
- peroxisome enzymes
- structure of flagellated sperm is very similar
- formation of a phragmoplast
What is the advantage to a shift toward the diploid generation in land plants?
Allows for greater genetic diversity
Gametophyte Generation
- haploid generation
* prominent in mosses, ferns, and liverworts
Sporophyte Generation
- diploid generation
* more prominent in gymnosperms and angiosperms
Bryophytes
- Close living descendants of the first land plants
- includes liverworts, mosses, and hornworts
- are nontracheophytes; no tracheids
- have other conducting cells for moving water and nutrients
- many have mycorrhizal associations: symbiotic relationship between fungi and plants
- liverworts and mosses have a non photosynthetic sporophyte that depends on a gametophyte for nutrients
Liverworts
- ancient phylum
- flattened gametophytes w/ flattened lobes that look like liver
- produce upright structures that contain gametangia
Mosses
- exhibit alternation of generations
- can withstand droughts
- stomata close in hot, dry conditions to minimize water loss
- have rhizoids
- have water-conducting tissues
- most mosses are highly sensitive to air pollution
- peat moss can absorb up to 25 times their weight in water
Hornworts
- stomata in sporophyte open and close to regulate gas exchange
- sporophyte is photosynthetic
Ecological and Economical Importance of Mosses
- help retain nitrogen in the soil
- mosses can live in very cold or dry areas as they can lose most of their body water & then re-hydrate when the moisture is available
- Sphagnum or peat moss does not readily decay; low temp, pH, and oxygen level of peat lands inhibit decay of moss and other organisms - some have preserved corpses for thousands of years
- peat is used as a fuel source in Ireland and Canada
- Peat moss is used as a soil conditioner; it can absorb 20 times its weight in water
- Peat lands contain roughly 30% of the worlds soil carbon
Xylem
Conducts water and minerals from roots
Cooksonia
1st known vascular land plant
- vascular tissues allows for distribution of nutrients
Phloem
Conducts sucrose and hormones
Vascular tissue
- allows for distribution of nutrients
- develops in sporophytes
- vascular plants have reduced gametophyte
Vascular plants exist as these 3:
- Lycophytes
- monilophytes
- seed plants
Stems
Evolved before roots did
Roots
• provide structural support and transport capability
Leaves
• evolved more than once
- Lycophytes; no vascularization in leaves - ferns and seed plants have true leaves
Seeds
- are another innovation in some phyla
- protects embryo from drying out
- protection from predators (somewhat)
Lycophytes
- earliest vascular plant
* 1st plants to have a dominant sporophyte generation
Monilophytes
- ferns
- horsetails
- whisk ferns
- require water for fertilization and are seedless
Whisk ferns
• lost their roots and leaves secondarily
Horsetails
- have jointed stems w/brush like leaves
* stems have silica deposits in epidermal cells w/their ribs
Ferns
• have fronds that bear sori
- sori are sporangia located on underside of fern fronds - gametophyte is heart-shaped and can live independently
