Land Plants: Seedless vascular Plant Diversity Flashcards
How has the diversity of land plants changed over time?
90% are angiosperms today, but they are recent addition
What are the two types of seedless- vascular plants?
Lycophytes, and ferns and horsetails
How do seedless vascular plants fertilize and disperse?
water (sperm), and air (spores)
compared to the Bryophytes are seedless vascular plants more or less gametophyte dominant/reliant?
less
when is the first record of vascular plants?
roughly 425 million years ago
What did evolution of xylem and phloem give vascular plants an advantage in?
size and hydration
What was the structures of Early vascular plants?
small, branched repeatedly, formed sporangia at tips of branches, no leaves, and ‘root’ structures were underground stems with small hairlike extensions, had ability to synthesise lignin
What is lignin?
complex organic polymer of cell walls, especially found in sclerenchyma and associatedwith xylem vessels
What is the function of lignin?
provide support and rigidity: support of plant body (especially for plants of larger size
What is a stele?
vascular bundles
WHat is the protostele? describe its structure
the ancestral stele - vascular tissue is organized as a simple, compacted central strand; a cylindrical strand of xylem surrounded by a region of phloem
How did the Stele (vascular bundles) evolve?
changes led to more peripherally arranged vascular tissues (siphonostele)
WHat is the structure of the siphonostele?
the ring of vascular tissue forms a hollow cylinder filled with pith
What is a leaf gap?
often on siphonosteles - interruptions in the vascular strand where leaves originate
What species today are siphonostele stems found in?
most ferns and horesetails
WHat species today is the protostele found in?
lycophytes, whisk ferns and in roots of most eudicots
What is the eustele?
further changes from siphonostele
a system of discreet strands around a pith (eudicots) or interspersed with parenchyma tissue (monocots)
What species today is the Eustele found in?
stems of seed plants (gymnosperms/angiosperms)
What are microphylls?
small scale-like photosynthetic apendages with only a single vascular strand (=vein of xylem and phloem)
emerge from stems with protosteles (lycophytes)
no leaf gap
What are megaphylls? (true leaves)
leaves with a complex network of veins (xylem and phloem)
emerge from stems with siphonosteles or eusteles
found in ferns and seed plants
leaf gap
What is homospory?
only one type of spore produced (ancestral state)
found in most lycophytes and most ferns
WHat is heterospory?
produce two types of spores (microspores, megaspores) in two types of sporangia (microsporangia, megasporangia)
found in some lycophytes, a few ferns, and the seed plants
WHen did Giant Lycophytes exist?
occured roughly 400-296 million years ago
WHat environments did Giant Lycophytes live in?
swampy environments alongside early seed plants
WHy did Giant Lycophytes go extinct?
due to changing climates to drier conditions
WHat happened when the GIant Lycophytes died?
when the trees dies they often fell into swamps and decomposed; the dead organic matter was converted to coal
What are features of Extant Lycophytes?
sporangia with spores (homospores; ancestral condiotion)
protostele in roots and stem
microphylls
What are the three extant lycophyte lineages?
lycopodium group (club mosses)
Selaginella group
Isoetes (quillworts)
Where do Club Mosses live?
artic to tropics
WHat is the sporophyte of club mosses?
rhizomes with roots; aerial branches
What leaf atttachment type do Club mosses have?
microphylls on aerial stem
WHat are the spore producing vessels in Club Mosses?
Homosporous (only one type of sporangium)
Sporangia often located on upper surface of sporophylls (leaves bearing sporangia)
WHere do Sellaginella live?
mostly tropical, wet habitats
What are the spore producing vessels in Sellaginella?
Sporophylls (mega- and microsporophylls in strobili with mega- and microsporangia)
Heterosporous (microspores, megaspores)
WHere do Isoetes (quillworts) live?
mostly along the margins of lakes/ponds and slow-moving streams
What makes Isoetes (quillworts) unique among living Lycophytes?
has a vascular cambium, indicating tree-like ancestors
What is spore producing like in Isoetes (quillworts)?
Heterosporous
What are features of horsetails?
occur in moist damp habitats
jointed stems
rough texture (silica in their epidermal cells)
underground stem (= rhizome)
How does branching and leaves work in horsetails?
small, scale-like leaves in whirl at node
branches arise at nodes, alternate with leaves
What does the stem cross section of a horsetail lok like?
hollow pith surrounded by ring of carinal canals and vascular tissue
What is the structure of whisk ferns?
have photosynthetic stems without leaves and do not form roots
resemble fossils of early vascular plants
What are aquatic ferns?
ferns that float on the surface of the water
WHat is a species of aquatic fern with its common use to humans?
Azolla - free-floating aquatic fern that has been used for centuries in Asia as a biofertilizer of rice paddies due to its symbiotic association with nitrogen-fixing cyanobacteria
Where is a tree fern found?
tropical forests
how do tree ferns grow tall?
10+m by producing an erect rhizome that forms the trunk
trunk is supported by a fibrous mass of rhizomes that expands as the tree fern grows
WHat are Polypod ferns also called?
Adder’s tongue ferns
WHat are features of Polypod or Adder’s TOngue ferns?
simple, spoon-shaped leaves and an upright spore-bearing stalk
What is the stele of polypod ferns?
protostele in rhizome
siphonostele with leaf gaps in stem
WHat does the leaf of a polypod fern look like?
megaphyll
frond - usually compound
young frond coiled - fiddlehead
Rhizomes and rachis usually have hairs, scales
Where is sporangia located in polypod fern?
on lower surface of frond or modified fronds
WHat is a sorus?
cluster of sporangia
WHat is Indusium?
outgrowth of leaf that covers sporangia in some species
in polypod ferns describe thereproduction?
gametophyte bisexual
antheridia is among rhizoids
archegonia is near notch
water is required for fertilization
Describe a fern life cycle
Sperm is released when moisture is present (n)
fertilization
the sporophyte (2n) is initially supplie d with nutrients by the gametophyte
vascular tissues allow sporophyte to grow tall and become independent
Sporangia are produced on the lower surfaces of leaves
under meiosis produce haploid spores (n)
spores are released into air thoese that are land in a suitable site will germinate and grow into new gametophytes
