Gymnosperms Flashcards
What are the four living phyla of the gymonsperms?
- coniferophyta, ginkgophyta, cycadophyta, gnetophyta
What is the dominant generation in gymnosperms?
sporophyte - gametophyte is fully dependant on sporophyte
Are the seedless vascular plants heterosporous or homosporous?
- all of them are heterosporous (develop endosporically)
What kind of seeds do they produce?
- naked seeds
Describe the vascular elements in the seedless vascular plant phyla
- coniferophyta, ginkgophyta, cyadophyta = tracheids
- gnetophyta: tracheids and vessel elements
what do gnetophyta have in common with angiosperms?
- no archegonia and they have both tracheids and vessel elements
What is primary and secondary xylem?
- primary xylem: tracheids
- secondary xylem: tracheids and vessel elements
what is a casparian strip?
- forces water/nutrients to pass through endodermal cells, regulating entry into vascular system
how does water enter the plant?
- enters through the root hairs of the root
Are xylem cells dead or alive cells?
- xylem cells are dead at maturity, while phloem is made of live cells
Describe the difference In structure between vessel elements and tracheids?
- vessel elements: short, wider (perforation plates)
- tracheids: long, tapered
how is water pulled up a plant? what part of the leaf regulates this activity?
- water pulled up through transpiration, and adhesion of cells
- capillary action and weak hydrogen bonds
- stomata in the leaves drive evaporation and pull water up through the plant
describe the parts of the stem
- pith, xylem, phloem, cortex, epidermis, vascular cambium
What makes up the bark?
-phloem, cortex, epidermis
What is the vascular cambium?
Between the outermost layer of xylem and phloem is the vascular cambium, when these cells divide the daughter cell alternates between becoming a xylem or phloem cell.
what does older xylem become? how about younger xylem?
older = heartwood,
younger = sapwood
What causes variation in xylem size? when might xylem be larger or smaller?
- the amount of water available changes the size: expands as more available water
- in spring xylem is larger
- later summer/fall narrower
- changes with water availability
How do you determine the age of a tree?
- count the number of rings starting from the xylem
what are the three cross sections of a stem?
longitudinal radial (middle), longitudinal tangential (side/middle), cross section (horizontal cut)
what is unique about cycadophyta?
- emerges from woody stem
- emergence of leaves from a central base
what do fern fronds emerge from?
- rhizomes
What type of leaves are found on ginkgos?
- megaphylls: multiple veins
Describe pine needles
- needle/scale like leaves of coniferophyta
What kind of leaf are pine needles?
microphyllic
what is the function of endodermis? Hypodermis?
- endodermis: regulates movement of water, ions, hormones in and out of vascular tissue
- hypodermis: provides structural support and prevent water loss
Why are stomata recessed in pine leaves?
- to prevent water loss in harsh climates (wind/dry air)
What are the functions of the leaf?
gas exchange (stomata) and photosynthesis
how do conifers grow so tall?
- vascular tissue and secondary xylem
- determinate growth due to resource constraints
Where are male cones located in the tree?
lower in the tree to prevent self pollination
What do male pollen cones look like? How would you identify them?
What are the leaves called?
- they are small, flakey with pollen on them
- leaves are called microsporophylls
how are gnetophyta similar to angiosperms?
- no archegonia and they have both vascular elements and tracheids
how many microsporangia are on each microsporophyll?
- 2 microsporangia on each microsporophyll
describe the process of pollen formation on the male cone
- microsporophyll = microsporangia = microsporocyte - (meiosis)–> tetrad of microspores
What occurs to the tetrad of microspores?
- each tetrad in the microspore become a winged pollen grain (from 2 prothallial cells and a tube cell and a generative cell)
Is a male cone a strobilus?
yes
What cells make up the male pollen?
- two prothallial cells (non functional, left over), generative cell (forms two sperm cells through mitosis), and a tube cell
How are sperm pollen dispersed? what conditions are they dispersed?
- two air bubbles aid in dispersal by wind
- dispersed in dry, windy conditions
What is the male gametophyte in gymnosperms?
- pollen
when are sperm cells released from pollen?
when the pollen reaches the ovule
how are sperm cells dispersed in bryophytes and seedless vascular plants? what is different in gymnosperms?
- a) in water
b) gymnosperms use wind
where are the female cones found on the tree?
- upper portion of the tree to prevent self pollination
What are the stages of seed development (year 1-3)?
year 1: cones small, at the end of branches
- sporophyte tissue, NOT gametophyte tissue yet
- develops megasporocyte which undergoes meiosis to form 4 megaspores, 1 survives
year 2: gametophyte formation (pollination)
year 3: fertilization/seed development
What triggers the production of the gametophyte in the female cones?
- pollination
Describe the second year cone’s appearance
- larger but the scales (megasporopohylls) remain closed, sometimes with sap attached
Describe the 3rd year cone’s appearance
- scales are open and seeds are dispersed
- two lighter patches on scales are sterile bracts: where 4 megaspores develop only 1 survives and the remaining 3 are degenerated
What are sterile bracts?
- woody megasporophyll
- the two light patches on the bottom half of the megasporophylls: 4 megaspores develop here
what makes up the ovule?
- the ovule is the megasporangium
- megaspore mother cell (megasporocyte) and integument (which becomes seed coat)
- the entire ovule is surrounded by the integument which becomes the seed cot
how does the archegonium form?
- the pollen attaches to micropyle (opening) –> forms 4 megaspores –> 3 disintegrate –> last megaspore develops megagametophyte
Describe the archegonia
- two eggs within the archegonia
- within the megagametophyte
- remits of megaspore
- within ovule (megapsorangium)
- fleshy arms = integument (becomes seed coat)
- two pollen tubes originate at microtubule - grows towards archegonia
What is the ovuliferous scale?
- the woody megasporophyll that the megagametophyte sits on
what does endosporic development for megagametophytes mean?
- megagametophyte develops within the megasporangium
Are there ovaries in pine?
- there is no ovary, only ovules which become the seed
what parts of the ovule is diploid? Haploid?
diploid - megasporangium and integument
haploid: megagametophyte and remaining megaspore
what is the role of the mega gametophyte in the seed?
- provides nutrients to the embryo (the new sporophyte)
Describe the seed that forms?
- two arms = cotyledon (first leaves)
- epicotyl: is the bump between the cotyledon
- radicle: the red spot at the base, developing root
What are the cotyledons?
- first leaves
What is the space between cotyledons called?
- the epicotyl
What is the radicle?
- the red spot at the base of the seed, developing root
Describe juniper berries?
- blue at maturity
- not fruit, fleshy cones!!
what are the four types of branching?
- alternate, dichotomous, opposite, whorled
do gymnosperms have antheridia?
no, the spore produces sperm from the generative cell so antheridia are not produced, only archegonia
- an gnetophytes have no archegonia!!
how are gnetophytes different from the other gymnosperms and similar to angiosperms?
- they have tracheids and vascular tissue AND no archegonia
how many vascular bundles are within a single pine needle?
- two vascular bundles (bean shaped, at the centre)
what are the 10 (!) parts of the pine needle?
- ectoderm, hypoderm, mesoderm, endoderm, vacuole bundle, xylem (the darker cells of the bean), phloem, resin duct, stoma, transfusion tissue
