Gymnosperms Flashcards
What are the four types of gymnosperms?
- conifers
- gnetophytes
- ginkgo
- cycads
What is the name for the bundled structure of pine needles?
fascicle
What is the hypodermis?
layer of secondary celled tissue before epidermis that limits water loss
What is transfusion tissue?
tissue around vasculature that supports exchanges between mesohyll and vascular bundles
What is the mesohyll?
the bulk of volume in the leaf which is photosynthetic and can contain defensive chemicals like tannins
What are resin ducts?
hollow openings made up of living cells that release resin as a chemical defense
What sexual system are most conifers?
monoecious (have both male and female cones/strobili)
What cells are in the immature and mature microgametophyte (male cone)?
immature
- 2 prothallial cells
- 1 tube cell
- 1 generative cell
mature
- 2 prothallial cells
- 1 tube cell
- 3 sperm cells
Where does the pollen go once caught in a pollination droplet?
into the micropyle (female cone)
What are the three components of a seed-scale complex?
- ovule
- bract
- ovuliferous scale
What are the stages of ovule development?
- megasporocyte (2n) undergoes meiosis to form a megaspore (n)
- the megaspore (n) divides to produce the female gametophyte (n) as a pollen tube forms from a pollen grain into the sporangium
- sperm travels into the ovule and fertilizes the egg to create a zygote
Describe the general characteristics of a cycad
- stout stems surrounded by previously shed leaves
- fern-like pinnate leaves
- vascular bands around a large empty pith
What special roots do cycads have?
coralloid roots - contains N-fixing bacteria and grow against gravity (upwards in soil)
What sexual system are cycads?
dioecious (separate male and female parts)
What features do male and female cycad strobili have?
male = fleshy
female = can be feathery or closed/armoured
What is unique about gingko leaves?
they have fanlike veins with no central vein and are deciduous
What are the pollen cone and ovule of ginkgos like?
pollen cone = catkin-like collection of microsporangia
ovule = no female cone but forms a berry-like integument
How are gnetophores similar to angiosperms?
- strobili resemble clusters of flowers
- xylem have vessels
- no archegonia in female gametophytes
What are the three groups of gnetophores?
- welwitschia
- gnetum
- ephedra
