The timing of angiosperms Flashcards
Describe angiosperm characteristics
- stigmatic pollen germination (pollen tube growth through carpel tissue)
- stigma/style/ovary (carpel)
- seeds (ovules) enclosed in carpel
- carpel(s) becomes the fruit
- ovules bitegmic
- bithecate
- highly reduced gametophytes
- pollen mostly tectate/columellate
- phloem and companion cells derived from same mother cell
- mostly vessels rather than tracheids
Bithecate
- two thecae
- 2 sporangia in each thecae
Describe the pollen grain of an angiosperm
- nucleated vegetative cell
- exine
- pore
- 2x gametes
Describe pollen apertures
- monosulcate
- tricolpate
bitegmic
two integuments
Describe Dicotyledons
- two cotyledons in embryo
- primary root persists as a strong taproot, with similar secondary roots
- herbaceous or woody
- tricolpate pollen
- ring of vascular primary bundles with cambium; secondary growth in stem diameter
- stem differentiated into cortex and stele
- net-veined broad leaves (seldom sheathing)
- petiole bearing stipules
- flowers: 4s or 5s
- 78%
List some Dicotyledons
- buttercups
- carnations
- magnolias
- water lilies
- cacti
- Leguminosaea
- Asteraceae
List some Monocotyledons
- grasslike flowers
- petaloid monocots
- palm trees
List some grasslike flowers
grasses, sedges, rushes
List some petaloid monocots
orchids, daffodils, tulips, hyacinths, snowdrops
cotyledons
seed leaves
tricolpate
having three furrows or pores
net-veined leaves
pinnate or palmate
petiole
stalk
Describe Monocotyledons
- one cotyledon in embryo
- endosperm likely
- primary root has short duration (replaced by adventitious roots; fibrous or fleshy bundle system)
- mostly herbaceous (few arborescent)
- monocolpate pollen
- numerous scattered vascular bundles; no definite arrangement in ground parenchyma
- cambium only exceptionally present
- no differentiation into cortical and stelar regions in stems
- leaves parallel-veined; oblong or linear and sheathing at the base
- petiole seldom developed
- stipules absent
- threes or multiples petals
Describe Magnoliids - the basics
Dicots with monocot pollen
Summarise angiosperm phylogeny
- extant gymnosperms
- ANA
- monocots
- Ceratophyllaceae
- Chloranthaceae
- magnoliids
- eudicots
ANA
- Amborellaceae
- Nymphaeaceae
- Austrobaileyales
When did angiosperms radiate?
- Cretaceous
- 0-75%
Describe pollen grain indicators
- more widely dispersed
- occur in greater quantities
- higher preservation potential in a wider range of sediments
- directionality
Summarise the angiosperm fossil record
- 144Mya: K-T boundary; no evidence
- 135Mya: Valangian/Hauterivian; monosulcate pollen
- 125Mya: Barremian; triaperturate pollen
- 120Mya: Barremian/Aptian; leaves, flowers, carpels
Describe the Cretaceous origin of angiosperms
- rapid rise in angiosperms
- steady increase in species numbers
- stepwise increase in the number of morphological types
- fossil record congruent with tree
- absence of angiosperm pollen in pre-Cretaceous rocks
Describe the congruence between fossil record and phylogenetic angiosperm tree
monosulcate magnoliid dicots appear first in fossil record, magnoliid flowers also present
Describe Axelrod’s Hypothesis
Upland Hypothesis