Plants IV Flashcards
Angiosperm defining features
- flowers
- double fertilization to make endosperm
- seeds covered by mature flower tissue (ovary)
When did they come about? and from where?
- maybe seed ferns?
- oldest fossils from 125 mya
Differences in Angiosperm when compared to gymnosperm
- gametophytes
- 2x fertilization
- ovule
- x/p
- reproduction in general
- reduced gametophytes (7 celled f) (2-3 celled m)
- endosperm
- 2 integument layers
- vessel elements in primary x and companion cells in p
- cheaper and faster reproduction
Whorls
Sepals = outermost whorl– sometimes green – called a calyx when fused
Petals = 2nd whorl – colored if animal pollinator – called a corolla if fused
stamen = fused microsporangia (anthers) supported by stalk (filaments)— can be fused to each other or to petals
pistil = central structure made of one or more carpals (leaves with ovules) rolled into tubes – stigma, style, ovary
Anfiosperm common ancester with gymnosperm
- super ancient
- not an offshoot of any one particular group of gymnosperm
Amborella trichopoda
- most primitive angiosperm
- dioecious, small, unisex flowers with spiraled parts
- no vessels
Regular vs Irregular
Complete vs Incomplete
Perfect vs Imperfect
- regular = whorls are similar size/shape
- complete = have all 4 whorls
- perfect = has stamen and pistil
Hermaphroditic angiosperm
-has perfect flowers
monoecious angiosperm
imperfect flowers, but have staminate and pistilate flowers
-begonia, corn, pine
dioecious angiosperm
plants have only staminate or pistilate flowers
-holly, wilow, ginkgo
pollen development
- happens inside anthers
- tapetum cells nourish the spores and then degenerate
- microspore mother cell makes 4 microspores
- microspores divide 1x to make 2 celled gametophyte (1 tube cell and 1 generative cell)
- mature pollen is brought to stigma by animal or wind
- germinates and grows pollen tube to carry sperm to ovary
Female gametophyte
- develops inside ovule in ovary
- comes from 1 megaspore
- 3 mitotic divisions forms 7 celled female gametophyte (embryo sac)
- 2 polar nuclei migrate from either end into the center
- 3 antipodal cells go to end without micropyle
- 2 synergid cells border egg cell
- 1 egg cell
pollination
generative cell divides to form 2 NON FLAGELLATED sperm cells
double fertilization
- 1 sperm fuses with egg to form zygote
- 1 sperm fuses with polar nuclei to form endosperm nucleus
- nucleus dvlps into endosperm
angiosperm seed parts
- seed coat (2n) = remnants of integument and nucellus of parent sporophyte
- endosperm tissue (3n) = serves as food supply for embryo
- embryo (2n) = daughter plat of adult sporophytes
How do angiosperms save energy during reproduction?
- smaller gametophytes
- can abort seed/fruit if resources are limiting
legume seeds
embryo food is stored in cotelydons
-usually no endosperm at maturity of embryo
Grain and coconut seeds
abundant endosperm
monocot seed
- zea (corn)
- outer wall (pericap) = fused seed coat and fruit wall
- extensive endosperm
- embryo with single cotyledon
Evolution of endosperm
- double fertilization in gymnosperm makes 2 embryos which are fed by female gametophyte
- double fertilization in basal angiosperm makes a 2n embryo and a 2n endosperm
- double fertilization in derived angiosperm makes 2n embryo and 3n endosperm
basal angiosperm vs derived angiosperm
- basal have 4 celled female gametophytes and 2n endosperm
- Amborella has 7 celled female gametophyte and 3n endosperm even though its basal
benefits of endosperms
- energy efficient: smaller/less costly than gymnosperm female gametophytes –> also made later
- flexibility : can abort ovules they can’t afford to mature, but gymnosperm have to commit to maturing their female gametophytes
Trends over time in land plant evolution
- increase in size of vascular plants
- increase in protection of reproductive tissue
- Reduction of gametophyte size of vascular plants
