BIO
201: Botany
DIVISION ANTHOPHYTA: FLOWERING PLANTS
Most abundant group of plants in terms of # species
UNIQUE CHARACTERISTICS
1.
presence of a complex reproductive structure = FLOWER
2.
protection of the female reproductive structure in an OVARY
as seeds develop protected in same structure
= FRUIT
3.
two fertilization processes
one to produce the ZYGOTE ----> EMBRYO
second to produce TRIPLE FUSION NUCLEUS ---->
ENDOSPERM
4.
complexity of vascular tissue – several types of xylem
water transport tissue
REPRODUCTIVE STRUCTURE
Reproductive structure = FLOWER (an organ)
commonly see both sexes together in the same flower
Axis on which the flower parts are attached = RECEPTACLE
Four WHORLS (parts) to a flower
SEPALS – protect the developing flower
collectively called CALYX
typically green, leaf-like
PETALS – attract pollinators (transfer male reproductive
cells to female reproductive cells)
collectively called COROLLA or PERIANTH
typically color related to type of pollinator
STAMENS – male reproductive
filament + anther
4 spore producing chambers per anther = LOCULE
Pollen development:
MICROSPORE MOTHER CELL (2n)
à
(meiosis)
4 MICROSPORES
à
(one mitotic division +
thickening wall)
POLLEN
Diagramatic version of pollen development:
Pollen consists of:
1 generative nucleus
1 tube nucleus
CARPELS – female reproductive
collectively called PISTIL (stigma + style + ovary)
1 to many chambers in each ovary = LOCULE
contain OVULES
one to many OVULES per locule
ovule structure:
integument (surrounding protective layer)
ovule development:
MEGASPORE MOTHER CELL (2n)
à
(meiosis)
3 die
1 MEGASPORE (1n)
à
(mitosis)
8-NUCLEATE EMBRYO SAC
1 egg cell + 2 synergids + 3
antipodals + 2 polar nuclei
Diagramatic version of embryo sac development:
Outcome: 8-nucleate embryo sac:
Flower terminology:
COMPLETE -- all 4 whorls
INCOMPLETE -- lacking one or more whorls
PERFECT -- both stamens & carpels
IMPERFECT -- only one sex
MONOECIOUS -- stamens & carpels on same plant (separate flowers)
DIOECIOUS -- stamens & carpels on different plants
POLLINATION
Pollination = pollen landing on the stigma
Types of pollination:
1. self pollination -
most common on first flowers of season
guarantees some seed production
Ex.: violets (flowers never open)
2. animal pollination (biotic) -
a. INSECTS: typically complete flowers, some imperfect
strong odors or very colorful
beetles - sweet, white (night)
Ex.: night-flowering water lily
flies - rancid, burgandy (day)
Ex.: carrion flower
moths - sweet, white (night)
butterflies - sweet (day)
Ex.: butterfly bush, thoroughwart
bees – colorful
Ex.: sunflowers, most composites
wasps – colorful
Ex.: orchids, amaranths
b. BIRDS: color + smell
hummingbirds - red tubular flowers
Ex.: trumpet flower
c. BATS: sweet smell
greenish corolla, strong odor (night pollinated)
Ex.: numerous tropical plants
3. wind & water pollination (abiotic) -
flowers typically lack sepals & petals
in SC most commonly monoecious plants
Ex.: corn, oaks, hickory, pecan
some are dioecious (not always)
staminate + ovulate flowers
Ex.: some grasses
POLLEN TUBE DEVELOPMENT
pollen germination - pollen tube development
tube grows through style into ovary & to an ovule
opening in integument of ovule = MICROPYLE
during elongation of tube the 2 nuclei migrate
tube nucleus guides development
generative nucleus
à
2 sperm (mitosis)
the two sperm released into the embryo sac
FERTILIZATION
1 sperm + 1 egg à ZYGOTE (2n)
1 sperm + 2 polar nuclei à TRIPLE FUSION NUCLEUS (3n)
process = DOUBLE FERTILIZATION
EMBRYO DEVELOPMENT
Triple Fusion Nucleus
à
ENDOSPERM
rapid mitosis without cell wall formation
Zygote
à
mass of cells (=PROEMBRYO)
basal cells develop into the SUSPENSOR (anchor for embryo)
terminal cell develops into the EMBRYO (next generation plant)
Continued development of embryo to produce tissues:
COTYLEDON -- first leaves ("embryonic leaves")
EPICOTYL -- portion above cotyledon
à
growing shoot
HYPOCOTYL -- portion below cotyledon
à
lower stem + roots
Extent of embryo vs. endosperm in mature seed varies
Types of embryo development
1. only one cotyledon develops = MONOCOTYLEDONS
seeds typically with small embryos & large endosperm
2. two cotyledons develop = DICOTYLEDONS
seeds variable in amount of endosperm
bean seed structure (dicot)
corn seed structure (monocot)
FRUITS
Fruit tissue develops from ovary wall
Functions:
1. protection
a) spines or thorns
b) hard outer wall (pericarp)
2. dispersal
a) wings or fluff - wind
Ex.: tulip poplar, maple, many grasses
b) barbs - stuck to animals, esp. mammals
Ex.: cocklebur, beggar's ticks
c) fleshy - eaten, seeds eventually deposited unharmed
Ex. tomato
d) round, hollow - float on water
Ex.: walnut
Amount of fruit tissue varies from one species to another
little: pea, bean
a lot: apple, watermelon
Review of flower to fruit development:
ovary
à
fruit
ovule
à
seed
zygote
à
embryo (epicotyl + cotyledon + hypocotyl)
TFN
à
endosperm
integument
à
seed coat
ovary wall
à
pericarp
Methods to categorize fruit types:
1) number of ovaries and/or flowers involved
a) SINGLE - one ovary on one flower (tomato, watermelon)
b) AGGREGATE - two or more ovaries of a single flower (blackberry, magnolia)
c) MULTIPLE - more than one flower (pineapple, mulberry)
2) type of flower parts involved besides ovary
a) SIMPLE - only ovary involved
has a superior ovary (note in flower) (tomato)
b) ACCESSORY - ovary + other parts
has an inferior ovary (note in flower) [apple (core), banana, squash]
3) fleshiness
a) FLESHY - wet (tomato, watermelon)
b) DRY - loss of water (pecan, okra)
4) dehiscence
a) DEHISCENT - breaks open at maturity (okra)
b) INDEHISCENT - does not break open (tomato, squash)