Week 12 Flashcards
angiosperm reproduction
sexually to increase genetic diversity
Sexual reproduction of angiosperms
meosis in plants produces spores, after which mitosis produces gametes
cells that form gametes develop into adult organisms
carpels
female sex organ
contains developing female gametophytes
stamens
male sex organs that produce microspores
perfect flowers
both male and female reproductive organs
imperfect flowers
only one male or female organ
monoecious
male and female flowers on same plant
physical separation of male and female flowers or maturation at different times to prevent self pollination
dioecious
individual plants have only male or female parts
cant self pollinated
megametophyte
female gametophyte
embryo sac
arises from megaspore
microgametophyte
male gameteophyte
pollen grains
from microspores
pollen grain - cells
generative cells
tube cells
generative cells
divide by mitosis to form 2 sperm cells
tube cells
forms pollen tube that delivers sperm to embryo sac
wind pollinated flowers
have sticky featherlike stigmas
produce greater number of pollen grains
animal pollinated flowers
increases probability that pollen will get to female gamete of same species
self pollination
reduces reproductive fitness of offspring
self incompatible
pollen from same plant is rejected
endosperm
formed by sperm and polar nucleus
food for developing embryo
integuments
tissue layer surrounding female gamete
develop into seed coat
functions of fruit
protects seed from damage by animals and infection
aids in seed disperal
Annual plants
complete lives within a year
biennial plants
take 2 years, vegetative growth first year, reproductive growth second year
perennials
live 3 or more years
flower every year
inflorescence meristem
shoot apical meristem that produces floral parts
floral meristem
produces single flower
Photoperiod
flowering only occurs when days reach certain length
synchronises flowering of same species promoting cross pollination
short day plants
flower when day is shorter than critical maximum
long day plants
flower when day is longer than critical minimum
phytochrome
located in leaf
recieves signal for flowering by a chemical
florigen
chemical that triggers flowering
passes through plasmodesmata
disadvantages of asexual reproduction
no genetic diversity
advantages of asexual reproduction
parents can pass on good allele combinations
avoids cost of producing flowers
guarantees pollination
apomixis
asexual reproduction of seeds
asexual reproduction
diploid cell becomes embryo and seed
plant pathogen response
constitutive or induced
constitutive
always present
leaves have waxes that prevent fungal spores and bacteria from entering
induced
produced in reaction to presence of pathogen
induced response: elicitors
molecules made by pathogen that trigger plant defence
general immunity
triggered by elicitors called PAMPS
PAMPS
molecules that produced by pathogens
specific immunity
triggered by specific elicitors
bind to r receptors in cytoplasm that trigger specific immunity
stronger than general immunity
Signalling pathways
formation of NO and other reactive oxygen species
polymer decompostion
hormone signalling
changes in gene expression
Pathogen related proteins
break down pathogen cell walls
serve as alarm signals to cells that are yet to be attacked
hypersensitive response
cells around site of infection undergo apoptosis and produce lignin to seal off plasmodesmata and prevent spread
systemic acquired resistance
general increase in resistance to a range of pathogens
herbivore affect
cause physical damage and can spread pathogens
Constitutive defenses: herbivores
leaf hairs, thorns, spines and insoluble salt crystals that damage insect tissue
Chemical defense: herbivores
secondary metabolites
releases canavanine and nicotine
canavanine
replaces insect protein and creates abnormalities in insect
Nicotine
inhibits insect nervous system
jasmonate
triggers defenses to remove herbivore
xerophytes
plants adapted to dry environments
specialised leaf anatomy
trichomes that diffract and diffuse sunlight
aerenchyma
aquatic plants
have large air spaces
stores o2
low metabolism
Halophytes
plants adapted to saline environments
take Na and Cl to central vacuoles
have salt glands that excrete salt
meristems
permenant stem cells that allow growth
post embryonic organ formation
can develop new organs throughout life time
differential growth
resources can be allocated for beneficial growth patterns
dormant
development of embryo stops
photodormancy
seeds require period of light and dark to germinate
thermodormancy
seeds require period of high or low temp
dormancy advantages
ensures survival
results in germination
helps seeds survive disperal
germination
seed grows
imbibition
seed takes up water is coat is permeable
monocot seed development
shoot is protected by sheath of cells
eudicots seed development
shoot is protected by cotyledons
gibberellins
hormone in plant growth
stem elongation
fruit growth
seed germination
Auxin
hormone
root initiation
leaf abscission inhibition (removes old leaves)
ethylene
promotes leaf abscission and ripening of fruit
photomorphogenesis
growth contorlled by light