Plant R+D+G Flashcards
unlike animal development plants dont undergo
cleavage or gastrulation
describe the process of cell division in plants
microtubules align themselves in a paticular orientation
nucleus moves to the middle
cell division occurs
cell plate is formed
preprophase band dictates where the cell plate is formed
how is the 3 dimensinal plant form determined
depends on the orientation and growth rate of the current cells
4 stages of development in a plant
early globular - epidermis starts to form
late globular
heart stage
torpedo stage - group of cells get set apart to become stem cells
what are the two groups of meristem?
shoot apical meristem - stem cells are produced for the shoot
root apical meristem - root cells are produced
the meristem can be described as a ________
strucutre pattern generating machine
how do cells know where they are within a plant
interpret the concentration of a morphogen which changes down a gradient = french flag model
describe why without pin proteins auxin would be trapped in plant cells
IAA (auxin) can be protonated (IAAH) or deprotonated (IAA-)
at normal pH of around 7.2 in the cytoplasm IAA- is favoured
charged molecules cant move across membranes
describe the action of pin proteins
can transport auxin across membranes
- into cell wall and into matrix where pH is 5 IAA- becomes IAAH
- auxin import proteins are involved
move into neighbouting cells where pH is 7.2 again hence is deprotonated
new vascular tissue forms where morphogen level is _____.
high
where are pin proteins formed?
nextdoor to high auxin concentration cells
how is auxin promoted growth self limiting
the growth of an area means the concentration of auxin across that area reduces
what pattern of growth is found to be most common in plants
spiral
where is the primary and secondary mersitems in root
primary at the bottom
pericycle secondary meristem
plant development depends on the distribution of ___________ . which are generated by _____ _____ meristems
secondary meristems
primary apical
axilary meristems have cells arrested in ___
G0
what type of meristems lie within the stem
lateral
what two areas of the stem do stem cells lie in?
vascular cambium - grow and divide for a huge amount of time
corck cambium - generates the tough outer part
what can the meristems in the pericycle form
new lateral roots whic allow the plant to explore its environment
name a plant that forms budlets from stem cells
kalanchoe
where female gametes found iin angiosperms
carpel
male part of an angiosperm is the
stamen
describe the ABC model of flower formation
three gene domains A B and C
where only A is expressed you get a sepeal
where only C is expressed you have carpel
A and B gives a petal
B and C gives a stamen
which transcription factor is required to switch the meristem from making leaves to making a flower. when is it activated?
leafy
signalling between different parts of the organism followed by complex signalling within a tissue
what process occurs in male plants to form microspores and where. then what process forms the sperm nuclei
meiosis
sporangium
mitosis to forms sperm nuclei
describe the process of making female gametes in angiosperms
megaspore undergoes meiosis - 4 daughter cells - 3 die - 1 haploid cell = mega spore then each haploid cell undergoes mitosis to have two nuclei
egg cell and polar nuclei are formed
describe the double fertilisation event that occurs in angisperms
pollen generates two sperm nuclei
1 sperm nucleus fuses with the two polar nuclei - triploid endosperm formation
1 sperm nucleus fuses with the egg - diploid zygote formation
what is important about the endosperm
most grains come from endosperm
what hormmone is activated in seeds to start growth?
alpha amylase
how do plants avoid asexual reproduction?
carpel and stamen may mature at different times
self incompatibiity factors = genotypes on pollen that block germination if they are the same as that of the carpel
where is the embryo kept?
within the seed
what triggers seed germination?
environmental factors
uptake of water leading to activation of metabolism
lots of cell division occurs at the bottom of the root but there is limited ______. where as there is in the zone of elongation there is vey little division but lots of _______
growth
growth
what is the internal hydrostatic pressure of the vacuole called?
turgor
describe the structure of the plant cell wall
cellulose - long unbranced glucose polymer
is connected to pectin - glucorminc acid based polymer
linked together by hemicellulose
cellulose provides high ______ strength to the cell wall. Pectin provides __________ to compression.
tensile
resistance
what chemicals enable the expansion of the plant cell wall and how do they do this?
expansins interact and loosen the inter molecular forces. polymers slide over each other for the plant to grow
describe auxins effect on the cell wall permeability
enzymes controlled by pH, cell wall pH is controlled by proton pumps. proton pump activity is controlled by factors including auxin
describe how the cell wall grows in relation to cellulose
cellulose molecules alligned in different ways
- growth occurs perpendicular to the allignment of the microfibirls
describe how microfibres are controlled by enzyme complexes
emzyme complexes generating cellulose move along the membrane but cant pass the microtubules
- acts like railway tracks by directing their movement
generalised functions of the following - auxin cytokinin - gibberlelin - abscisic acid - ethylene - brassinosteroids
auxin - growth promoter
cytokinin - cell division promoter, senescene inhibitor
gibberellin - growth promoter, seed germinator
abscisic acid - growth inhibitor promote senescence
ethylene - inhibit growth promote fruit ripening
bassinosteroids - inhibit growth
where does gibberelic acid lead to seed growth? how does it do so?
in germination of seeds
- indirect outcome of amylase production stimulating starch breakdown to release sugars for growth
-
plants will move towards _____ and _____ light but away from _____ light
blue and white
red
thigmotropism
touch sensitivity in plantz
seed germination is promoted by _______ light at ___nm. seed germination is inhibited by _______ light at _____.
red - 670
far red - 700
short day plants have a critical threshold of night length under which they _____
will grow
describe phytochrome
consists of two identical proteins joined to form one functional molecule
chromophore - absorbs a wavelngth of light
light receptor that phosphoryolases a kinase enzyme
describe the forms of phytochromes and how you get from one to the other
switches between Pr and Pfr
Pr is inactive
shine red light and it becomes Pfr and is activated - kinase now active
shine far red and becomes inactive Pr form again
describe the signals the phytochrome can send
alters the expression of levels of transcription factor FT in leaves - transported to the meristem to alter fate
how do plants respond to gravity
statoliths at the root tip mediate gravity response
heavy starch granules shift down one side and promote growth
describe the plants response to a biotic factor: a catipillar eating its leaf
catippilar nibbles at leaf
chemical in the saliva causes signal transduction pathway synthesising volatile attractants.
catipillar predators become evolved to follow the volatilies to kill the catapillars
describe how agrobacterium can manipulate a plants development
trasnfers its DNA into plant cells form galls - mass of cells
_____ attractants cause bacterium to get closer to the plant. the bacteria then release _____ factors which are ________ causing the ______ to close
chemo
nod
oligosaccharides
root hairs
what is a signal transduction response
where signals are percieved by a receptor and passed on
list the order of plant evolution
charophyceans bryophytes pteridophytes gymnosperms angiosperms
higher plants have a ______ sporophyte and a ______ gametopjyte
dominant
minor
lower plants have a ______ sporophyte and a _____ gametophyte
minor
dominant
how large is the gametophyte stage in angiosperms
8 cells surroned by sporophyte tissue
eggs come from the _________ and sperm from the _______ in ferns
archegonium
antheridium
three bits of evolutionariy evidence for conservation of the development of stomata
moss and arabidopsis have the same transcription factors
mutation of homologus genes in distinct lines leads to similar phenotypes
swapping gene of moss to arabidopsis gives normal phenotype
evidence for the root hair being evolutionariliy conserved
RHD like gene from a bryophyte into angiosperm mutant without root hairs restores root hairs
use duckweed to describe why asexual reproduction can be advantegous
rapid reproducing - double in less than 30 hours
take up all the sun on the pond and outcompete
