Roots: Plant Structure and Function
Summary
TLDRThis lecture delves into the structure and function of angiosperm plant bodies, focusing on the interdependence of the shoot and root organ systems. It explores the three primary root functions: anchoring, nutrient absorption, and gas exchange. The lecture distinguishes between taproot and fibrous root systems, emphasizing the role of root hairs and mycorrhizae in nutrient uptake. It also touches on root modifications for storage and support, and their economic significance in food, medicine, agriculture, and more.
Takeaways
- πΏ Angiosperms, or flowering plants, have two organ systems: the shoot system (above ground) and the root system (below ground).
- π± The root system performs three main functions: anchoring the plant, absorbing water and nutrients, and storing food.
- π Eudicots have a taproot system with a main root and lateral roots, while monocots have fibrous roots that branch out immediately from the stem.
- π± Roots absorb essential minerals like ammonium and phosphate ions, which are crucial for plant growth and nitrogen cycling.
- π³ Mycorrhizae, a mutualistic relationship between fungi and plant roots, aid in the absorption of phosphate ions.
- π§ Roots are responsible for taking up water and oxygen from the soil, with oxygen being vital for cellular respiration.
- π± Root hairs increase the surface area for absorption, allowing for more efficient uptake of water and minerals.
- π¦ The vascular cylinder in roots contains xylem and phloem, which transport water and nutrients throughout the plant.
- π± Some roots are modified for storage, holding starches and sugars that can be used by the plant when photosynthesis is not occurring.
- πΏ Roots exhibit indeterminate growth, meaning they can continue to grow as long as resources and conditions are favorable.
- π± Roots have adaptations like aerial roots in epiphytes, and some roots are parasitic, stealing nutrients from other plants.
Q & A
What are the two main organ systems in plants?
-The two main organ systems in plants are the shoot organ system and the root organ system.
How are the shoot system and root system of a plant interdependent?
-The shoot system and root system are interdependent because the root takes in products and/or makes products that are important for the shoot system, and the shoot system makes and transports products that are important for the root organ system.
What are the three main functions of roots in plants?
-The three main functions of roots in plants are anchoring the plant, absorbing water and nutrients, and food storage.
What is the difference between a taproot and a fibrous root system?
-A taproot system has a main root with lateral roots coming off of it, typically found in eudicots. A fibrous root system has roots that branch out immediately from the stem without a main root, typically found in monocots.
Why do roots need to absorb oxygen from the soil?
-Roots need to absorb oxygen from the soil for cellular respiration in their cells, as they require oxygen to produce ATP.
What is the role of mycorrhizae in plant roots?
-Mycorrhizae are mutualistic relationships between fungi and plant roots that aid in the absorption of phosphate ions, improving the plant's nutrient uptake.
How do root hairs contribute to a plant's ability to absorb water and minerals?
-Root hairs are extensions of the plasma membrane in root cells that increase the surface area for absorption of water, minerals, and other nutrients.
What is the purpose of the vascular cylinder in roots?
-The vascular cylinder in roots contains the xylem and phloem tissues, which are responsible for transporting water, minerals, and sugars throughout the plant.
How do plants regulate the absorption of water and minerals into their roots?
-Plants regulate the absorption of water and minerals through selective transport proteins in the root hair cells and the presence of a waxy, hydrophobic Kasparian strip that prevents unregulated movement of water and minerals into the xylem.
What are some economic roles of roots in agriculture and industry?
-Economic roles of roots include being a source of food (e.g., carrots, beets), ingredients for herbal teas and medicines, materials for dyes, and their use in crop rotation to replenish soil nitrogen.
Outlines
πΏ Overview of Angiosperm Plant Body
The lecture introduces the structure and function of flowering plants, focusing on the interdependence of the two organ systems: the shoot and root systems. The shoot system, typically above ground, and the root system, typically below ground, exchange products crucial for their survival. The lecture will explore each organ's structure and how it facilitates its function, such as leaves, stems, and roots. Roots are highlighted for their three main functions: anchoring the plant, absorbing water and nutrients, and storing food. The structural differences between eudicot (taproot) and monocot (fibrous roots) plants are discussed, along with the role of bacteria in nitrogen fixation and the absorption of minerals like ammonium and phosphate ions.
π± Root Functions and Absorption Mechanisms
This section delves into the root's role in water and nutrient absorption, emphasizing the importance of root hairs for increasing surface area. It explains how roots absorb water and minerals through both symplastic and apoplastic pathways, regulated by the selective permeability of the plasma membrane and the presence of the Casparian strip. The lecture also touches on the mutualistic relationship between plants and mycorrhizal fungi, which aids in phosphate absorption. Additionally, the physical structure of roots, including the vascular cylinder with xylem and phloem, is described, highlighting the differences between eudicot and monocot roots.
π± Growth Patterns and Hormonal Regulation in Roots
The paragraph discusses how plants exhibit indeterminate growth, which is influenced by resources and the plant's structure. It explains primary growth occurring at the tips of roots and shoots through apical meristems, which are regions of stem cells. The process of cell division, elongation, and differentiation in roots is described, leading to the formation of root hairs and the connection to the vascular cylinder. The response of roots to gravity, known as positive gravitropism, is attributed to the hormone auxin, which affects cell elongation. The paragraph also introduces various modifications of roots, such as aerial roots in epiphytes and adaptations for parasitic plants.
π³ Economic and Ecological Roles of Roots
This section covers the economic importance of roots, including their use as food, in the production of herbal teas and bitters, and as a source of various medicinal compounds. It also discusses the role of roots in agriculture, particularly in crop rotation for nitrogen replenishment and in preventing soil erosion. The paragraph mentions the use of roots in dye production, such as red root and smooth sumac, and in the creation of soap from saponin-containing roots. The lecture concludes by emphasizing the significance of understanding roots' economic roles for various applications.
π Summary and Learning Resources for Plant Roots
The final paragraph serves as a summary, reminding students to review the provided packets and notes to gain a comprehensive understanding of plant roots. It suggests that the information covered in the lecture is essential for learning about the various aspects of roots in plants.
Mindmap
Keywords
π‘Angiosperm
π‘Organ System
π‘Taproot
π‘Fibrous Roots
π‘Vascular Cylinder
π‘Root Hairs
π‘Mycorrhizae
π‘Nitrogen Fixation
π‘Growth from Tips
π‘Gravitropism
π‘Economic Roles
Highlights
Plants have two organ systems: the shoot organ system and the root organ system.
The shoot organ system is typically above ground, while the root organ system is below ground.
Roots and shoots are interdependent, with each providing essential products for the other.
Roots have three main functions: anchoring, absorbing water and nutrients, and food storage.
Eudicots have a taproot system, while monocots have fibrous roots.
Roots absorb minerals, such as ammonium and phosphate ions, which are essential for plant growth.
Nitrogen fixation bacteria in soil nodules help plants obtain nitrogen.
Mycorrhizae, a mutualistic relationship with fungi, aid in phosphate absorption by plant roots.
Root hairs increase the surface area for absorption of water and minerals.
Roots have a vascular cylinder containing xylem and phloem for transport of water, minerals, and sugars.
Water and minerals enter plant roots through regulated channels and transport proteins.
The Casparian strip, a waxy layer, regulates the movement of water and minerals into the xylem.
Some roots are modified for storing organic nutrients like starch and sucrose.
Plants exhibit indeterminate growth, growing from their tips as long as resources are available.
Root growth occurs at the apical meristem, with cells differentiating into various root structures.
Roots respond to gravity through positive gravitropism, aided by the hormone auxin.
Aerial roots are adaptations for plants like epiphytes that absorb water and nutrients from the air.
Parasitic plants use roots to steal nutrients from other plants.
Roots can be modified for support, such as buttress roots in certain tree species.
Roots have economic importance, including as food sources (e.g., carrots, beets) and in agriculture for crop rotation.
Roots are used in the production of herbal teas, medicines, and dyes.
Transcripts
okay this is a lecture about the
angiosperm plant body so we're looking
at flowering plants and specifically
structure function I think we're gonna
have a lecture for each of the organs
and so let's look at that overall so we
know there's an organism and then the
grouping or the category which I say the
next level of organization under an
organism is the organ system so plants
have two organ systems the chute organ
system and the root organ system
typically the chute organ system is
above ground and the root is below
ground but that's not always true
they're interdependent meaning that the
root takes in products and/or makes
products that are important for the
shoot system and the shoot system makes
products take some products the
transports products that are important
for the root organ system so there's all
kinds of labels on here you just want to
know this it's pretty straightforward
and we'll look at them as we go through
each of the organs but here are the
three main organs the leaf organ the
stem organ and then the root root organ
here roots have I'm classifying it into
three major functions and we'll see how
the structure of roots facilitate the
function so the first function is to
anchor vascular plants and they absorb
water and nutrients large part minerals
which are metal ions from the soil you
also see in a minute that roots are
going to actually take up oxygen from
the soil because they need that for
foetus that excuse me for cellular
respiration in their cells
so yes roots quote-unquote breathe I
wouldn't call it that because breathing
is an active process but these are they
do gas exchange and then also food
storage some roots are modified for that
so let's look at anchoring let's just
look at two main types of roots in
general the eudicots or you can call
them eudicots that's one group of
flowering plants it is the most
widespread and diverse of the the
angiosperms today they have what's
called taproot so we have a main route
here and then we have lateral roots
coming off of it and then you have subs
lateral roots coming off of that
and a monocot which is another type or
another group of angiosperms have what
we call fibrous roots so you can see at
the end of the stem and this would be
the part below ground
the leaves are excuse me the roots just
come off the stem and then they branch
out right away they don't have this main
root and you can see here that fibrous
part I do have to say that I have dug up
plants in the yard before and I know
they're eunuch offs because of their
leaves and other and they're poking of
flowers and all that but they have
fibrous roots sometimes Woody fibrous
roots which is you'd expect woody to go
with you dicots and so what I discovered
is that if you grow a eudicot plant from
a cutting so sometimes with plants you
can cut part of a parent plant and then
grow it into a new plant if you do that
most of the time are often it will form
fibrous roots the new plant so this
going for the seed is when you get the
tap root so anyway do you ever pull up
planting like I did this with hibiscus
once and I was like I know hibiscus
isn't you dicot why does it have fibrous
roots or at least structure of fibrous
roots not a tap root and that turned out
to be what second function roots
absorbing water and minerals from the
soil so the minerals themselves are
things like ammonium ions and phosphate
ions we're looking at ions here and part
of what is the cycling in the
environment that plants are really
important for here is nitrogen so in
order for animals to get nitrogen they
can't take it up directly they have to
eat a plant or eat something that ate a
plant and where did the plants get their
nitrogen they get it from absorbing it
from the soil or they can get it from
these bacteria in the nodules so the
soil is going to have nitrogen
being formed into products that the
plant can absorb by bacteria the
nitrogen fixation bacteria and then the
ammonification nitrification
so all those bacteria that live in the
soil and there's other groups that the
types of bacteria like rhizobia we
talked about that in the bacterial
section that live in these little
nodules on certain types of plants and
those bacteria fix nitrogen in there why
would they need new nitrogen they need
for nucleic acids and this is true of
all organisms all organisms have to
build RNA and DNA chaff the nitrogenous
bases and they have to build proteins
which are made of amino acid subunits
which have amino groups which have
nitrogen in them then you need phosphate
atoms for ATP triphosphate and nucleic
acids again your DNA and RNA have
phosphate groups and then the absorption
of those is aided by mycorrhizae so the
mycorrhizae or remember is this
mutualistic relationship between the
fungus you can see that here and the
root the root cells and you can see the
fungus branches into the root the fungus
helps the plant absorb phosphate ions
better so that's a mutualistic
relationship so we have both of those
water is also brought in through the
roots for the plant so when you water a
plant you watering the leaves is not
going to do anything if it's really hot
out it might cool the leaves down which
could be helpful just the water
evaporation taking away the heat but
it's not going to be able to get water
in through its leaves it has to get
water in through the roots and so that's
why you water the soil instead of the
leaves of a plant and then you can see
also like I mentioned oxygen is coming
into those roots for cellular
respiration in the mitochondria because
every cell in the plant that's living
does cellular respiration to make ATP
and then co2 is a byproduct of cellular
respiration and in the roots because
there's no photosynthesis it's not used
up there it's just released into the
environment
we also have a physical structure called
root hairs then sir root hairs are these
cells that have an extension of the
plasma membrane so you can see all these
circles are our individual cells and
these ones just have a long extension
and what that does is it increases
surface area for absorption of water
minerals and that would be across the
membrane through channels and
transporters but the root hairs they're
so little it doesn't have very much
volume so it doesn't actually require
much more energy and resources to
maintain but it gets you a lot more
absorption but the thing to note about
the roots is that first of all they have
what we call a vascular cylinder so the
vascular cylinder in both of them you
can see is in the middle vasculature
refers to the types of tissue that move
things around the plant just like our
like our cardiovascular system is you
know what you're looking at the heart
and then all the blood vessels in this
case their version of vessels are the
xylem carrying water and minerals from
the root and the phloem which is
carrying sugars primarily and that's
going to the root we'll see where that's
made later this is basically taking a
root and you've cut it and now you're
looking down on it
so the vasculature is in the middle in a
route you dicot has its asylum in the ex
shape which is convenient so it has
these and then the phloem is around the
arms of the xylem
whereas the monocot root has a ring of
xylem and phloem okay so you just want
to be able to identify that if I gave
you a picture of a cross-section which
is a monocot which is a you die pod is
it a root is the stem the point of this
I'm not going to be too detailed about
it at least unless I let you know
differently is that the ranking there's
regulation of what goes into a plant
water can't water and minerals can move
two different ways one is actually going
into the root hair into the cytosol and
being transported through the
plasmodesmata between cells until it
gets to the xylem and so this growing
across the plasma membrane means it has
to go across in a regulated way because
the only way to get in is by going a
mentioned through channels and transport
proteins and their selective right so
that's the regulation however there is
another way that water and minerals can
get into a plant root so it's actually
it's called a plastic and what it is is
that it kind of travels along the cell
walls and the hydrophobic or the scuse
me the hydrophilic characteristic of the
cellulose and the water can hydrogen
bond together and so it can travel
between the cells really and so that's
not selective so in the end though in
order to have selectivity there's this
strip of waxy material and it's in
between all the cells so this is
actually wraps around the whole cell and
waxes are lipids and lipids as we know
are hydro phobic so that means when the
water and minerals get to this Kasparian
strip the waxy layer they can't get
through hydrophobic hydrophilic and so
then they are transported or or shunted
into the cell and then have to go if
they get in across the membrane and then
there's more regulation and so it's
actually in the end it never just gets
to go into the vasculature unless it
goes through some transport proteins
the third function I mentioned was that
some routes are modified to store
organic nutrients and by organic
molecules
I pretty much mean starch which is a
polysaccharide type carbohydrate and
then the plant can access that starch
and break it back down into glucose
monomers in order to use it later when
maybe it's not doing photosynthesis and
making those carbohydrates all the time
there's also some storage of the sucrose
itself that's why you can get you know
sugar beets sugar is the sucrose and
carrots are a little bit sweet it's also
Oh like when you cook beets if you cook
them like by cutting them up real small
they get caramelized it's very sweet and
that's because there are those those
sugar storage in there it's also why
nutritionally you have to consider root
vegetables pretty much a carbohydrate
and a carbohydrate that can be used in
humans for energy also why if you're
somebody who's diabetic you have to take
into account like a carrot is not like
eating a lettuce leaf lettuce leaf is
mostly cellulose carbs those don't we
can't break those down but a carrot has
the carbohydrates we can break down into
glucose in the form of starch you're
trying to make sure your glucose stays
at a certain level you do have to
consider the glucose that will come from
eating a root vegetable like carrot so
plants only grow from their tips tips of
the chutes which are the branches and
the main stem and the tips of the roots
and that's how they get longer so
primary growth is growing longer just
some terms and some interesting things
so determinate growth which is what we
think of usually animals because we are
one there basically means the organism
grows to a certain size and then that is
the life you know that's the adult
version of the organism and then it just
stops
so that's determinate plants exhibit
indeterminate growth it's dependent upon
resources and structure of the plant but
they can just keep
as long as they have those resources and
space and the structure to keep it
oriented correctly so they would just
keep growing from the tips and you might
hear these terms when you do gardening
so annual plants mean that they go from
seed to seed so they're grow from the
seed and produce seeds themselves in one
year biennials would be completing life
cycle in two years and then perennials
would live for many years so perennials
are the ones you plant in your garden
and then they look like they die or they
go away but then they'll come back the
next year our basis plants all monocots
some new dicots
what that means is that they are not
woody so they're real you know bendy
type stems they look green versus woody
stems some you dicots and this is also
for roots too ok so primary growth I
mentioned it's just at the tips all
growth in plants happens at regions of
stem cells so these meristem so though
named meristem the word there so stem
cells so the meristem is where these
stem cells are located apical so you can
think of I'm not sure if you're familiar
being Mike Smith you might know the word
apex a PE X apex which is like the apex
of a mountain is the top of it so apical
meristems are the mara stands at the
tips these are ones on the roots where
the purple is showing and so the roots
only grow from the tips you probably in
bio one looked at onion root tips
because there was mitosis to see cell
division so why is there cell division
that's where the stem cells are so
you've got a root cap on the end that
helps protect the root as it's pushing
through soil then you have the region of
division which makes sense because as it
divides it's just going to grow from the
tips so it has the dividing cells and
then elongates then they differentiate
and you can see like for example become
a root hair cell lateral
actually they're gonna have to connect
to the vascular cylinder right because
that's where all the water minerals go
into the rest of the plant also where
the food comes down into the root and so
what it actually does is it grows out of
the vascular cylinder pushes through and
then you have a lateral root and it's
connected with xylem and phloem there
and this is a cool picture here you can
see the vascular cylinder here it's a
root and you can see the attachment of
this lateral root 2 that vascular
cylinder so the plants grow down through
the tips they can also grow laterally
but it's still through tips how to roots
know where to grow they respond to
gravity so positive gravitropism means
it grows towards the direction of
gravity and so you can see here here's a
root growing sideways and if you left it
that root would curb down to grow
towards gravity and why does that happen
that happens because of hormones so if
you recall hormones are like ants or
ligands that are produced in one part of
an organism and then travel to another
part of an organism or even outside of
the organism and work there
remember the ligand or ligand is the
signaling molecule and then just recall
with signaling the ligand binds the
receptor and that's reception then
there's a bunch of molecular steps that
happen in between called transduction
and then something in the end happens we
call it a cellular response how do the
roots detect gravity there's certain
types of cells with the saddle lifts in
them which are like sacs of membrane and
I bleed they're usually filled with
starch but we got these sacs here and so
this root has been turned on its side
okay so this root has been turned like
this on its side and so what happens the
saddle lifts fall in the cell in the
cytoplasm and they end up on the side of
the cell where gravity is and in a root
there's a hormone in it's in other parts
of the plant but the hormone that I'm
going to concentrate on here are the
auxins so auxins job when it's in
relatively low concentrations it
stimulates cells to elongate and if you
have it in high concentrations it
inhibits the cells from elongating and
if you have no oxen it's not going to
elongate either so what happens is that
the falling of the Stata ellipse induces
a difference of toxin production so the
side that's away from the stat ellipse
basically this side of the root is going
to end up with lower aux-in so auxin
will turn on but not too much so that
makes the cells on that side get longer
the concentration on this bottom side
here towards gravity has a lot of
options so it's a high concentration
which means the cells actually don't
elongate so if you have cells elongating
on the top and not the bottom and so
that bends the route towards gravity and
that's why even if you turn a plant
upside down the roots will turn around
if you will and grow towards gravity so
here's some modifications of roots so
there's some roots that are outside of
soil so we call these epiphytes epi
means on top of fight is going to be
plants
phyto plant or plant like so epi fights
are plants that live on top of other
plants or they could live like on a
power line or something and so they have
roots called aerial roots you can see
those here in orchid that's a classic at
the fight and here's this aerial roots
and so basically they are going to
absorb they still absorb the water they
just have to do it through water vapor
epiphytes don't hurt the plants then
there's also adaptations for nutrition
parasitic plants will live on other
plants or other organisms and they
basically steal their new tree
so mistletoe ironically even though it's
a you know winter Christmas holiday I
love you thing is actually a parasitic
plant that kills the plant it's growing
on and it doesn't look like Halle
Berry's either look up what mistletoe
looks like it's totally different than
what you probably think in any case it
does do photosynthesis but it's gonna
steal the nutrients from that plant then
you have some very unusual plants though
that don't even do photosynthesis they
get all their carbon from being a
parasite on other plants there are other
organisms don't we talked about storage
roots that's an adaptation to store
starches and sugars until later we have
modifications for supporting plants some
of these are angiosperms and some are
gymnosperms the buttress roots you can
see here few different types of trees
and in fact if you look around houston
we have them all over the place there's
cypress trees these are very large but
reserves
obviously that's a person and they are
kind of sheets that come out from upper
up on the trunk so their roots part of
its above ground which is you know more
unusual and they are going to help
support that tree from falling over
typically that's because it's in some
sort of boggy so like you'd see in
either of these there's also a type of
root similar function called prop root
Corrin has it it's a hollow tree in
Hawaii
you also have roots that help plants get
oxygen or probably this is probably
their function so they're new metaphors
pneumo is always meaning like lung it's
gonna be the the oxygen gas exchange
might have also heard them called knees
so mangroves are classic new matter for
plants cypress trees besides the
buttress roots they also have no matter
force for probably gas exchange up here
so all of these are just extensions of
parts of the roots of all these other
trees of all the trees
there's also roots that can grow around
plants so often you see stem
growing around other plants but roots
can do it too some of them are strangler
roots which means they kill the host in
the end and often they'll kill the host
and then they have the structure now of
the host basically and they'll just
exist because they can stand up now you
might also see them growing on buildings
they're quite destructive and then we're
looking at economic roles that's
something important I will ask you about
tell me some economic roles of each stem
or each organ in plants so food so you'd
want to know
food examples of roots carrots beets
sugar beets sweet potato not yam yam and
sweet potatoes are different sweet
potato though radishes turnips parsnips
tapioca cassava we also have drinks to
Zayn's or tis ons are we call them
herbal tea and some of those are made
with roots like if you look on herbal
teas you'll see often it says this root
mark mallow root and valerian root and
all that kind of stuff
bitters that you might use in alcoholic
beverages are primarily roots some types
of medicine sort of alternative
medicines or supplementary medicines
some of which have supported function
and some of which don't but they're you
know people use by a lot of these so
it's monetarily important so health
supplements like ginseng is a root it's
supposed to give you energy I don't
think there's a lot of evidence for that
one licorice root though can help with a
twith the pain so cough drops to soothe
the pain in the throat might have
licorice root in it - thanks there are
teas with licorice root in it that are
supposed to be for sore throats and
stuff and then if you look at essential
oils a lot of those are roots as well
like valerian is a classic one and those
are used for a variety of purposes some
of which are useful and some of which
are perhaps not supported
you just have to be careful with that
then we also have economically
agriculture you can't just say roots are
part of plants we grow plants because
their crops and so roots are important
that's know but you can specifically say
roots the ones from legumes or clovers
that have the nodules can be important
in crop rotation and so that's because
it replenishes nitrogen to the soil
which then the next year when you plant
different crops it has nice it has
nitrogen in the soil so it's good for
that next round of crops of food for
grazing livestock ie like grasses and
then grasses because of those fibrous
fruits also help with erosion prevention
so if you're having problems with you
know parts of your yard or or river bank
of roading plant some grass on there and
you can keep that alive it'll help
prevent the erosion which is important
there also dies if you're going to use
die as an example in your on your exam
you need some specific examples of die
because pretty much every plant part can
probably you used for a die you cannot
use it for all five plant parts but in
this case we have a red matter root and
smooth sumac for black those have been
used in the past to dye things you can
also make soap ingredients out of roots
so saponin are like surfactants their
soap type molecules and so you cough can
be used for that supports I have some
pictures of that here so so we've got
soapwort plants so now you should have
enough information to fill in any
packets or notes that I've given you to
learn about the plant roots
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