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We've done some discussion on plant nutrients
what the plant needs for growth and reproduction
we have done some discussion regarding transport of those nutrients within the plants and how they
get them through fertilizers and agriculture and compost and organic farming
but what happens if you're just a plant in the middle of the rain forest?
you might be healthy like our example here
you might have some sort of nutrient deficiency
it might surprise you that while the rain forest is a very biodiverse location
the soils are actually pretty terrible
so what we have to consider is in these extreme environments or environments with
variable environmental factors such as heavy rainfall
drought changes in
the amount of sunlight in given periods
all of these things
we have to take into consideration
so we can understand how plants are surviving so well
in these extreme environments so to speak without the aid of humans
so first of all
when we talk about nitrogen and plants we've mentioned before that nitrogen is actually the
largest limiting factor in plant growth and success
nearly every plant on this planet has nitrogen deficiency
most also have phosphorus (deficiency) but focusing on nitrogen for just 1 minute
I think this is often confusing to folks because our atmosphere is full of nitrogen
so why is it that plants are nitrogen deficient?? don't they just take it out of the atmosphere with
with the carbon dioxide that they need the oxygen that they need to do so respiration
why is it that they are so deprived of nitrogen given this?
well it turns out that plants cannot directly take nitrogen from the atmosphere
they cannot use N2 gas so they are very dependent on
what we call nitrogen fixing bacteria to help them convert that nitrogen into a form they can use
plants actually perfer nitrates
so nitrate as you see over here near our root is actually NO3 so we have to convert N2 atmospheric
nitrogen into NO3 or at least into NH4. ammonium is another way that plants can take in nitrogen and use it fairly efficiently
we actually apply ammonium as a fertilizer
so this is a decent way but if they had their choice nitrates would be a better way for them So you see I have three different types of
bacteria on our diagram here. The nitrogen fixing bacteria are going to be responsible for converting that atmospheric nitrogen for us
into NH3 ammonia and then NH4 ammonium
we also have ammonifying bacteria so they are ones that are actually going to eat
organic materials
decaying in the soils convert that nitrogen in those organic materials or release those nitrogen
in the organic materials into the ammonia and ammonium eventually with the addition of hydrogen
decaying and
dead organic matter
provide it produces quite a bit of ammonia so this isn't a big step for us
but those ammonifying bacteria speed up the process
Nitrifying bacteria are really a plant roots best friend
so these bacteria
are going to take that ammonuium and actually convert it into nitrates and make it an even better form for the plant to take in
so what do you use nitrogen for? ok -- so you gotta think! Where in your system (your body) do you see a whole lot of nitrogen
well we give you a clue here with amino acids
every amino acid in your body is based in nitrogen
what do you use amino acids for?? what do they make up? what is the macro molecule that is made up of amino acids? think about it!
it's a critical critical compound not only for our plants here but also for you
so these bacteria are great but there are a number of plants that have gone above and beyond to
really make sure they have nitrogen available to them
Mycorrhizae are a big factor in nutrient depleted soils! So, mycorrhizae are actually a
fungus that cover the roots of plants before you get too worked up
fungus in this case are not working to decompose the plant remember fungus feed on dead things they are composers
so yes I know you can get athletes fought and it works on your feet and you're not dead
got it! but in this case what we're looking for are these fungal filaments
to actually surround the root much like our root hairs do -- increasing the service area of the rude but what they're really looking to do is help
to collect the nitrogen from the decaying matters in the soil
and make them more available to the plant
this is something we call a symbiotic relationship
symbiosis means both organisms in a relationship are benefiting so obviously the plant
is getting nitrogen we just said that what do you think the benefit of the plant is to the fungus?
what is the plant giving to the fungus to make this
a symbiotic relationship? mutually beneficial. so, think about that
what could that fugus possibly be getting from the plant
the other way that plants may go is to actually produce these nodules and you see these kind of
wort looking things along the roots
turns out that many
plants that produce these
nodules will actually be found in some
nutrient poor scenarios but there is a specific type of plant known as a legume
so you may have heard of legumes before
legumes we often refer to with soybeans. soybeans are terrific example of a
legume that we see in agriculture and has become very popular in recent years with
with the production of soy milk and soy oils and so on
these nodules actually contain bacteria if you look up here on this top image you can see
a TEM or a transmission electron microscopy image of the bacteria inside the nodules. So, what are they doing in there??
well the nodules are acting as a home for the bacteria
the bacteria are actually converting nitrogen from the soils and the decaying matter and making them
very available to the plants because they're connected directly to the roots
why is this so important?? well again this is a
mutualistic relationship. this is a symbiosis. So think! what is the plant getting from
the bacteria?
nitrogen. it's no different than a taking it up from the soils after bacteria converted it but this is a much more direct route if the bacteria that are
converting the nitrogen are actually living in your roots
but what is the bacteria getting from the plant??
think about it
another strange one that we see
are
what we refer to as epiphytes. Now the most common epiphyte that you would likely know is an orchid and orchids are big beautiful flowers
they have huge flower shows dedicated just to the orchid so why am I saying here that they're
an epiphyte which means essentially that they grow off of another plant
well in this case
they actually are just using
those other plants to get better access to minerals and water
so these are orchids are typically found in rain forest type environments
I will show you a picture in just a second of one actually living on a tree but what we want to look at is they have modified themselves so that
their roots do not grow in the soil
orhid roots actually grow on
mosses and on the bark of trees
not that their invasive so much as that they are gaining an advantage of being more closely associated with the rain waters and
minerals that are available at the tops of the canopy and rain forest
Ok?
so another one -- parasitic plants the most common one that you would know off here is mistletoe
we think about mistletoe at Christmas time as being this wonderful
kind of loving symbol around the holidays
turns out that parasitic plants such as mistletoe
actually
do not typically do their own photosynthesis
they simply push their roots into the roots of other
plants and into the vascular system of other plants and just steal the sugars and minerals from
the host plant directly so there doing nothing on their own to produce their own foods
this is an orchid growing on the trees in a rain forest -- these are very similar orchids to what you would see
now
in this case
they actually growing them in that type of greenhouse in this situation so their growing and they've attached them to these little
twigs and bamboo to help you see the orchids better but it will be on a similar tree in the rain forest just like this
now our mistletoe friend we see a mistletoe
grows into this very very large kind of advanced plant type structure
under perfect conditions but the problem is
that that mistletoe has actually invaded this plant
and you see that the tree that it is attached to has actually died so
what we're concerned about there with these parasitic plants of course is the health and well being of the host plant
and as you can see it's not a very healthy or well-being planted its attached to it this point
and I think the favorite of all students in our in our nutrient depleted plants that have to make
some sort of change in lifestyle so to speak are the carnivorous plants
so these are typically are Sundew plants many of you may know the Venus flytrap plan and the
idea here it is that these plants still photosynthesize. these are plants!
they are doing the job of a plant
they're photosynthesizing making their own sugars but the problem is
nutrients. Sugars not the problem here! the problem is a lack of nitrogen
and typically phosphorus as well so one of the best sources for these plants for nitrogen in
such nitrogen depleted soils like the rain forest is to actually
trap insects and sometimes small mammals
and look at the conversion then of that or the digestion of that organism into the nutrients that the plant actually needs
so you see here fly is stuck in our Venus flytrap on and the larger winged probably an ant attached to
our Sundew plant here -- but there are all kinds of varieties of these carnivorous plants
and you see here pitcher plant also very common example
of a carnivorous plant. Small animals as I mentioned will get trapped by the sticky surfaces on the Venus flytrap
and it will close shut now
many people think about this as kind of the plants selecting for and choosing to close
its jaws around this organism!! not the case at all!!
Rather the plant is triggered that something is touched the sticky surface and it actually uses its vascular
tissue to close around and surround this organism
and then digestive enzymes would be secreted and very very slowly this organism will be digested same is true of the sundew's
they'll actually wrap around vascular tissue contraction here in this case and changes in the vascular tissue structure and it will actually curl
up on where this ant has become stuck to the surface it will curl up
on over top of the ant and digest it. And then of course
Little Shop of Horrors for those of you who remember Audrey II