Vascular Systems of Plants That dripping sap usually comes from the

phloem.
Xylem and phloem make up the big
transportation system of vascular plants. As you Plant Reproduction - They'll Make More
get bigger, it is more difficult to transport
nutrients, water, and sugars around your body. If you are an organism, you will need
You have a circulatory system if you want to to reproduce. Otherwise, there will be no more
keep growing. As plants evolved to be larger, of your species and the species will die off. You
they also developed their own kind of may have heard of endangered animals. There
circulatory systems. The main parts you will are also endangered plants. These endangered
hear a lot about are called xylem and phloem. species have very few individuals left and
scientists/naturalists are working together to
It all starts with a top and a bottom. Logically, it make sure the species don't become extinct.
makes sense. Trees and other vascular
plants have a top and a bottom. The top has a We talked a little about reproduction when we
trunk, branches, leaves, or needles. The bottom discussed meiosis in the cells tutorials.
is a system of roots. Each needs the other to Reproduction is one of two things.
survive. The roots hold the plant steady and
(1) One cell can split into two, giving you two
grab moisture and nutrients from the soil. The
identical cells. That type is asexual
top is in the light, conducting photosynthesis
reproduction.
and helping the plant reproduce. You have to
(2) The second type is when two cells, each with
connect the two parts. That's where xylem and
half of the DNA needed, combine and create a
phloem come in.
living cell. That type is sexual reproduction.
Zippy Xylem
When plants hit a point in evolution, the second
The xylem of a plant is the system of tubes and is the one that occurs more often.
transport cells that circulates water and
Making More Mosses
dissolved minerals. As a plant, you have roots to
help you absorb water. If your leaves need Sporophytes are the reproductive structures
water and they are 100 feet above the ground, it you will find in mosses. They are actually a
is time to put the xylem into action! Xylem is phase of the moss life cycle that feeds off the
made of vessels that are connected end to end green parent plant (the gametophyte). The
for the maximum speed to move water around. sporophyte is a stalk that grows after the
They also have a secondary function of support. haploid sperm of one moss plant is able to mix
When someone cuts an old tree down, they with the haploid egg of a female moss plant.
reveal a set of rings. Those rings are the remains The resulting diploid cell grows into the
of old xylem tissue, one ring for every year the sporophyte stalk. When ready, spores stored in
tree was alive. the sporophyte are released and they grow into
new moss plants.
Phloem Fun
Conifers and Their Cones
The fun never stops in the plant's circulatory
system. Most plants have green leaves, where While there are male and female mosses,
the photosynthesis happens. When those conifers produce two types of cones on the
sugars are made, they need to be given to every same tree. One of the cone types gives off
cell in the plant for energy. Enter phloem. The pollen (the staminate cone). The other type of
phloem cells are laid out end-to-end throughout cone catches the pollen if the wind is moving in
the entire plant, transporting the sugars and the right direction. Better yet, the wind blows
other molecules created by the plant. Phloem is the pollen to another conifer of the same
always alive. Xylem tissue dies after one year species, and a cone (called theovulate cone)
and then develops anew (rings in the tree catches the pollen. Again, the pollen and
trunk). What is the best way to think about megaspore (receiving haploid cell) are haploid
phloem? Think about sap coming out of a tree. and combine to form a diploid cell. That diploid
cell grows into a zygote (baby conifer) that have developed. Their growth is not a random
eventually lives in a seed. growth like a tree or weed. They grow in
specific geometric patterns. Flowers
Flowers and Pollen
Flowers have developed such a wide variety.
The most advanced of the plants have their own That variety is often dependent on what kind of
way of sexually reproducing. It is a very fancy creature helps out with the pollination. If I am a
and very complex process. Plants that rely big insect, I will be looking at plants with big
on flowers for reproduction are also very flowers. If I am a tiny little bug, I might live my
dependent on outside help such as insects and whole life inside a flower. There are also a
animals. While conifers have the two structures variety of colors that attract different insects
on one tree, flowering plants went one step and animals.
further and put the devices that make and
receive pollen in the same structure. Stems

How does that help? A bee might go to one Stems are a good place to store water. It's very
flower and get a little pollen on its back. If it efficient to develop a big protected area. Think
goes to another flower of the same species, about a barrel in hot areas where water is
that pollen can land on the stigma. From that scarce. Enter a cactus. All stem and trunk. No
point, one haploid male nucleus combines with leaves. Having no leaves means very
a female nucleus and the other haploid male little evaporation on hot days. Other extremes
nucleus combines with a polar nucleus. If are plants with no stem. They could grow one,
successful, an embryo andseed/fruit develop being vascular plants, but they have found it to
respectively. be an advantage to stay near the
ground. Vines are another extreme.
Different Parts = Different Advantages
The bark of a tree or plant can also perform a
Obviously, not all plants look the same. They specific function. Corks in wine bottles are
have different flowers, stems, and even root actually from the bark of a tree (cork tree).
structures. Extreme examples have given some Some bark has been designed to peel away as
plants big advantages. These advantages have the tree grows. Other types of bark are very
let them settle in new environments and thick to protect the plant from animals and
become more successful. insects.
Specialized Leaves Epiphytes - Specialized Roots
What kinds of leaves are there? What kinds Not all plants even live in the ground. Some
aren't there? There are thick ones for storing specialized plants called epiphytes actually live
water as in succulents. There are long on the side of other trees or on rocks. They are
twisting vine-like leaves that can wrap around able to collect water themselves but do not use
and dig in for support as in grapes. There are roots to gather it up. Their roots have been
also thorns. Nothing says, "Don't eat me" like a specialized to dig in or grab on to the larger
bunch of sharp thorns on your branches. object. They don't always hurt the trees; they
just hang out on the outside. Epiphytes can
Focus On: Succulents Even
include some seedless species, bromeliads, and
though succulent species are flowering plants,
orchids. There are also epiphyte species that
we thought it might be nice to add an example
can grow very large and even break tree limbs.
of plants that are able to survive with little
They can suck nutrients away from the tree and
water. Instead of leaves, succulents have fleshy
weaken it over time. Several ficus species are
structures that efficiently store water. Many
killer parasitic epiphytes.
succulents have also developed thorns for
protection. Many animals in arid environments
feed on succulents because they provide a Mosses and Liverworts These are the little ones.
source of water in their tissues. This image The most important feature of mosses and
displays a spiral pattern that several succulents
liverworts is that they have no vascular system. They Like Water
A vascular system in plants is a series of tubes
that can transport water and nutrients over a Ferns are often used in landscaping. There's a
distance. That vascular system of xylem and good chance you've seen them. They are also
phloem allows redwood and sequoia trees to able to live in a variety of climates as long as it is
grow to over one hundred feet tall. moist. You will find ferns in Canadian rain
forests just as easily as you will find them near
Limited in Size Without a vascular system, the equator. They are similar to mosses in that
mosses, and liverworts cannot grow very large. they need liquid to reproduce. When water is
If you have seen mosses, you know that they around, they are able to have baby ferns
are actually carpets of individual plants. They called zygotes. Ferns have some neat structural
are rarely taller than one inch high. Another features. Some have large stems, several feet in
important characteristic of these little guys is length. Scientists call those bad boys the tree
that they require water to reproduce. It's ferns. Ferns also have specialized leaves
another characteristic of their low place in plant called fronds. They unroll as they mature and
evolution. While all plants need water, mosses spread out in a fan shape.
and bryophytes need droplets of water to
enable their haploid reproductive cells to Horsetails
combine. They are all known as the bryophytes.
Horsetails are related to ferns in that they have
Mosses Let's start with mosses. These are waxy a vascular system. They never developed the
little plants with no leaves and no stem that use ability to reproduce with seeds. They might be a
each other to stay upright. Their inability to stay little hard for you to see because many of them
up is why you never see one little moss plant; are extinct. Because they are better able to
it's always a group. That grouping also helps survive in various environments, you can find
them retain water in the area. A waxy covering them from very northern and southern latitudes
across their bodies helps keep water from to the equator. Unlike ferns, these are tough
evaporating. You will usually find them in moist plants. While ferns are soft, horsetails are rough
areas out of the direct sunlight. plants and even have silica (silicon-based
compound) in their epidermal cells. Ouch!
Good Worts

We'll cover liverworts and hornworts together. Gymnosperms - First Plants with Seeds So
If you can believe it, the worts are even simpler you've got a vascular system. What comes
than mosses. These are considered to be the next? Seeds. Seeds let you send your offspring
simplest of all plants and often grow flat along out into the world. Seeds provide a protective
the ground in large leaf-like structures. None of coat so that the embryo plant can develop when
the bryophytes have roots. They all it finds a nice piece of soil. But remember this:
have rhizoids (little hairs), and the worts are no gymnosperms have not developed the ability to
exception. Like mosses, they are found in very make flowers.Flowers are an evolutionary
moist areas, and some species even spend their advancement after seeds. So if you have a
whole lives in the water. vascular system, seeds, and no flowers, what
are you? A gymnosperm!
Ferns and Horsetails -
First Plants with Pipes Seeds are a protective structure that lets a plant
embryo survive for long periods of time before
These are the first of the vascular plants you will it germinates. Seeds have food sources pre-
study. Mosses and worts are non-vascular. packaged for plant embryos to provide for an
The ferns were the first plant species to develop embryo's needs in early growth. Seeds let
a circulatory system that lets them grow larger. plants spread their embryos over large areas.
They have roots, leaves, stems, and trunks. Some are even so lightweight that they are
With their new vascular system, the sky was the carried across the planet by strong winds. Seeds
limit for plants. are an advantage if you want to be a plant that
can grow anywhere. Seeds are da bom'!
Cycads in the Tropics Looking like a fern. this species survive beyond all of its close
Looking like a palm tree. It's actually neither! It's relatives.
a cycad. These are another favorite of
landscape designers. These are sturdy little Angiosperms - First Plants with Flowers
plants that can survive in harsh conditions. You
We asked it before. What would give you an
won't find them in cold areas like the
advantage if you were a plant? You have a
conifers. Cycads need warmer weather to
vascular system to transport nutrients. You
survive. They have cone-like structures for
have seeds for reproduction that allow your
reproduction. Instead of being on branches,
babies to spread out in new areas. What
their cones are in the center of the plant and
next? Flowers! Flowers are the most recent
can get really large. They also have
evolutionary advantage for plants.
big waxy fronds, and when it's time to
reproduce, the female plants have a great fruit Looking Good for the Birds and Bugs
that grows in the middle of their stem.
When we talked about gymnosperms, we spoke
Conifers in the Forests Pine, cedar, redwood, of seeds. That was a big advantage. The
and spruce. Sounds like we're at a hardware angiosperms took it one step further. They not
store buyinglumber. Not so. We are listing off a only have seeds, but they also have flowers.
bunch of trees that are called conifers. If you've What kind of an advantage is that? Many
ever gone skiing or to northern latitudes you angiosperm species use wind for pollination the
have seen loads of conifers. The conifers most way that gymnosperms do. What if you didn't
people think of are pine trees. Every year need to rely on the wind to spread
millions of trees are grown for Christmas and your pollen around anymore? What if another
they are all conifers. They usually have needles creature could do it for you? Maybe an insect?
and cones (thus the name CONifer). Sounds like a new advantage.
They are also evergreens: even in cold winter Those specialized flowers are able to attract
months they are able to keep their needles. organisms to help pollinate and distribute
That ability is one reason they do so well in seeds. Another cool advantage is the fruit/seed
northern latitudes. The ever-present needles packaging. Would you rather eat a pine cone or
allow conifers to take advantage of the Sun an apple? A lot of animals would go for the
whenever it is around. They are also some of apple. When they do, they are able to spread
the tallest plants in the world. They are able to the seeds across wide areas after the animal
get very tall and strong because of heavy-duty poops out the seeds.
xylem that hardens and makes them sturdy.
That sturdiness is why these kinds of trees make Some Withy One Cotyledon
good lumber - hard and strong wood.
There are two kinds of seeds in the
Ginkgoes on Your Street angiosperms, monocots and dicots. Monocot is
short for monocotyledon. A cotyledon is the
Not every plant made it to the modern seed leaf. When you are a monocot, your seed
day.Fossil evidence shows what plants used to only has one package of food. "Mono" means
be alive in other geological eras. The Ginkgo is one or a single cotyledon. Monocots are made
one of the ones that made it. Some people call up of simple flowering plants like grasses, corn,
it a "Maidenhair Tree". It's the last one of its palm trees, and lilies. Two of the characteristics
kind. It has needles that have combined to form of monocots are that their flowers have petals
very sturdy leaf-like structures. You need to in numbers of three and their leaves are made
remember they are not like leaves in the of long strands. Think of the leaves of grass or a
traditional sense. You've probably seen these all palm frond. +
over. Landscape designers love to use them
because they look very nice and are very And Some with Two
resistant to pollution. They are great for cities.
Being able to resist insects and disease has let The other kind of plant in the flowering plant
world is called a dicot. Dicot is short for
dicotyledon. "Di" means two or a double plants that are resistant to disease and bugs.
cotyledon. These plants have seeds that have These stronger plants will allow our crops to
two cotyledons, two seed leaves of food for the give us more food from the same amount of
embryo. Most of the flowers you see every day space.
are dicots. They have flowers with petals in
numbers of four and five. They also have really
complex leaves with veins all over, not long like Medicines One of the good examples of plants
monocots. Some examples of dicots are roses, giving medicine to man is an aloe plant. Inside
sunflowers, cacti, apple, and cherry plants. the leaves of an aloe plant are compounds that
soothe burns on our skin. Man also gets
Humans and Plants Humans need plants. All something called digitalis from plants. The truly
animals do. Humanity's relationship with plants exciting discoveries are in the future. Scientists
has actually made it possible for us to have a are analyzing plants every day to find out if they
civilization. Before we had cities, humans went have any compounds that can help humans
around in little packs and were hunter- survive and lead a better life.
gatherers. We ate rats, birds, berries, and
whatever food we could find. It wasn't very And Places to Live
efficient. One day someone had the bright idea
If you live in a house, chances are it was made
to plant the plants we like to eat. When humans
with wood or there is wood in the house. We
did that, they were able to stay in one place full
have used wood to build our homes for
time. Then came the cities and a huge system of
thousands of years. Huge lumber companies
agriculture to support millions of people.
grow entire forests to supply the amount of
Big Time Farming As time has passed, we have wood needed for our world. As buildings got
taken farming to new levels. We have larger, construction turned to concrete and
manipulated species to create big apples and steel. You will probably still find wood fixtures
large ears of corn. The plants would never have such as paneling inside these large steel
done it in the wild. It took man to change the buildings.
plants. We are also moving toward the genetic
alteration of plants. We're trying to make