What Are Plants Made Of? Crash Course Botany #2
Summary
TLDRCrash Course Botany explores the unique organs of plants, contrasting them with those of animals. Host Alexis explains that plants, evolved from single-celled organisms, have different modes of growth and organization. Stems, leaves, and roots are the main organs of vascular plants, each with specific roles like structural support, photosynthesis, and nutrient absorption. The video also delves into the botanical definitions of 'fruits' and 'vegetables,' challenging common misconceptions and highlighting the diversity and adaptability of plant life.
Takeaways
- đż Plants have different organs compared to animals, adapted for their unique functions.
- đŹ Plant organs are made up of tissues, which are groups of cells that perform similar functions.
- đ± Plants and animals evolved independently from single-celled organisms over a billion years ago.
- đł The three main organs of vascular plants are stems, leaves, and roots.
- đ± Stems provide structural support and transport water and sugars throughout the plant.
- đ Leaves are primarily responsible for photosynthesis, converting sunlight into energy.
- đ„ Roots are involved in absorption of water and nutrients, and anchor the plant to the soil.
- đ„Š Many edible plant parts we consume are actually stems, leaves, or roots, not fruits.
- đ Botanically, a tomato is a fruit, but it is legally considered a vegetable in the U.S. due to culinary usage.
- đ True berries, according to botanical definitions, develop from a single ovary and include blueberries and cranberries.
- đż The diversity of plant organs contributes to the vast array of plant life forms observed by Charles Darwin.
Q & A
What are the three main organs that comprise a plant body?
-The three main organs that comprise a plant body are stems, leaves, and roots.
What is the function of apical meristems in plants?
-Apical meristems are clusters of stem cells at the tip of every stem and root that continually produce the materials needed to build new body parts.
How do plants differ from animals in terms of stem cell production and organ development?
-Plants are always producing new organs from the moment they germinate, while animals have most of their stem cells only fleetingly in embryos before they are used up to make organs.
What is the primary function of stems in plants?
-Stems provide the structural framework of the plant, support the plant, and transport water and sugar throughout its body.
Why are leaves often flat and wide?
-Leaves are often flat and wide to maximize their photosynthetic capabilities by providing more surface area for harvesting light energy.
What is the main function of roots in plants?
-Roots are responsible for absorption of water and nutrients from the soil and anchoring the plant.
What is the difference between vascular and non-vascular plants?
-Vascular plants have stems, leaves, and roots with vascular tissue for support and transport, while non-vascular plants, like mosses, lack such specialized tissues.
Why are tomatoes considered vegetables in the U.S. despite being botanically fruits?
-In the U.S., tomatoes are legally considered vegetables because of a Supreme Court ruling in 1893 that classified them as such based on culinary usage, not botanical characteristics.
What is the botanical definition of a 'berry'?
-A berry is a fleshy fruit that comes from a flower with a single ovary, according to botanical definitions.
How do plants grow and develop new organs throughout their life?
-Plants grow and develop new organs through meristems, which are regions of undifferentiated cells that can continuously divide and differentiate into various cell types to form new organs.
What is the significance of phyllotaxy in plant leaves?
-Phyllotaxy, or the pattern in which leaves grow around a stem, is significant because it determines the arrangement of the plant's branches and influences the plant's overall structure and light exposure.
Outlines
đ§ Plant Organs: More Than Just Artichoke Hearts
This introduction discusses the different organs in animals and plants, highlighting that plants, unlike animals, have organs such as stems, leaves, and roots that perform specific functions. The narrator, Alexis, draws comparisons between human and plant organs, noting that while animals have fixed organ systems, plants continually produce new organs throughout their life due to their unique evolutionary path. The paragraph emphasizes the continuous growth of plants via stem cells and sets the stage for exploring plant anatomy, starting with a trip to the grocery store.
đ The Role of Leaves and Phyllotaxy in Plant Growth
This section delves into the structure and function of leaves, explaining how they play a vital role in photosynthesis by converting carbon dioxide into sugars using sunlight. Leaves, with their wide, flat shapes, are common in the grocery store and are often attached to stems, showcasing their phyllotaxy (leaf arrangement). Examples of leaves, such as lettuce and kale, are discussed, and the paragraph explains how to differentiate between stems and leaves, using the presence of buds as a key indicator. It also touches on the complexity of organs like onions, which have layers of leaves around a modified stem.
đ± Roots: The Hidden Powerhouses of Plants
This paragraph focuses on roots, describing their primary functions of absorption and anchorage, along with their ability to store food and exchange nutrients with fungi underground. Roots like carrots, radishes, and beets are common storage roots found in grocery stores. The paragraph explains that roots lack phyllotaxy, making them easy to identify. A surprising fact is revealed: while russet potatoes are often thought of as roots, they are actually underground stems due to their regular pattern of 'eyes,' which can grow buds, branches, and leaves.
đ Vegetables, Fruits, and the Botanical Terminology
This section clarifies the difference between vegetative and reproductive plant organs, noting that 'vegetable' is not a botanical term but rather a culinary one. It explains that many commonly referred-to vegetables are actually fruits, botanically speaking, because they are mature, ripened ovaries containing seeds. The paragraph uses humorous examples, such as tomatoes and strawberries, to demonstrate the confusion between culinary and botanical definitions. The famous legal case determining that tomatoes are legally vegetables in the U.S., despite being fruits botanically, is also discussed.
đ„Š Have Plant Organs for Every Meal
This concluding paragraph encourages viewers to embrace a variety of plant organs in their diet, suggesting that fruits and vegetables are simply different plant parts. It teases the next episode, which will focus on plant cells and hormones, and promotes another PBS Terra series, 'Women of the Earth,' that highlights the contributions of female land stewards to climate healing. The episode closes with a fun quiz about Brussels sprouts, prompting viewers to leave their answers in the comments, and a call to support Crash Course via Patreon.
Mindmap
Keywords
đĄOrgans
đĄStem cells
đĄApical meristems
đĄVascular tissue
đĄPhyllotaxy
đĄRoots
đĄPhotosynthesis
đĄBulbs
đĄStorage roots
đĄFruits
Highlights
Plants have different organs compared to animals, adapted for their unique functions.
Plant organs are made up of tissues, which are groups of cells with similar functions.
Plants and animals evolved from single-celled organisms independently over a billion years ago.
Stem cells in plants are unspecialized and can become various cell types, unlike in animals where they are mostly used in embryonic development.
Plants continuously produce new organs throughout their life from clusters of stem cells called apical meristems.
The three main organs of vascular plants are stems, leaves, and roots.
Stems provide structural support and transport water and sugar in plants.
Leaves are responsible for photosynthesis and are often flat and green to maximize light absorption.
Roots are for absorption of water and nutrients and provide anchorage to the soil.
Asparagus is an example of a plant stem that is edible when tender.
Onions are bulbs, which are mostly leaves arranged around a modified stem.
The term 'vegetable' is not botanical but refers to edible parts of plants, which can include stems, leaves, roots, and even fruits.
Fruits are botanically defined as mature, ripened ovaries containing seeds.
The tomato was legally declared a vegetable in the U.S. due to culinary usage, despite being botanically a fruit.
Many foods labeled as berries, like tomatoes and avocados, are actually berries by botanical definition.
Botanists use a precise language to describe plant organs, which can differ from everyday terminology.
Plants have diversified into a vast kingdom with unique forms due to their distinct evolutionary path.
Transcripts
Brains and hearts.
Lungs and kidneys.
No, this is not an ingredient list for a zombie cookbook.
Itâs just a few of the organs that animals like us have
to keep our bodies in working order.
But plants have totally different organs
â despite what you might have heard about artichoke hearts.
And unlike most of our organs,
which you can only see with an X-ray,
youâve come across a lot of plant organs.
Youâve seen plant organs alive,
whether growing in the woods,
beside the road,
or in your bathtub full of houseplants.
And youâve seen them dead â
severed plant organs piled on top of each other in bins.
There they sit beneath harsh white lights,
damp from routine mistings,
just waiting to be picked up and carried away.
Hi! I'm Alexis, and this is Crash Course Botany.
Grab your cart and couponsâ weâre going to the grocery store.
[THEME MUSIC]
Like animals, plants are made up of organs,
or body parts that carry out specific functions
and consist of more than one type of tissue.
Not tissues like Kleenex;
tissues like groups of cells that look similar
and serve similar purposes in a living thing.
But plants have totally different modes of developing,
growing, and organizing their bodies.
Thatâs because they evolved from the simplest form of life,
a single-celled organism,
independently of animals like us.
In other words,
it wasnât like there were single-celled organisms that evolved into plants,
that then evolved into animals.
The evolutionary ancestors of plants and animals diverged over a billion years ago,
and then each evolved on a totally separate path.
Which explains why our bodies work so differently from plant bodies.
Like, in both plants and animals,
there are these things called stem cells.
Stem cells are special because they are unspecialized.
They have the potential to become tons of different types of cells.
Theyâre like the clay you use in art class.
You could make it a vase, a mug, a bust of your favorite botanist.
Love you, Linda Black Elk!
For humans and other animals,
most of our stem cells exist only fleetingly
in embryos before they get used up to make our organs.
Which is perfect because we animals are born with essentially the same body plan
that weâll carry into adulthood.
That means the number and location of our organs
wonât really change throughout our life,
barring surgery or injury.
In contrast, plants are always producing new organs
from the second they germinate, or begin to grow
â canât stop wonât stop!
Clusters of stem cells, called apical meristems,
at the tip of every stem and root
continually produce the materials needed to build new body parts.
They also have lateral meristems that allow roots and stems to thicken as the plant grows.
The three main organs that comprise a plant body are stems, leaves, and roots,
and their presence is one of the defining characteristics of a category called vascular plants.
Non-vascular plants, by the way, are often low-lying plants like mosses
â and weâll cover them in another episode.
But for now, weâre on the hunt for our rascally vasculies.
Stems provide the structural framework of the plant,
whether dainty daisy stems
or thick tree trunks
âyes, tree trunks are stems!
Stems are typically, though not always,
found above-ground and contain vascular tissue that supports the plant
and transports water and sugar throughout its body.
As we head down the grocery aisles,
we might not find a lot of stems,
mostly because the tissues that make them strong enough to hold up a plant
are a little too tough to be tasty.
Asparagus, though, is a great example of a stem:
we harvest asparagus plants when theyâre still tender,
and we often snap off the bases that have become too woody to eat.
Stems also hold a plantâs leaves â
another crucial organ â
up to the sunlight.
That lets the leaves do their main job:
photosynthesizing, or converting carbon dioxide gas into sugars,
using energy from the sun.
To maximize their photosynthetic capabilities, leaves are often flat and wide
â which gives them more surface area â
and green, which makes them more efficient at harvesting light energy.
Their veins shuttle nutrients in and out of the leaf,
and the cells in between are packed full of chloroplasts,
the cellular machines responsible for photosynthesis.
Leaves are a lot easier to find at the grocery storeâ
their wide, frilly shapes give them away.
Lettuce, kale, spinach, cabbage â these are all classic leaves.
Some will still be attached to their original stems,
which show off their phyllotaxy
â or the pattern in which leaves grow around a stem.
So in asparagus, the little scales at the top of the spears
are leaves with beautiful spiral phyllotaxy.
The chunky part of kohlrabi is also a stem,
and its much larger leaves have spiral phyllotaxy as well.
At the point where each leaf meets the stem, thereâs a bud,
which is a new meristem that has the potential to grow into a branch and
start producing its own stem and leaves.
Because of this, the leaf pattern determines the arrangement of the plantâs branches.
So the difference between a stem and a leaf is obvious, right?
I mean, you know which organ this isâŠright?
Itâs trickier than youâd think!
Onions are bulbs, which means theyâre mostly leaves
around a modified stem
thatâs evolved to swell up and store food for the plant during the winter months.
So even an onion isnât very straightforward.
Hey, they have layers!
A good rule of thumb is if the plant organ is bearing other organs, itâs probably a stem.
And the trick to telling stems apart from leaves is to look for a bud
nestled above the thing that looks like a branch.
If thereâs a bud, itâs a leaf.
And now, for the third item on our list: roots.
Roots are the typically underground organs of a plant
that are responsible for absorption and anchorage to the soil
orâŠthe face of a cliff!
[Alexis sings a rockin' guitar lick]
Plants are pretty hardcore!
Their epidermis, or outermost layer of tissue,
produces billions of tiny hairs that absorb water and nutrients,
and their vascular tissue transports the nutrients up to the stem and leaves.
The longer roots grow, the more they can explore the soil and absorb the good stuff.
If the root needs to branch off,
a new root with its own meristem
busts out from the center of the old one, Alien-style.
So yeah, roots come in a variety of shapes and sizes.
Many have also evolved functions beyond anchoring and absorption
such as storing food,
providing housing for helpful organisms like bacteria,
and exchanging nutrients with fungi underground,
like swapping chicken fingers for Lunchables beneath the cafeteria table.
And many roots, we eat!
In the produce section, youâll find carrots, radishes, beets, and sweet potatoes.
All of these foods are storage roots that are filled with deliciousness
originally meant to help the plant through hard times,
like a dry period or cold winter.
The way to spot a root is that it should be an organ with no phyllotaxy
â meaning no pattern of leaves around it.
Now, you might be saying,
âAlexis, youâre forgetting about my favorite kind of root to eatârusset potatoes!
Weâre talking the plant that birthed French fries and tater tots,
latkes and hash-browns.
The root that is so delightfully creamy
when mashed up,
it earned a place in the Hall of Fame of Side Dishes!
Why would you neglect such a versatile food
âone thatâs even been honored with its own emoji?â [Angelic voices singing]
Well, pick up a russet potato
and youâll find those little notches in the skin, called eyes.
And from those eyes, buds, branches, and leaves can grow.
On top of that, youâll notice the eyes are arranged in a
suspiciously regular patternâŠ
Yep, russet potatoes have phyllotaxy.
Which means, unlike sweet potatoes, russets arenât rootsâ
theyâre underground stems!
I know, mic drop.
You might be wondering why, despite
all this hanging out in the grocery store, we havenât mentioned two very common words yet:
vegetables and fruits.
The thing is, âvegetableâ isnât actually a botanical term.
Itâs just a useful regular-person word to describe some edible plant parts.
The word âvegetableâ could refer to stems, leaves, rootsâŠ
and even
âare you ready for this?â
fruits!
Okay, letâs rewind for a second.
So far weâve only talked about vegetative plant organs,
which refers to a type of organ that contributes to a plantâs
overall growth and structure.
But plants also make reproductive organs
of a variety of different sizes, shapes, and colors,
which help them have plant sex and create plant babies.
Botanists have a vast and precise language for describing them,
including the word âfruit,â
which refers to a mature, ripened ovary containing seeds.
[Gameshow Host Alexis]: Welcome to Not a Fruit,
[Audience applauds] where the game is to name a plant
thatâs not a fruit!
[Contestant Alexis]: Cucumber!
[Gameshow Host Alexis makes a buzzer noise]
[Contestant Alexis]: Eggplant?!
[Gameshow Host Alexis]: Also [buzzer noise]
[Contestant Alexis]: Zucchini??!!
[Gameshow Host Alexis makes a buzzer noise]
Nope, [Contestant Alexis sighs]
[Gameshow Host Alexis]: all fruits!
Meanwhile, some of the things we call fruits
arenât fruits at all!
Like, the tasty part of the strawberry is actually the base of the flower,
not the ovary.
Strawberry fruits are technically the little nubbins that we would call seeds.
[mind blown noise]
And there is one food in particular that has been the subject of the
fruit/vegetable debate for centuries.
And thatâs gotta be the tomato, like Theo here.
Letâs go to the Thought BubbleâŠ
The year was 1886.
New York was a major port city,
and wholesalers were starting to introduce the U.S. to fruits
and vegetables from other countries by
shipping them across the ocean.
But there was some controversy over shipping regulations.
Whenever anyone imported vegetables,
they had to pay a 10% tariff on them,
while fruits didnât have the same tax.
So when a guy named John Nix received a shipment of tomatoes
from the Caribbean and was forced to pay the vegetable tariff on it,
he was not happy.
He claimed that tomatoes werenât vegetablesâ
they were fruits, so he should get his money back.
Theo was havingâŠa bit of an identity crisis.
By 1893, Nixâs case had gone all the way to the United States Supreme Court.
During the trial, the witnesses
âwhich were not bananas and broccoli as youâd expect,
but humans in the produce industryâ
debated multiple dictionary definitions of âfruitâ and âvegetable.â
Nobody asked the tomatoes what they thought of all this.
Ultimately, the judge declared that despite any botanical similarities to fruits,
tomatoes were vegetables because they were, quote:
ââŠusually served at dinner in, with, or after the soup,
fish, or meatâŠ, and not, like fruits generally, as dessert.â
And this remains true to this day in the U.S.
Even though tomatoes are botanically fruits,
they are legally vegetables.
What can I say?
People, like tomatoes, are messy.
Thanks, Thought Bubble! [Audience applauds]
[Gameshow Host Alexis] And weâre back with everyoneâs favorite game show, Name a Berry.
Where the game is⊠you get it.
[Contestant Alexis]: Blackberries!
[Gameshow Host Alexis makes a buzzer sound]
[Contestant Alexis]: Raspberries!
[Gameshow Host Alexis]: Additional [buzzer sound]
[Contestant Alexis]: Mulberries?!
[Gameshow Host Alexis makes a buzzer sound]
[Contestant Alexis]: I don't wanna play this game anymore
According to the botanical definition,  [crash]
a berry is a fleshy fruit that comes from a flower with a single ovary.
In a nutshell, [ripping sound] ow
blueberries and cranberries are pretty much the only fruits with
âberryâ in their name that are actually berries.
Meanwhile, tomatoes, avocados, bananas
â yep, berries.
So now we have a pretty good feel for the rulebook of botanical body-building
âas in, forming bodies made of organs, not getting swole.
Plants evolved different rules than we did,
and through variation in just a few different organ types,
theyâve diversified into a magnificent kingdom
full of, as Charles Darwin put it, âendless forms most beautiful.â
Botanists have deciphered these rules and translated them into a precise and consistent language,
one weâll be exploring in future episodes.
Sometimes that language is at odds with how weâre used to talking about plants in our everyday lives.
But now you know that when the doctor recommends 5 servings of fruits and veggies a day,
you have a variety of plant organs to choose from.
I say go wild and have plant organs for breakfast, lunch, and dinner.
[crunch]
Next time,
weâll be zooming in on plant cells and hormones
âthe tiny structures and chemical signals
that allow plants to do amazing things.
Calling all inhabitants of Earth!
There's a new series over on PBS Terra that will make you think,
"Where would we be without women?"
Women of the Earth explores the resilient work of female land stewards across the country
and how they're leading the world toward effective climate healing.
You'll meet the powerful forces behind the practices that are healing communities
from climate change
and discover why women's contributions to our Earth are essential today.
Check out the link in our description to watch it now!
Hey, before we go, letâs branch out!
What part of the plant is a Brussels sprout?
Find the answer in the comments!
[Gameshow Host Alexis]: Thanks for watching this episode of Crash Course Botany
which was filmed at the Damir FerizoviÄ Studio and made in partnership with PBS Digital Studios and Nature. Â
If you want to help keep Crash Course free for everyone, forever,
you can join our community on Patreon.
I donât know what that isâŠ
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