Science 5: Transport in Stems
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Today's lesson is all about the great plant transporter, played none other than Jason Stath—wait no. Transporters of plant nutrients are the xylem and the phloem. We always get those mixed up with Jason Statham.
|Elementary and Middle School||5th Grade|
Well water is also used by humans to transport stuff. [Man pushes cargo onto ship]
And cruise ships...
…and very relaxed people sitting awkwardly in donut-shaped floating devices. [People floating in the water on dingys]
But in the case of plant stems, it's the plants doing the moving – and what are they moving?
Water. In a plant stem, the transportation of fluid [Arrows showing transport of water]
throughout the plant is handled by the xylem and phloem.
Put those two together and you get…a great musical instrument! …well…almost. [Person playing the xylophone]
The xylem's job is to move the water up the plant from the root, into the shoot.
But seeing as plants don't have pumps like a heart to move all that liquid around...
…the water moves through the plant using what's called a “transpiration stream,” [Arrows moving through the plant]
which involves vessels in the xylem. Water moving upwards against gravity without
a pump. Sounds a bit like magic, huh? [Magician on stage as water travels up through a plant]
Well, it all happens because of something called “capillary action.”
This works because water molecules are charged, meaning they're basically like a group of
BFFs – they love to stick together.
Now think of the solids on the inside of a plant stem as a super-cool birthday party [A disco with people dancing]
that these water molecule besties really want to get invited to.
Water is attracted to the very center solids of the stem, which is what draws it upwards.
This is capillary action, and it's what keeps the water crawling upwards along the xylem [Arrow pointing to capillary action of water molecules]
and against the force of gravity. And when the stomata open up to let in carbon
dioxide to be used for photosynthesis, some of this water moves out of plant and into the air.
This happens because the plant has more water inside of it than outside in the surrounding
air, so it decides to share. [Water molecules travelling around the plant]
How nice. Someone raised that plant right!
When this water evaporates out of the stomata, new water molecules are pulled into the stem, [Water evaporating from plant]
going all the way through the root.
Think of it like the line up outside of a club. When some party-goers leave, the bouncer
lets in new ones from the front of the line. [Bouncer lets water molecules into a party]
This entire process keeps the water molecules moving and the plant a-planting.
Let's just hope the molecules in line are dressed appropriately.