What is Transpiration? Video Lecture | Science Class 7

so we know all about the xylem and the
phloem but now we need to know exactly
how water and minerals move around the
plant you should already know about the
structure of the leaf but if not watch
this video to remind you let's have a
look at transpiration and the xylem
transpiration is the evaporation of
water from the aerial parts of the plant
so the leaves and stems by water
evaporating out of these parts mostly
the leaves the suction pressure is
created which draws up the water through
the plant this is called the
transpiration pool but what exactly
happens in transpiration let's start at
the roots roots have root hairs giving
them a large surface area for water
absorption water passes in from the soil
by osmosis passing down the
concentration gradient and into the root
hair cells cytoplasm and then on to the
xylem vessels water moves through the
xylem vessels from the root to the stem
to the leaf transpiration at the leaf
causes a transpiration pool and because
water molecules are cohesive water is
pulled up through the plant in the
transpiration stream as well as the leaf
cells needing water for photosynthesis
water also keeps the cells turgid which
supports the plant inside the leaves
water is drawn out of the xylem cells to
replace the water loss through
transpiration because of the cohesive
nature of water which also pulls the
water through the plant as water leaves
the xylem and moves into the leaf it
again pulls more water molecules behind
it but it isn't just about water the
transpiration stream also transports
mineral ions that are dissolved in the
water from the roots to the leaves the
transpiration rate isn't constant there
are many different factors that affect
it environmental factors are similar to
those that make you sweaty the
temperature the humidity but also wind
and light intensity
then there are also physical factors
like doesn't have a waxy cuticle almani
stomata does it have the nature of the
guard cells how large is the leaf
surface area and if the leaf is folded
or flat if the rate of transpiration
increases then the rate of water
absorption by the roots needs to
increase to when water is scarce or if
the roots are damaged the plant needs to
reduce its transpiration rate by closing
some of their stomata there are guard
cells on either side of the stomata
which regulate this during daylight
hours chloroplasts produce sugar this
lowers the water potential of the guard
cells and they take in water by osmosis
this makes the guard cells turgid
because the guard cells have a different
cell wall thickness when turgid they
Bend more on the outside into sausage
shapes
this opens the stomata or the pore water
can then be lost during the night all
the sugar produced by the chloroplasts
gets used up so the water potential of
the guard cells increases more water
near sugar the guard cells lose water by
osmosis and become flattening and the
stomata starts to close this reduces
water loss so you now know about water
movement through the plant up the xylem
and pulled along the transpiration
stream by the transpiration pool and
unsurprisingly the plant has methods to
control water loss by closing the
stomata based upon how flaccid or turgid
the guard cells are so in the final part
of this video we are going to look at
the movement of glucose after all water
may be important but so is food
you