B4e: Transport in plants Flashcards Preview

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Flashcards in B4e: Transport in plants Deck (17):

Describe xylem(4)

plant tissue made up of dead cells

have a hollow cavity called the lumen

stacked on top of one another to form long, hollow tube-like vessels

particularly thickened, strengthened cellulose cell walls


What are the functions of xylems(2)

transports water and dissolved minerals from roots to shoots and leaves in the transpiration stream

gives plant support


Describe phloem(2)

plant tissue made of columns of living cells with perforated end-plates to allow substances to flow through

cells stacked on top of one another to form long, hollow, tube-like vessels


What are the functions of phloems(2)

transports food substances made in leaf to all other parts of the plant through translocation


Vascular bundles in root (3)

roots have to resist crushing as they push through the soil

vascular bundles and xylem located in the centre

gives root strength; helps it act like an anchor


Vascular bundles in stem (3)

located around outer edge of stem

xylem forms 'scaffolding'; phloem always around outside of stem

provides strength to resist bending of stem in breeze


Vascular bundles in leaf (2)

vascular bundles (xylem + phloem) form a network of veins

supports softer leaf tissues


What does xylem and phloem form in leaves, stems and roots

continuous systems


What is transpiration

the evaporation and diffusion of water from inside leaves through stomata


What does transpiration cause? (3)

creates shortage of water in leaf

more water is drawn up from the rest of the plant through the xylem vessels to replace it

means more water is drawn up from the roots, so there's a constant transpiration stream of water through plant


What is the transpiration stream

continuous flow of water up through the xylem of a plant, from the roots up to the leaves where it evaporates


What is transpiration a consequence of(3)

the way in which leaves are adapted for efficient photosynthesis
-leaves have stomata in them so that gases can be exchanged easily
-because there's more water inside plant than in air outside, water diffuses from leaves through stomata


Factors increasing transpiration rate (4)

+light intensity = +stomata open (because of photosynthesis) = +diffusion; (until all stomata are open)

+temperature = +KE of water molecules = +rate of evaporation/diffusion

+air movement = +water molecules outside of the plant moved away= +concentration gradient = +rate of diffusion

-humidity = -water in air = +concentration gradient = +rate of diffusion


Roots description and purpose in the transpiration stream (2)

tiny root hairs extend between soil particles

increases surface area of roots for absorption of water from soil (higher conc) into root hair cell (lower conc) via osmosis


Benefits of transpiration (4)

provides plants with water for:
-cooling effect during evaporation
-entering cells via osmosis, making them turgid = helps support plant
-transporting dissolved minerals in water as it moves through the plant


How is the structure of a leaf adapted to reduce excessive water loss(6)

thick waxy cuticle on upper and lower surfaces = -evaporation

-stomata = -diffusion

+stomata on underside where it is darker/cooler = -rate of diffusion

stomata close at night when no ps = -diffusion

-SA:V ratio = -rate of evaporation/diffusion

changes in guard cell turgidity (due to light intensity and availability of water) to regulate the holes of the stomata


How do stomata open and close automatically? (3)

thick inner walls and thin outer walls

more light and water = guard cells take up water via osmosis, photosynthesis produce sugars = guard cells turgid = guard cells curve = stoma open

less light and water = guard cells lose water via osmosis, less photosynthesis produce less sugars = guard cells = flaccid = guard cells straighten = stoma close