transport and coordination in plants Flashcards
photosynthesis
carbon dioxide + water –> glucose + oxygen
xylem
- transports water and mineral ions from roots to leaves
- made up of thick walled vessels
- dead cells, contain no cytoplasm, hollow, end to end
- end walls disappeared so form continuous transport system throughout plant
phloem
- living cells
- tubes formed by end to end cell arrangement, cells walls made of cellulose
- sugar made in photosynthesis is converted to sucrose
- transports sucrose, amino acids from leaves to growing points or storage areas
- moving sucrose and amino acids requires energy
transport of water
- take in water from soil through root hairs, main site of water absorption by roots
- hairs increase surface area of root epidermis
- function of root hair= absorb water and minerals from soil
- each hair= single specialised cell of root epidermis
- long thin outer projection penetrates between soil particles reaching soil water
- water has some solutes dissolved in it, concentration much lower than concentrations of solutes inside root hair cells
- soil water- high conc of water molecules, water enters by osmosis- dilutes contents of soil, increasing conc of water molecules
- water moves from root hair cell into cortex cells of root
- continues down water conc gradient, where there are more water molecules to where there are fewer water molecules
- gradient maintained, taken up by xylem in middle
- carried in xylem vessels
transpiration
evaporation of water from the surface of a plant
loss of water by the leaves
- osmosis and transpiration
- water passes out of stomata as water vapour
- water leaves cells of mesophyll and evaporates into air spaces between spongy mesophyll
- vapour diffuses through stomatal pores- lower conc of water molecules
- draws water by osmosis from surrounding mesophyll cells
- xylem vessels supply leaf mesophyll tissues with water
- transpiration- water pulled up xylem in stem and roots in continuous flow- transpiration stream
temperature- transpiration rates
hot day= water evaporates quickly
rates increase as temp increases
humidity- transpiration rates
very humid air- contains water vapour so accepts less from plants
rates slow down
dry air- diffusion of water vapour from leaf to atmosphere rapid
rates increase if humidity decreases
wind speed- transpiration rates
still air- saturated with water vapour so no more can escape from leaf
rates slow down
moving air- water vapour swept away as fast as it diffuses
speeds up rate
rates increase as wind speed increases
light intensity- transpiration rates
doesnt affect evaporation itself
daylight- stomata open to supply co2 for photosynthesis
more water diffuses from leaves to atmosphere
water supply- transpiration rates
short supply and losing water by transpiration faster than being taken up then plant will wilt
before- stomata close, reducing transpiration and delaying wilting
potometer
measures uptake of water by freshly cut stem
as water is drawn up by stem, air bubble pulled along
rate of movement in control shoot is compared to rate of movement in similar shoots
transport of sugar made in leaves
leaves make carbs by photosynthesis
carbs make amino acids, proteins, oils
sugars and amino acids transported from leaves to part of plant in phloem
TRANSLOCATION
sap inside phloem contains a lot of sugar- sucrose
movement of water and salts in xylem is always up (soil to leaf)
phloem- transport of sugars and amino acids may be up (grown buds or fruits) or down (roots/storage organs)in stem
energy needed to make sap move through phloem tubes- active process
phototropism
\+ stem tip growth towards light max light for photosynthesis - root tip growth away from light less chance of drying out
geotropism
\+ root tip towards gravity more chance of finding moisture - stem tip away from gravity more chance of finding light
