transport in plants

• functions of xylem: transport water up the plant, transport minerals & ions up the plant and support the plant
• transpiration is the loss of water by diffusion into the atmosphere out of plant via stomata, from higher to lower water vapour concentration gradient
• cohesion-tension theory states that water molecules are attracted to one another (cohesive forces) so they stick together forming columns of water which pull other water molecules along with them as they move upwards.
• hydrostatic pressure is created by osmosis between soil solution and root cells, causing water to enter roots and push against cell walls creating turgor pressure
• water evaporates at spongy mesophyll
• xylem vessels have lignified walls to prevent them from collapsing
• xylem vessels have pits in walls to allow lateral movement to bypass blockage
• function of phloem: translocation and transport sucrose & assimilates & products of photosynthesis in both directions
• phloem is made up of sieve tube elements and companion cells
• symplast pathway is when water travels through cytoplasm and passes through plasmodesmata
• apoplast pathway is when water travels through cell wall and after reaching Casparian strip, water is forced to enter xylem using symplast pathway
• Casparian strip is impermeable and found in the endodermis
• xerophyte: a plant which needs very little water.
• hydrophyte: a plant which grows only in or on water.
• translocation is an energy requiring process transporting assimilates including sucrose, amino acid between sources & sinks
• Leaf diagram

  A) palisade mesophyll

  B) xylem

  C) phloem

  D) spongy mesophyll

  E) stomata

  F) lower epidermis

  G) cuticle

  H) upper epidermis

  
• transverse section of stem

  A) sclerenchyma

  B) phloem

  C) cambium

  D) xylem

  
• transverse section of roots

  A) epidermis

  B) root hair

  C) cortex

  D) xylem

  E) phloem

  F) endodermis

  
• stomata open when guard cells become turgid to allow gaseous exchange and stomata close when guard cells become flaccid to minimise water loss
• phosphate ions are used to make phospholipids in cell membranes
• magnesium ions are used in the production of chlorophyll
• nitrate ions are used to make amino acids and proteins
• ions enter the root hair cell by active transport to decrease water potential before water is taken up by root hair cells
• label root

  A) epidermis

  B) parenchyma

  C) endodermis

  D) pericycle

  E) phloem

  
• phloem tissue

  A) sieve plate

  B) sieve pore

  C) cytoplasm

  D) parenchyma

  E) plasmodesmata

  F) cellulose cell wall

  
• diffusion, facilitated diffusion and active transport are used to transport sucrose
• mass flow is a continuous column of water that moves up the xylem
• adhesion is when water molecules stick to the walls of xylem vessels