A revision summary of OCR A level Biology Transport in Plants 3.1.3
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Need for transport system
- High metabolic rate, Small SA: V (stem), Large sizes Water transport in plants
Transport in Dicotyledonous plants Root hair cell – large SA: V, microscopic size can
Stem Root Leaf penetrate between soil particles, thin cell wall, solutes in
cytoplasm maintain conc gradient for osmosis
1. Mineral ions enter RHC, ↓ᴪ and water follows by
osmosis. Through each cell.
2. Water moves through cortex cells by osmosis (ions ↓ ᴪ
Vascular bundles Mid vein supports in adjacent cell) pulled through cohesive forces.
Vascular bundles in Apoplast – in between cell walls and does not pass
around the edge structure and
middle help plant membranes. Mineral ions are carried with water.
give strength & transports vascular
withstand tugging Symplast – enters cytoplasm, travels cell to cell
support tissue
forces through plasmodesma
Vacuolar – water enters vacuoles of cells.
Vessel Function Features 3. Endodermis cell layer (into xylem) is surrounded by
Xylem Transport Continuous column of the Casparian strip – waxy suberin forms waterproof
of water, dead cells – does not layer. Blocks apoplast pathway forcing water into
inorganic impede mass flow of water. symplast pathway. Selectively permeable CSM excludes
ions, small Cohesion & adhesion toxic solutes reaching cytoplasm.
organic Thick lignin walls – 4. Water enters vascular bundle (xylem)
molecules strength & waterproof, 5. Endodermal cells move mineral ions into xylem by
from roots layered in spiral so plant active transport. ↓ᴪ so water moves via osmosis
upwards can sway 6. Root pressure theory – initial flow into vascular
Pits – lateral flow of water tissue forces water up the stem.
Narrow – prevents water 7. Capillary action - charged water molecules attracted
column breaking to sides of xylem & are pulled up by adhesion.
Phloem Transport Sieve plates – connect 8. Transpiration pull – water molecules are attracted to
of organic sieve tubes & let contents each other by cohesion forming a continuous column.
substance flow Water is pulled upwards to replace water lost by
s from Companion cells – lots of transpiration.
source to mitochondria (ATP) for Evidence for cohesion-tension theory
sink metabolic functions. - Trees are narrower in the day during transpiration. Transpiration
(sucrose, Infoldings in CSM for ↑SA increased tension in xylem vessels causing diameter to decrease.
hormones, Plasmodesmata – link - When a stem is cut – air is drawn in and water does not leak out
products sieve tube & companion cell
of photo- for assimilates to move
synthesis through
No nucleus/ cytoplasm –
reduces friction &
maximises space
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller hyaldridge. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £5.48. You're not tied to anything after your purchase.
