mass transport in plants

Question 1

Whats transpiration

Answer 1

*evaporation of water by leaves

Question 2

Whats translocation

Answer 2

*transportation of organic substances- sucroses from source to sink by phloem

Question 3

EXplain cohesion- tension theory

Answer 3

*Water evaporates from leaves
2. decreases water potential , conc gradient creates tension/pulls up water
3. Hydrogen bonds/cohesion/adhesion maintains column;

Question 4

How is water lost in transpiration

Answer 4

water leaves mesophyll- travels down air spacs out of stomata.

Question 5

Xylem structure

Answer 5

*lignin cell wall- provides support nd withstands pressure
*no nucleus- maximise space for water flow
*no end walls- continus column of water
*pits in side walls- allow latent water movement

Question 6

Phloem structure

Answer 6

*no nucleus/few organelles- maximise space for orgnic substance flow
*companion cells- many mitocondria for aerobic respiration to create ATP for active transport
*end walls w perforations/sieve plates- allow easy movement of phloem sap between sieve tube elements

Question 7

Whats mass flow hypothesis

Answer 7

Movement of sucrose from spurce to sink

Question 8

Explain mads flow hypothesis

Answer 8

*photosynthesis occurs in source and produces sucrose- lower water concentration
*water from surrounding cells and xylem move in by osmosis.
*increases hypostatic pressure, forcing liquid to go to sink via phloem.
The sink has low hypostatic pressure cause sink respires and uses sugars, this causes high wp. Water moves out to surrounding cells decreasing volume of water and hydrostatic pressure

Question 9

Translocation- sucrose from source to sink (miss estruch)

Answer 9

*photosynthesis creates organic Substances
*creates high conc of sucrose at source
*sucrose moves down conc gradient by FD.
*active transport of H+ from companion cells into spaces in Wall.
*creates conc gradient- H+ move down via carrier proteins
*co-transporr of sucrose and H+ occurs via co-transporter protein and transports sucrose into sieve tube element.

Question 10

Movement of sucrose within phloem

Answer 10

*increase of sucrose in sieve tube element lowers WP.
*water enters from xylem by osmosis
*hydro pressure increases forcing liquid down sink

Question 11

Describe the use of tracer experiments to investigate transport in plants

Answer 11

1. Leaf supplied with a radioactive CO2
2. Radioactive carbon incorporated into organic substances during photosynthesis
3. Thin stem sliced, placed on x ray film
   *when slice on film, area containg sugars turns blk- shows where phloem is

Question 12

Describe the use of ringing experiments to investigate transport in plants

Answer 12

*remove ring of bark
*bark above ring swells because sugars cant be transported due to phloem removal
*4. Tissues below ring die as cannot get organic substances
*analysis of liquids show substnace is sugar.