9.4 Translocation

Question 1

Assimilates definition:

Answer 1

Temperature

Question 2

Where do plants transport organic compounds?

Answer 2

From sources to sinks

Sources e.g. green leaves/stems, storage organs like tubers or food stores in seeds

Sinks e.g. Roots, meristems or any part of plant laying down food stores

Question 3

translocation

Answer 3

the movement of dissolved substances, such as sucrose and amino acids, from parts of the plant where the substances are made to other parts of the plant where they’re needed.

Question 4

Apoplast route of phloem loading

Answer 4

1. Active transport of H+ ions by proton pump via carrier proteins ( Higher conc of H+ ions outside of companion cell
2. Lower H+ conc inside companion cell= H+ ions moving into companion cell via facilitated diffusion
3. As H+ goes into co-transport protein, sucrose is co-transported into the companion cell, against conc gradient ( electro-chemical gradient provides the necessary energy)
4. Conc of sucrose in companion cells increases= low water potential=water goes into cells via osmosis= greater turgor pressure
5. Water carrying assimilates moves into tubes of sieve elements to reduce pressure, movement of solutes into sinks

Question 5

Phloem unloading

Answer 5

sucrose is unloaded from phloem at any point to cells that need it
–> sucrose rapidly moves into other cells by diffusion so that sucros conc gradient is maintained