Transport in plants Flashcards
1
Q
State what is meant by the terms source and sink.
A
source= where sucrose loads into phloem
sink= where sucrose unloads from phloem
2
Q
Explain the significance of the relationship between rate of diffusion and the surface area to volume ratio for large plants (2)
A
(large plants) have a, small / low, SA : VOL ratio ;
idea of diffusion too slow (to supply requirements) ;
idea of need transport system (for water / minerals /
assimilates) ;
idea of need (special) surface area for, gaseous exchange
/ uptake of minerals ;
3
Q
State the function of this spiral band of lignin and explain why it is important that the xylem vessel becomes lignified in this way.
A
- lignin strengthens/thickens the xylem wall to prevent collapse of xylem
- lignin waterproofs walls
- improves adhesion of water molecules
- reduced water loss
