mass transport

Question 1

what is root pressure?

Answer 1

created as a result of water entering the root by osmosis. this is encouraged by the high cocentration of mineral ions in the root hair cells

Question 2

define translocation

Answer 2

the process by which organic substances are transported from their site of production (sources) to sites where they will be used or stores (sinks)

Question 3

describe the structure of phloem

Answer 3

• composed of sieve tube elements which form end to end
• end walls are not completely broken down, but perforated to form sieve plates
• ploem cells remain alive, but are supported in their function by being closely associated with companion cells

Question 4

what are some adaptation of the xylem?

Answer 4

• absence of cross walls or protoplasm - enables water to move easily through the lumen
• lignin deposited on walls of xylem vessles - strengthens wall and prevents from collapsing
• long, hollow tubes frmed from xylem cells laid end to end - allows water and mineral salts to be conducted from roots to stem and leaves

Question 5

describe the structure of xylem

Answer 5

• dead
• end walls broken down
• no cell contents
• lignified cell walls
• strength and flexibility
• continuous column of cells
• borderd pits