Biology :))

Question 1

Functions and structure of xylem

Answer 1

Functions : conducts water and dissolved minerals salts from the roots to the stem and leavse, it also provides mechanical support for the plant
Structure: made of many dead cells fused together at the end to form a king hollow tube, long continuous lumen with no crosswalls or protoplasm, lignin deposits in the inner walls of xylem vessels

Question 2

What are the types or different patterns if lignification?

Answer 2

• annular, spiral and pitted

Question 3

Advantages of annular/spiral lignification?

Advantages of pitted lignification?

Pits are present in heavily lignification xylem vessels to allow lateral transport of water out of the vessel and into neighbouring tissues.

Answer 3

1. To accommodate the growth of the plant as it allows the xylem vessels to stretch with the region that is growing
2. More lignin deposited equates to more mechanical support for the plant. This type of lignification often found in older parts of the plant,

Question 4

Function of phloem?

Answer 4

• to transport manufactured food (sucrose and amino acids) from leaves to other parts of the plant

Question 5

Structure of phloem? 3 things

Answer 5

1. Sieve tube cells are elongated cells that lack nuclei and have thin layers of cytoplasm
2. Sieve tube elements are made of sieve tube cells that are joined end to end to form a column with sieve plates in between.
3. Sieve plates are cross walls with many small sieve pores

Question 6

Structure of phloem (companion cell) 2 thinggbs

Answer 6

1. Narrow, thin walled cell with cytoplasm nucleus and numerous mitochondria
2. A mature sieve tube does not have many of its organelles, therefore it is always associated with a companion cell. The companion cell keeps the sieve tube cell alive by providing it with nutrients and energy.

Question 7

How is the phloem adapted to its function? 4 things

Answer 7

1. Phloem sieve tube elements have very little protoplasm and are arranged to form a continuous column. -> reduces resistance to flow of substances within the phloem
2. Pores within the sieve plates allow rapid flow of manufactured food substances
3. Companion cell have multiple mitochondria to release energy for the loading of sugars into the phloem sieve tubes
4. Every phloem sieve tube cell has an associated companion cell to survive

Question 8

Adaptations of xylem

Answer 8

Xylem
- lignified walls so that when bundled together, provide more mechanical support
- no cross walls to ensure that water can be transported unimpeded
- empty lumen without protoplasm, so that there is no blockage and water can be transported easily

Question 9

Adaptations of phloem:

Answer 9

• pores in the sieve plates between sections of the sieve tube cells to allow flow of manufactured food substance in the sieve tube through translocation
  Presence of companion cells , to release energy for transport of manufactured food substances to the sieve tubes

Question 10

What is translocation?

Answer 10

• Transport of sucrose and amino acids in the phloem from regions or production to regions of use
• bidirectional
• food substances can move down phloem tissues to roots or up to the leaves

Question 11

What is translocation?

Answer 11

• Transport of sucrose and amino acids in the phloem from regions or production to regions of use
• bidirectional
• food substances can move down phloem tissues to roots or up to the leaves