Plants Flashcards
1
Q
The xylem
A
- Transports water and minerals up the plant
- dead cells - their walls are lignin
- xylm tubes help to support the plant
- offer little resistance to water
- made from columns of cambium cells their protoplasts and end walls die leaving hollow tubes
- cell walls are impregnated with the lignin in spirals and rings
- non - lignified areas called boarderd pits
2
Q
The phloem
A
- conduct sugars and other organic materials
- living tissues , made up of sieve tube members joined end to end
- sieve tube members lack a nucleus and vacuoles
- walls between members are called sieve plates which have pores and plasmodesmata
- sieve tube members are associated with a companion cell
- connected by plasmodesmata
- carry out all the cellular functions
- like normal plant cells but more metabolically active
3
Q
Movement of water up the plant
A
- Transport systems in plants use mass flow
- mass flow of water and minerals is through the xylem
- water movement through roots, the stem and leaf is different
- normally the air spaces of a leaf are more humid than the air
- water transpired out of the stomata and is lost
4
Q
Movement of water in the roots
A
- The apoplast pathway
2 the symplast pathway - Cohesive and adhesive forces
5
Q
The apoplast pathway
A
- water travels from cell through to cell wall
- water uses adhesion to stick to the walls
- evaporation of water in the airspace’s of the leaf creates a tension that pulls in water from walls or surrounding cells
- water is transported by cohesive forces
- H+ bonding in water
6
Q
The symplast pathway
A
- some water is lost to air spaces from cytoplasm of surrounding cells
- water potential of cytoplasm is lower
- between adjacent cells are tiny strands of cytoplasm called plasmodesmata
- water passes along these from cells with a higher water potential
7
Q
Movement of water
A
- cohesive forces
- due to H+ bonding of water
- passive
- adhesive forces
- attracted to sides of xylem
- Tension is provided by transpiration
