Journey Of Water In Plant

Question 1

Absorption of water occurs by

Answer 1

• inactive process
• bulk flow
• simple diffusion
• depending on conc gradient
• aquaporins ( facilitated diffusion)

AQUAPORIN
Activates and inactivation depends on phosphorylation, pH, divalent cations
6 transmembrane alpha helix (1-6)
5 loops (A-E)
Loop B and E has + NPA (AA) MOTIFS

When plant absorbs water from soil, soil creates negative pressure gradient and therefore creates a pull and water from nearby region comes there by bulk flow

Question 2

Movement of water radially

Answer 2

Epidermis to cortex to endoderms to stele

When low transpiration
Root absorb water
Ions in absorbed water goes into xylem
Chemical potential of xylem sap decrease
Creates positive hydrostatic pressure

When high transportation
Water moves fas
No time for root pressure
Due to transpiration negative hydrostatic pressure

Question 3

2 types of radial moment in root

Answer 3

apoplastic pathway
Fast
Occurs in cotex
Therefore the major part
No plasma membrane involved

Symplastic pathway
Slow
When water encounter endodermis’s casperian strip it moves inside cell
By plasmodesmata

Question 4

How does water and minerals move vertically? Name and mechanism

Answer 4

Ascent of sap
Transpirational pull/cohesion-tension theory. By dixon and jolly
-pulls water

Occus by
Cohesive force (same type of molecules)
Adhesive force (water w walls of trachea of xylem)
Surface tension

Question 5

What is cavitation/ embolism. And how plant prevent ot

Answer 5

Water in xylem can cause cavitation (gas bubble)
Which blocks water transport

Plants prevent it by
-Having pores
- end walls of vessel

Question 6

Driving force of transpiration?

Answer 6

Diff in water vapours pressure

Question 7

Types of transpiration

Answer 7

Cuticular- cuticle=wax and cutin. 5-10% of total
Lenticular-1-5% of total transpiration
Stomatal- turgor operated valves 90%

Question 8

Mechanism of Opening of stomata

Answer 8

-sunlight
- blue light perception by guard cell by zeaxanthin
-activation of serine/therionine kinase
- phosphorylation of H-ATPase
-opening of K channels
- maintain by Chloride
- production of malate and sucrose
- increase in solute
-decrease water potential
- water moves inside
-guard cell flaccid
Transpiration

Question 9

Factors effecting transpiration

Answer 9

Humidity - inversely
Wind- proportional
Temp- proportional
Soil water- proportional
Light- proportional

Internal factor
No of stomata
Thickness of cuticle
Leaf area
Distribution of stomata

Question 10

Transpiration ratio

Answer 10

Water lost to carbon dioxide fixed

c3 plant- 500
C4 plant- 250
CAM- 50

Question 11

Driving force for guttation

Answer 11

Positive hydrostatic root pressure
Occurs when transpiration low and absorption high
I.e humid damp night

Question 12

Guttation occurs through

Answer 12

Hydathodes/ epithem cell