Chp 6 Plant Water Realtion

Question 1

Freely permeable

Answer 1

Permeable (allows) the entry of all solutes and solvents

Question 2

Selectively permeable

Answer 2

Permeable (allows) the passage of water and solutes only

Question 3

Semi permeable

Answer 3

Permeable (allows) the passage of water only

Question 4

Gravitational water

Answer 4

Water percolates deep due to the gravity in the soil, which is called gravitational (free) water

Question 5

Hygroscopic water

Answer 5

Find soil particles imbibe/adsorb water and hold it. This is called hygroscopic water

Question 6

Combined water

Answer 6

Water present in form of hydrated oxides of silicon , aluminium etc is called combined water

Question 7

Capillary water

Answer 7

Some amount of water is held in the pores present between the neighbouring soil particles due to capillarity. This is called capillary water. Only this water is available for absorption by plants

Question 8

Dp

Answer 8

Diffusion results in diffusion pressure (dp) which is directly proportional to the number of diffusing particles. Dp of pure solvent is always more than the dp of solvent in a solution . Water around the cell wall has more dp than the cell sap.

Question 9

Dpd

Answer 9

The difference in the dp of of pure solvent and the dp of solvent in a solution. It is also called as suction pressure. Nowadays the term water potential is used for dpd.
Dpd is actually the thirst of a cell with which it absorbs water from the surrounding.

Question 10

What happens in tp

Answer 10

Turgor pressure (tp) is the pressure exerted by turgid cell sap on the cell membrane and cell wall. In a fully turgid cell, dpd is 0. Cell wall being thick and rigid , exerts pressure on the cell wall which is called as Wall pressure (wp). In fully turgid cells TP=WP but operating in opposite directions. Now tp is termed as pressure potential

Question 11

Osmotic pressure

Answer 11

O.P is the presser exerted due to osmosis. Osmotic pressure of a solution is equivalent to the pressure which must be exerted upon it to prevent flow of solvent across the semipermeable membrane. 
D.P.D = O.P - T.P
(T.P=W.P)
D.P.D = O.P - W.P
in a flaccid cell T.P is zero DPD = OP
in turgid cell DPD is zero TP=OP

Question 12

Facilitated diffusion

Answer 12

The passive absorption of solutes when mediated by a carrier, is called facilitated diffusion. Particles that are lipid soluble can easily diffuse through lipoproteinous cell membrane. The diffusion of hydrophilic solutes has to be facilitated because their diffusion across the membrane is difficult. Membrane proteins provide such sites fir facilitated diffusion. The movement of substance across membrane by the help of these proteins is without the expenditure of energy.concentration gradient must be present in the molecules.