give reasonable values for a plant at dawn osmotic potential

8. (a Give able values for the following table for a nt at dawn reason pla water potential osmotic potential pressure potential location soil next to root hair ,O2 root hair vessel in root vessel in leaf mesophyll cell in leaf (b) Give reasonable values for the same plant at 2pm osmotic potential pressure potential water potential location soil next to root hair root hair vessel in root vessel in leaf mesophyll cell in leaf

Solution

Ans 8: Water movement in plant take place through transpiration process by xylem tissue from root to leaves.There are three different types of potential exist during the movement of water in plant. The water potential is the potential energy of water per unit volume relative to pure water in reference condition. Pure water has maximum water potential which is 0, because it does not contain any solute.Water potential is the sum of osmotic potential or solute potential and pressure potential. Osmotic potential are always negative whereas pressure potential are always positive. Osmotic potential are the potential of water molecule to move from a hypotonicsolution (more water,less solute) to a hypertonic solution (less water, more solute) across semipermeable membrane and pressure potential are the component of water potential due to hydrostatic pressure. Environmental condition has great influence on these potential. As the question asked about the effect of different potential at two different times one is at dawn condition at that time mositure content is high in soil and rate of transpiration is low, the value for different potential on different tissues are as follows:

Soil next to root hair: O.P= -.02, P.P= +5,W.P= -.02+(+5)=4.98

Root hair: O.P= -.02, P.P= +6, W.P= 5.98

Vessel in the root, O.P=-.04, P.P= +7, W.P= 6.96

Vessel in leaf, O.P= -.06, P.P= +7, W.P= 6.94

Mesophyll cell in leaf, O.P= -.06, P.P= +8, W.P= 7.94

In afternoon at 2 Pm , rate of transpiration is high, so the effect of O.P, P.P and W.P will be different on plant issue

Soil next to root hair, O.P= -0.2, P.P= +7, W.P= 6.8

Root hair, O.P= -0.2, P.P= +7, W.P= 6.8

Vessel in the root, O.P= -0.4, P.P=+8, W.P= 7.6

Vessel in the leaf, O.P= -O.6, P.P= +12, W.P=11.4

Mesophyll cell in the leaf, O.P=-0.6, P.P=+13, W.P=12.4