Question

Water potential in plant tissues is affected by three factors, namely dissolved solutes, matric forces acting on water ( such as intermolecular attractions and binding of water to surfaces) and hydrostatic pressure exerted by cell walls, Thus total water potential (Ψ_T) in plants is expressed as :

Ψ_T = Ψ_s +Ψ_m +Ψ_p = where T = total, s = solute, p = pressure and m = matric poteptial. A few statements about the water potential or these factors are given. 

State whether each of them is true (T) or false (F) 

a. In a rapidly transpiring spruce tree, water flows upwards, down the water potential gradient, from soil (-1.5 MPa) to termial shoot (-0.04 MPa). ______

b. Water potential in xylem of gutting plants whose hydathodes release water drops must be positive. ________ 

c. Water potential of apoplast will have Ψ_m m as the major contributing factor while that in a vacuole will have Ψ_s as a major contribution factor. ________ 

d. If Ψ_w of vacuole is lower than Ψ_w of apoplast, then there will be a net efflux of water across cytoplasm resulting into a flaccid cell. ________

Answer 1

a. In a rapidly transpiring spruce tree, water flows upwards, down the water potential gradient, from soil (-1.5 MPa) to termial shoot (-0.04 MPa). False

b. Water potential in xylem of gutting plants whose hydathodes release water drops must be positive. True

c. Water potential of apoplast will have Ψ_m m as the major contributing factor while that in a vacuole will have Ψ_s as a major contribution factor. True

d. If Ψ_w of vacuole is lower than Ψ_w of apoplast, then there will be a net efflux of water across cytoplasm resulting into a flaccid cell. False