18. Give reasons for the following statements I

1. Minerals cannot be passively absorbed by the roots.

 

a. Minerals exist in the soil as chargedneutral particles that are unable to cross cell membranes.

 

b. The mineral concentration in the soil is lowerhigher than the mineral concentration in the root.

 

2. Guard cells are responsible for opening and closing of stomata.

 

a. Changes in the  turgorconcentrationof the guard cell cause the stomata to open and close.

 

b. The entry and departure of oxygenwater  into and out of the guard cells causes turgor variations in the guard cells.

 

c. During the nightday, water from subsidiary cells enters the guard cells, making it fully turgid and forcing the stomata to open.

 

d. During the daynight, water from guard cells enters subsidiary cells, making the guard cells flaccid and forcing the stomata to close.

 

3. The movement of substances in the phloem can be in any direction.

 

a. As food travels uphill or downwards to reach plant parts such as stems, leaves, flowers, buds, seeds etc., the material movement in the phloem can be in any direction. FalseTrue