The process of guttation takes place
1. When the root pressure is high and the rate of transpiration is low
2. When the root pressure is low and the rate of transpiration is high
3. When the root pressure equals the rate of transpiration
4. When the root pressure as well as rate of transpiration are high

The evolution of C4 photosynthetic system is probably one of the strategies for:

Advantages of transpiration to the plants include:
I. evaporative cooling.
II. mineral transport.
III. increased turgor.
1. I and II only
2. I and III only
3. II and III only
4. I, II and III

Unloading of mineral ions occurs at the fine vein endings through:
1. diffusion and, are passively taken up by the sink cells
2. active transport and, are passively taken up by the sink cells
3. diffusion and, are actively taken up by the sink cells
4. active transport and, are actively taken up by the sink cells

An analysis of xylem exudates will show that most of the nitrogen is carried as:
1. Inorganic ions
2. Ammonia dissolved in water
3. Dinitrogen
4. Organic compounds such as amino acids