1. How do cacti perform photosynthesis even though the stomata are closed during day time?

The stomata of many cacti are closed during the day, when temperatures are high, and open at night when evaporation is at a minimum. This strategy requires a slightly different form of photosynthesis. At night, carbon dioxide diffuses in through the open stomata and is incorporated into an organic acid. In the day time, the stomata are closed, but this organic acid breaks down to yield carbon dioxide which is then built into sugars  by photosynthesis.

2. Explain the nature of the liquid which travels through the xylem.

The liquid which travels in the xylem is not , in fact, pure water. It is a very dilute solution, containing from 0.1 to 1 percent dissolved solids, mostly amino acids, other organic acids and mineral salts.

3. What is translocation?

Translocation is defined as the movement of soluble materials such as minerals, proteins, hormones and sugars within the plant. Translocation occurs primarily in the vascular parts of the plant which are the xylem and phloem. These can be compared to the blood vessels which is present in animals.

4. Why is translocation essential in plants?

Translocation is defined as the movement of soluble materials such as minerals, proteins, hormones and sugars within the plant. Translocation occurs primarily in the vascular parts of the plant which are the xylem and phloem. These can be compared to the blood vessels which is present in animals. The xylem transports mainly water and minerals dissolved in it; these are raw materials which originally came from outside the plant and absorbed through its roots which was then transported upwards into the xylem. The phloem transports organic materials, materials which was manufactured by the plant such as glucose, hormones and proteins. If there is no translocation in plants, they would not be able to obtain the nutrients such as water and minerals they need in order to manufacture food. Also if translocation didn't occur the food manufactured by the leaves would not be received by other parts of the plant.

5. Explain the pathways of water through a root.

The cytoplasm of the root hair is partially permeable to water. The soil water is more dilute than the cell sap and so water passes by osmosis from the soil into the cell sap of the root hair cell. This flow of water into the root hair cell raises the cell’s turgor pressure. So water is forced out through the cell wall into the next cell and so on, rightly through the cortex of the root to the xylem vessels.

6. Explain the process of transport of gases in plants.

The process of diffusion accounts for the movement of gases in and out of a plant. During respiration, oxygen is taken in and carbon dioxide given out. When photosynthesis is faster than respiration, carbon dioxide diffuses in and oxygen diffuses out. In leaves and green stems, the gases enter and leave through the stomata. Then they diffuse through the air spaces between the cells to reach all parts of the plant shoot. In woody plants, gases pass through small opening of the bark called lenticels. Roots obtain their oxygen from the airspaces in the soil. Much of this oxygen will be dissolved in the soil water which enters the root through the growing region and the root hairs.

7. What are systemic pesticides?

Some insecticides and fungicide sprays are absorbed through the leaves and translocated through the plant. Such pesticides are called systemic because they enter the plant’s system.

8. What do you mean by foliar feeding?

Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to their leaves.  It has been known for many years that plants are able to absorb essential elements through their leaves. The absorption takes place through the stomata of the leaves and also through the epidermis. Movement of elements is usually faster through the stomata, but the total absorption may be as great through the epidermis. Plants are also able to absorb nutrients through their bark.

9. What is a potometer?

A potometer is a device used for measuring the rate of water uptake of a leafy plant shoot. The main reason for water uptake by a cut shoot is transpiration (evaporation in plants) and is affected by the transpiration stream.

10. Describe an experiment to show that water travel up in the vascular bundles.

Place the shoots of several leafy shoots in a solution of 1 percent methylene blue. Busy Lizzie or celery stalks with leaves are usually effective. Leave the shoots in the light for 30 minutes or more. It can be seen that after this time, the blue dye will appear in the leaf veins. If some of the veins are cut across, the dye will be seen in the vascular bundles. These results show that the dye, and therefore, probably also the water, travel up the stem in the vascular bundles.