Deck 5: Roots and Soils

Question 1

Japanese gardeners regularly trim away parts of the root system to assist in dwarfing a plant. A plant's food is obtained through photosynthesis in the leaves; can you suggest why trimming the roots can cause dwarfing?

Answer 1

Dwarfing is a process in which the plants become significantly smaller. This effect can be genetic or hormonal. The root tip secretes hormone called cytokinins which is a shoot promoting hormone. If the roots are cutted the production of cytokinins is reduced. Cytokinins promote cell division. This hormone removes apical dominance and works against auxin which is produced at the root tip and travel to shoot. This causes the dwarfing of plants. Thus trimming away the parts of the root system assist in dwarfing a plant.
Photosynthesis in plants occurs in leaves. Leaves contain waxy substance called cuticle which retains the water. It contains stoma for the passage of C O₂ and O₂ to escape. Sunlight is absorbed by chlorophyll a green pigment in chloroplast. These are the sites of photosynthesis. Carbon dioxide, water and sunlight are the three elements required for the synthesis of food in the leaves by a process called photosynthesis. The equation can be summarised by the following equation:
Carbon dioxide + water + (light energy) oxygen + glucose

Question 2

Distinguish between a tiny root and a root hair. What is the function of a root hair?

Answer 2

During the germination of seed the tiny root arise from seed called radical. It develops into embryo and grows into first root. This develops into thick tap root and thin branched adventitious roots.
Cells mature and differentiate into different types cell types from the primary tissue called root hair zone. Large number of hair like delicate protuberances develops from the epidermal cells which give rise to root hair zone. The protuberances called root hairs. Root hairs greatly increase the surface area absorption.
Functions of the root:
• Roots absorb water and minerals in the solution.
• Anchoring and absorbing.
• Store water and food.
• Perform specialized functions.

Question 3

It was suggested that roots perceive gravity through the root cap. Would it really matter if roots grew randomly in the soil instead of responding to gravity?

Answer 3

Yes, it would really matter if roots grow randomly in the soil instead of responding to gravity. It is because the plant usually contains either tap root or fibrous root system (adventitious roots). The tap roots grow to the deeper regions of the soil where it enhances the full potency to the plant. The fibrous root system develops randomly on the upper layers of the soil which would not give the support to the plant. Fibrous root system would appear mostly in herbs and shrubs. Thus the randomly growing roots cause the fall down of the tree since the gravity is not helping to support the tree to stand.
Thus the plant growing randomly in the soil would falls down due to less support to the plant.

Question 4

What is the difference between parasitic roots and mycorrhizae?

Question 5

From the viewpoint of the plant, can you suggest a practical reason for branch roots originating internally instead of at the surface?

Question 6

If you were shown cross sections of a young root and a young stem from the same dicot plant, how could you tell them apart?

Question 7

When you eat a yam or a sweet potato, what kinds of compounds and cells are you consuming?

Question 8

What is the function of the root cap, and from which meristem does it originate?

Question 9

Persons associated with commercial nurseries and greenhouses often sterilize their soil by heating it to get rid of pests, but then they have to wait for a short time after it has cooled to use it. Why?

Question 10

How do endodermal cells differ from other types of cells?

Question 11

Where do branch roots originate?

Question 12

List some spices and drugs obtained from roots.

Question 13

What is soil parent material? Where does it come from, and how does it become soil?

Question 14

What is the difference between soil texture and soil structure?

Question 15

What types of soil water are recognized? What is available soil water?