List of top two experiments on plant movement:- 1. Demonstration of Different Kinds of Movement 2. Determination of the Temperature Coefficient (Q10) on Physiological Process.
Experiment # 1. Demonstration of Different Kinds of Movement:
Plant movement can be defined as the change in position of an organism or a part of its body. It may be autonomic (i.e. spontaneous) or induced (i.e. paratonic).
Methods used for determination of some kinds of movement are presented:
(a) Phototropism:
It is the light-induced tropic movement. The movement takes place towards the source of light due to unequal curvature of growth in the growing apex.
Materials Required:
1. Some young potted seedlings
2. Heliotropic chamber — A wooden cabinet having holes of different diameters which can be closed or opened as desired (Fig. 3.32)
3. Artificial light sources
Procedure:
1. Place the potted plant inside the heliotropic chamber.
2. Close the holes of the chamber at first to cut off the light sources.
3. Allow the plant to grow in darkness for 2-3 days.
4. Open one hole of suitable diameter to diffuse light inside the chamber.
5. A potted plant of the same species is grown in darkroom as control.
Observation:
After 2 or 3 days it is observed that the plant bends towards the incident light, whereas the plant grown in darkness is straight.
Explanation:
If a seedling is exposed to unilateral light it results in an unequal distribution of hormones on the two sides of the tip. The darker side always has more hormone content than the illuminated side. Light causes the destruction of hormone on the illuminated side. Due to differential hormone distribution, the phototropic curvature takes place.
(b) Geotropism:
It is the gravity induced tropic movement of plant organs.
Materials Required:
1. Some young gram seedlings
2. Glass jar
3. Cotton.
Procedure:
1. Place some young gram seedlings in different positions on the moist cotton inside a glass jar, so that some have the plumular end downward; others have the plumular end upward while still others have the plumular end in horizontal position (Fig. 3.33).
2. Allow the seedlings to grow for a few days.
Observation:
It is observed that in all the cases the radicle grows downwards and plumule upwards.
Explanation:
Roots are primarily positively geotropic i.e., bend towards the centre of the earth and stems are negatively geotropic, i.e., grow vertically upwards. These geotropic curvatures are again due to unequal growth of root and shoot apices of the seedlings and unequal hormonal distribution and their differential growth effect result into these curvatures.
Experiment # 2. Determination of the Temperature Coefficient (Q10) on Physiological Process:
The influence of temperature on the rate of biological processes is extremely important. Most-of the physiological processes in the living plant cells are the result of series of chemical reactions, the velocity of which is related to temperature. This is known as “Vant Hoff’s Law” or “temperature coefficient (Q10)”.
It is the ratio of the reaction rate (velocity) at 10°C higher by the velocity at particular temperature:
Temperature Coefficient (Q10) = Velocity (T0 +100)/Velocity at T0
When temperature acts directly on any physiological process, a rise of temperature by 10°C usually cause a doubling or trebling of the rate of biological activity and is termed as Q10 2 or 3.
However, in physical reactions such as diffusion and photo driven reactions, the Q10 is relatively low (1.2 to 1.4). For enzymatic reaction the Q10 values may be higher (1.3 to 5.0), of course within a certain temperature range (i.e. from 20°-40°C).
Materials and Equipments Required:
1. Pea seeds
2. Beaker, distilled water
3. Balance with weight box
4. Graph papers, pencils, stop-watch, blotting papers etc.
Procedure:
1. Take 5 gms of dry pea seeds separately in three beakers.
2. Add about 50 ml of dist. water to each beaker and maintain the water temperature within an incubator at 20± 1°C, 30± PC and 40 ± 1°C for an hour. Perform the experiment in triplicate.
3. Then remove wet seeds and blot carefully. Take the final weight.
4. Calculate the percentage of water absorption against each temperature and graphically plot the data.
Results:
Inference:
Temperature has profound effect on physiological processes.