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Top 16 Experiments on Respiration in Plants (With Diagram)
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The following points highlight the top sixteen experiments on respiration in plants. Some of the experiments are: 1. Demonstration of Aerobic Respiration in Plants 2. Demonstration of Anaerobic Respiration 3. Demonstration of Alcoholic Fermentation 4. Determination of Rate of Respiration 5. Comparison of Rate of Respiration in different Plant Parts and Others.
Experiment # 1
Demonstration of aerobic respiration in plants:.
Experiment:
Aerobic respiration in plants can be experimentally proved with the help of a simple apparatus like :
(i) Respiroscope which consists essentially of a stout vertical tube which is bent into a bulb at the one end (Figure 19a), or
(ii) With the help of a long-necked round-bottomed flask fitted with a centrally-bored cork at the mouth through which passes a glass tube (Figure 19b).
The effects of temperature or other factors upon the respiration and RQ of seeds and plant tissues may be measured by this apparatus.
(b) By Pettenkoffer’s gas stream method of CO 2 estimation Principle and description of apparatus:
The principle of this method is that CO 2 liberated by respiratory tissue is removed from its chamber along with CO 2 free gas stream and absorbed in baryta (Barium hydroxide solution) taken in Pettenkoffer’s tube to form barium carbonate.
This is then titrated by a standard acid (HCL) to know its CO 2 content. CO 2 free air is drawn through a system as shown in Figure 24.
Experiment # 9
Demonstration of loss of weight in respiration :.
About 50 seeds are surface sterilised with, 1% HgCL 2 , washed thoroughly and 5 such seeds are separately placed in ten petridishes containing soaked filter paper. The pertidishes are kept in dark and seeds are allowed to germinate. The fresh and dry weights of each lot of seedlings are taken every alternate day.
The percentage loss in dry weight is calculated in each case and the results are graphically plotted taking loss in weight as ordinate and days as abscissa.
Respiration is a catabolic process which takes place by breaking down of stored carbohydrate and liberating CO 2 , H 2 O and energy. Since the seedlings are grown in dark the anabolic process, i.e., photosynthesis, cannot take place and as a result of which loss in weight occurs as the plants grow.
Experiment # 10
Effect of wounding on respiration:.
Experiment can be conveniently performed either with Warburg’s method or Pettenkoffer’s method. Two lots of potato tubers are taken; one lot is slightly larger than the other.
The larger potatoes are peeled off and surface area is made comparable with the other lot. Approximately the equal weights of these two lots are washed and dried and the two samples are placed in two respiration chambers of the Pettenkoffer’s apparatus or in the flasks of Warburg’s apparatus. The rate of respiration is determined in both the cases at a constant temperature.
Respiration rates in millilitres of CO 2 per gram dry tissue per hour are plotted. The dry weights of the samples are determined at the end of the experiment.
Injury to a given plant tissue often causes the respiratory activity to increase. Generally, in case of injured plant tissues the rate of respiration increases for the time being and this increase gradually rises to a maximum point and then the rate decreases.
Wounding generally initiates meristematic activity in the area of the wound, resulting in the development of “wound callus”. It has been shown that a considerable increase in sugar content (about 70%) around the injured cells takes place.
Perhaps the increase in respiration due to wounding is caused by increased availability of respiratory substrate and meristematic cells.
Experiment # 11
Effect of pre-treatment with carbon dioxide on the rate of respiration :.
Equal weights of three lots of potato tubers are taken. Two lots are taken in two petridishes placed on, two ground glass plates and each is covered with a 1litre bell jar having an outlet at the top (Figure 25).
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