Respiration intensity is one of the most important indicators of plant life activity and is necessary to be measured in plant physiological research and production practice. In this experiment, we will practice the technique of determining the respiration intensity using the wide-mouth vial method (small basket method) and learn the effect of different conditions on the respiration intensity.
Operation method
Experiments for the determination of respiratory strength
Principle
The intensity of respiration of a certain plant material can be measured by calculating the amount of CO2 released per unit time. The CO2 given off by respiration can be absorbed by barium hydroxide solution and measured by titration. If you compare the respiration intensity under different conditions, you can find out the effect of different conditions on the respiration intensity. Move I. Materials and equipment For more product details, please visit Aladdin Scientific website.
1. Plant materials: (1) dry wheat seeds; (2) germinated wheat seeds; (3) wetted but ungerminated wheat seeds.
2. Instruments and appliances: (1) a set of wide-mouth flask respirometry device, (2) a rack of pallet balance, (3) an acid buret and an alkali buret, (4) a set of burette rack, (5) a thermostatic water bath.
3. Reagents: (1) 1N oxalic acid solution (each ml of 1N oxalic acid is equivalent to 1mgCO2); (2) 0.1N barium hydroxide solution; (3) phenolphthalein indicator.
II. Methods
1. Determination of respiratory intensity:
(1) Take a 500 ml wide-mouth bottle, plus a one-hole rubber stopper. Hole diameter of about 1 cm, for titration, usually with a small rubber stopper plug tightly, below the stopper hang a wire basket, in order to load plant material. The whole device can be called "wide-mouth bottle respiration device".
(2) accurately add 20 ml of 0.1 N barium hydroxide solution to the bottle, and immediately tighten the rubber stopper (without a small basket). Shake the bottle fully for a few minutes, after all the CO2 in the bottle is absorbed, pull out the small rubber stopper and add 3 drops of phenolphthalein reagent, insert the buret into the hole, and perform a blank titration with 1/22N oxalic acid solution until the red color just disappears.
(3) Pour out the waste solution, washed with CO2-free distilled water (boiled), re-added the same barium hydroxide solution 20 ml, while weighing the plant material (germinated wheat seeds) 5 grams, loaded into a small wire basket, hanging in the rubber stopper under the stopper, the stopper over the bottle, began to record the time, after 20-30 minutes, during which time, gently shaking a number of times, so that the surface of the solution of barium carbonate film is destroyed and conducive to the CO2 The solution surface barium carbonate film was destroyed to facilitate the full absorption of CO2. To the predetermined time, gently open the plug, the small basket containing plant material quickly removed immediately re-plugged tightly, shaking fully for 2 minutes, so that the CO2 in the bottle is completely absorbed, and then pull out the small rubber stopper, add phenolphthalein 3 drops, titrate with oxalic acid as before. Care was taken to prevent the intrusion of exhaled gas from the mouth into the bottle.
(4) Calculate the intensity of respiration (milligrams of CO2 released per gram of tissue per hour):
Respiratory intensity (mg CO2/g tissue-hr) =
2. Effect of different conditions on respiratory intensity:
(1) Use four respiratory flasks of the same size as previously described (may be done jointly by four experimental groups) and treat as above:
① Add 100 dry seeds (wheat or other seeds, the same below) on a 30 ℃ constant temperature water bath:
② Add 100 soaked seeds on a thermostatic water bath at 30°C;
③ Add germinated seeds 100 seeds, on a 30 ℃ constant temperature water bath;
④ Add 100 pcs of germinated seeds, at room temperature around 10℃.
(2) After 30 minutes, gently remove the seeds from the respiration vials, and then titrate with oxalic acid as before and calculate the respiration intensity of each vial (the number of milligrams of CO2 given off by 100 seeds in 1 hour) using the following formula: 
(3) Record the results of the measurements for the different treatments in the table below and interpret them. 