The "triple reaction" experiment with yellowing pea seedlings

Summary

Ethylene is a gaseous hormone that has multiple effects on plant metabolism, growth and development. Treatment of yellowing pea seedlings with ethylene gas inhibited the elongation of the seedling epigyne, and caused the epigyne to expand and grow laterally. These three responses of yellowed seedlings to ethylene are called the "three responses" and can be used as a diagnostic identification method for ethylene.

Operation method

The "triple reaction" experiment on yellowing pea seedlings

Principle

Ethylene is a gaseous hormone that has multiple effects on plant metabolism, growth and development. Treatment of yellowing pea seedlings with ethylene gas inhibits the elongation of the seedling's epigyne, and causes expansion and lateral growth of the epigyne. These three responses of yellowed seedlings to ethylene are known as the "three responses" and can be used as a diagnostic identification method for ethylene. This method is based on the main physiological effects of ethylene. It has been reported that ethylene increases the number of microfibers deposited on the inner surface of the cell wall in the longitudinal direction, which restricts the longitudinal extension of the cell and enhances the transverse expansion of the cell, resulting in restricted elongation of the epiblast axis and transverse expansion. Lateral growth is caused by ethylene inhibiting the lateral transport of growth hormone from the upward to the downward side of the epiblast axis, so that the upward side has more growth hormone than the downward side, and thus grows faster. This difference in growth between the upper and lower parts of the embryo is known as epinasty, and is a reaction characteristic of ethylene and its analogs (e.g., acetylene, propylene, etc.) as well as ethylene-producing substances (e.g., growth hormone analogs). The reaction is sensitive (low concentration that is reactive), occurs rapidly, and became the first application of a biological identification of ethylene. In modern times, gas chromatography is mostly used for quantitative determination of ethylene, but sometimes it needs to be applied in conjunction with bioassay.

Materials and Instruments

Yellowing pea seedlings
Ethylene gas
Flower pots Vermiculite Shelf Black cloth cover Glass test tubes with rubber stoppers Filter paper

Move

I. Materials and methods

Stage I: cultivation of yellowing pea seedlings

Instrumentation

Flower pots, vermiculite, rack, black cloth cover, glass test tubes about 4 cm in diameter and 20 cm in length with rubber stoppers, 10 per group, filter paper, ethylene gas or vinyl solution ^10-1, ^10-2, ^10-3, ^10-4 M, syringes, measuring cylinders 100 MM ³, 10 MM ³, dark cabinet

II. Experimental Steps

1. Selected pea seeds were soaked in a supersaturated bleach solution for 15 minutes, placed in a clean gauze bag, and siphoned up for one day in running tap water.

2. The seeds were sown in pots with vermiculite and placed at 25°C, under dark conditions.

3. Test yellowing pea seedlings when they reach about 4 cm (about one week).

4. Fill the test tube with water and then pour the water into a measuring cylinder to measure the actual volume of the test tube;

5. Wash the test tube with a small amount of alcohol and make a filter paper bridge at the bottom of the test tube;

Filter paper bridge practice: cut the filter paper into a width of about 1.2cm, about 10cm long, in the middle of the filter paper dug a small hole, the size of the hole allows pea shoots through can be, will be folded into three folds of filter paper into the test tube.

6. Pea seedlings from the hole in the filter paper inserted, so that the roots soaked in water, and then the test tube with a rubber stopper tightly;

7. Based on the measured test tube volume calculations, inject the corresponding ethylene gas with a syringe so that the concentration of ethylene gas in the test tube is 0, 0.5, 1.5, and 10 pp M .

Steps 6-7 above should be carried out in full light as far as possible.

8. One set of test tubes (with different concentrations of the treatments) is placed at 25°C for 2 days in the dark; the other set is placed in the light (200-500 foot-candles) for 2 days and observations are recorded.

II. Observation and documentation

1. Measure and record the length of seedlings treated with different concentrations of ethylene as described above, using concentration as the horizontal coordinate and length as the vertical coordinate;

2. Plot the effect of different concentrations of ethylene treatments on the morphology of yellowing pea seedlings.

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