Analysis of Effect of Compound Salt Stress on Seed Germination and Salt Tolerance Analysis of Pepper (Capsicum annuum L.)

This study provides theoretical guidance for breeding salt tolerance pepper varieties and calibrating high yield and quality in saline-alkali soil. The experimentation period is 15 days with high efficiency, faster speed, good repeatability, and accurate results. This technology can provide technical references and theoretical guidance for the evaluation of salt tolerance of other crops.

Desire preliminary expert to rather evaluate the salt tolerance of seeds. Begin by preparing the crop seeds for Hongtianhu 101 cultivar with strong salt tolerance, and Xinxiang 8 cultivar with low tolerance. Prepare 2000 milliliters of 0.2%potassium permanganate solution as a seed disinfectant reagent just before the use.

Prepare the mixed salt solution using seven salts, including sodium carbonate, sodium bicarbonate, sodium chloride, calcium chloride, magnesium chloride, magnesium sulfate, and sodium sulfate. Then prepare single use, nine centimeter Petri dishes, and nine centimeter medium speed qualitative filter paper. Select pepper seeds with consistent size and full particles from each variety, with an average diameter of 4.2 millimeters for Hongtianhu 101 and 3.7 millimeters for Xinxiang 8 seeds.

Calculate the total number of seeds selected according to the test workload. For seed disinfection, soak selected pepper seeds in 0.2%potassium permanganate solution. After 15 minutes, rinse the seeds five times with distilled water.

Transfer the sterilized seeds to distilled water for 24 hours for soaking. Once done, rinse the seeds several times with distilled water before drying them for further use. Prepare six concentrations of the mixed salts and measure the conductivity of the salt solution, using a conductivity meter.

In a Petri dish with two layers of filter paper, evenly place 40 pepper seeds. Prepare the seeds for six experimental treatments and five replicates. Add a suitable amount of the six mixed salt concentrations to the Petri dish for germination, to ensure the filter paper is moist.

Place the seeds in an air incubator at 28 degrees Celsius and 80%air humidity for germination in the dark. After seed germination, allow the seedlings to grow for 14 days in approximately 450 lux light intensity. With the light cycle of 12 hour dark, and 12 hour light period in the incubator.

Replenish the solution in the culture dish every 12 hours to retain a moist filter paper, and completely wash the filter paper every 24 hours with the corresponding concentration of the mixed salt solution, to keep a constant mixed salt concentration in the Petri dish. For the seed germination indexes, determine the germination rate, daily, after sowing with the radical breaking the seed coat, reaching half the seed diameter length as the germination marker. To determine the seedling growth index, randomly select 10 representative seedlings from each Petri dish on day 14 after sowing, and measure the root length and hypocotyl length.

Use a knife to divide the pepper seedlings into radical and above ground parts. Remove the water from the seedlings by wiping, and weigh the seedlings separately to determine the fresh weight. To preserve the pepper seedlings, select approximately 24 grams of representative whole pepper seedlings from each treatment on day 14 after sowing.

After removing the surface water, immediately freeze the seedlings in liquid nitrogen for one minute. And store them in a refrigerator at minus 80 degrees Celsius. Retrieve approximately one gram seedling sample from each treatment collected in triplicate.

Immediately, place the seedling sample in a centrifuge tube. Add liquid nitrogen, and grind the sample using a grinding rod to determine the physiological indexes of the seedlings, including the seedling protective enzyme activity, malondialdehyde, and proline contents. As the mixed salt concentration increased, the germination potential and germination index of Hongtianhu 101 and Xinxiang 8 decreased significantly.

As the mixed salt concentrations increased, the germination rate of the two varieties gradually decreased, and the relative salt damage rate for the varieties increased. The seed germination vigor index of Hongtianhu 101 was higher than that of Xinxiang 8 at each mixed salt concentration level. At 15 grams per liter mixed concentration, the root length of Hongtianhu 101 and Xinxiang 8 decreased by 89.4%and 91.1%and the root fresh weight decreased by 81.7%and 71.2%respectively, compared to the control.

Based on the varietal differences, the hypocotyl length, and fresh weight above ground of Xinxiang 8, were higher than Hongtianhu 101 at each salt concentration. At five and three grams per liter concentrations of malondialdehyde and proline contents reached their lowest values respectively. At the salt concentration of three to 15 grams per liter, the proline content of Xinxiang 8 slowly increased and remained relatively stable, whereas the proline content of Hongtianhu 101 increased rapidly.

As the mixed salt concentration increased, the catalase, peroxidase, and superoxide dismutase activities of Hongtianhu 101 and Xinxiang 8 seedlings decreased, and then increased, with the lowest values obtained at three grams per liter. The catalase and peroxidase activities of Hongtianhu 101 were higher than Xinxiang 8, and the difference between them increased gradually. Keep a constant of mixed salt concentration in the Petri dish by retaining a moist filter paper and completely washing the filter paper.

Researchers can innovate on the basis of this experiment, such as changing the ratio of different mixed salts to obtain more extensive and in-depth results.