Six Methods to Improve Licorice Germination Rate
Licorice is a perennial herbaceous plant of the Fabaceae family, with its dried roots and rhizomes used as medicine. It has the effects of tonifying the spleen and replenishing qi, resolving phlegm and relieving cough, clearing heat and detoxifying, relieving urgency and stopping pain, harmonizing the properties of various medicines, and neutralizing the toxicity of a hundred medicines. Licorice is not only a major medicinal material, but also an excellent calorie-free sweetening additive in food, and an important auxiliary material for cigarettes and other industries, so the demand for licorice is growing ever larger. As natural licorice resources are increasingly depleted, artificial cultivation is necessary. Due to reasons such as the dense structure of the licorice seed coat and protein dehydration and denaturation, cultivating licorice suffers from problems such as slow germination, uneven germination, and low germination rate. To improve the licorice germination rate in production, seeds should be collected rationally, that is, choose plants over 3 years old and, during the flowering and fruiting period, remove the flowers or fruits near the tips of the branches, so that seed maturity is more uniform and large, plump seeds can be obtained. Seed collection is best done when the seeds inside the pods have just turned from green to brown; such seeds have a low hard-seed rate, are simple to treat, and give a high germination rate. In addition, before sowing, the licorice seeds must also be treated, and the specific methods are the following 6.
1 Boiling water seed soaking method
Put the selected fresh seeds into 100°C water (an equal multiple of water) and stir until naturally cooled, soak for 6-8 hours, then remove the seeds and rinse off the mucus on the seed coat with clean water.
2 Warming and repeated soaking method
Put the seeds into warm water and soak for 6-8 hours. At this point, 2/3 of the seeds have absorbed water and become plump, and they separate into 2 layers from the seeds that have not absorbed water (the hard seeds that have not been thoroughly soaked), with the unsoaked seeds below and the soaked seeds above, but not floating on the water surface. The soaked seeds can be poured out along with the water, repeating several times until all the soaked seeds have been poured out. Put the unsoaked seeds into 100°C boiling water and soak for 2-3 seconds, remove them and immediately put them into cold water to shock them, so that the seed coat receives a cold-hot stimulus, then put them into 60°C warm water and soak for 2-4 hours, combine them with the seeds that were floated out, and wash off the mucus on the seed coat. Seeds treated by this method can reach a germination rate of 91.3% and a germination rate of 90%.
3 Sand grinding and soaking method
Mix the seeds with 1/3 fine sand, put them in a basin and grind for 3-5 minutes, until the seed surface loses its luster and has sand scratch marks, remove all the fine sand, put them in 60°C warm water and soak the seeds for 6-8 hours, and wash off the mucus on the seed coat.
4 Rice milling method
Spread the seeds on a millstone, 3 cm thick, and turn the seeds as you mill, paying close attention to changes in the seed coat. When milling until the seed coat is greenish-white, put the seeds in 40°C warm water and soak for 2-4 hours, and wash off the mucus on the seed coat. Seeds treated by this method can reach a germination rate of 90% and a germination rate of 85%.
5 Electric rice milling machine grinding method
First sieve and grade the seeds, then use the high-speed rolling of the rice milling machine to make the seeds rub against each other at high speed so as to scratch the seed coat, grinding until close to the cotyledons but without damaging the cotyledons and with the seeds intact. The way to check whether the treatment is up to standard is to take a little of the milled seeds and put them in a dish, soak them in a small amount of water for 2-4 hours; if most of the seeds have already swollen, it shows the treatment is up to standard, and those not up to standard can be milled again. If the seed coat has already broken after milling, it shows it has been over-milled and will also not germinate. This method saves labor and time, has good results, can reach a germination rate of 97%, and is suitable for treating large quantities of seeds.
6 Concentrated sulfuric acid soaking method
Use the corrosive effect of concentrated sulfuric acid on the seed coat to make the seed coat thinner. Specific method: add 30-34 mL of 98% sulfuric acid per 1 kg of seeds, mix evenly, and stir continuously so that the seeds fully contact the concentrated sulfuric acid; after an appropriate time, quickly rinse clean with clean water and dry them. Generally about 70 minutes of corrosion is needed, and for some seeds with thick seed coats the treatment time should be appropriately extended. Generally, it is best when black round corrosion spots appear on most of the seeds. Properly treated seeds can reach a germination rate of about 90%.