Tea is one of the most widely consumed beverages in the world. How to effectively preserve its genetic resources is particularly important. Since tea seeds do not belong to normal (dehydration tolerance) seeds, they cannot be preserved using conventional methods of seed bank storage. The preservation of tea seeds has been a research hotspot in the field of seed biology. Successful preservation of tea seeds, whose tolerance to dryness is the key, and in the past reports, the ability of tea seeds to be collected from different places varies widely. However, what causes this difference is still a mystery.
Dr. Chen Hongying, Germplasm Resource Library, Kunming Institute of Botany, Chinese Academy of Sciences, in collaboration with experts from the Millennium Seed Bank of the Kew Gardens of the Royal Botanic Gardens in the UK, from 2007 to 2010, dehydrated the tea seeds distributed in the three collection sites of Kunming, Linyi and Puer. A comparative study of drying and cryopreservation showed that tea seeds from three different locations exhibited different dehydration tolerance. Kunming's tea seeds have the strongest tolerance and can be dehydrated to 8% moisture content, followed by tea seeds from Pu'er and Linyi. This difference is related to the habitat and intraspecific variation of the collection site. After treatment with 0.5M and 1M hydrogen peroxide (H2O2), the germination rate of the seeds after the drying treatment can be improved.
The results of the above seed dehydration experiments and the three habitats collected (such as the months during which the seeds matured during the dry season) and the seed coat and seed weights indicated that the tea seeds from these three sites were not stubborn (dehydration). Sensitive) seeds. Although the tea seeds collected in Kunming were more resistant to dehydration, they all died completely after cryopreservation at -20 degrees for one month. The reasons for this need further study.
For the first time, this study compared different varieties of tea seeds collected in different places, and analyzed and compared the dehydration tolerance of tea seeds.
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Under a certain dry condition, the curve of the relation between tea moisture change and time is called the drying curve. The drying curve is related to the airflow speed, tea layer thickness and drying temperature through the tea layer. It is the drying curve of the specific air flow rate and the thickness of the specific tea layer. The diagram shows that in the initial stage of tea drying, the moisture content of the dry base decreases linearly, which is the constant drying period of the tea. In the constant drying period, the vaporization of moisture is mainly carried out on the surface of the tea and provides a drying operation. The heat is mainly used for moisture vaporization, and the temperature of the tea leaves remains basically unchanged. The thinner the material layer and the higher the drying temperature (hot air temperature), the shorter the constant rate period.
As the drying process continues, free moisture on the surface of the tea granules disappears, and the vaporization of the tea leaves depends on the outward diffusion and transfer of internal moisture. At this time, the temperature of the tea begins to gradually increase, and the rate of decrease of the moisture content gradually slows down. Into the slow-drying period. Since then, as the water content of tea leaves continues to decrease, the vaporization rate of water has become less and less; when the moisture content of tea leaves falls below 5% to 6%, the drying process proceeds quite slowly. Therefore, From the point of view of production efficiency, energy conservation and storage preservation, it is advisable to control the moisture content of the tea at the end of 5%.
Because tea is a relatively loose and thin material with high moisture content, the surface moisture after rubbing or kneading is more, so compared with dried food, the constant rate segment of the drying curve is obvious, and the slope is relatively large; In the early period of fast-waterfall, because the moisture diffusion is relatively easy, the curve is still relatively steep. This is the characteristic of tea drying.
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