Seed Preservation and Biometrics

These stages take place within the laboratories of genebanks, botanical gardens, and nature reserves, and go from drying and sieving seeds to preservation, viability testing, and germination.

First: Drying Stage

• The drying process for the seeds begins immediately after the completion of the collection process, to ensure the integrity of the seeds and get rid of excess moisture before preservation. The seeds should be left for a while after collection, to ensure the ripeness of the seeds in case there are some fresh ones present.
• It may be noted that there are many insects accompanying the vegetative groups that are collected from the field, so it is necessary to get rid of these insects before starting to dry the seeds, by keeping the vegetative parts under low temperatures (- 20 degrees Celsius) for a period of not less than 6 hours and not more than 24 hours to kill all insects.
• The vegetative samples – which carry the seeds – are left to dry out of direct sunlight in a well-ventilated place or in isolated “dry” rooms at low humidity.
  

Secondly: Purification Stage

• After the seeds are completely dry, they are filtered from impurities, as well as from exotic species. Sieves of different diameters are used to eliminate impurities.
• After being purified, the seeds are placed automatically in a device (seeds blower) to separate any remaining light impurities from the seeds.
• Preservation conservation is accompanied by sterilization, fumigation, and cooling to ensure the seeds remain healthy and free from disease and insect infestations.

Third: Biometrics stage

Before storing and preserving the seeds in the special coolers, it is worth making some measurements of the seeds, which are:

• Seed weight and counting the number of seeds per gram using the seeds counter, as well as knowing the weight of a hundred seeds.
  
• Measurement of seed length, width, and thickness using the measuring calipers.
• Measuring the moisture content of the seed using a moisture meter, or by finding the difference between the weight of the dry, fresh seeds divided by the weight of the fresh seeds.
  
• Scanning the external features of the seeds using the stereomicroscope, which facilitates the study of the differences between seed shapes and classification.
• Take the measurements for each seed, such as the length, width, and thickness.

Fourth: Seeds Preservation stage

Studies have shown that the lifetime of the seeds is reduced by half for every increase in temperature of five degrees Celsius, for seeds kept at temperatures between 0 and 50 degrees Celsius, or for every increase in the percentage of moisture in the seeds of 1%, in seeds where the moisture content is between 5-14%.  Therefore, the condition for preserving the seeds is to reduce the moisture content and keep them under low temperatures. These seeds are stored after drying to reach a moisture content of between 3-7% (depending on the type of seeds), in sealed packages that are impermeable to water vapor under temperatures below zero degrees Celsius.

Genebanks rely on preserving and storing seeds inside freezers at temperatures below zero in sealed glass or plastic containers, where temperatures vary according to the type of preservation.

• Short-term preservation: Seeds are kept at temperatures between 10 and 15 degrees below zero.
• Long-term preservation: The seeds are stored in temperatures below 30-40 degrees below zero.