The QBG uses several laboratory methods to increase and preserve plants outside their environment and assure their continuation. These methods include:
- Seed Germination
- Increasing plants through vegetative methods in the nursery at the QBG.
Germination of seeds in the laboratory
It is known that desert plants can survive with difficult climatic conditions related to lack of water and high temperatures. From here, the question arises of how to germinate Acacia tortilis plants (for example) to be replanted and used again. In order to find out the best methods for germination of seeds, the factors affecting germination, such as the anatomy of the seed latency and seed treatments, must be addressed.
Dormancy in seeds
Dormancy means that the live seed will not germinate despite the availability of all appropriate external conditions for germination, such as the presence of water, and the appropriate temperature and humidity. Here, we emphasize that the seed must be intact in appearance, and it must be composed of an outer shell called the “Testa or seed coat”, surrounding the feeding endosperm or cotyledons where the embryo is located. Dormancy depends on the type of plant, the environment in which it grows, as well as the timing of expulsion and dropping of seeds.
The general shape of the seed, including all the components
Shape of the testa or seed coar: The outer crust of the seed
The endosperm or cotyledons of the seed. The upper fovea indicates the location of the embryo
Dormancy as a result of a thick seed’s coat
The embryo of the seed is surrounded internally by the nutrient membrane and externally by a thick, impermeable coating, which makes these seeds more susceptible to non-growth, or reduces the chances of germination, due to the presence of the outer shell called the seeds’ Testa or seeds’ coat.. The impermeable membranes hinder the necessary gas exchange and water absorption, as well as the expansion and growth of the fetus. Therefore, when growing cypress seeds and similar seeds, researchers must overcome the presence of the cotyledon and allow water and gases to enter the seed to allow germination.
Calculating of the percentage of germination
Desert plant seed germination needs temperatures between 27 and 30 degrees Celsius and humidity levels above 50%. Therefore, it is preferable to germinate seeds in germination rooms with controlled temperature and humidity or to plant them in plastic containers.
The germination percentage can be calculated by knowing the number of seeds that have grown- in a period of time – and dividing this number by the total number of seeds that were planted, then multiplying the result by 100 to obtain the percentage.
Seed treatments before germination
To start germinating desert plant seeds, it is necessary to break the seed latency first, then start planting and cultivating. Among the methods of treatment used to break down the Acacia tortilis seeds – which have a thick seed’s coat – are those shown below:
Soaking in water
This helps the hard seeds with impermeable membranes to break the seed dormancy, provided that the soaking time exceeds 24 hours, as this allows water to enter the inner membranes due to their saturation property. In the case of umbrella thorn seeds, the seeds are soaked in boiling water (at a boiling point of 100 degrees Celsius), and the seeds are left until the temperature drops to room temperature for a period of 24 to 48 hours, until the seeds swell noticeably. After that, the seeds are planted either in agar or directly into the soil. The process of soaking the seeds in regular and boiling water helps the germination of umbrella thorn seeds by 16% to 20%, respectively.
When the seeds are soaked in concentrated sulfuric acid at a concentration of 98% for a period of 10 to 15 seconds while stirring, this helps to erode the hard outer shell of the umbrella thorn seeds through the action of the concentrated acid, which helps to thin them. However, due to the short period of time, erosion is limited to the outer membrane of the seed and does not reach the inner membranes, which maintains the vitality of the healthy seed and does not affect its ability to germinate. The concentrated acid also helps erode the membranes of the outer layer, which helps the seed to absorb water and allows the fetus to expand and grow. Practical experience shows that soaking the seeds in concentrated sulfuric acid and then soaking them in water for 24 hours helps to stabilize the umbrella thorn seeds, with a germination rate of more than 80%, which is one of the most useful ways to grow desert umbrella thorn seeds.
Mechanical scratching of the seed’s coat
This is one of the methods used to thin and soften the thick crust, which increases the seed’s coat permeability for water and gas exchange. These scratches can be made in the cotyledon using sandpaper, where the seeds are placed between two sheets of sandpaper and then rubbed. Part of the outer membrane can also be cut using a sharp tool such as scissors. It is necessary to avoid the area where the fetus is located, otherwise the seed will not germinate. This method has proven to be very successful, as the germination rate of umbrella thorn increases through this method by up to 85%, whereby a small part of the seed is cut off and the seeds are soaked in water for a period not exceeding 24 hours. It is preferable to reduce the period of soaking the seeds in water (from 6 to 12 hours) after cutting the seed, so as not to negatively affect the inner membranes of the seed.
This means mixing the seeds with fine sand and placing the mixture between two layers of sand in a bowl. Sometimes cotton is used instead of sand, and the seeds are placed between two layers of cotton in a container, which is then kept in the refrigerator at a temperature of 4 ° C. The mixture is sprinkled with water regularly for more than a month. This method is needed by most desert seeds, as most seeds sprout in the winter and they need long periods of cold to germinate. In this process, the long night winter period is simulated, so the seeds are preserved after being mixed with sand in the refrigerator, and the mixture is only exposed to light for short periods of no more than 6 hours a day. It has been found that the percentage of seed germination does not exceed 15%, so it is advisable to expose the seeds to periods of cold, then follow up with one of the other treatments, such as physical scratching of the cotyledon.