The seeds needed for seedless watermelon cultivation are triploid watermelon seeds. Triploid watermelon seeds have the thick and hard seed shells of tetraploid seeds, and the degree of cork is high, especially in the beak, which is particularly thick and tight. The embryo is underdeveloped and its weight is low, accounting for only 38.5% of the seed weight (diploid embryo accounts for 50% of the seed weight), and its volume accounts for 60-70% of the inner cavity of the seed shell. At the same time, there are quite a few abnormal embryos, such as large and small embryos and folded embryos. Because of the above reasons, the radicle of triploid seeds is not easy to drill out the seed shell in the natural germination state, and the germination rate is low. In order to overcome the above difficulties, it is necessary to take measures to promote germination. 1. moisture
Accelerated germination must be carried out after the seeds have absorbed enough water, so it is necessary to soak the seeds. The purpose of seed soaking is to make seed coat and embryo absorb water, soften seed coat, make oxygen easy to penetrate, help the activity of young embryo protoplasm and accelerate germination.
2. Appropriate temperature, humidity and oxygen
When accelerating germination, the temperature (33~35℃) required for seed germination must be ensured, the humidity required for accelerating germination facilities should not be too high, and the air permeability should be good to avoid seed rot.
3. Shell breaking: it can reduce the resistance of seed embryo germination and promote seed germination. 1. Seed selection and drying
Firstly, according to the characteristics of varieties, according to the shape, color, size and fullness of seeds, tetraploid and diploid watermelon seeds are selected, and abnormal seeds, hybrids and inferior seeds are eliminated. Then, a few days before soaking, the seeds are dried for 1-2 days, which is beneficial to improve the germination potential of the seeds.
2 soaking seeds
Put the triploid seeds in warm water at 55℃ (twice flowering and once cooling), stir, then let the water cool naturally and soak the seeds for 6-8 hours. Warm water at 55℃ has dual functions of seed soaking and sterilization.
3 artificial shell breaking
The methods of hulling seedless watermelon can be divided into dry hulling and wet hulling. Dry seeds have high efficiency in breaking shells, but they are easy to damage seeds, and the soaking time and temperature are difficult to master, which affects the improvement of germination rate. Wet seeds are easy to slip when broken, and the working efficiency is low, but the soaking time has little effect on the germination rate, and it is easy to master, and the germination rate is high and stable. At present, wet seeds are mostly broken shells.
The specific method of breaking the shell of wet seeds is: soak the seeds, take them out and knead them for many times until the seed coat is not slippery. In order to clean the mucus on the seed surface, you can mix the seeds with plant ash, sawdust or fine sand, then rinse them with clear water for 2-3 times, then wipe off the water on the seed surface with a clean cloth, and gently bite the umbilical cord with your teeth (like eating melon seeds at ordinary times) to make it slightly open. Bite melon seeds gently, as long as you hear a "click". The opening of the seed coat should not be too big to prevent damage to the seed kernel. You can also open it with pliers and nail clippers. When using a vise, in order to control its clamping force, a rubber or rubber tube can be clamped at the back end of the fulcrum. Seeds soaked and shelled should be placed at a constant temperature of 33-35℃ to accelerate germination and maintain a certain humidity. After 24 hours, more than 90% of seeds with germination ability can germinate, seeds with a bud length of 0.5cm can be planted, and the rest can continue to germinate. After 36 hours, normal seeds basically germinated. The germinated bud should not be too long, and the radicle will be broken when sowing. Seeds that do not germinate after 48 hours of germination have lost their vitality and do not need to germinate again. In order to make seedless watermelon seeds germinate better, suitable germination bed and constant temperature facilities are needed.
1 germination bed
According to the local conditions, several germination beds suitable for seedless watermelon germination were introduced.
aspermous watermelon
1. 1 cloth rolling method
Zhengzhou Fruit Tree Research Institute of China Academy of Agricultural Sciences. The method is simple, convenient and has high germination rate. The specific operation is to soak the gnawed seeds in a piece of white cloth (preferably cotton cloth) or towel and wring them out (until the wet cloth is not wet by water to avoid being too wet), spread the 1-2 layer of seeds in a single layer, fold the four sides of the cloth, and roll them into a "seed cloth roll" shaped like a flower roll steamed stuffed bun from one end. Cloth rolls separate each layer of seeds with cloth or towel, and there is a gap between seed layers to increase air permeability; Moreover, the seeds cling to the wet cloth, which has good moisture absorption and moisture retention and is beneficial to seed germination.
1.2 sand bed method
Firstly, prepare river sand, sieve, remove organic matter, cook and sterilize, and rinse. The humidity is so high that when you hold it together, the water between your fingers can't come out, and then let it go and it will open. Specifically, the chewed seeds are evenly mixed with the same volume of river sand, put into a clay pot, and then put into a thermostat at 33-35℃ to accelerate germination. On the one hand, wet sand continues to supply the water needed for germination, keeping the radicle moist, on the other hand, it separates the seeds from each other and improves the ventilation conditions for seed germination.
1.3 sand table method
After seedless watermelon seeds are soaked and shelled, choose a rectangular enamel tray or washbasin to hold clean river sand with a thickness of 1.5cm, and then soak the river sand in boiling water for disinfection. Then put the wet sand into a small bag sewn with gauze or other cloth and squeeze out the water (the water content of the treated wet sand is about 24% of the dry sand). Pour wet sand into a pan or basin, pat it flat, draw a small square with a side length of 1cm on the sand surface, insert a small hole at the intersection of each square, and put the seed tip down with tweezers into the small hole. After all the seeds are put in, the sand is compacted to reduce the gap between the sand and the seeds, so that the end of the seeds is flush with the sand surface. Finally, cover the sand surface with wet gauze or cotton cloth, and then put the Petri dish into a thermostat or other heating equipment to accelerate germination. This is a method popularized by Jinhua Institute of Agricultural Sciences in Zhejiang Province.
1.4 absorbent paper method
Take 8 pieces of absorbent paper, soak it in distilled water or cold boiled water, drop off excess water, put it in a flat-bottomed lunch box or porcelain plate as a germination bed, put the treated seeds flat on the paper and cover it with a wet cloth. Then cover it, put it on a thermometer and put it in a thermostat to accelerate germination. You can also pad wet sand with a thickness of about 2cm under the absorbent paper to moisturize.
1.5 chaff charcoal method
In Guangxi, chaff charcoal is used as a substrate to accelerate germination. The method is to soak the burnt chaff charcoal in clear water for 2-3 hours, and then rinse it with clear water 1-2 times to reduce the alkalinity (chaff charcoal must be soaked in boiling water for disinfection if it is stored for too long or reused). Then spread the chaff charcoal with a thickness of about 3cm and a water content of about 400% on the bottom layer of the germinator, and then evenly spread the seeds on the chaff charcoal. The best sowing density is that the seeds do not overlap, and the seeds are covered with a layer of wet chaff carbon with a thickness of about 1cm. Finally, put it in a greenhouse or incubator to accelerate germination.
All the methods mentioned above can achieve good results, but it is recommended to use the cloth rolling method to accelerate germination. This method is simple, labor-saving and easy to master, and the germination rate of seedless watermelon seeds is high.
2. Constant temperature equipment
aspermous watermelon
The optimum germination temperature of seedless watermelon is 33-35℃. This requires the preparation of constant temperature facilities that meet this condition.
2. 1 electrothermal incubator accelerates germination.
Planting seedless watermelons on a large scale requires more seeds. Accelerating germination with electronic thermostat is a stable and reliable method. The temperature of this method can be automatically controlled, and germination can be achieved in 24-36 hours. This method is recommended if conditions permit.
2.2 temperature germination
This is a common method used by the masses and is suitable for accelerating germination of a small number of seeds. First, wrap the broken seeds with clean wet cotton cloth (cotton cloth is soaked and wrung dry until it is not wet by water), then put them in plastic bags without sealing or wrapped with film, then tie them around your waist or put them in your coat pocket, and don't take them out when you sleep. Open the film or plastic bag every 8- 10 hour for ventilation. It usually takes 24-30 hours to germinate by using body temperature to accelerate germination. Pick out the seeds with a bud length of 0.5cm, and then wrap them with a wringing wet cloth to continue to accelerate germination. This method can also ensure a constant temperature of about 33℃.
2.3 thermos accelerated germination
First put 35℃ warm water in the thermos bottle, about half a bottle, and then put the seeds wrapped in wet cloth, not too many seeds. Grasp the seed bag with a thin thread, don't touch the water surface, cover the thermos bottle, and press the thread end with a bottle cap. In order not to reduce the temperature in the bottle, the thermos bottle should be wrapped in a quilt and placed in a place with high indoor temperature. After more than ten hours, the germination was continued with warm water at 35℃.
2.4 Fire prevention and accelerated germination
A method commonly used in northern rural areas. Wrap the treated seeds with wet cloth and put them on the fire resistance to accelerate germination. Be careful not to let the seeds come into direct contact with refractories, in case the temperature is too high to burn the seeds. In the process of accelerating germination, turn the seeds 1 time every few hours to make the seeds evenly heated.
2.5 electric blanket germination
In recent years, electric blankets have been widely used in farmers' beds in northern rural areas, gradually replacing the kang for heating. This kind of electric blanket has a good effect on accelerating seed germination. The method is to fold the electric blanket into two layers, put some quilts in the middle, first observe the temperature with a thermometer, when the temperature is 33-35℃, wrap the broken seeds with cotton wet cloth, then wrap them with two layers of wet cloth, then wrap them with plastic film and put them into quilts to accelerate germination. It should be noted that if there are many seeds, don't wrap the plastic film too tightly to prevent the seeds from rotting due to insufficient air.
2.6 simple germination box to accelerate germination
According to the number of seeds and the heat of heat source, make a simple germination box with wood or cardboard. The box is divided into two or three layers, with movable ventilation partitions. The light bulb is installed on the bottom layer (when there is no power supply, it can be replaced by a small charcoal stove or oil lamp), and the upper layers are used for seed germination. Wooden cases (or cartons) are covered with old cotton wool, sacks or films for thermal insulation, and a thermometer is installed at the top. Before germination, adjust the temperature by increasing or decreasing the light bulb or controlling the firepower. When the temperature is basically stable (33-35℃), seeds are added to accelerate germination. Put some wet cloth in the box to increase the humidity. It is worth noting that the seeds should not be too close to the heat source to prevent the seeds from being burned due to insufficient humidity and high temperature.
In addition, there are some methods, such as wide-mouth earthenware method, horse manure pile soil temperature box, coal stove, chicken bed, fresh leaf basket, etc., which are used as heat sources to accelerate germination, so I won't introduce them one by one here. We should use local materials according to our actual situation to achieve the same goal. No matter what kind of heat source is used for heating, it must be measured with a thermometer in advance. Only when the temperature reaches the germination temperature (33-35℃) stably can the germination be accelerated. In the process of accelerating germination, we should always observe the change of temperature, not too high or too low, and maintain a certain humidity and air permeability, otherwise the germination rate will be low or not germinate at all.