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a young plant raised from seed for subsequent transplanting in a permanent location.
Seedlings are used in vegetable and seed culture, floriculture, forestry, and the cultivation of certain industrial crops. The use of seedlings is most common in vegetable culture. The planting of seedlings makes it possible to shorten the period of vegetation in the open ground, to grow valuable crops and varieties having a long vegetative period in regions with a short summer, to obtain earlier vegetable harvests, and to economize on planting material (three to five times fewer seeds are needed than when sowing in the open ground).
Seedlings to be transplanted in open ground are raised in hotbeds, heated plastic-covered greenhouses, seedbeds, and tunnels and portable plastic-covered shelters. For subsequent transplantation in sheltered ground (winter and spring green-houses), seedlings are prepared in pots (10×10 or 12×12 cm) in winter shelf greenhouses and plastic-covered hotbeds. Seedlings set out in greenhouses in January and February are provided with supplementary electrical lighting, which accelerates production by seven to 15 days and increases the yield of cucumbers by 15–20 percent and the yield of tomatoes by 20–30 percent. Seedlings to be set out in glass-enclosed or plastic-covered spring greenhouses in March or April are grown in pots (8×8 or 10×10 cm) without supplementary lighting.
Cucumbers, early white cabbage, early cauliflower, vegetable marrow, eggplant, peppers, and melons are sown in pots. Tomatoes and lettuce are sown in flats but are transplanted into pots when the first true leaves appear. Seedlings of celery, onion, and medium and late varieties of cabbage are not raised in pots but directly in the ground of greenhouses or hotbeds.
To obtain high-quality seedlings, the plants must have a nutritive medium (soil mixture, nutrient solutions). The seeds must be disinfected, and protective measures against insect pests and disease must be taken. Before seedlings can be planted in the open ground, they must be hardened off, that is, exposed to lowered temperatures (at night and in overcast weather, to - 14°C), moderately watered, and treated with phosphorus-potassium fertilizers. In hotbeds the frames should be removed five to seven days before the plants are transplanted in order to improve the light regime.
REFERENCESMarkov, V. M. Ovoshchevodstvo. Moscow, 1966.
Rubtsov, M. I., and V. P. Matveev. Ovoshchevodstvo. Moscow, 1970.
Z. S. CHEKUNOVA
a one- or two-year-old plant grown from seed in the sowing section of a fruit or forest nursery (without transplanting). The seedlings of fruit plants are used as stocks for propagating cultivated varieties; they are often called grafting stocks. In plant selection, hybrid seedlings are grown to develop new varieties. Tree seedlings are used for forestation.