The leaves are oblong-lanceolate, lanceolate, oblong or ovoid, the top is gradually sharp, and the base is gradually narrowed until the stem is ear-shaped and half-embracing. Inflorescence terminal, conical, flowery; Pedicel 5-20 mm long. Capsule ovoid or oblong, approximately equal to persistent calyx. Seeds round or broadly oblong, about 0.5 mm in diameter. , brown. Flowers and fruits in summer and autumn.
Tobacco is a thermophilic crop and is sensitive to temperature. Different temperature conditions have great influence on the quality and yield of tobacco. The temperature requirement of high-quality tobacco leaves in the growth period is lower in the early stage and higher in the later stage. When the average temperature of the day is higher than 35℃, the growth of tobacco plants is inhibited, the leaves become thicker and harder, the nicotine content is too high, and the quality becomes worse. Low temperature can promote the early development of tobacco plants, but different varieties have different responses to low temperature.
For all types of tobacco, the temperature below 65438 03℃ is generally not desirable, especially in humid weather conditions without light. Under the good growth conditions of sufficient sunshine and average daily temperature of about 27℃, tobacco ripens in 80-90 days after transplanting; In cold weather, it takes 100- 120 days to mature. Insufficient light will lead to the slow growth of tobacco, and the leaves can hardly mature normally, resulting in inferior tobacco leaves. In the middle and late stage of field growth, if the daily average temperature is lower than 20℃, the transformation and accumulation of assimilates will be inhibited, thus hindering the normal maturity of tobacco leaves. The lower the temperature, the worse the quality of tobacco leaves, such as frost leaves caused by early frost in the late growth stage, which will have no use value. However, if the temperature is too high at maturity, it will also cause the tobacco leaves to burn, and the phenomenon of burnt slices and burnt tips will appear, and the internal quality will become worse.
The heat condition at maturity has the most significant influence on the quality of tobacco leaves, so the temperature at maturity is usually used as an important index to judge the ecological suitability. Generally, varieties sensitive to sunlight are also sensitive to low temperature. Therefore, in the prophase and metaphase of tobacco plant growth, if it encounters low temperature for a long time, it will inhibit the growth of nutrition and promote the development of reproductive organs, which will easily lead to the early flowering of tobacco plants and affect the yield and quality of tobacco leaves. Taking 30 days of ripening temperature ≥ 24℃ as the boundary of tobacco production area and 60 days as the necessary condition for producing high-quality cigarettes.