- Dettagli della rivista
- Pubblicato per la prima volta
- 01 Jan 1992
- Periodo di pubblicazione
- 4 volte all'anno
- Accesso libero
Physiology and Biochemistry of the Tobacco Plant. 1. Growth and Development - Physiologie und Biochemie der Tabakpflanze: 1. Wachstum und Entwicklung
Pagine: 197 - 209
Growth and development processes of a tobacco plant affect the chemical composition of the leaf and therefore the usability of the leaf. Growth starts with the initial stages of germination and development stops with the cured leaf. Most tobacco seed will germinate in the dark and the first seeds to germinate from a seed lot tend to produce larger plants for transplant and harvest. Nicotine is found in mature seed and increased rate of germination increases rate of nicotine accumulation in the young seedling. Carbon / nitrogen balance in the leaf is important for leaf usability and is influenced by available soil water and soil nitrogen. Oriental leaf is produced typically with limited water and nitrogen supply and the leaf contains large amounts of carbohydrates and ether solubles but small amounts of nitrogenous substances. Cigar filler tobacco is grown on soils with a plentiful supply of soil water and soil nitrogen and the leaf contains large amounts of nitrogenous substances. Intermediate to these tobacco types is flue-cured tobacco which is grown with limited soil nirogen but adequate water and the leaf is relatively thin with high carbohydrate content. Maximum rate of leaf expansion is achieved early in development of a leaf. In flue-cured tobacco phosphorus and potassium concentrations remain constant during growth, whereas nitrogen, calcium and magnesium concentrations decrease. In Oriental tobacco the concentrations of nitrogen, phosphorus, potassium and calcium decrease during the growing season. However, Burley tobacco accumulates relatively greater amounts of nitrogen, phosphorus and potassium during the first half of the growing season relative to dry matter accumulation. Maximum growth per unit leaf weight occurs 14 to 21 days after transplanting, whereas maximum dry matter accumulation per day occurs 50 to 55 days after transplanting. Leaf development including senescence is controlled genetically and decreased chlorophyll and protein and increased nicotine contents are important changes associated with leaf senescence. Maximum nicotine content of leaf occurs at successively higher stalk positions as the plant matures.
- Accesso libero
Physiology and Biochemistry of the Tobacco Plant. 2. Physiological Malfunctions: Mineral Nutrients - Physiologie und Biochemie der Tabakpflanze: 2. PhysiologischeStörungen: Mineralstoffe
Pagine: 211 - 236
Quality tobacco leaf comes from plants grown with balanced mineral nutrition. The “structural nutrients” (carbon, hydrogen and oxygen) are approximately 90 % of the dry weight of cured leaf but are of little economic concern. The macronutrients (nitrogen, phosphorus, potassium, calcium, magnesium and sulfur) and the micronutrients (boron, chlorine, copper, iron, manganese, molybdenum and zinc) are of great economic concern and adequate amounts in the soil are essential for production of quality tobacco leaf. Nitrogen, phosphorus, potassium and magnesium are mobile within the plant and deficiency symptoms are observed first in the lower leaves and later in the upper leaves. Deficiency symptoms of the immobile nutrients calcium, boron, manganese, sulfur and iron are observed first on the upper leaves or terminal bud. Of all the mineral nutrients nitrogen has the greatest effect on shoot and root weight. As available nitrogen increases leaf nicotine increases and reducing sugars decrease; thus the sugar:nicotine ratio decreases dramatically. There is a positive relationship between amount of reduced nitrogen and reduced sulfur in the plant and this interaction is important as most of the reduced nitrogen and sulfur are utilized in protein synthesis. Total uptake of potassium is greater than for any other mineral. Because of the immobility of calcium and boron, deficiency of these nutrients results in physiological decapitation (topping) and consequently increased nicotine content of leaves. Excessive amounts of nutrients can also produce some problems. Excessive nitrogen increases yield but it also increases the incidence of disease, delays flowering and leaf ripening, and lowers leaf quality. Excessive addition of lime causes a basic soil pH which increases disease incidence and limits availability of phosphorus, iron, manganese and zinc. Excessive chlorine increases the hygroscopic property of the leaf and reduces burn rate. Soil applied magnesium oxide may reduce potassium absorption and therefore reduce burn rate.
- Accesso libero
Physiology and Biochemistry of the Tabacco Plant3. Physiological Malfunctions: Environment - Physiologie und Biochemie der Tabakpflanze: 3. PhysiologischeStörungen: Umwelteinflüsse
Pagine: 237 - 251
Environmental, biochemical and genetic abnormalities can induce physiological disorder in tobacco. Energy conversion results in production of many air pollutants including ozone which causes weather fleck. High incidence of weather fleck results in earlier flowering, lower yields and lower total alkaloids. More mature leaves are more tolerant to ozone damage than younger leaves. Tolerance to ozone is determined by genetic makeup of the shoot and abaxial stomata. plant damage from ozone or sulfur dioxide is enhanced by the presence of the other pollutant. Frenching is the formation of progressively narrower apical leaves. The cause of frenching is not known but the substance(s) appears to be leached from soils, similar to thallium induced chlorosis and narrow leaves, most active in soil above 35°C, and altering amino acid metabolism in the plant. Genetic tumours form on certain Nicotiana hybrids. These are not of economic importance to N. tabacum production but may be significant as interspecific hybridization is used to improve commercial tobaccos. Tumour formation appears to be controlled by genes on the chromosomes and show conventional segregation, linkage and mutation.