Effects Of Agronomic Practices On Tissue Structure And Physiological Characteristic In Leaves Of Flue-cured Tobacco

This paper takes Longjiang 911 flue-cured tobacco as material, studied the influence of different agronomic measures (Plastic film mulching, density, topping, fertilizer) on tissue structure and physiological characteristic (chlorophyll, starch) in flue-cured tobacco leaves. Results showed as follows:1. The leaf thickness together with the thickness of palisade and spongy tissues increased with the increase of maturity degree, and which decreased with the caducity of leaves. Effects on tissue structure in the upper leaves of the plant which were not removed plastic film mulching were notable. The thickness of palisade and spongy tissues increased slightly with the increase of maturity degree in flue-cured tobacco which removed plastic film mulching on the May 26. The leaf thickness and the width of palisade tissues in flue-cured tobacco were influenced deeply by topping. The thickness of palisade tissues was influenced primarily by plant density. However, topping and plant density influenced insignificantly the thickness of spongy tissues in flue-cured tobacco. The leaf thickness decreased, and the width of palisade tissues increased with the postponement of topping. The thickness of palisade and spongy tissues of leaves in the mature stage was small with no fertilizer application. The leaf thickness in flue-cured tobacco with specific fertilizer was thicker than flue-cured tobacco with no fertilizer application. The leaf thickness and clearance of tissue was appropriate in flue-cured tobacco with specific fertilizer and cake fertilizer. The thickness of palisade and spongy tissues of leaves with specific fertilizer and organic fertilizer was thickest in the mature stage.2. The content of chlorophyll in the leaves dropped along with the increase of maturity degree. When the chlorophyll degraded quickly, the maturity of leaves was best. Plant density had the greatest influence on the chlorophyll content in the lower leaves of the plant. The chlorophyll degraded quickly in the lower leaves of the plant with high density. With time of topping delay, rose in the content of pigment a, pigment b and chlorophyll in flue-cured tobacco leaves. Fertilizer application had the greatest influence on the chlorophyll content in the upper leaves of the plant. Rose in the content of chlorophyll in leaves with matching the special-purpose fat with the organic fat, and the flue-cured tobacco trend prolonged greening and mature later. The chlorophyll content of the flue-cured tobacco leaves which was not removed plastic film mulching to be low, especially in the upper leaves. Removing plastic film mulching on the June 5, the content of chlorophyll in the leaves dropped steadily in maturity.3. Starch content in leaves of flue-cured tobacco increased continually during maturation. Maturity was best with the highest starch content, and then decreased during senescence in leaves of flue-cured tobacco. Sequences of starch contents in each position stalk leaves were upper> middle> lower stalk position. Plant density affected significantly starch contents in each position stalk leaves of flue-cured tobacco. The time of starch contents in each position stalk leaves of flue-cured tobacco getting to the highest was much later; leaves were also much later to come to maturity as the increase of plant density. opping influenced significantly starch content in bottom stalk position in autumn. As it was fertilized with specialty fertilizer or was not fertilized starch content in each position stalk leaves of flue-cured tobacco was low and unstable. Co-applied specialty fertilizer with bioorganic fertilizer, starch content in each position stalk leaves of flue-cured tobacco in autumn was high and stable, but it was much later to get to the highest and leaves were also much later to come to maturity. As plastic film mulching was not taken off, starch content in each position stalk leaves of flue-cured tobacco was unstable greatly, and peak time of starch content came earlier in upper and middle stalk position leaves. Taken off the plastic film mulching at May 26^th, it suggested that starch content was stable and appropriate.4. Compared with flue-cured tobacco leaves grown in full sunlight, a smaller length of leaves, a thiner thickness of leaves and spongy tissues, a lesser content of chlorophyll were found in plants grown under shaded conditions. Leaf fresh mass, leaf dry mass, specific leaf mass, light saturation point (LSP), light compensation point (LCP), CO₂ saturation point (CSP), CO₂ compensation point (G) and the net photosynthetic rate also were higher in leaves grown in full sunlight than under shading.