Harold R. Burton

Accumulation of capsidiol in tobacco cell cultures treated with fungal elicitor

Abstract Addition of fungal elicitor to tobacco cell suspension cultures induced extracellular accumulation of capsidiol.

Glycosidically bound volatile components of Nicotiana sylvestris and N. Suaveolens flowers

Abstract Glycosidically bound volatile components were extracted from flowers of Nicotiana sylvestris and N. suaveolens and isolated using liquid column chromatography with an Amberlite XAD-2 resin. These glycosides, which were putative precursors of fragrance compounds, were hydrolysed enzymatically and a number of the volatiles released were subsequently identified by GC-MS including compounds not previously identified in the floral headspace of these species. Average yields of volatiles released from glycosides were ca 230 and 1050 μg g −1 for N. sylvestris and N. suaveolens flowers, respectively. Compounds in the glycosidically bound fraction were all phenylpropanoid-derived volatiles (e.g. benzyl alcohol, benzaldehyde, E -cinnamyl alcohol, benzyl salicylate) with the exception of the monoterpene α-terpineol. No pronounced diurnal changes in the levels of glycosidically bound volatile compounds could be noted from flowers of either species. However, pronounced differences were obtained in the concentrations of glycosidically bound volatiles at different floral maturity stages.

Chapter 2 – Biosynthesis of nicotine and related compounds

This chapter emphasizes recent biochemical advancements in alkaloid biosynthesis and on the biological aspects of nicotine biosynthesis. Nicotine is the principal alkaloid, usually accounting for greater than 90% of the alkaloid fraction, in commercial tobacco. Nornicotine, anatabine, and anabasine are the other predominant alkaloids in tobacco, but seldom do they individually accumulate to more than 5% of the total alkaloid fraction. Genes at two nonlinked loci, Nicl , and Nic2 , primarily control total alkaloid content of commercial tobacco. The Nic genes are expressed mainly in the plant roots and the result of the expression is mainly measured as leaf alkaloid content. The biology of alkaloid biosynthesis is likely to evaluate alkaloid biosynthesis in transformed root tissues and plant growth regulator effects on alkaloid biosynthesis. Nicotine synthase catalyzes the last step in nicotine biosynthesis, the decarboxylation, and condensation.

Effect of diurnal sampling on the headspace composition of detached Nicotiana suaveolens flowers

Abstract Compounds emitted over a 24 hour sampling period by detached flowers of Nicotiana suaveolens were examined after collecting flowers at 12:00 and 24

Improved Method For the Quantification of Nitrite In Plant Materials

Abstract A technique for stabilizing and decolorizing plant tissue extracts for subsequent automated colorimetric analysis of part per billion levels of nitrite is described. Extraction of plant material with a solution containing 1% KC1, 0.5% sulfanilamide and 0.1% Triton X-100 followed by filtration and decolorization with activated carbon (Norit A) produced clear extracts which, when sealed, were stable for more than 48 hours at room temperature. the detection of nitrite by the Griess reaction in the range of 20-100 PPB was accomplished using a Technicon Auto-Analyzer System II with a 50mm flow cell in the colorimeter. Analytical precision of ±2% with negligible blank determinations was obtained.

Effect of leaf maleic hydrazide concentration on yield and dry matter partitioning in burley tobacco (Nicotiana tabacum L.)

Abstract Maleic hydrazide (MH) is commonly used to prevent axillary bud (sucker) development in tobacco (Nicotiana tabacum L.) after inflorescences have been removed by topping. Although MH provides an inexpensive and effective method to control sucker development, high concentrations (> 80 μg g−1) of MH ratidue in cured leaves are undesirable. The objective of this study was to determine the effect of a wide range of MH rates on leaf MH residue, yield, and dry matter partitioning among plant parts of burley tobacco. The feasibility of using near infrared spectroscopy as a method to rapidly screen tobacco samples for MH residue also was tested. MH was applied at rates of 0 (suckers manually removed), 1.68, 3.36, 5.04, 6.72, 10.08, and 13.44 kg ha−1, where 3.36 kg ha−1 corresponds to the usual commercial rate. Adequate sucker control was provided for up to 3 weeks by 1.68 kg ha−1 MH. Concentrations in the leaves (midribs removed) increased progressively with increasing rate of MH. Concentration of MH decreased over time but plants treated with rates above 3.36 kg ha−1 had MH concentrations at or above 80 μg g−1 in air-cured leaves of the upper third of the canopy. Leaf MH concentration decreased from the top to the bottom of the plant, and at MH rate above 6.72 kg ha−1, the MH concetration was above 80 μg g−1 in leaves at the bottom of the canopy. Air-cured leaf yield was slightly increased for the 1.68 kg ha−1 MH rate compared with hand-suckered controls, but higher MH rates did not further affect yield. A large portion of the yield increased cured-leaf moisture content of MH-treated plants. Additionally, MH-treatment decreased partitioning of dry matter in stalks. On a whole-plant basis, dry matter accumulation was similar for all treatments. The results indicated that MH rates above 3.36 kg ha−1 did not alter plant development, yield, or sucker control, but did lead to excessive undersirable leaf MH concentrations. For cured-leaf and especially midrib tissue, there was a significant relationship between MH concentrations determined by the chemical method and estimated by NIR spectroscopy. These results indicated that the potential exists to use NIR spectroscopy to rapidly estimate MH residue levels of tobacco leaf tissue.