Substituted Naphthalenes and Their Role as Potato Sprout Suppressants

O'Hagan, Noreen (1991) Substituted Naphthalenes and Their Role as Potato Sprout Suppressants. PhD thesis, University of Glasgow.

Abstract

This thesis describes work relating to the substituted naphthalenes and their use as potato sprout suppressant chemicals. Sprout suppressants are used to control the sprouting of potatoes during extended storage. The study included estimating the volatility of certain substituted naphthalenes. This was attempted by developing a static method that allowed a simple, fast and reasonably accurate technique to be developed for screening the volatility of many substituted naphthalenes. The results obtained indicated that the headspace (concentration of chemical in the air surrounding the chemical source) increased with both time and temperature. However, the concentration remained relatively constant as the concentration of chemical was increased. The method was also used to relate the volatilities of selected chemicals - dimethylnaphthalene, ethylnaphthalene and chlororaethylnaphthalene to their activities as potato sprout suppressants. These were selected from a previous potato storage experiment carried out by Stephen and Duncan (1984). With realistic potato storage conditions in mind a dynamic model system was developed and used to study the headspace of ethylnaphthalene over a long period of time. This method enabled the behaviour of ethylnaphthalene to be predicted in a commercial potato store. The decrease of ethylnaphthalene headspace concentration with time indicated that ethylnaphthalene would need to be re-applied several times throughout the storage season. The effect that substituted naphthalenes had on the healing of tuber wounds was measured by following the development of resistance to water loss in cut potato discs. A syringe method was developed and used as a quick assay. Using this system the substituted naphthalenes were not found to give an inhibiting effect compared to the controls. The effect of the organic solvent masked the effects of the substituted naphthalenes. Thus the true effect of the substituted naphthalenes on wound healing was unable to be seen. The general indication from past work (McGee 1984; Wilson et al 1987) was that the substituted naphthalenes would have an inhibiting effect on the healing of whole wounded tubers under commercial conditions. Thus substituted naphthalenes could not be applied to potatoes entering the store immediately after harvest as it is necessary for wound healing to take place in advance to prevent water loss and the entry of fungal and bacterial pathogens. So in order that substituted naphthalene residues could be determined, sensitive and accurate methods for the extraction, clean-up and quantification of dimethyl-naphthalene from potatoes were derived. Both Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) analysis methods were developed. The recovery of the GC method was calculated at 90.4%+/-2.6% and levels down to 0. 006mug of dimethylnaphthalene could be detected and levels of 0.5mg kg-1 of potato residue. The recovery of the HPLC method was slightly lower at 85.9%+/-1.7% but was slightly more sensitive, detecting levels of dimethylnaphthalene down to 0.005mug and levels of 0.42mg kg-1 in potato residues. The remainder of the work in this thesis described a potato storage experiment comparing different sprout treatments. It was concluded that diisopropylnaphthalene and ethylnaphthalene gave better control of sprout growth and the number of eyes opened than untreated tubers. However, as the storage period increased the treatments became less effective. This effect was thought to be related to the relatively high volatility of the substituted naphthalenes and the loss of chemical by dissipation with time. Correspondingly, the chemical residues also decreased with time. Critical residue values were found to be 0.4 - 0.6mg kg-1 (Beveridge 1981b).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Plant sciences
• Date of Award: 1991
• Depositing User: Enlighten Team
• Unique ID: glathesis:1991-78242
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:35
• Last Modified: 30 Jan 2020 15:35
• URI: https://theses.gla.ac.uk/id/eprint/78242