Emissions, biogenesis and metabolic utilization of chloromethane by tubers of the potato (Solanum tuberosum)

Abstract

CH $ Cl emissions by freshly harvested tubers of 61 potato cultivars ranged from less than 4 to 650 ng g −" f. wt d −" . In experiments with Anna, the cultivar displaying the highest release rate, maximum emission of CH $ Cl occurred at 20mC but the rate diminished after 48 h, a decrease due in part to inhibition of CH $ Cl release by the accumulation of CH $ Cl in the headspace. In 1995 and 1996, CH $ Cl emission by tubers was first detectable 6 wk before the normal harvest date. If tubers were stored at 20mC immediately following harvest, release attained a maximum of 350 ng g −" f. wt d −" about 4 d after harvest, falling to less than 4 ng g −" f. wt d −" within 3 wk of harvest. On storage at 6mC post-harvest, maximum release of CH $ Cl (c. 600 ng g −" ) was delayed until 5 wk after harvest and release fell below 4 ng g −" f. wt d −" after 200 d. Release of CH $ Cl was not significantly affected by cutting or bruising tuber tissue, and CH $ Cl biosynthesis occurred in both core and superficial tissues of the tuber. The Smethyl group of either L-or D-methionine acted as a precursor of CH $ Cl in sliced tubers, but the methylating system was specific for Cl − . An isotope dilution technique using C#H $ Cl demonstrated that the amount of CH $ Cl metabolized by the intact tuber was approximately 36% of the net release. However, investigations with "%CH $ Cl showed that only a small proportion (7%) of the CH $ Cl metabolized was fixed in involatile form in the tuber. In both skin and core tissues, fixed "%C was located primarily (80%) in the fraction soluble in phosphate buffer, but the specific activity of skin tissue was about twice that of core tissue. Autoradiography demonstrated that "%C fixation in the tuber was greatest within the lenticels, possibly indicating a microflora adapted to use the locally high concentrations of CH $ Cl. Significant "%C fixation was also associated with the periderm but was not attributable to labelling of the O-methyl groups of the phenolic components of suberin. Within the core of the tuber, "%C fixation was located primarily in the phloem, pith and medullary rays.

Continuous flow stable isotope methods for study of δ13C fractionation during halomethane production and degradation

“…For experiments in which δ 13 C values for CH 3 Cl and CH 3 Br released by tubers of the potato Solanum tuberosum were measured, intact washed tubers (300 g) were incubated at 20 °C in the dark in 5‐L glass vessels as previously described7 and headspace samples (1 mL) in duplicate were taken via the sampling port after 24 h. For determination of δ 13 C of CH 3 Cl and CH 3 Br released by the halophyte Batis maritima , green aerial shoots (ca. 5‐cm length, 1–2 g wt) were placed in triplicate screw capped vials (40 mL) fitted with PTFE‐lined butyl rubber septa and containing a culture medium (4 mL) consisting of seawater diluted with distilled water (ratio 2:1 v/v).…”

“…Chloromethane (CH 3 Cl) and bromomethane (CH 3 Br) are, respectively, the most abundant volatile chloro‐ and bromocarbons in the troposphere and are believed to be responsible for approximately 30% of halogen‐catalysed strato‐spheric ozone destruction 1,, 2. Both halocarbons originate from natural and human‐influenced sources, including biomass burning, oceanic emissions, wood‐rotting fungi and several species of higher plants 3–8. The atmospheric CH 3 Br burden also has a substantial anthropogenic component arising from release during fumigation and combustion of leaded petrol 8,, 9.…”

Halomethane:Bisulfide/Halide Ion Methyltransferase, an Unusual Corrinoid Enzyme of Environmental Significance Isolated from an Aerobic Methylotroph Using Chloromethane as the Sole Carbon Source

“…A variety of microhabitats where biological CH 3 Cl production can lead to sufficiently elevated concentrations of the gas to permit CH 3 Cl-dependent growth probably exist both in the soil and on the surfaces of plants. Investigations by Harper et al (21) have suggested the presence of colonies of CH 3 Cl-metabolizing microorganisms in the lenticels of potato tubers. These pores represent the main points of efflux of CH 3 Cl generated within the tuber.…”

Halogen biogeochemistry of invasive perennial pepperweed (Lepidium latifolium) in a peatland pasture

“…Known terrestrial sources include coastal salt marshes [Drewer et al, 2006;Manley et al, 2006;Rhew et al, 2000], mangroves [Manley et al, 2007], freshwater wetlands [Dimmer et al, 2001;Varner et al, 1999], woodland and forest soils [Drewer et al, 2008;Varner et al, 2003], and fungi [Mead et al, 2008;Redeker et al, 2004a]. Specific plants are potentially large emitters of methyl halides, including agricultural crops such as rapeseed (Brassica napus), cabbage (Brassica oleracea), rice (Oryza sativa), and potato tubers (Solanum tuberosum) [Gan et al, 1998;Harper et al, 1999;Redeker et al, 2000;2002;Khan et al, 2011;Saini et al, 1995]. Salt marsh plants also emit methyl halides [Ni and Hager, 1999;Wuosmaa and Hager, 1990], with Batis maritima and Frankenia grandifolia plants showing the largest per area emissions of CH 3 Cl and CH 3 Br yet observed [Manley et al, 2006;Rhew et al, 2000;Rhew and Mazéas, 2010].…”