In leek

R. C. Snellgrove, W. E. Splitstoesser, D. B. Strubket, and P. B. Tinker. The distribution of carbon and the demand of the fungal symbiont in leek plants with vesicular-arbuscular mycorrhizas. New Phytologist 69 15 (1982). 

Recent work has shown the presence of pyrazine and 2,6-dimethylpyrazine in leek (75), pyrazine and alkylpyrazines in the volatile constituents of tamarind (76), five alkylpyrazines in soong-neung (extract of cooked and roasted rice) (77) and in shoyu (soy sauce) (78), and alkylpyrazines in white bread (79). Murray and Whitfield (80) have examined vegetable tissue for 2-isopropyl-, 2is-butyl-, and 2-isobutyl-3-methoxypyrazines and observed at least one of these compounds in 23 of the 27 samples studied. 2-Methylpyrazine and 2,5- and 2,6-dimethylpyrazines have been determined in black tobacco and in the smoke of nonfilter cigarettes made from these tobaccos (81). 

Rosen, K., Zhong, W. L., and Martensson, A. (2005). Arbuscular mycorrhizal fungi mediated uptake of Cs-137 in leek and ryegrass. Sci. Total Environ. 338, 283-290. 

The principal phenolic acids in these vegetables are ferulic and p-coumaric acid derivatives, the green parts of chives and leeks containing more than in the white part. In leek, the white tissue contains 6-7 mg ferulic acid per kg f.w., while this compound reaches concentrations of 23-39 mg/kg in the green parts [64]. In the case of chive, p-coumaric acid derivatives reach 21-51 mg/kg and ferulic acid derivatives 32-76 mg/kg. In garlic a different pattern of phenolic metabolite accumulation is observed in skins and internal tissues. The external tissues contain 49-58 mg/kg p-coumaric acid, 27-31 mg/kg ferulic acid and 27-25 mg/kg sinapic acid, whereas the internal tissues only contain 2mg, 6-8 mg and 2 mg/kg, respectively. In addition, the internal tissues contain 12-13 mg/kg p-hydroxybenzoic acid [64]. 

Fipronil s high intrinsic activity against Dipterans allows its successful use as a seed treatment in several crops for control of root maggots. In cereals, fipronil provides excellent control of wireworm and wheat bulb fly (Delia coarctata) at rates of 50 g per 100-kg seed [8]. In leeks, seeds filmDelia antiqua) as well as thrips and onion moth [106, 107]. 

Gassagne, G Bessoule, J-J Schneider, F Lessire, R Sturbois, B Moreau, P Spinner, G. Modulation of the very-long-chain fatty acid (VLGFA) formation in leek. In Kader J-K, Mazliak P, editors. Plant Lipid Metabolism. Dordrecht Kluwer, 1995, 111-114. 

Figure 1. Effect of ATP on elongation in leek microsomes. CoA[ C]18 0, lane 1, [ C]18 0-CoA, lane 2, no primer, lane 3, 18 0, lane 4, 18 0-CoA,. lane 5. In samples (1) and (2) malonyl-CoA was added, whereas in samples (3)-(5) [ C]malonyl-CoA was added. NADPH, DTT, Mg", ...

Figure 2. Effect of CoASH on acyl-synthetase activity in leek microsomes. Acyl- CoA synthetase was measured in the presence of [ C]18 0, ATP, Mg- ...

Acyl-CoA synthetase activity is dependent on the presence of ATP, Mg, free fatty acid and CoASH. Therefore, we examined the effect of CoASH on elongase and acyl-CoA synthetase activities. In leek microsomes, acyl-CoA synthesis was stimulated by increasing concentrations of CoASH (Fig.2). In the absence of exogenously added CoASH, no acyl-CoA was detected (Fig.2). However, elongation of 18 carbon acyl chain was higher in the absence of CoASH than in the presence of CoASH, regardless of concentration (Fig.3). Elongation of 20 carbon acyl chain was stimulated with CoASH (Fig.3). 

Bessoule, J-J., Creach, A., Lessire, R. and Cassagne, C. (1992) Evaluation of the amount of acyl-CoA elongases in leek (Allium porrum L.) leaves. Biochim. Biophys. Acta 1117, 78-82. 

Cutworms, bean seed fly, onion fly, leek moth and thrips can be a problem in the crop. Rust, foot rot, leaf blotch, white tip and white rot are the main disease problems in leeks. 

Fresh root vegetables (such as carrots and parsley) are usually about 90% water cabbage contains about 92% water and lettuce and tomatoes about 95%. There are slightly lower water contents in some bulbous vegetables (89-93% in onion, 83-89% in leek and 61-68% in garlic). 

From the end of March until mid-April the specific activity of 1-131 in leek exceeded the detection limit by more than an order of magnitude. After 11.04.2011 the values decreased gradually to less than the detection limit of 40 mBq kg" by the end of April. Specific activities of Cs-134 and Cs-137 exceeded the detection limits in the samples from the 8 and the 11 of April only. 

It has been shown vitro that in leek (Allium porrum L.) epidermis cells very long chain fatty acids (VLCFA) are synthesized in the endoplasmic reticulum. Moreover, VLCFA are more abundant in the plasma membrane (up to 20% of the total fatty acids) than in the endoplasmic reticulum. It was suggested that an eventual transfer of VLCFA from their site of synthesis (ER) to the plasma membrane could occur. ... 

In the course of our study, we identified two active thioesterase activities 16 0-ACP and a 18 0-ACP thioesterase in leek epidermis. Here we report the isolation, purification and characterization of one thioesterase from leek epidermis,... 

MODULATION OF THE VERY-LONG-CHAIN FATTY ACID (VLCFA) FORMATION IN LEEK... 

What makes that an acyl-CoA elongase from Simmondsia chinensis forms only monounsaturated VLCFA whereas those from leek leaves form exclusively the saturated ones It has been postulated that this could result from either the specificity of the elongases towards saturated or unsaturated acyl-CoAs, or from the competition of other enzymes for the same substrates. The first hypothesis was ruled out in leek when it was demonstrated that the purified elongases had no specificity towards the acyl chain-length or the unsaturation (3). 

In our laboratory, studies of lipid transfer in leek seedlings in vivo, have already shown the existence of a vesicular process for the transfer of phospholipids and particularly of very long chain fatty acid-containing lipids [6]. This process follows the vesicular endoplasmic reticulum- Golgi apparatus- plasma membrane pathway. Using the cell-free system developed by Morre and coworkers, we have reconstituted in vitro the vesicular transfer of some phospholipids between the ER and the GA. This transfer is ATP and cytosol-dependent, is N Ethyl Maleimide and temperature sensitive and specific for the ER as donor and the GA as acceptor. The phospholipids transferred via an ATP-dependent manner in vitro between the ER and the GA were phosphatidylcholine (PC +79%), phosphatidylethanolamine (PE +67%) and phosphatidylserine (PS +123%) [7]. All those results are in favour of a vesicular transport of phospholipids between the ER and the GA of leek seedlings, and brought us to purify these transition vesicles issued from the ER. 

Previous work in our laboratory showed that thiocarbamates altered surface lipid synthesis by inhibiting formation of the precursor very long chain fatty acids [1,3]. Recent work has provided more evidence (P.B. Barrett and J.L. Harwood, this volume) that the thiocarbamates are oxidised to their sulphoxides and it is the latter which are responsible for the specific inhibition of fatty acid elongases. In germinating peas, as in leek, we have found separate chain-length specific elongases. The stearate and arachidate elongases are located in the endoplasmic reticulum and are much more sensitive to sulphoxides than to the parent thiocarbamate. 

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