Lettuce types

Loose-leaf lettuce types (Latuca sativa) such as ... 

Fig. 8 shows typical HPLC chromatograms of Lollo rosso phenolics, and Fig. 9 a characteristic chromatogram of Romaine lettuce. The main difference in the phenolic compound patterns of both lettuce types is that... 

Lettuce is perhaps the most widely grown member of this family, eaten, along with chicory and endive, as a salad. All three can be very decorative, with leaves in diverse shapes and colors. Some cultivars produce a hearted lettuce individual leaves can be picked from the "loose leaf" types over several weeks. Chicory and endive are often blanched to reduce their bitterness. Using a selection of cultivars, and winter protection under glass, these crops can provide leafy salads all year. They also do well In an unheated greenhouse, and are useful for Intercropping and for growing in containers. 

Interestingly, the persistence of viruses such as polio has been shown to be dependent on the vegetable type. When introduced onto lettuce or cabbage, a 1 log reduction in polio virus was observed over 8 days. In contrast, viruses introduced onto green onions remained stable for over 14 days (Kurdziel et al., 2001). The underlying factors associated with the persistence of enteric viruses on fresh produce remain to be elucidated. 

Lettuce (different varieties), tomatoes (different types), celery, cucumber, sweet pepper (red and green)... 

In a more recent study, Webster et al. (2006) report the expression and characterization of lettuce-derived measles vaccine. The MV-H protein expressed in lettuce was demonstrated to be immunogenic in mice following intraperitoneal injection in the absence of adjuvant in addition to intranasal inoculation in the presence of a mucosal adjuvant. The highest response was observed in mice primed first with MV-H DNA and then boosted with an oral formulation of freeze-dried MV-H lettuce in conjunction with a mucosal adjuvant. In addition to this, the type of immune response was found to depend largely on the manner in which MV-H is presented to the immune system. Secreted and soluble forms of MV-H were demonstrated to induce a Th2 type response, while membrane-bound MV-H protein was found to be associated with a Thl response. 

Franz, E., van Diepeningen, A.D., de Vos, O.J. and van Bruggen, A.H.C. 2005. Effects of cattle feeding regimen and soil management type on the fate of Escherichia coli O157 H7 and Salmonella enterica serovar Typhimurium in manure, manure-amended soil, and lettuce. Applied Environmental Microbiology 71 6165-6174. 

It can be seen from Table 7.11 that spinach, lettuce and beetroot had significantly higher nitrate contents than the other types of vegetables analysed. Tomatoes contained the lowest concentrations. Seasonal differences in nitrate concentrations were observed for potatoes, lettuce, carrot, cauliflower and onion samples. Nitrate concentrations in potatoes were lowest in the summer period... 

Lettuce is a hardy annual grown for its lacer leaves. The 3 most common types of err ce are leaf or bunching, head (including TEoerhead and crisphead), and cos or romaine. 

Isolated lettuce chloroplasts could epoxidize zeaxanthin in the presence of reduced pyridine nucleotides and oxygen and the process was stimulated by bovine serum albumin (which protected the epoxidase system from inhibition by fatty acids). Detailed study led to the conclusion that the epoxidase was an external monoxygenase and that the violaxanthin cycle (of which epoxidation of zeaxanthin is a part) was a trans-membrane system wherein de-epoxidation took place on the loculus side and epoxidation on the stroma side of the membrane. This arrangement requires migration of the carotenoids of the violaxanthin cycle across the membrane in a type of shuttle. The possible role of this cycle in some regulatory mechanism of photosynthesis at the membrane level was also discussed. 

Case Histories. The evolution of metalaxyl resistance in the Bremia lactucae population in the United Kingdom and in the Phytophthora Lnfestans population in Northern Europe illustrate many of the principles discussed in this chapter. Mutation to resistance in the B. lactucae population is apparently a very rare event. Metalaxyl was used very effectively for five years (and maintained very low populations) before resistance became a problem (11). However, once established, selection was extremely strong for the resistant type and it quickly dominated B. lactucae populations in the lettuce growing areas of the United Kingdom. 

Light-harvesting Chi a/b complexes contain carotenoids of the /3-/3 type (/8-carotene, violaxanthin, antheraxanthin, zeaxanthin, neoxanthin) and of the /3-e type (lutein). Some higher plants like lettuce contain an , -carotenoid, lactucaxanthin, both in the major and in minor Chi a/b complexes which may replace either lutein or other xanthophylls (Phillip and Young, 1995). Among /3,/3-carotenoids, violaxanthin, antheraxanthin, and neoxanthin contain epoxides whereas the others do not. In order to... 

Work by Ruiz et al. in the analysis of water soluble inorganic phosphates in vegetables, such as tomato, lettuce, marrow, mushroom, celery, cauliflower, chard, onion, carrot, used SPE with Sep-Pak C18 cartridges for removal of organic compounds prior to IC analysis. Spiro and co-workers studied the kinetics of extraction of inorganic anions, including phosphate, from different types of tea into water. 

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