Biochemical and Histochemical Localization of Monoterpene Biosynthesis in the Glandular Trichomes of Spearmint (Mentha spicata)

The primary monoterpene accumulated in the glandular trichomes of spearmint (Mentha spicata) is the ketone (−)-carvone which is formed by cyclization of the C₁₀ isoprenoid intermediate geranyl pyrophosphate to the olefin (−)-limonene, hydroxylation to (−)-trans-carveol and subsequent dehydrogenation. Selective extraction of the contents of the glandular trichomes indicated that essentially all of the cyclase and hydroxylase activities resided in these structures, whereas only about 30% of the carveol dehydrogenase was located here with the remainder located in the rest of the leaf. This distribution of carveol dehydrogenase activity was confirmed by histochemical methods. Electrophoretic analysis of the partially purified carveol dehydrogenase from extracts of both the glands and the leaves following gland removal indicated the presence of a unique carveol dehydrogenase species in the glandular trichomes, suggesting that the other dehydrogenase found throughout the leaf probably utilizes carveol only as an adventitious substrate. These results demonstrate that carvone biosynthesis takes place exclusively in the glandular trichomes in which this natural product accumulates.     

Environmental factors affecting the lipid metabolism in Rosmarinus officinalis L

The effect of some environmental factors on the lipid metabolism was studied in two chemotypes of Rosmarinus officinalis L. Epicuticular hydrocarbons (EH), epicuticular fatty acids (EFA), whole leaf fatty acids (WLFA) and essential oils (EO) were extracted and analysed by GC-MS during winter 1991–1992 and related to temperature and moisture variations. Leaf fresh and dry wts were determined along with some morphophysiological parameters such as specific leaf weight (SLW) and specific leaf area (SLA). Leaf areas were calculated by image analysis and statistically processed as for chemical data. The results indicated that in R. officinalis the response to some environmental factors, with particular reference to temperature and moisture, was an increase in epicuticular hydrocarbons and a decrease in epicuticular fatty acids, leaf fatty acids and essential oils. Qualitative changes in the chemical composition of the above lipid classes were found to be correlated with temperature changes. From a chemosystematic viewpoint, a clear separation between the two chemotypes was achieved only when epicuticular hydrocarbons and essential oils were considered as chemosystematic characters.     

Volume regulation by flounder red blood cells in anisotonic media

The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation.     

The effect of membrane phospholipid acyl-chain composition on the activity of brain-beta-N-acetyl-D-glucosaminidase.

The phospholipid acyl-chain dependence of the membrane-bound lysosomal beta-N-acetyl-D-glucosaminidase has been examined on control membranes from rat brain primary cell cultures and on membrane modified by culturing the cells in media supplemented with polyunsaturated fatty acids. The relationship between beta-N-acetyl-D-glucosaminidase activity and the membrane phospholipid acyl-chain composition has been evaluated. An increase in the unsaturation level of phosphatidyl ethanolamines and phosphatidylcholines, the most abundant phospholipids in this membrane fraction, is related to the rate of the enzymic reaction. The Arrhenius plot of the enzyme activity in modified membranes shows break-temperatures, starting from approximately 15 degrees C. The apparent activation energy below and above the break-temperature is not correlated with phospholipid acyl-chain unsaturation.     

Pineal Body and Magnetic Sensitivity: Homing in Pinealectomized Pigeons under Overcast Skies

Since birds use the earth's magnetic field for compass orientation when astronomical cues are lacking and it has recently been suggested that the pineal body is part of their magnetic compass, test releases have been performed in overcast conditions with pigeons deprived of the pineal body. On the whole, both experimental and control birds were capable of homeward orientation, though the bearings of experimental were rather more scattered. No differences in homing speed or success were recorded. Thus, the pineal body does not appear to play an important role in the homing of pigeons.     

Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.     

Interspecific relationships in co‐occurring populations of social parasites and their host ants

Myrmica ant colonies host numerous insect species, including the larvae of Maculinea butterflies and Microdon myrmicae hoverflies. Little is known about the interspecific relationships among these social parasites and their host ants occurring in sympatric populations. We investigated communities of social parasites to assess the strategies allowing them to share the same pool of resources (i.e. Myrmica colonies). The present study was carried out at five sites inhabited by different social parasite communities, each comprising varying proportions of Maculinea teleius, Maculinea nausithous, Maculinea alcon, and Microdon myrmicae. We investigated their spatial distributions, host segregation, the degree of chemical similarity between social parasites and hosts, and temporal overlaps in colony resource exploitation. Spatial segregation among social parasites was found in two populations and it arises from microhabitat preferences and biological interactions. Local conditions can drive selection on one social parasite to use a Myrmica host species that is not exploited by other social parasites. Myrmica scabrinodis and Myrmica rubra nests infested by larvae of two social parasite species were found and the most common co‐occurrence was between Ma. teleius and Mi. myrmicae. The successful coexistence of these two species derives from their exploitation of the host colony resources at different times of the year. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 699–709.