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2001 (1)
1992 (2)
1Author    P.-G Gülz, G. BoorRequires cookie*
 Title    Seasonal Variations in Epicuticular Wax Ultrastructures of Quercus robur Leaves  
 Abstract    Already the very young leaflets of oak (Quercus robur L.), newly emerging from their buds, are covered by a thin wax layer, but at this time it lacks any wax sculptures or crystalloids. Both in its amount and its composition this wax layer is quite different to that of mature leaves. After leaf unfolding a dynamic biosynthesis of wax lipids is started. Ten days after the leaf has emerged from its bud, wax crystalloids are seen for the first time, developing out of the wax layer in the form of platelets. These crystalloids increase in size and quantity within the next weeks and are present on both leaf surfaces. On the adaxial side a dense and uniform arrangement of fringed edged platelets is observed. Similar dense arrangements of platelets are found on the abaxial leaf side, but with an intensive concentration and orientation around the stomata. All platelets are composed of tetracosanol, the main wax component, accounting for more than 40% of wax. Variations in surface wax ultrastructures are observed in July. Well formed platelets and melted away crystalloids are found close together in distinct parts of the same leaf, both on the adaxial and on the abaxial sides of the leaf. These observations pertain to preparations made from July to November with a trend toward recrystallization in October. High temperature and essential oils may be the reasons for the melting away or solution of the platelets. 
  Reference    Z. Naturforsch. 47c, 807—814 (1992); received June 9 1992 
  Published    1992 
  Keywords    Quercus robur, Fagaceae, Leaves, Wax Ultrastructure, Seasonal Variations 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0807.pdf 
 Identifier    ZNC-1992-47c-0807 
 Volume    47 
2Author    A. Lberto Dos, Santos Pereira3, AnaClaudia Fernandes, Am Aralb, M. Argareth De, A. Raujo Silva3, Francisco Radler, AquinoN. Eto3Requires cookie*
 Title    Seasonal Variation of the Chemical Constituents from Croton Species  
 Abstract    The terpenes, sterols, alkaloid (glaucine) and a-tocopherol show seasonal variation for Croton hemiargyreus hemiargyreus and Croton echinocarpus. The amounts o f triterpenes are higher during the tropical summer and in most samples the major sesquiterpene was characterized as caryophyllene. The seasonal variation of glaucine showed a maximum be­ tween June and O ctober for C. hemiargyreus, and was present only in January and June in C. echinocarpus. 
  Reference    Z. Naturforsch. 56c, 357 (2001); received October 9 2000/February 20 2001 
  Published    2001 
  Keywords    C roton, Chemical Constituents, Seasonal Variation 
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 TEI-XML for    default:Reihe_C/56/ZNC-2001-56c-0357.pdf 
 Identifier    ZNC-2001-56c-0357 
 Volume    56 
3Author    P.-G Gülz, E. MüllerRequires cookie*
 Title    Seasonal Variation in the Composition of Epicuticular Waxes of Quevcus robur Leaves  
 Abstract    The epicuticular leaf waxes of Quercus robur were analyzed continuously over a two years vegetation period with preparation every week from April to November. The folded leaflets in buds have waxes quite different in yield and composition from those of mature leaves. They contain homologous series of hydrocarbons, wax esters, primary alco­ hols, fatty acids and triterpenoids from the beginning, but not aldehydes. After leaf unfolding a dynamic biosynthesis of alcohols, aldehydes and fatty acids is observed in May and June. Wax content is doubled per dry weight or in cm2 leaf surface area and 80-fold per one leaf in that time. During leaf development tetracosanol becomes the dominant epicuticular wax component comprising ca. 40% of the wax. In both years of the study a reactivation of wax ester biosynthesis is observed in October and November. Esters with chain length C36 and C38 increased particularly. From July to November the wax composition remained nearly constant within mean values and their stand­ ard deviations. Within the two years studied most values concerning wax composition are reproducible and are therefore genetically determined. In spring the growing processes are influenced by climatic factors. 
  Reference    Z. Naturforsch. 47c, 800—806 (1992); received June 9 1992 
  Published    1992 
  Keywords    Quercus robur, Fagaceae, Leaves, Epicuticular Wax Composition, Seasonal Variation 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0800.pdf 
 Identifier    ZNC-1992-47c-0800 
 Volume    47