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Abstract. Sucrose-phosphate synthase (SPS; E.C. 2.4.1.14) was studied in 1-year-old leaves of the xylem-parasitic mistletoe (Viscum album L.), growing on Abies alba. Glucose-6-phosphate served as an allosteric activator of mistletoe SPS, increasing the affinity for both substrates, fructose-6-phosphate and UDP-glucose. The activation state of SPS, i.e. the ratio of substrate limited versus non-limited...
Abstract. In a water-exclusion experiment, five different ecotypes of beech (Fagus sylvatica L.; representing regions of different environmental and climatic conditions in Baden-Wrttemberg, Germany) were subjected to drought conditions of different severity between July and September of two consecutive years. Drought stress as characterised by the water content and the pre-dawn water potential of...
AbstractEctomycorrhizas are formed between certain soil fungi and fine roots of woody plants. An important feature of this symbiosis is the supply of photoassimilates to the fungus. Hexoses, formed from sucrose in the common apoplast at the root/fungus interface, can be taken up by both plant and fungal monosaccharide transporters. Recently we characterised a monosaccharide transporter from the ectomycorrhizal...
AbstractDevelopment of spruce needles starts with high levels of starch. These are derived from imported sucrose, and, with some fluctuation, largely vanish during sink/source transition (Hampp et al. 1994, Physiol Plant 90: 299306). In order to get more information about starch metabolism during this period, we collected current year needles of approximately 25-year-old Norway spruce trees [Picea...
Abstract. Plant cell protoplasts derived from leaf tissue of two different tobacco species (Nicotiana tabacum L., N. rustica L.) were exposed to short-term (sounding rocket experiments) and long-term (spacelab) microgravity environments in order to study both (electro) cell fusion and cell metabolism during early and later stages of tissue regeneration. The period of exposure to microgravity varied...
Summary. As a part of the D2 Spacelab mission, tobacco (Nicotiana tabacum L.) protoplasts were cultured for 10 days in microgravity and successfully regenerated into microcalli, which, after further cultivation on the ground, gave rise to intact oplants. Protein analysis was performed on samples taken during the initial microgravity period and compared to ground controls. Total protein content and...
AbstractDespite the importance of the vascular cambial differentiation, little is known about its regulation. In order to address this problem we attempted to biochemically characterize differentiating xylem and phloem elements during the early stages of development. By applying techniques of quantitative histochemistry we show that the total pool size of pyridine nucleotides is similar in the phloem...
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