Selective Diffusion of Basic and Acidic Products of CO2 Fixation into the Transpiration Stream in Grapevine

When ¹⁴CO₂ was supplied to the leaf of a grape-vine shoot, radioactivitywas found in the wood of the shoot and in the fluid extractedby suction from the wood adjacent to the fed leaf. Some radioactivematerial was transported upwards in the transpiration streambut the labelled compounds were not representative of the labelledcompounds either in the wood or in the vacuum-extracted sap.The results suggest that labelled glutamine aaand malic acidare selectively released into the transpiration stream and partlyreabsorbed by the surrounding tissues higher up the shoot, wherethey are converted to glutamic, aspartic, -amono butyric, andcitric acids. Any labelled sugars entering the transpirationstream are preferentially reabsorbed from it.     

Genome‐wide association mapping and biochemical markers reveal that seed ageing and longevity are intricately affected by genetic background and developmental and environmental conditions in barley

Globally, over 7.4 million accessions of crop seeds are stored in gene banks, and conservation of genotypic variation is pivotal for breeding. We combined genetic and biochemical approaches to obtain a broad overview of factors that influence seed storability and ageing in barley (Hordeum vulgare). Seeds from a germplasm collection of 175 genotypes from four continents grown in field plots with different nutrient supply were subjected to two artificial ageing regimes. Genome‐wide association mapping revealed 107 marker trait associations, and hence, genotypic effects on seed ageing. Abiotic and biotic stresses were found to affect seed longevity. To address aspects of abiotic, including oxidative, stress, two major antioxidant groups were analysed. No correlation was found between seed deterioration and the lipid‐soluble tocochromanols, nor with oil, starch and protein contents. Conversely, the water‐soluble glutathione and related thiols were converted to disulphides, indicating a strong shift towards more oxidizing intracellular conditions, in seeds subjected to long‐term dry storage at two temperatures or to two artificial ageing treatments. The data suggest that intracellular pH and (bio)chemical processes leading to seed deterioration were influenced by the type of ageing or storage. Moreover, seed response to ageing or storage treatment appears to be significantly influenced by both maternal environment and genetic background.     

Studies in the distribution of insects by aerial currents. III. Insect drift over the sea

ABSTRACT.

• 1 Aerial samples caught in nets slung from ships mastheads contained predominantly small, weak-flying insects.
• 2 From over 102 trips with a total sailing time of over 1151 h, some 1825 insect specimens were collected.
• 3 In a specified area over the North Sea more than 160 km from land (seventy-five samples), catches averaged 1 insect h^?1; in the English Channel, in a smaller area more than 80 km from the coasts, hourly catches averaged 4 insects h^?1.
• 4 Lists of orders, families, genera and species caught are appended.
• 5 Aphids, which constituted more than 60% of the total, apparently originated mostly from the west or north-west, i.e. from Europe, whereas most other insects seem to have originated from the north-east and south, i.e. from Britain.
• 6 These data have implications for the spread of agricultural pests to and from Britain.

     

Silver Plated Ribosomes

WE recently reported that dissociation of free 70S ribosomes from E. coli to 30S and 50S subunits could occur during sedimentation in buffer containing K⁺ as the predominant monovalent cation¹. Spermidine at a physiological concentration (1 mM) specifically prevented the dissociation and we suggested that the dissociation that occurred in its absence was due to loss of the polyamine from the 70S ribosome. We have subsequently found that this hypothesis is wrong and that the dissociation that took place in the original experiments was due not primarily to loss of spermidine, but to a reaction with silver present in very small amounts in the AR KCl used in the buffer.