Resistance to potato leafroll luteovirus can be greatly improved by combining two independent types of heritable resistance

Twelve potato clones were exposed to infection by aphids with potato leafroll luteovirus (PLRV) in three field trials in order to assess their resistance to infection. Up to 92% of the plants of some clones became infected, although other clones were relatively resistant to infection and one clone remained virus-free in all three trials. The resistance of the same 12 clones to PLRV multiplication was assessed in glasshouse-grown plant: lants were graft-inoculated and their daughter tubers were used to grow plants with secondary infection. High concentrations of PLRV were found in some clones (c. 1700 ng/g leaf) while in others much less virus accumulated (as little as 60 ng/g leaf). However, clones in which little virus accumulated were not necessarily those which were most resistant to infection in the field, and there was no association between the two types of resistance. Nevertheless, both types of resistance were found in some clones. The clone G8107(1), which remained virus-free in all the field exposure trials, was also the most resistant to PLRV multiplication. The combination of these two types of resistance in cultivars should help to eliminate the spread of PLRV in crops.     

NOTES ON THE INTRODUCED TERRESTRIAL PULMONATA (GASTROPODA:MOLLUSCA) OF NEW ZEALAND

The New Zealand Pulmonate fauna contains 22 naturalized terrestrialspecies. For each, a bibliography is given for the New Zealandliterature and comment made on its biology and distribution.Vertigo ovata SAY and Oxychilus draparnaldi (BECK) are newlyrecorded from New Zealand. (Received 11 February 1981;     

Studies in the Respiratory and Carbohydrate Metabolism of Plant Tissues1: XVI. FURTHER STUDIES OF THE INFLUENCE OF IODOACETATE AS A STIMULANT OF RESPIRATION IN STRAWBERRY LEAVES

Low concentrations of iodoacetate produced large increases inCO₂ output of strawberry leaves which were not completely accountedfor by the observed losses of sugars and starch. No significantchange was observed in RQ in iodoacetate but the values, eitherin water or in iodoacetate, were generally below unity. Thus,in addition to other carbohydrates not estimated in our work,there may also be respiration of protein or organic acids. The increased rate of CO₂, output in iodoacetate was associatedwith rises in pyruvate and oxaloacetate but citrate and -ketoglutarateremained unchanged. The former changes suggested a faster trafficinto the tricarboxylic acid cycle; the content of oxaloacetateappeared to be a close index of the rate of this traffic. Atentative interpretation is given of the anomalous behaviourof citrate and -ketoglutarate in iodoacetate.     

Internal and external photoprotection in developing leaves of the CAM plant Cotyledon orbiculata

Leaves of the CAM plant Cotyledon orbiculata produced a dense epidermal wax which decreased the absorption of light, possibly functioning as an external photoprotective mechanism (Robinson et al. 1993). However, developing leaves did not accumulate wax until after 21 d with full wax coating not achieved until at least 35 d. In addition, young leaves had lower rates of electron transport than mature leaves. Leaf development therefore occurs at higher incident PFD than that experienced by the mature leaves, and, for young leaves, can lead to an increase in the proportion of light energy which is excess to requirements and must be dissipated non-photochemically. Changes in the photosynthetic capacity, PSII efficiency, rate of energy dissipation, and the content of chlorophyll (Chi), carotenoids, wax and anthocyanins were followed in developing leaves of C. orbiculata in an attempt to elucidate the relative importance of the various photoprotective mechanisms during leaf ontogeny. The largest pools of xanthophyll cycle pigments (on a Chi basis) were found in the waxless, young leaves and were correlated with greater levels of energy dissipation activity. The importance of xanthophyll cycle-dependent energy dissipation in young C. orbiculata leaves prior to development of a reflective wax covering, and full photosynthetic capacity which for CAM plants includes appreciable nocturnal acid accumulation, is discussed. Also, we consider the possibility that anthocyanin pigments in the upper and lower epidermis may increase reflectivity and act as external photoprotectants.     

Effects of Ammonium and Potassium Ions on Some Physiological and Biochemical Processes of Excised Cucumber Cotyledons

Incubation of excised cucumber cotyledons (Cucumis sativus L.) with NH₄Cl solutions exceeding 0.001 M inhibited their greening, fresh weight increases, and incorporation of ¹⁴C-leucine into insoluble N compounds. The absorption of ¹⁴C-leucine during incubation and retention of moisture by the excised cotyledons after incubation were greatly diminished by the NH₄Cl treatments. Treatment with KCl solutions of the same concentrations as the NH₄Cl stimulated the greening, fresh weight increases, and the absorption and incorporation of ¹⁴C-leucine. Desiccation of cotyledons stored at 5°C for 10 days was inhibited by dilute KCl solutions. The toxicity of NH₄Cl was alleviated by KCl solutions at low concentrations.     

Octopamine in the Lobster Nervous System

A search for catecholamines which might serve as transmitters in the lobster nervous system demonstrated only small amounts of dopamine (about 0.2 µg/g tissue) and failed to detect noradrenaline or adrenaline (limit of sensitivity, 0.1 µg g^?1) (unpublished results of D. L. B., using standard procedures for isolation of catecholamines on alumina¹ and fluorescence assays^1,2). Octopamine (the phenol analogue of noradrenalin, Fig. 1) occurs in large amounts in the posterior salivary glands of Octopus vulgaris³ and recently has been identified as a normal minor constituent of sympathetically innervated tissues of rat⁴. The possible occurrence of octopamine or other phenolamines in the lobster was therefore investigated. Here we report the presence of octopamine in the lobster nervous system, its endogenous distribution and its biosynthesis from tyrosine.     

A PAPER NAUTILUS (OCTOPODA, ARGONAUTA) FROM THE MIOCENE PAKHNA FORMATION OF CYPRUS

Abstract:  The fossil organic trace of an argonaut shell from the Pakhna Formation (Serravillian, Middle Miocene) of southern Cyprus is described. The new find represents one of only a very few argonaut egg cases reported from the fossil record of the Tethyan region and is the first to be reported from the eastern Mediterranean. It is assigned to a new species of Argonauta as A. absyrtus sp. nov.