Oxidative Assimilation of Glucose by Scenedesmus quadricauda

The utilization of glucose by Scenedesmus quadricauda has beenstudied by manometric methods. With small amounts the oxidationonly goes to about 16 per cent. of completion, the remainderof the glucose being built up into an acid-hydrolysable polysaccharidewhich is not starch, and which is built up from a hexose otherthan fructose. The extent of the oxidation is not affected by sodium azideor 2:4-dinitro-phenol, but can be varied by altering the pHof the suspension medium; more oxygen is absorbed per unit weightof glucose at pH 8 than at pH 5. It is suggested that there is no fixed relation between thetwo processes of oxidation and synthesis, as has previouslybeen suggested, but that the glucose, after phosphorylation,saturates the oxidation system, and the excess hexose-phosphateis built up into a polysaccharide. Mannose is also utilized in the same way, but at a slower rate,and less oxygen is used up compared with glucose. Galactosegives only a slight stimulation of the respiratory rate, andfructose, sucrose, and lactose are not absorbed.     

A Method for Determining Tracheid Lengths in Petrified Wood by Analysis of Cross Sections

A method is presented for estimating the length of tracheidsin fossilized secondary xylem by analysis of intersected cellsin cross sections. A two-dimensional model depicting cell positionin wood is used to derive an equation which relates the totaltracheid length to the length of the tracheid apex and the ratiobetween the number of intersected tracheid shafts and apicesobserved in cross section. Use of the technique is demonstratedin an investigation of the wood of Sphenophyllum plurifoliatum,an anatomically preserved Carboniferous arthrophyte with extremelylong tracheids. The values obtained in the analysis correspondclosely to lengths determined by indirect measurement. An examinationof the assumptions on which the method is based reveals thatthe accuracy of the cell length estimates will vary accordingto the shape of area being analysed and intrinsic structuralfeatures of the wood. Sphenophyllum plurifoliatum, Carboniferous, plant fossil     

Evidence for a calcium-binding site on the eggshell of Globodera rostochiensis with a role in hatching

Two inhibitors of hatching in Globodera rostochiensis, ruthenium red and lanthanum, have been shown to bind to the eggshell using the techniques of microdensitometry for ruthenium red and X-ray microanalysis for lanthanum. Neither inhibitor penetrated or adhered to unhatched or hatched viable juveniles. Scatchard analysis for binding of lanthanum and ruthenium red to eggshells gave dissociation constants (K) of K_La 32.5 ± 14.0 μM and K_Rured 33.5 ± 5.0 μM respectively. Both values are within the 95% fiducial limits of those shown to cause 50% inhibition of hatch in previous work. Pretreatment with sodium hypochlorite separated an outer part of the eggshell from an inner region which exclusively bound ruthenium red. It is the inner lipoprotein layer that is believed to include the membranes controlling the permeability of the tylenchid eggshell. The rate of binding of ruthenium red was similar for intact and isolated eggshells with 50% binding occurring after 6.11 ± 0.91 min and 4.95 ± 2.38 min but the latter gave a significantly higher maximum binding suggesting that rupture of the eggshells made available additional binding sites on their inner surface. The binding of ruthenium red to the eggshells was pH dependant over most of the range pH 2.8–8.5 with 50% binding, given with its standard deviation, occurring at pH 5.75 ± 0.85. Competitive binding of lanthanum influenced the binding of ruthenium red to the eggshells from which Scatchard analysis gave K_la of 176 ± 79 μM. Similarly, calcium influenced the binding but this caused a biphasic plot with high and low affinity binding sites of K“_ca of 0.423 ± 1.16 μm and K‘_ca of 1078 ± 462 μM. The existence of a high affinity site for calcium that also binds ruthenium red, suggests that the eggshell membrane includes a calcium binding glycoprotein as found in some other receptor mechanisms.     

Studies on plant growth-regulating substances: Interactions between auxins and inactive analogues

Applications of streptomycin sulphate or protectant fungicides reduced numbers of secondary infections in severely infected hop plantings. When primary infected shoots treated with streptomycin were left on plants for 3 weeks no significant increase in secondary disease resulted. Streptomycin, which was absorbed rapidly by hop plants, could not be detected in expressed shoot sap by early June and had no effect on crop yield or quality.     

The detection of salivary enzymes of phytophagous Hemiptera: a compilation of methods

The role of Hemipteran saliva and salivary enzymes is central to an understanding of the etiology of damage that these insects cause to plants. The dilute nature of the salivary secretions and the minute quantities in which they are often obtainable have made analysis and detection of salivary components very difficult. Such investigations in this laboratory have led us to formalise the techniques involved and we believe that the compilation of these methods presented herein may be useful to other research workers in this area. Methods are described for acid and alkaline phosphatase, esterase, /S-glucosidase, carbohydrases, invertase, amylase, proteinase, pectinase, cellulase, catalase, peroxidase, catechol oxidase, superoxide dismutase and ascorbic oxidase.     

WIND DIRECTION AND THE INFESTATION OF BEAN FIELDS BY APHIS FABAE SCOP.

Bean fields are often attacked by Aphis fabae very heavily along the edges: and on a field at Rothamsted in 1948 the sides facing the wind during the primary migration had more colonies than those in the lee of the crop (Johnson, 1950). Additional observations on the distribution of colonies were made on six bean fields at Sutton Bonington in 1950–2.
At Rothamsted in 1948 it was assumed that the more numerous colonies on the windward sides of the field followed a heavier deposition of primary migrants there, though the migrants themselves were not observed on the crop. In 1950–2 the locations of primary migrants, as well as of colonies, were recorded in three out of the six fields observed.     

Sites of virus retention in the alimentary tract of the nematode vectors, Xiphinema diversicaudatum (Micol.) and X. index (Thorne and Allen)

Electron microscopy of thin sections of Xiphinema diversicaudatum and X. index fed on plants infected respectively with arabis mosaic and grapevine fanleaf viruses showed that the viruses are retained as a monolayer of particles adsorbed on to the cuticle lining the lumina of the odontophore (stylet extension), anterior oesophagus and oesophageal bulb. During the moult of the nematode the cuticular lining is shed and together with the detached virus particles is ingested into the intestine through the oesophago-intestinal valve; this supports the limited experimental evidence that viruses transmitted by X. diversicaudatum and X. index are not retained through the moult.