The effects of ultraviolet-B (UV-B: 290–320 nm) radiation on blister blight disease of tea (Camellia sinensis)

Sunlight is known to reduce the incidence of blister blight disease of tea, caused by Exobasidium vexans . The effects of the ultraviolet-B (UV-B: 290–320 nm) component of solar radiation on the disease and the development of E. vexans were studied in the field in Sri Lanka using UV-screening filter materials held over a commercial crop. Exclusion of UV-B radiation by Polyester, which reduces fluxes in the UV-B region by approximately 75–85%, increased both the number of translucent spots (immature sites of infection) and number of sporulating blisters (mature sites of infection), but it had little or no effect on the sporulation of the pathogen. When basidiospores were artificially inoculated on leaves, and were exposed to full or filtered solar radiation, their survival and germination increased when UV-B wavelengths were removed; significant differences were found 62 h after inoculation. However, UV-B did not affect the extension of germ tubes. This study indicates that the UV-B component of solar radiation plays an important role in the natural regulation of blister blight disease in the field.     

Development of a powder formulation of Pseudomonas fluorescens for control of rice blast

Pseudomonas fluorescens strain Pf1, inhibitory to the growth of the rice blast pathogen Pyricularia oryzae in vitro , was developed as a talc-based powder formulation. When rice seeds were treated with this formulation, the bacteria spread to roots, stems and leaves of the plants and protected against leaf infection by P. oryzae . When applied as a foliar spray, the bacteria survived on the leaves. The powder formulation controlled leaf blast under greenhouse conditions. In tests as a seed treatment and foliar spray in four field trials it effectively controlled the disease and increased grain yield.     

Major mechanisms in formation of spodic horizons

Current explanations of the formation of spodic horizons do not accomodate all features of the horizons in their natural state. In this paper, a more complete explanation of major mechanisms is proposed, using two principles of colloid chemistry: (1) organic substances may form hydrophylic colloids with surface charges, and (2) the hydrophylic character and negative surface charges determine the dispersibility of the colloids. The hydrophylic character is due to the presence of hydrophylic radicals as parts of the organic compounds in soils. The surface charges are the result of dissociation of -COOH and possibly phenol-OH radicals.The neutralization of the surface charge can in principle occur: (1) through electrostatic or physical adsorption and (2) through chemisorption. The first case is typical for monovalent alkali cations. The adsorbed cations are distributed in a double layer, which favours dispersion. Chemisorption occurs mostly with polyvalent cations. This process corresponds in reality to the formation of organo-metallic compounds. It results in a relatively complete disappearance of the double layer and in the formation of large immobile “polymerized” organo-metallic compounds. Because these compounds contain much hydrophylic water, they form a gel. Transition into the solid state is accompanied by the loss of most of the hydration water. The dehydration may be induced by a decrease in thickness of the double layer. At a certain stage of the dehydration process, Van der Waals bonds and protonic bridges can form and bring about a certain degree of hydrophoby.In soils, mobile organic substances are formed during breakdown of plant remains. If at the top of the mineral soil enough polyvalent cations, especially Al and Fe, are available, the mobile organic substances formed are immobilized immediately and no migration occurs. In case insufficient amounts of Al and/or Fe are available to completely immobilize the mobile compounds, these cations are complexed by the mobile compounds and transported downward. Immobilization may occur at some depth through supplementary fixation of cations, through dessication or on arrival at a level with different ionic concentration.In nature, spodic horizons range from loose, with many roots, to very cemented with few roots. These differences can be related to changes in microstructure. Loose spodic horizons have a predominance of polymorphic pellets and aggregates, whereas organans or monomorphic coatings prevail in cemented horizons. The former horizons have many features suggesting major biological influences during their formation, viz., high numbers of roots, thorough mixing of the organic units with clay and silt, the presence of pedotubules and relatively young mean residence times. The latter horizons have features consistent with organo-metallic compounds immobilized in a gel-state, viz., the coatings are strongly cracked, indicating the transition of a gel into a solid; they contain much Al or Al plus Fe but very little or no Si, and the mean residence time is considerably higher than in loose horizons.The two processes seem to operate simultaneously during the formation of spodic horizons and their relative intensities determine the composition of each spodic horizon at any moment in its evolution. As long as the biological activity predominates, the horizon remains loose; if the accumulation of mobile organo-metallic compounds starts to prevail, the horizon is gradually cemented and fossilized.     

Analysis of fat-soluble vitamins. XXIII. High performance liquid chromatographic assay for vitamin D in vitamin D3 and multivitamin preparations.

Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E.     

Estimating the abundance and diversity of butterflies

Concern about the apparent decline in butterfly populations has led to projects designed to obtain quantitative information on their abundance and diversity. Three methods of sampling communities of butterflies are suggested, and the use of a diversity index, β, is recommended. This index gives an estimate of the probability that an individual sampled at random from a community will be different from the previous individual sampled. Change and stability in diversity can be used as a guide for conservation and management programmes.     

THE ERROR IN PREDICTING PASTURE DRY–MATTER DIGESTIBILITY FROM FOUR DIFFERENT METHODS OF ANALYSIS FOR LIGNIN

The lignin content of 50 samples of five grasses of known in vivo digestibility were determined by the methods of Armitage, van Soest and two modifications of the van Soest technique. The error in predicting DM digestibility varied from ±3.1 for tbe Armitage metbod to ±5.0 for the van Soest method. This error compares nnfavourably witb ±2.1 previonsly obtained on tbe same samples with the in vitro technique of Tilley and Terry.