A MEDIUM FOR THE CULTIVATION OF LACTOBACILLI

SUMMARY: An improved growth medium for lactobacilli is described. It supports good growth of lactobacilli generally and also is particularly useful for a number of fastidious strains which grow only poorly in other general media. In addition, tomato juice, a highly variable material, is not required. In a slightly modified form, it can also be used as a basal medium for fermentation tests.     

Changes in a Leaf-growth Substance in Cotyledons and Primary Leaves during the Growth of Dwarf Bean Seedlings

The growth of etiolated dwarf bean leaf disks in darkness wasused to assay leaf-growth substances extracted from plant tissuesand separated on chromato-grams. A leaf-growth substance, with the same Rf value in isopropanol/ammoniaas gibberellic acid, was found in the acidic fraction of extractsfrom dwarf bean primary leaves and cotyledons. Neither neutralnor basic leaf-growth substances were found in primary leafextracts. The amount of leaf-growth substance per cotyledon reached amaximum at the 4th day in cotyledons, whether bean plants weregrown in the light or dark. Primary leaves of dwarf bean plantsgrown in the light reached their maximum content of leaf-growthsubstance later than the cotyledons; the time of maximum contentcoincided with the maximum growth-rate of the primary leaves.Leaf-growth substances did not accumulate in primary leavesof plants grown in the dark.     

Effect of Removing Cotyledons, Apical Growing Region, or Trifoliate Leaves on the Growth and Growth-substance Content of Dwarf French Bean (Phaseolus vulgaris)

The growth of the primary leaf on intact plants was comparedwith that on plants from which the cotyledons, apical growingregion, or trifoliate leaves had been removed. Removing thecotyledons early decreased the final area of the primary leaves,this response being partially accounted for by a decrease intheir cell number, and increased the concentration (but notthe quantity) of gibberellin and auxin in them. This responsewas not altered by applying any of several growth substances.Early removal of the apical growing region increased the finalarea of the primary leaves; it also increased the gibberellincontent and concentration at Day 10 but did not influence theauxin content and concentration. Primary leaf expansion wasaffected less by detaching young trifoliate leaves than by removingthe entire apical growing region.     

Host plant finding in the specialised leaf beetle Cassida canaliculata: an analysis of small-scale movement behaviour

Abstract.  1. Host plant finding in walking herbivorous beetles is still poorly understood. Analysis of small-scale movement patterns under semi-natural conditions can be a useful tool to detect behavioural responses towards host plant cues.
2. In this study, the small-scale movement behaviour of the monophagous leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) was studied in a semi-natural arena ( r = 1 m). In three different settings, a host ( Salvia pratensis L., Lamiales: Lamiaceae), a non-host ( Rumex conglomeratus Murr., Caryophyllales: Polygonaceae), or no plant was presented in the centre of the arena.
3. The beetles showed no differences in the absolute movement variables, straightness and mean walking speed, between the three settings. However, the relative movement variables, mean distance to the centre and mean angular deviation from walking straight to the centre, were significantly smaller when a host plant was offered. Likewise, the angular deviation from walking straight to the centre tended to decline with decreasing distance from the centre. Finally, significantly more beetles were found on the host than on the non-host at the end of all the trials.
4. It is concluded that C. canaliculata is able to recognise its host plant from a distance. Whether olfactory or visual cues (or a combination of both) are used to find the host plant remains to be elucidated by further studies.     

Food consumption and utilization responses to dietary dilution with cellulose and water by velvetbean caterpillars, Anticarsia gemmatalis

Abstract Dilution of an artificial diet with water or cellulose to nutrient levels of 32% (undiluted), 19% and 10% fresh weight (fw) resulted in increased fw and dry weight (dw) food consumption (both absolute amounts and weight-relative rates) by velvetbean caterpillars, Anticarsia gemmatalis Hübner. Despite these increases, the absolute amount and relative rate of nutrient intake by the caterpillars declined with dilution, as did their dw gain and dw (% fw) and lipid (% dw) contents. The proportion of consumed food (dw, including cellulose) that was digested and absorbed declined with increased dietary cellulose; however, the proportion of consumed nutrients (dw, excluding cellulose) that was digested and absorbed was not affected by the presence of cellulose, although it increased slightly (but significantly) with dietary water. The efficiency with which the absorbed nutrients were converted to biomass energy showed a negative relationship with the various measures of food consumption and thus a positive relationship with dietary nutrient level.
The compensatory increases in feeding mitigated the deleterious impact of dietary dilution on growth, which would have declined further without the increased feeding. These data suggest that food consumption is regulated primarily through an evaluation of food nutrient level, and that the metabolic costs associated with the increased consumption and processing of food may be substantial, especially on the most diluted diets. Another hypothesized cost of increased feeding, reduced efficiency of digestion and absorption as food presumably passes more rapidly through the gut, was not detected.