Fourteen tomato genotypes, eastern black nightshade, and 35 Lycopersicon accessions were screened for tolerance to acifluorfen. Tolerant and susceptible genotypes occurred in most species. Fifteen genotypes were chosen for further study depending on their fresh weight after acifluorfen treatment Over all 15 genotypes, there was no correlation between trichome density and acifluorfen tolerance; however, in L. esculentum, cultivars with the most trichomes were the most tolerant There was an inverse relationship between stomata density and tolerance. Amount and composition of epicuticular wax and cuticle thickness did not correlate to acifluorfen tolerance.

Absorption of triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} by tanoak [Lithocarpus densiflorus (Hook. & Am.) Rehd.] leaves was investigated. Greater amounts of 14C-triclopyr were absorbed by immature leaves than mature leaves and by abaxial than adaxial surfaces. Both surfaces of immature and mature tanoak leaves were characterized. Stomata were present only on the abaxial surface and were more numerous on immature leaves than mature leaves. Immature leaves had less epicuticular wax and thinner, more permeable cuticular membranes than mature leaves. Stellate trichome densities were greater on abaxial surfaces than adaxial surfaces and on immature than mature leaves. Absorption of 14C-triclopyr was influenced by each of the leaf surface features studied.

The tomato red spider mite Tetranychus evansi Baker & Pritchard is a serious pest of solanaceous plants worldwide. Management of this oligophagous pest in African nightshades has been a challenge to smallholder African farmers due to its high reproductive rate and rapid development of resistance to synthetic pesticides. The aim of the present study was to determine the influence of leaf trichomes on T. evansi by comparing its fecundity and movement on the leaf surfaces of five African nightshade species, namely Solanum sarrachoides Sendter, S. villosum Miller, S. tarderemotum Bitter, S. americanum Miller and S. scabrum Miller. Data were recorded in the laboratory at 23 ± 1°C, 50–70% relative humidity and a 12 h light:12 h dark photoperiod for the effect of trichome type and density of the abaxial leaf surface on mite fecundity. Distances travelled by mites on the leaf surface from the edge of a thumbtack pin inserted on the leaf were also recorded. Different trichomes, glandular and non-glandular types, were identified. There was a significant negative correlation of fecundity and distance walked by mites with the density of glandular trichomes. Significantly fewer eggs were laid on S. sarrachoides in comparison with the other Solanum species. The distance walked by mites was also significantly shorter in this species, indicating that higher densities of glandular trichomes interfere with mite movements. These results suggest that African nightshade genotypes differ in their levels of resistance to T. evansi, which is partially associated with differences in trichome types and their densities.

Morphology of foliar trichomes was analyzed in Quercus variabilis by electron microscopy and three-dimensional surface profiling. Leaves from suppressed or dominant sprouts of the oak species were collected after a forest fire to unravel the effects of the disturbance factor on sprouting of the oak species. Scanning electron microscopy revealed two types of trichomes depending on the leaf surface. The trichomes on the adaxial surface were branched and constricted, and possessed a single row of thin-walled cells with a collapsed morphology (glandular branched uniseriate trichomes). Meanwhile, the trichomes on the abaxial surface were star-shaped, unfused with each other, and had 6 to 10 rays (nonglandular simple stellate trichomes). An apparent proliferation of trichomes was evident on the adaxial surface of the dominant sprouts. Uniseriate trichomes could be discernable as an elevation from the surface by white light scanning interferometry. By transmission electron microscopy, thin and convoluted cell wall, degenerated cytoplasm, and a single row of cells were characteristic of the trichomes on the adaxial surface. The thick cell walls of the mature trichomes on the abaxial surface represented the nonglandular nature. This is the first report on the morphological and ultrastructural characterization of foliar trichomes of the oak species.

Introduction. Mature green vanilla pods accumulate 4-O-(3-methoxy-benzaldehyde)-β-D-glucoside (glucovanillin), which, upon hydrolysis by an endogenous β-glucosidase, liberates vanillin, the major aroma component of vanilla. Sites of storage of glucovanillin in the pod have been controversially reported for decades; we aim, using precise and widely accepted technical terminology, to clarify this controversy by providing an anatomical, histochemical and biochemical evidence-based picture of glucovanillin accumulation sites. The pod also synthesizes an oleoresin and a mucilage of unknown constitutions; we report here their localization and structures. Materials and methods. The pod anatomy was examined by light and epifluorescence microscopy. A protocol was established allowing fine hand-dissection of diverse anatomical parts of the pod (mesocarp, placentae, trichomes, intralocular interstitial cell-free region and seeds). Glucovanillin and γ-pyranones were extracted and analyzed by HPLC, while the structures of the mucilaginous polysaccharides were determined after permethylation. Results and discussion. Glucovanillin is essentially stored in the placentae (92%) and marginally in trichomes (7%); traces were measured in the mesocarp and intralocular interstitial cell-free medium. Trichomes store massive amounts of a fluorescing oleoresin (44%) rich in alkenylmethyldihydro-γ-pyranones and synthesize a mucilage made of a glucomannan and a pectic polysaccharide carrying monomeric arabinose and galactose side-chains. Conclusion. To date, the physiological roles of glucovanillin, long-chain pyranones, and mucilage remain unknown.

Two new species of Begonia (Begoniaceae), Begonia ozotothrix and Begonia hekensis, are described from the Indonesian island of Sulawesi. Both species belong to Begonia section Petermannia. Begonia ozotothrix is unusual amongst Asian Begonia in having branched trichomes on the stems, petioles and the abaxial lamina surfaces, and it is unusual amongst species of Begonia section Petermannia in having extremely compressed cymose-subumbellate male partial inflorescences.

A new species of Begonia (Begoniaceae) is described from Khammouan Province in Laos. The new species, Begonia cladotricha M.Hughes, belongs in Begonia sect. Diploclinium, and is unusual amongst Asian Begonia in having basally branched hairs on all vegetative parts of the plant.

One hundred and five okra cultivars were evaluated in the field for resistance to the leafhopper Amrasca biguttula biguttula (Ishida) during the 1989–1990 season. On the basis of nymphal abundance and leafhopper injury index two resistant (Siswal Local and IC 7194) and nine moderately resistant [IC 6653, IC 8899, IC 13617, Sel. 1, HB 94, IC 6316,6 Dhari, Sel. 2–2 and Line 6(1)] genotypes were identified. Both of the resistant, two moderately resistant (Line 6(1) and IC 13617) and two highly susceptible (Pusa Sawani and Pusa Reshmi) genotypes were retested in 1990–1991. Resistant genotypes had significanlty (P < 0.05) fewer nymphs (18.5 to 22.0 nymphs/leaf) and lower values of injury index (2.2) compared with the other varieties. Nymphal duration was also longer (9.3 to 9.8 days) and nymphal survival lower (41.7 to 47.5%) in resistant cultivars. Higher trichome density, longer trichome length and higher concentration of sugars, silica, potassium, tannins and phenols in the leaves of resistant cultivars were associated with resistance to leafhopper.

The shootfly, Atherigona soccata Rondani, is a major seedling pest of sorghum in many areas of tropical Asia, Africa and Mediterranean Europe. A chronological review of the progress made in various programmes on the screening techniques (natural and artificial) with artificial diets, sources, stability and mechanisms of resistance, bases (physico-morphological and biochemical factors) of resistance, inheritance and breeding for resistance is made. Many resistant varieties have been identified and sources of resistance utilized in breeding programmes to transfer resistance in high yielding background are listed. In addition, the glossy and trichome traits identified is sorghum cultivars are also reported. Glossy leaf surface and trichomes are frequently associated with shootfly resistance.