Genetics of dioecy and causal sex chromosomes in plants

Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and roecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 and WZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.     

Chemical retting of flax using chelating compounds

A wide range of concentrations of ethylenediaminetetra acetic acid (EDTA) was tested as a retting agent at a range of temperatures, pHs and stem: liquor ratios. Treatment of stems at 2 and 3 g/litre at 40 °C in a liquor ratio of 1:10 at pH 11 produced the finest and strongest fibre. Dried-green stem retted slightly better than the glyphosate-desiccated stem and after multiple retting with EDTA, Trilon TB and diethyltriaminepenta acetic acid (DTPA), the dried-green stem produced the finest fibre. Trilon TB and DTPA retted better than EDTA and produced a high yield of fibres. The fluidity of fibres scutched from the dried-green stem was lower than the fluidity of the fibres from glyphosate-desiccated stem.     

Studies on Nucleolus and Nucleolar Chromosomes in Angiosperms. XI. Plantago L.

The number and morphology of nucleotar chromosomes is describedfor 11 species of Plantago. The possible significance of interspecificdifferences in number and morphology and their potential valuein phylogenetic studies are discussed. Plantaginaceae, Plantago L., karyology, NOR, nucleolus, nucleolar bivalents, NOR evolution     

Diapause in twenty-three populations of Plodia interpunctella (Hübner) (Lep., Pyralidae) from different parts of the world

Abstract. 1. The incidence of diapause in twenty-three populations of Plodia interpunctella from fifteen countries representing all continents of the world was examined. The origins of populations varied from 52°N to 35°S and included two from equatorial regions.
2. Diapause occurred in all population samples at 20°C in short photoperiods (LD 11:13) and in continuous light, although the proportion of larvae doing so was less than 25% in samples from the equatorial belt.
3. The critical photoperiod was less than 13 h in five samples, all from the tropics, or southern hemisphere. The remaining samples, including three from the southern hemisphere, had critical photoperiods of 13 h or more.
4. Diapause was completely avoided by a 15 h photoperiod at 20°C in thirteen of the twenty-three samples, including all but one of those from the southern hemisphere.
5. At 25°C larvae entered diapause in short photoperiods (LD 9:15) in about half of the samples tested in both hemispheres, but the proportion per sample was always less than a third.     

The retting of flax after preservation with sulphur dioxide

Experiments were carried out to compare the retting of moist flax preserved with sulphur dioxide with that of green dried flax, using whole straw samples. When retted in water at either a constant 20°C or 28°C dried flax was fully retted after 15 and 10 days respectively whereas the sulphur dioxide treated flax (20 g sulphur dioxide kg“¹ flax DM) had undergone almost no retting after 20 days at 20dC or 10 days at 28°C. Pre-soaking the treated flax for 24 h in water and changing the acidified water, raised the pH of the retting liquor to a more normal value but did not significantly increase the rate of retting. Addition of the pectinase enzyme preparation ‘Flaxzyme’ to retting liquor at the rate of either 1.5 g kg^-1 or 3.0 g kg^-1 water, and at a constant temperature of 20°C, substantially increased the rate of retting of both sulphur dioxide treated and dried flax. Optimum degree of retting was achieved at 24 h with the treated flax and at 97 h with the dried flax. Pre-rinsing of the sulphur dioxide treated straw only served to reduce the rate of retting. It was concluded that natural water retting of sulphur dioxide treated flax is retarded by the presence of acidic residues of sulphur dioxide, while enzyme retting is enhanced by these. In further smaller scale experiments using bundles of cut flax straw Flaxzyme was added at concentrations ranging from 0–8.0 ml litre ¹ to containers containing flax in water at ratios from 1:10 to 1: 600 flax:water and the producion of galacturonic acid was used as an indicator of retting progress. Retting took place more rapidly at higher flax to water ratios for a given enzyme concentration. This effect was attributed to the lower pH of higher flax to water ratios which created pH conditions closer to the pH optimum for the retting enzymes. When enzyme retting was compared at a range of buffered pH's the optimum was pH 4.0. At a buffered pH of 4.0 and a temperature of 19°C, retting of sulphur dioxide treated moist flax (flax to water ratio of 1:10) was achieved with Flaxzyme concentrations as low as 0.5 ml litre”‘,much lower than the previously reported minimum of 3.0 ml litre’.     

Identification of antibodies directed against O-acetylated sialic acids in visceral leishmaniasis: its diagnostic and prognostic role

A significantly increased O-acetylated sialic acid (O-AcSA) binding fraction was purified from serum of visceral leishmaniasis (VL) patients by affinity chromatography on immobilized bovine submaxillary mucin (BSM) and found to be immunoglobulin in origin. The serodiagnostic and prognostic potential of BSM as a capture antigen was established by ELISA with no cross reactivity with coendemic diseases like malaria, tuberculosis, leprosy, chagas disease and cutaneous leishmaniasis; however, a strong cross reactivity was present with trypanosomiasis patients. In 56 clinically diagnosed VL patients, the BSM-ELISA was compared with diagnosis by microscopy using Giemsa stained tissue smears and direct ELISA using crude parasite antigen (parasite-ELISA); 49/56(87.5%) and 5/56(9.0%) were positive and negative respectively by all 3 methods. The BSM-ELISA failed to diagnose 2/56(3.5%) patients which were biopsy and parasite-ELISA positive. The prognostic potential of the BSM-ELISA in 18 longitudinally monitored VL patients before and after conventional antimonial treatment showed a significant decrease in anti O-AcSA titres in drug responsive patients whereas anti O-AcSA levels persisted in drug unresponsive patients. The IgG subclass distribution of antibodies directed against O-AcSA showed increased IgG2 levels in VL patients as compared to healthy controls. The BSM-based ELISA holds great promise as a serodiagnostic and prognostic assay for VL.     

An alternative method of flax retting during dry weather

During exceptionally dry and hot weather undesiccated flax (Linum usitatissi-murri) and flax desiccated with glyphosate that was pulled and laid on the ground to dew-ret, retted 1–2 wk before flax that was desiccated and left as a standing crop. This was because dew-retted flax was colonised by fungi faster than that left standing. Cladosporium herbarum, Epicocum nigrum and yeast, including Aureoba-sidium pullulans, appeared first; they were followed by Alternaria alternata, Fusarium culmorum and Phoma, Mucor and Rhizopus species. The standing crop retted more slowly despite the presence of greater concentrations of cell-wall degrading enzymes. However, the fibres of flax retted as a standing crop retained more of their strength than those of flax retted on the ground. Thus dew-retting provides means of retting when the weather is dry and hot.