Induced Bivalent Interlocking and the Course of Meiotic Chromosome Synapsis

WHEN chromosomes pair at meiosis the bivalents so formed do not normally interlock. Heat-treatments can, however, induce bivalent interlocking in the locust Locusta migratoria. Only the longest bivalents interlock and usually only two are found per cell; two “rod” bivalents, with single chiasmata, two “ring” bivalents, each with two or three chiasmata, or one “rod” and one “ring” bivalent (Fig. 1a, b and c). The nature of this interlocking and the metaphase orientational and congressional properties of interlocked bivalents are analysed in detail elsewhere¹.     

Synthesis and Dissolution of Starch labelled with 14Carbon in Tobacco Leaf Tissue

Tobacco leaves depleted of starch, were detached and allowedto assimilate equal amounts of ¹⁴CO₂ and ¹²CO₂in succession,and vice versa. Distribution of radioactivity in starch, andsugars was determined after assimilation and after disks cutfrom the leaves had been kept in darkness for times up to 40hours. The amount and activity of the CO₂ was also determined.¹⁴C and ¹²C were incorporated in equal amounts into starch independentlyof the order in which they were supplied. In contrast sucrosehad high activity ¹⁴C was given last, and hexose a low one.The reverse was true when ¹²C was given last. Activity of respiratoryCO₂ was slightly higher when ¹⁴C was assimilated last as comparedwith ¹²C. In the dark only ¹⁴C or ¹²C was at first lost fromstarch, in accordance or removal of discrete layers. Analyticalresults show that starch is the main respiratory substrate andto account for the redistribution of radioactivity in passageto CO₂ it is concluded that sucrose occurs at two sites separatedinter-or intra-cellularly, one of which is in equilibrium withthe system intrconverting starch and CO₂ and at the other hexosesare produced by inversion. A starch-like polysaccharide is formedduring assimilation which persists in the dark and there isa significant contribution to respiration of carbon from non-carbohydratesources when leaf disks are kept on the dark.     

Symbols of Substance: Bimin-Kuskusmin Models of Procreation,Death, and Personhood

The Bimin-Kuskusmin of the West Sepik interior of Papua New Guinea elaborate a complex folk theory of procreation that becomes the ‘natural’ foundation of some ideologically significant constructions of the individual, the person, gender, and societal continuity. Drawing on certain aspects of Weiner's model of reproduction and regeneration, symbols of substance and insubstantial ‘spirit’ that form this ‘natural’ foundation of the Bimin-Kuskusmin ideology of birth, death, and rebirth are explored in contexts of rites of passage that mark the course of the life-cycle from conception to death and ancestorhood. The key symbols of this cultural ideology are the enduring substances of bone, bone marrow, and finiik spirit, which are the basis of reckoning the cyclical regeneration of clan categories.     

Variation in the glucosinolate content of oilseed rape (Brassica napus L.) leaves

The glucosinolate content of oilseed rape {Brassica napus) leaves was monitored over the growth period 30–70 days after planting, and a comparison made between a single-low cultivar (low in erucic acid), Bienvenu, and a double-low cultivar (low in erucic acid and glucosinolate), Cobra. In older, fully-expanded leaves the glucosinolate concentration was very low (< 0.3 μmol/ml tissue water) and did not alter during the course of the experiment. In developing sixth leaves glucosinolate content increased rapidly and reached a maximum concentration (4–5 μmol/ml tissue water) 40 days after planting (6 days after leaf emergence). The concentration then declined, to about 1 μmol/ml after 60 days although the total glucosinolate content in leaves continued to increase until 50 days; much of the reduction in concentration was simply a result of leaf expansion. No major differences were seen between the two varieties in total glucosinolate content or in the individual compounds present. Cv. Cobra developed more quickly than cv. Bienvenu so direct comparison between leaves of the two cultivars was complex. When comparing the glucosinolate content of oilseed rape leaves, between cultivars or between treatments, it is vital to ensure that carefully matched leaves of comparable developmental age are selected.     

Recapture studies of the harvester ant, Pogonomyrmex owyheei Cole, using a fluorescent marking technique

Abstract.

• 1 Mark—recapture sampling must be stratified because populations of foragers and defenders are partitioned by trunk trails and order of emergence respectively.
• 2 Foragers and defenders form overlapping subsets of the total colony population, each of which is correlated with total colony population size.
• 3 Foragers and defenders have an average life expectancy of approximately 2 weeks.
• 4 The fluorescent marking procedure did not significantly affect harvester ant mortality and only temporarily affected their behaviour.
• 5 Combinations and mixtures of fluorescent ink allow at least eight groups in a colony to be distinctly marked for periods exceeding 4 months.