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DORMANCY in Trifolium subterraneum L. (subterranean clover) has been reviewed by Morley1. Dormancy in imbibed seed is usually high at harvest maturity but declines with time at rates which differ with strain. High temperatures are inhibitory to germination, and the younger the seed the lower is the inhibiting temperature. Ballard2,3 has shown that dormancy in new seed is readily overcome by cold treatment and also by subjecting the imbibed seed to an atmosphere enriched with carbon dioxide at temperatures of up to 25° C; above 25° C, carbon dioxide is unable to abolish completely the inhibition of germination at high temperatures. Dormancy may also be relieved by heat treatment of dry seed4, by removal of the seed coat5 and by other means1. The presence of an inhibitor in the seed which is soluble in water has in the past been questioned6 if not discounted2.

WHEN flour beetles1, ground squirrels2, rats3,4 and hamsters5 were subjected after learning to temperatures of 5° C and below, their retention of a task, measured at normal temperatures, was not significantly less than that of controls. Flour beetles given cold treatment even showed an improvement in retention over controls. Experiments on protozoan habituation dealing with both acquisition and retention, measured at one of three temperatures, indicated that the retention of the response increases as the temperature decreases6. We carried out a new experiment to determine whether subjecting protozoa to cold treatment after acquisition of a response at room temperature (22° C) also affected retention.

PEACH seeds normally have to be stratified at a low temperature for approximately two months before they germinate. Unstratified seeds can be made to germinate by removal of the seed coats1, and experiments performed at this Institute2 indicate that unstratified embryos lack the power to overcome the mechanical resistance offered by the seed coats. The seedlings obtained from unstratified excised embryos develop dwarfed shoots with abnormally short internodes and the leaves are often distorted. This shows that the chilling requirements are not concerned with germination alone. The shoot apex of the embryo appears to be the main part of the seedling which requires cold treatment to ensure normal development. The roots show no apparent abnormal symptoms, and shoots which develop from lateral buds seem normal in all respects.

IN an earlier communication1 I described the “leaf vernalization” of leaf cuttings of Lunaria biennis. After cold treatment, such cuttings from leaves of adult plants regenerate and yield flowering plants, while without a cold treatment no flowering occurs. It was left undecided exactly where in the leaf cutting the vernalization takes place—in the leaf as a whole or in meristematic cells only. Evidence has been obtained now that the locus of vernalization consists of cells which are in the process of mitosis.

Preliminary investigations of the air-dried roots of Heracleum mantegazzianum grown under greenhouse conditions were conducted. Seed germination requires moist cold treatment. The germination rate appears to be directly related to the length of the moist cold period. Gibberellin seed treatment did not substitute for the cold requirement. Thin-layer chromatography revealed the presence of 6 coumarins which were tentatively identified as bergapten, isobergapten, pimpinellen, isopimpinellen, sphondin, and umbelliferone. Results also indicate that the plant can cause photosensitization.

SYSTEMIC administration of corticotrophin, cortisone and hydrocortisone causes degranulation and other changes in mast cells1–3. Exposure of rats to cold caused the number of mast cells in lung and thymus tissue to increase in rats weighing 185 g and decrease in rats weighing 380 g (ref. 4). Cold treatment of the heavier rats increased the number of dermal mast cells and decreased mesentery (intervascular) mast cells5.

Gibberellic acid, when applied in lanolin to apices of three Japanese varieties of Chrysanthemum morifolium, induced bolting and flowering. These varieties are not sensitive to photoperiod but require a cold treatment in order to flower. On the other hand, the varieties of Chrysanthemum which belong to the short-day group are not induced to flower by gibberellic acid.

MANY data exist on natural and induced polyploidy in Amphibia1,2; but knowledge on the subject still remains scanty in other groups of vertebrates. Spontaneous and experimentally produced polyploidy has been studied in mouse embryos3–7. Among fishes, production of triploidy by cold treatment has been reported up to cleavage stages8. The present work has been undertaken to induce triploidy by heat and cold treatment of the eggs of the three-spined stickleback and to keep alive the triploids thus produced.

IT has been suggested1,2 that the deoxyribonucleic acid content of Trillium chromosomes in the roots falls after cold treatment, and that the competition for available nucleic acid often leads to starvation of the heterochromatic segments. Photometric determinations of the Feulgen stain content of nuclei before and after cold treatment3,4 support this view. We have now made estimations of the deoxyribonucleic acid content in root tips of Vicia, Trillium and Paris, both with and without cold treatment (Tables 1–3). In each case, terminal 1-cm. segments were used.

CACAO seed sensitivity to cold was first demonstrated by Boroughs and Hunter1. Previous investigations by Ibanez2,3 have shown that a treatment of 4° C for 10 min will destroy viability in these seeds. Such a viability loss, however, was reversible if the seeds thus chilled were immersed for 10 min in a water bath at 37° C. Under such conditions, at least 85 per cent of the seeds remained viable and grew into healthy plants. After 15 min of such a cold treatment, however, no amount of post heat treatment could prevent ultimate death of the seed.

IN Trillium grandiflorum and other species of the same genus, cold treatment reveals differences between homologous chromosomes with regard to number and/or length of heterochromatic segments1. In our experiments, differences have been found in the B-, C- and E-chromosomes (Figs. 1, 2A). According to the number and length of these segments, the following types of chromosomes have been distinguished: B 1, B¼, C 1, C 2, E 2 and E 3 (where the suffixes give the number or length of the heterochromatic regions).

SPRING cereals differ from winter cereals in their ability to initiate ears immediately under a favourable day-length, without cold treatment of the seed. Unvernalized winter cereals will eventually initiate ears, but even under the most favourable conditions this has not been found to occur until 6–8 weeks after planting1. ‘Vernalization’ or cold treatment of the just-sprouted seed before planting will eliminate this period of delay before ear initiation, and field studies certainly suggest that the growing plant is also capable of responding to cold treatment during this period2–5. However, direct evidence of the response of the green plant of the winter cereal to cold treatment is scanty. (Possibly Gunar and Krastina6 have evidence on this point, but this is not clear from the abstract available to me.)

Some isolates of ryegrass mosaic virus are mild in all but a few plants, others are more severe. Infection with a severe isolate reduced the yield of a ryegrass population by 24% under field conditions and reduced survival following cold treatment by 85%. Field isolates from the short-lived Italian ryegrasses are generally severe while those from the long-lived late-flowering perennial ryegrasses are generally mild. This variation appears to be adaptive in origin since in the case of perennial ryegrass proneness to infection by severe isolates would probably lead to the elimination of both host and virus whereas Italian ryegrass can escape infection readily by copious production of seed.

Previous investigations have shown that, in healthy children, active renin values, measured as plasma renin activity (PRAact), and plasma aldosterone (PA) values are increased when compared to adult values. No correlation between PRA and PA was observed. Inactive renin values (PRAinact) obtained after cryoactivation did not decrease with age. Moreover, in some children, mainly infants, PRA decreased after cold treatment. In the present investigation it was shown that, in healthy children, active renin values, measured as plasma renin concentration (PRC), are also increased. There was a significant correlation with angiotensin II (AII) values. No correlation, however was found between AII and PA values, confirming the earlier suggestion that other factors than the RAA-system are involved in the high aldosterone secretion. Although the mean activation rate of inactive renin was higher with cold than with acid treatment, the difference between both methods was not obvious in individual cases. After addition of o.phenanthrolin to the blood samples, no negative values for PRAinact were observed. It is suggested that the previous negative values were due to insufficient inactivation of the Ca- and Zn-dependent enzymes involved in the system.

Genetic differences in developmental response to photoperiod or cold treatment may be a major cause of the observed distribution of species and populations (Cooper 1960; Calder 1966). Species are unlikely to survive in areas where daylength and temperature conditions are inadequate to allow the production of sufficient viable seed during the available growing season. In this paper we report studies of the developmental response of Avenafatua and A. barbata collected from a wide geographical range in Western Australia (Paterson 1976).

Both X and gamma rays have been used to investigate the effect of dose rate on the induction of pink mutant cells in stamen hairs of Tradescantia clone 02. For inflorescences exposed to doses of 60-80 rads of X rays at 0.3 to 503 rads/min there was a progressive increase in the number of $\text{mutations}/\text{rad}/10^{4}$ hairs as the dose rate was increased from 0.3 to 105 rads/min. However, 300 rads/min did not further increase the mutation rate, and at 503 rads/min the effect was slightly less, but approximately equal to that at 30 rads/min. With 58-79 rads of137 Cs gamma rays the mutation rate increased progressively with dose rate over the entire range studied (0.0034-30 rads/min). Some inflorescences were held at 8 C before and during irradiation to slow development so that low dose rates (3.4-12 mrads/min) could be delivered within a given development period. The mutation rate during cold treatment was higher than when the same dose rates were given during a period of more ra...

SUMMARY (1) The effects of temperature upon seed dormancy and germination were studied in eleven populations of tetraploid Festuca pratensis var. apennina from the Italian Alps and Apennines. (2) Three populations from the Apennines had a smaller cold requirement to break dormancy. There was no correlation between cold requirement to break dormancy and the altitude from which the population was collected. (3) Populations from the Apennines germinated over a wider range of temperature than those from the Alps. Populations from lower altitudes had a lower optimum temperature for germination than those from high altitudes. (4) The seeds of all populations had a high optimum germination temperature (c. 27 0C), when given only a short period of cold treatment. As the period of exposure to low temperatures was increased, the range at which germination occurred extended to lower temperatures. The relationship between optimum germination temperature and the period of exposure to low temperatures may provide an adaptive mechanism which ensures survival at high altitudes.

Banksia canei J . H. Willis consists of four distinct geographically isolated forms (topodemes). The variation noted between these by means of experimental cultivation is documented and a hypothesis to account for this variation is proposed. The relationship of this species with other Eubanksia species with a requirement for a cold treatment is also examined.

ALLOW me to submit to your readers the following sketch of an apparatus for producing extreme cold, by which it might perhaps be practicable to liquefy or even solidify the elementary gases which have hitherto resisted the efforts of chemists.

The effect of cold shocks of various kinds on the mutation rate of Drosophila is reported. No effects on mutation rate were found.

Alterations of intrascrotal temperature markedly affect spermatogenesis and sperm counts. In euspermic subjects, scrotal exposure for 30 minutes to a 150-watt electric light bulb resulted in reversal of the scrotal-rectal temperature ratio by a mean of 2.9 C. Such treatment on 14 consecutive days caused depression of spermatogenesis followed by rebounds to temporarily high sperm counts. Application of an ice bag to the scrotum for a mean of about 30 minutes cooled the testicular environment by a mean of 6.9 C. Such cold treatment on 14 consecutive days, beginning not less than 12 days following cessation of exposure to heat, stimulated spermatogenesis without initial inhibition, nearly trebling the mean pretreatment count. Oligospermic subjects responded to both heating and cooling faster and to a relatively greater degree, but less predictably, than did euspermics. The greatest increase in spermatogenesis followed sequential application of heat and cold, which suggested possible therapeusis in oligospermia.

The present paper deals with the induction of lesion formation by heat or cold treatment on TMV- or CMV-infected systemic hosts and also TMV-infected lesion hosts predisposed to systemic infection.1) TMV-inoculated leaves of systemic hosts, N. tabacum Xanthi, N. tabacum Samsun, and Petunia hybrida, developed local lesions if they were immersed 2 days later in hot water (50°C) for 2min. CMV-inoculated leaves of systemic hosts, N. glutinosa and Petunia hybrida, also developed local lesions by the heat treatment.2) The similar heat treatment resulted in local lesion formation on TMV-inoculated leaves of local lesion hosts, N. glutinosa, Xanthi nc and Samsun NN, during incubation at 30°C, a temperature at which no lesions appear and TMV spreads systemically.3) TMV-inoculated leaves of local lesion hosts, N. glutinosa, Xanthi nc, and Samsun NN, developed local lesions if they were immersed 2 days later in ice water for 5 sec to 2min during incubation at 30°C.4) The similar cold treatment occasionally resulted in local lesion formation on TMV-inoculated leaves of systemic hosts, Xanthi, Samsun, and Petunia hybrida.5) Usually, heat treatment applied 2 days after inoculation induced dark necrotic rings which appeared in 15 to 20 hours after treatment, whereas cold treatment resulted in white necrotic rings which appeared in 1 to 2 hours. When leaves of N. glutinosa bearing lesions induced by heat treatment 2 days after inoculation with TMV were immersed in ice water 4 days after inoculation, dark necrotic rings developed around each original lesion during incubation at 30°C.

BALB/c mice subjected to temperatures of 10–12 deg C during the first week of life showed less emotional reactivity in an open field than did controls. It was found, however, that cold treatment of pups produces changes in maternal behavior which lead to an increase in the general stimulation level of the pups, and that this phenomenon may be confounding the data with regard to reductions in emotional reactivity.