Cumulative Effects Of Temperature Research Articles

Body size and cell size in Drosophila: the developmental response to temperature

In Drosophila, like most ectotherms, development at low temperature reduces growth rate but increases final adult size. Cultures were shifted from 25°C to low (16.5°C) or to high (29°C) temperature at regular intervals through larval and pupal stages, and the flies of both sexes showed an increase or decrease, respectively, in the size of thorax, wing and abdominal tergite. Size changes in the wing blade resulted from changes in the size of the epidermal cells (with only a small increase in cell number in males reared at low temperature). The temperature-shifts became less effective as they were made at successively later developmental stages, demonstrating a cumulative effect of temperature on adult size. The thorax and wing develop from the same imaginal disc, with most cell division occurring in larval stages, but they differ in timing of temperature sensitivity, which extends only to pupariation or into the late pupal stage, respectively. Growth of the adult abdomen occurs largely after pupariation but its size is temperature-sensitive through both larval and pupal stages. We discuss growth control in Drosophila and the likely effects of temperature on food assimilation, growth efficiency and allocation of nutrients to the production of different tissues.

Short‐term fluctuations in death by cause, temperature, and income in the United States, 1930–1985

Disclosures that this decade has had the five hottest years ever recorded globally raise concern that extreme temperatures might be associated with higher mortality. An analysis of fluctuations in annual case-specific deaths, seasonal temperatures, and annual income per capita in Massachusetts, Michigan, Washington, Utah, North Carolina, and Mississippi, 1930 to 1985, suggests that, on the contrary, a temperature increase throughout the year was associated with fewer deaths from all causes combined, including deaths from infectious diseases, heart diseases, cerebrovascular diseases, pneumonia, and influenza. An average temperature increase of one degree Fahrenheit was associated with a more than 2 per cent decline in deaths from pneumonia and influenza. The only category of deaths showing no significant association was death from malignant neoplasms. Compared to spring, summer, and fall temperature fluctuations, unusually cold winter temperatures had the strongest fatal effects, but only in North Carolina and Mississippi. The greatest cumulative temperature effects on mortality were found in the same two states. Controlling for annual fluctuations in income per capita did not influence the relationship between temperature and mortality. There was evidence suggesting that the level of wealth ameliorated the fatal effects of extreme temperatures. In conclusion, unusually warm weather was followed by fewer deaths; unusually cold weather, by more deaths.

Foliar moisture content variations in four coniferous tree species of central Alberta

Trends of foliar moisture content variations were determined for jack pine (Pinusbanksiana Lamb.), black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and balsam fir (Abiesbalsamea (L.) Mill.) in central Alberta. New and old tree foliage was periodically sampled between early March and mid-September during 2 consecutive years. The seasonally recurring variations in foliar moisture contents were characterized by (i) early spring declines of moisture in the old foliage, (ii) flushing of new foliage at high bud moisture contents when the contents in the old foliage were low, and (iii) summer recoveries of moisture in the old foliage and simultaneous decreases of moisture in the new foliage until both eventually converged toward comparable moisture contents. The cumulative effects of temperature, in terms of degree days above 6 °C, were reflected in timing of the declines and the recoveries of moisture in the old foliage. These results may be applied in rating the crowning potential of local forest fires.

Genetic studies on Cosmos bipinnatus. IV, Determination of the sensitive period to the cumulative effect of temperature on the phenotypic expression of the flower-type genes

In my preceding report (SAMATA 1959 b) it was noted that the expession of MS and MD genes which modify the flower-types in cosmos is subject to the influence of temperature to a considerable degree. The present experiment was designed to determine the sensitive period to the cumulative effect of temperature of these genes. Fourteen stra:ins with known genotypes were selected as materials for this experiment. Each strain was propagated by cutting and many individuals belonging to the same clone were grown. All individuals were divided into five groups in such a way that each group was sure to include one individual of each strain. After the interval of 12 days, four of these groups were removed, one by one, into the greenhouse kept at 30°C constant temperature where they were left until flowering. By this method they were subject to high temperature treatment at different stages of flower development. One group was left out of doors all the time, and was used as the control. When the plants came into bloom, each flower type of the treated groups was compared with th.at of the control of the same clone, and the changes of flower-types between them were examined with the naked eye and by comparing the photographs taken at different periods of fiowering. By this experiment it was made clear that the changes of both ray and disk florets take place only when the plants have been placed at least l0-15 days before flowering in the room kept at 30°C. From this it may be asserted that the sensitive period to the cumulative effect of temperature of MS or MD genes is l0-15 days before anthesis. To ascertain this period, another experiment wascarried out in which several plants with different flower-types growing in the field were transplanted into pots at the flowering time and placed in the room kept at 30°C. After 14 days an examination of the flower-types revealed that those with Ms or MD were changed to such types as had been expected. The third experiment was made to examine the cumulative effect of low-temperature in the case of MD gene. Two of the three plants which prdduced the single type of flower-head during the hightemperature season were placed in a room with lO-13°C constant temperature and it was found that they change from single to double flower-type after 30 to 45 days in the room, showing that, the sensitive period to low-temperature of MD gene is within a certain period of time after flower-initiation.