Axillary Bud Inhibition Induced by Young Leaves or Bract in Euphorbia pulcherrima Willd

In plants held under long days in the vegetative stage, youngexpanding leaves of poinsettia (Euphorbia pulcherrima Willd.‘Brilliant Diamond’) are the main source of axillarybud inhibition, while the apical bud, which includes the meristem,primordial leaves and small unfolded leaves, is a secondaryinhibition source. Removal of these expanding leaves resultedin rapid release and growth of axillary buds. Decapitation ofthe apical bud resulted in delayed axillary bud release. Inreproductive plants kept in short days, the pigmented bractsare the primary source of axillary bud inhibition and the cyathiaare the secondary source. Applications of NAA —substitutedfor both young leaves and bract inhibition — maintainedapical dominance. The concentration of endogenous auxin washighest in the apical bud. However, when calculated on wholeorgan basis the auxin level was greater in young developingvegetative leaves and in reproductive bracts than in the apicalbud. Euphorbia pulcherrima Willd, apical bud, apical dominance, auxin, correlative inhibition, cyathia, poinsettia, IAA, NAA     

Growth and population studies on Tilapia galilaea in Lake Kinneret

SUMMARY. Between 1967 and 1977, catches of Tilapia galilaea in Lake Kinneret fell from an annual average of about 200 tonnes to a low of 70 tonnes in 1974, and then returned to their former level. Total yearly mortality ( Z ) was estimated at 1.84 between 1970 and 1976. Assuming a natural mortality ( M ) of 0.94, total stock size averaged 300–700 tonnes in that period, while recruitment averaged < 0.7–3 million per year. Three broods hatched in years of relatively high water levels (1970, 1971 and 1972) yielded especially low recruitment.
The Von Bertalanffy growth coefficient ( K ) was estimated at 0.67, and final length (L∞) at 25–36cm total length. First year's growth, 23–152mm, was closely related to final length, which appeared to be affected by genetic variation in the population. Yearly fluctuations in size distribution were attributed to changes in the proportions of fast- and slow-growers, as well as in the abundance of year-classes. Recruitment to the fishery, at 17–20cm, occurred between ages l+and3+.
The highest growth rates for age-1 T, galilaea , 1–2% mean weight per day, occurred in April and May, the Peridinium season. However, only a small proportion of age-1 fish reached marketable size by July, when their food supply began to diminish. During the autumn months, there was hardly any length increment, and all T. galilaea became lean, especially the age-0 group. It is surmised that recruitment of stocked fish could be increased by introduction in December and by use of fingerlings which are potentially able to grow to marketable size in less than two seasons.     

REPRODUCTIVE TECHNOLOGIES IN DEVELOPING COUNTRIES

Are there any ethical concerns about reproductive technologies that are specific or unique to developing countries? Three ethical concerns often mentioned specifically in regard to developing countries are (1), the “overpopulation argument”; (2) the limited resources argument; and (3) the ethical problem of poorly trained practitioners offering their services to unsuspecting and uninformed infertile individuals or couples. Each argument is explored in some detail, with the conclusion that ethical problems do, in fact, exist but are not unique to developing countries. Nevertheless, the difficulties relating to reproductive technologies are likely to be greater in developing countries than in developed ones because of limited resources and a larger number of poor people residing there.     

Femoral dimensions and mid-thigh circumference in Alligator mississippiensis

The mid-thigh circumference of the intact hindlimb in Alligator mississippiensis is tightly correlated with transverse dimensions of the proximal and distal articular surfaces of the femur, and with minimum midshaft femoral circumference. Maximum diameter of the proximal articular end, width across the distal articular end, and midshaft circumference are the best femoral predictors of circumference of the intact thigh. Regression equations of mid-thigh circumference against these femoral dimensions can be used to estimate the transverse dimensions of the intact hindlimb in extinct crocodylian-like archosaurs.     

Polyethism and nestmate recognition in the alarm reaction of Atta leaf-cutting ants

Abstract.  Ethological studies are conducted under laboratory conditions using workers of Atta sexdens sexdens and Atta opaciceps collected from field colonies to investigate the mechanisms involved in the alarm response and intra-specific recognition in leaf-cutting ants. Hexane extracts from the heads of gardeners and generalist workers elicit higher levels of alarm response in foragers from the same colony than do mandibular gland extracts from foragers and soldiers, indicating that gardeners, generalists and foragers are primarily responsible for the production of alarm pheromone. Foragers subjected to extracts from non-nestmates exhibit significantly greater alarm responses than are induced by similar extracts derived from nestmate workers, suggesting that the alarm pheromone may have a role in nestmate recognition.     

Apostasy and selection for crypsis in the marine snail Littoraria filosa: an explanation for a balanced colour polymorphism

The marine snail, Littoraria filosa, is polymorphic for shell colour, with yellow, brown, and pink morphs that correspond in both appearance and frequency to the predominant background colours of its habitat. Previous research on this polymorphism has found indirect evidence of apostatic selection and selection for crypsis by unknown agents, probably crabs, and direct evidence of selection for crypsis by the parasitoid fly Sarcophaga megafilosia. In the present study, we report on field experiments to investigate whether S. megafilosia and shell‐crushing predators exert apostatic selection on L. filosa. For S. megafilosia, seven experimental treatments containing yellow and brown snails in the proportions of 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, and 0.9 of each colour were established on mangrove trees and used to separately quantify the proportions of each colour attacked on grey/brown trunks and yellow/green leaves. The results obtained confirmed an earlier finding of selection for crypsis, but only showed slight, but significant, anti‐apostatic selection by S. megafilosia. For shell‐crushing predators, seven experimental treatments containing yellow and brown snails in the proportions of 0.08, 0.17, 0.33, 0.50, 0.66, 0.83, and 0.92 were established on two types of trees that differed in their background proportions of brown and green: (1) trees which had been pruned of approximately 90% of their foliage and (2) unpruned trees. The results obtained showed both selection for crypsis and apostatic selection. Furthermore, a selectively neutral frequency for yellow L. filosa was found for each background, and was less on pruned trees than unpruned ones (and vice versa for brown L. filosa), which can therefore account for the maintenance of a colour polymorphism where the proportions of each morph tend to resemble and correspond in frequency to the colours of the background. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 62–71.     

Frost in a future climate: modelling interactive effects of warmer temperatures and rising atmospheric [CO2] on the incidence and severity of frost damage in a temperate evergreen (Eucalyptus pauciflora)

Although plants are more susceptible to frost damage under elevated atmospheric [CO₂], the importance of frost damage under future, warmer climate scenarios is unknown. Accordingly, we used a model to examine the incidence and severity of frost damage to snow gum (Eucalyptus pauciflora) in a sub‐alpine region of Australia for current and future conditions using the A2 IPCC elevated CO₂ and climate change scenario. An existing model for predicting frost effects on E. pauciflora seedlings was adapted to include effects of elevated [CO₂] on acclimation to freezing temperatures, calibrated with field data, and applied to a study region in Victoria using climate scenario data from CSIRO's Global Climate Model C‐CAM for current (1975–2004) and future (2035–2064) 30 years climate sequences. Temperatures below 0 °C were predicted to occur less frequently while the coldest temperatures (i.e. those below ?8 °C) were almost as common in the future as in the current climate. Both elevated [CO₂] and climate warming affected the timing and rates of acclimation and de‐acclimation of snow gum to freezing temperatures, potentially reducing the length of time that plants are fully frost tolerant and increasing the length of the growing season. Despite fewer days when temperatures fall below 0 °C in the future, with consequently fewer damaging frosts with lower average levels of impact, individual weather sequences resulting in widespread plant mortality may still occur. Furthermore, delayed acclimation due to either warming or rising [CO₂] combined with an early severe frost could lead to more frost damage and higher mortality than would occur in current conditions. Effects of elevated [CO₂] on frost damage were greater in autumn, while warming had more effect in spring. Thus, frost damage will continue to be a management issue for plantation and forest management in regions where frosts persist.