The Physiology of a Wilty Pea: Abscisic Acid Production under Water Stress

‘Wilty’ (JI 1069), a mutant of Pisum sativum, hasbeen examined for its ability to produce abscisic acid (ABA)under water stress. ABA was measured using combined gas chromatography-massspectrometry and multiple-ion-monitoring employing a deuteratedinternal standard. In intact droughted plants, ‘Wilty’produced less ABA than a non-wilty line (JI 1194) and maximumproduction was delayed. Detached leaves of the wilty mutantlost significantly more water than control leaves but did notshow an increase in ABA content. Non-stressed mutant materialfrom both intact plants and isolated leaves contained less ABAthan control tissue. Key words: Pea, Wilty mutant, Abscisic acid     

Aspects of the biology of Pilot whales (Globicephala melaena) in recent mass strandings on the British coast

Five mass strandings of Pilot whales, involving from 23 to 40 animals, occurred on the British coast between 1982 and 1985. The sex ratio in all strandings was biased towards females (62% overall), but more than one mature male was present in each group. A multi-male, polygynous social system is suggested. Growth is rapid from a mean body length at birth of 1.78 m to about 3 m at 2–3 years. Thereafter, males grow faster than females and attain a greater body length by some 18–25%. Maximum body lengths in this study were of a 6.3 m male and a 5.5 m female. The greatest ages determined were of a 20-year-old male and a 25-year-old female, but there is a possibility that readable dentine is not deposited in the teeth of older animals and that some whales are thus of a greater age than can be detected. Females become sexually mature at about seven years of age and a body length of 3–4 m. Some reach sexual senility before death. Males mature at a greater age and at about 5 m in length. Annual calf production is about 11% and no seasonality in parturition could be detected. Pollutant levels are generally within the range of those published for odontocetes, but PCB levels are higher than any yet found in other Pilot whale populations. Evidence of squid was found in three digestive tracts. Blubber thickness increases with the size of the animal, reaching 35–65 mm in adults. The existence of an annual, rigid north-south migrational pattern is unlikely.     

Patterns of morphological variation in the Acacia species (Mimosaceae) of northern Sudan

KORDOFANI, M. & INGROUILLE, M., 1991. Patterns of morphological variation in the Acacia species (Mimosaceae) of northern Sudan. A numerical taxonomic review has been carried out on the morphology of northern Sudanese Acacia species. Fifty-one characters were scored from 12 species sampled at 12 sites. There is evidence of large scale population variation. Within a single site species are distinct but a comparison of plants between different sites may obscure species differences. Each species has a peculiar local variant in each sampled site, even when sites are separated by only a few kilometres. The possible significance of this pattern of variation is discussed. Species complexes are delineated and useful species diagnostics described.     

RAPID METHOD FOR SCREENING THE TOLERANCE OF YEASTS TO ZINC (II) AND CHROMIUM (III)

Rapid screening of the tolerance of yeasts to zinc (II) and chromium (III) was performed by an agar diffusion test. A rapid and reliable procedure for the determination of metal ion concentration gradients on agar plates was developed. Different species of yeasts from the following genera were investigated: Arthroascus, Bulera, Dekkera, Debaryomyces, Dipodascopsis, Eremothecium, Candida, Hansenula, Kluyveromyces, Hormoacus, Geotrichum, Lipomyces, Pachysolen, Pichia, Saccharomyces, Schizosaccharomyces, Schizoblastosporion, Schwan-niomyces, Sporobolomyces, Yarrowia, Torulaspora, Zygosaccharomyces and Williopsis. The experimental conditions were defined as a constant volume of malt agar 32 cm³, and a temperature of 29C. After periods of 24, 47 and 72 h, the concentration intervals of growth inhibition were determined, and the yeasts investigated were grouped in different classes according to their tolerance to Zn (II) and Cr (III). Yeasts were found to be tolerant to significantly higher zinc (II) concentrations in the malt agar medium (5.9 mM to 20 mM) in comparison to chromium (III) (1.5 mM to 6.9 mM). Yeasts showed inter- and intra-generic differences in zinc (II) and chromium (III) tolerance.     

The reaction time of leech and triclad species to crushed prey and the significance of this for their coexistence in British lakes

1. Three species of leeches, Erpobdella octoculata, Glossiphonia complanata and Helobdella stagnalis, and four species of triclads, Polycelis nigra, P. tennis, Dugesia polychroa and Dendrocoelum lacteum, commonly coexist on stony shores in productive British lakes. All species are food limited and there is much overlap in their diet. For both leech and triclad communities, coexistence of species is through the occurrence of food refuges. Leeches are more successful than triclads at capturing live prey, whereas both groups feed on damaged prey, comprising incapacitated, live or dead animals that are leaking body fluids. If triclads are better than leeches at exploiting damaged prey, this could be a mechanism for their coexistence. 2. Laboratory experiments investigated the comparative speeds at which leeches and triclads responded to crushed prey. Young and adult predators were offered a crushed specimen of the oligochaete Tubifex tubifex, the snail Lymnaea peregra, the crustacean Asellus aquaticus or the chironomid Chironomus sp., and their reaction times recorded. These four prey groups constitute the main diet of the predators in the field. Only D. polychroa and D. lacteum showed a significantly different reaction time between young and adults to crushed prey, and the reason for this is unclear. All predators, except H. stagnalis and D. polychroa, showed a difference in reaction time to the four types of prey, presumably a consequence of differences in both the ‘quality’ and ‘concentration’ of the different prey fluids, and there were some differences between predators in their speed of reaction to the same prey type. The following sequence, from fastest to slowest, in general reaction time to prey was obtained: E. octoculata, D. polychroa, P. tenuis, D. lacteum, P. nigra, H. stagnalis and G. complanata. 3. The location of the damaged food by the predators can be explained partly in terms of their foraging behaviour, with E. octoculata, D, polychroa and P. tenuis exhibiting a more seek-out strategy than other species which have a more sit-and-wait behaviour, and partly on the level of sophistication of their chemosensory system used to detect leaked prey fluids. This system is highly developed in triclad species but poorly developed in leeches. 4. In a second type of experiment in which prey, L. peregra, A. aquaticus or Chironomus sp., were offered at different time intervals after crushing to H, stagnalis and P. tenuis, few predators fed on food crushed for 24 h or longer, although a few leeches fed on Chironomus crushed for up to 72 h. 5. It is concluded that coexistence of leech and triclad species on stony shores in lakes is assisted by partitioning of food on a damaged or live basis.     

Recovering endangered species and restoring ecosystems: conservation planning for the twenty-first century in the United States

The Endangered Species Act of 1973, as amended, is one of the most significant pieces of conservation legislation ever passed in the United States. The passage of this act spawned the creation of the Endangered Species Program of the US. Fish and Wildlife Service (USFWS). Under the Act, the USFWS has responsibility for implementing many provisions of the Act: listings, consultations, enforcement of prohibitions and recovery planning. Recovering threatened and endangered species, as well as other declining species yet to be listed, is accomplished through many of the activities that occur under the auspices of the Act, not only through the formal recovery planning process. The Act is fundamentally an instrument for ecosystem conservation, although this aspect of the Act is often over-looked. Planning and implementing an ecosystem approach to conservation activities is a priority for the USFWS, not only for threatened and endangered species but for all wildlife. The recent emphasis on regional habitat conservation planning and the development of regional and multi-species recovery plans are indicative of the priority placed on sound ecosystem conservation planning. All of these processes are implemented with the participation of the potentially affected communities and state wildlife management agencies through a public review process. State conservation agencies are part of the process through a special grant programme.     

Studies on plant cuticle

The cuticles of plants of the Saxifragaceae, Rosaceae and Leguminosae are compared by chemical methods. Wide differences occur in the deposits of surface wax and cuticular membrane even within species of one genus. The relative proportions of four hydroxy-fatty acids in the cutin acids of plants of the families are assessed and the value of cutin analysis as a taxonomic criterion is discussed.     

Adaptations of Polygynous Breeding in the Bobolink, Dolichonyx oryzivorus

In some species of polygynous songbirds, males assist in feedingnestlings of their first (primary) female but ignore offspringof subsequent (secondary) mates. A number of adaptations importantin minimizing the disadvantages of a secondary status in femaleBobolinks (Dolichonyx oryzivorus) have been discovered. In Bobolinks, clutches of secondary females are significantlysmaller than those of primary females, thereby adjusting broodsize to correspond better with food delivery capabilities ofsecondary hens. Commencement of incubation with deposition ofthe penultimate egg allows additional brood size adjustment,for the resulting hatching asynchronism promotes efficient cullingof the late-hatching chick in times of food shortage, withoutendangering the entire brood. Secondary females differ fromprimary pairs in food exploitation techniques by capitalizingon insects found close to the nest and by showing less discriminationin food selection. Such behavior permits compensation in therate of food delivery trips to secondary nestlings so as toequal the tempo maintained by both members of the primary pair,yet results in quantitative disparities in food brought to primaryand secondary nestlings. Flexibility in male feeding responses,resulting in partial male assistance at secondary nests in situationswhere secondary brood size is exceptionally large, is also importantin helping to maximize the reproductive performance of birdsengaging in this mating strategy.     

Infection of stored celery plants by Centrospora acerina

Chlamydospores in tissue near the bases of plants and in attached soil particles were the main form of inoculum of Centrospora acerina (Hartig) Newhall found on celery plants prepared for storage. Most of these spores remained ungerminated for several weeks but subsequently formed germtubes, terminal appressoria and infection-pegs, which usually penetrated the plant surface through either the intact cuticle or damaged areas. For several weeks after the beginning of storage the plants were highly resistant to infection. During this time, appressoria failed to penetrate the intact cuticle and, if the fungus entered through damaged areas, hyphal growth in tissue was suppressed. Infection was often found to be associated with abrasion or splitting of the cuticle in commercially stored plants and, in experiments, deliberate damage enhanced the probability of infection. The development of the disease was much slower at 2 d?C than at 15 d?C.