Effects of long-term atmospheric CO2 enrichment on the growth and fruit production of sour orange trees

In July of 1987, we planted eight 30-cm-tall sour orange tree seedlings in a field of Avondale loam at Phoenix, Arizona and enclosed them in pairs in clear-plastic-wall open-top chambers. Since 18 November of that year, we have continuously pumped ambient air of ≈400 ppmv [CO₂] through two of these enclosures, while through the other two we have continuously pumped air of ≈700 ppmv [CO₂]. By the end of the second year of the study, the trunk plus branch volume of the [CO₂]-enriched trees was ≈2.75 times greater than that of the ambient-treatment trees. Three years later, this factor had dropped to ≈2.0; but the decline in the [CO₂]-enriched/ambient-treatment ratio of trunk plus branch volume was nearly perfectly offset by the relative fruit production advantage enjoyed by the [CO₂]-enriched trees over that period. In Years 6, 7 and 8, however, there was a moderate drop in total productivity enhancement. This decline may be a delayed acclimation response, or it could be due to enhanced self-shading in the [CO₂]-enriched trees or to the fact that, starting early in Year 6, many branches of the [CO₂]-enriched trees grew all the way to the walls of their enclosures, so that many blossoms and young fruit were destroyed by intermittent physical trauma produced by the action of wind against the taut plastic in that year and in all succeeding years. Hence, we will have to maintain our experiment for several more years for this lateral growth obstruction to occur to the same degree in the ambient-air chambers as it has in the [CO₂]-enriched chambers, in order to determine the long-term equilibrium effects of atmospheric [CO₂] enrichment in a spatially confined environment.     

Feeding Behavior, Aggression, and the Conservation Biology of Flamingos: Integrating Studies of Captive and Free-ranging Birds

SYNOPSIS. Flamingos (Aves, Phoenicopteridae) represent an ancientlineage of long-legged, microphagous, colonial wading birds.Although often perceived as tropical, flamingo distributionis more closely tied to the great deserts of the world, andto hypersaline sites, than it is to equatorial regions. Manyaspects of flamingo behavior and ecology can be studied in captivity.Experimental studies involving captive birds, when combinedwith observational studies of free-ranging birds, offer researchersopportunities to address questions that are unanswerable withfield work alone. Zoo populations of flamingos are prime candidatesfor such studies. Here, we use samples of our own work to illustrate the synergisticeffects of combining zoo and field research. Our first exampledescribes how studies of salt tolerance in captive birds areplaying a key role in assessing the impact of salt as an ecologicaldeterminant of flamingo distribution. Our second example describeshow aggression and dominance interactions affect the feedingbehavior of flamingos. We assess the implications of this researchin terms of both avicultural practices and the fundamental ecologyof the birds. We believe that similar collaborations involvingother zoo animals would yield comparatively productive results.     

The Influence of Sucrose and Abscisic Acid on the Determination of Grain Number in Wheat

Using detached ears of wheat cultured in nutrient solution theeffect of sucrose and ABA supply on grain number was examined.In ears detached prior to ear emergence, to correspond withthe time of pollen mother cell meiosis, higher levels of sucroseuptake were associated with higher grain number per ear. ABAindirectly caused a reduction in grain number by decreasinguptake of sucrose through decreasing stomatal conductance andtranspiration. There was possibly also a direct effect of ABAon grain number. At higher levels of ABA the negative effecton grain number was decreased by increasing the sucrose concentration.In ears detached one to three days after anthesis grain numberwas also influenced by the amount of sucrose taken up. althoughgrain number was not as sensitive to the sucrose supply at thistime as it was at meiosis. The influence of ABA following anthesiswas limited to an indirect effect on grain number through reductionsin sucrose uptake. Key words: Wheat, Sucrose, ABA, Grain number     

What Rationality Adds to Animal Morality

Philosophical tradition demands rational reflection as a condition for genuine moral acts. But the grounds for that requirement are untenable, and when the requirement is dropped morality comes into clearer view as a naturally developing phenomenon that is not confined to human beings and does not require higher-level rational reflective processes. Rational consideration of rules and duties can enhance and extend moral behavior, but rationality is not necessary for morality and (contrary to the Kantian tradition represented by Thomas Nagel) morality cannot transcend its biological roots. Recognizing this helps forge a complementary rather than competitive relation between feminist care-based ethics and rationalistic duty-based ethics.     

Intraspecific Strategic Responses of African Elephants to Temporal Variation in Forage Quality

ABSTRACT Mammalian herbivores adopt foraging strategies to optimize nutritional trade-offs against restrictions imposed by body size, nutritional requirements, digestive anatomy, physiology, and the forage resource they exploit. Selective or generalist feeding strategies scale with body size across species. However, within species, where constraints should be most similar, responses to limitation have rarely been examined. We used African elephants (Loxodonta Africana) to test for changes in seasonal diet quality of individuals of differing body size and sex through measurement of fecal nitrogen and phosphorus. We measured physiological stress response of these age and sex classes to seasonal change by fecal glucocorticoid metabolite levels (i.e., stress hormones). Large body size increased tolerance to lower-quality forage. Adult males and females exhibited divergent trends; females had higher diet quality than males, irrespective of body size. When limited by forage availability or quality during the dry season, diet quality declined across all body sizes, but weaned calves ingested a higher-quality diet than larger-bodied adults. On release from restriction during the wet season, weaned calf nitrogen concentrations were consistently high and stress hormone levels decreased, whereas adult female phosphorus levels were highest and less variable and stress hormone levels were unchanged. The ability to adjust forage quality is an important strategy used to ensure adequate nutritional intake according to body size limitations. Although body size is a key determining factor of dietary differences between adult elephants, foraging strategies are also driven by specific nutritional requirements, which may override the body size effects driving foraging decisions in some cases. The diversity of intraspecific response highlights ecologically segregated entities within a species and should be a concern for population management planning, particularly for threatened species. Fecal diet quality and stress hormone analysis could provide an early and sensitive indicator for monitoring age and sex class responses to resource restriction in high-density elephant populations.     

Ontogenetic changes in the feeding system of the red-sided garter snake, Thamnophis sirtalis parietalis. I. Allometric analysis

The ontogenetic growth pattern of selected components of the skeleton, muscle mass, and muscle lever arms within the head of the red-sided garter snake, Thamnophis sirtalis parietalis , were investigated. The results of this analysis appear to indicate an ontogenetic shift from an early emphasis upon prey manipulation to a later emphasis upon striking. The ecological, morphological and phylogenetic evidence for this shift is described and specific testable hypotheses are proposed.     

Regulation of Crustacean Molting: A Multi-Hormonal System

SYNOPSIS. In order to increase in size, arthropods must firstmolt (shed) their confining exoskeleton. This molting processis under the immediate control of the steroid molting hormone20-hydroxyecdysone (20-HE). Both the initial rise in circulatinghormone concentration and a coordinated decline are necessaryfor successful molting. Synthesis and/or release of ecdysone,the precursor to 20-HE, is regulated by the neuropeptide molt-inhibitinghormone (MIH). We have determined the primary amino acid sequenceof MIH in the lobster, Homarus americanus. This peptide hasa high degree of identity with the lobster hyperglycemic hormone.Another endocrine factor that appears to be involved in moltingis the juvenile hormone-like terpenoid methyl farnesoate (MF).We have characterized hemolymph MF binding proteins during themolt cycle. In addition, recent data indicate that MF may stimulatethe secretion of 20-HE in vivo and in vitro.