Malic Acid Accumulation in Roots in Response to Flooding: Evidence Contrary to its Role as an Alternative to Ethanol

Across a time course of flooding the malic acid content in rootsof the swamp tree Nyssa sylvatica var. biflora increased 5-foldfrom 1 week to 1 month of flooding and remained at that levelthrough a full year of flooding. Alcoholic fermentation ratesaccelerated within the first month of flooding but dropped tovery low levels under long-term flooding. The theory that, underflooding, malic acid accumulates as an alternative anaerobicend product to ethanol is unlikely in this instance since (1)malate is initially associated with high alcoholic fermentationand (2) the reduction in alcoholic fermentation is accountedfor by increased internal aeration of the roots.     

Intraspecific taxonomy and ecology characterize morphological divergence among cutthroat trout (Oncorhynchus clarkii ssp. Richardson) populations

We compared the proportion of morphological variation accounted for by subspecies categories with the proportion encompassed by ecologically based categories in cutthroat trout ( Oncorhynchus clarkii ssp.), as a means of assessing the relative importance of each approach in identifying intraspecific diversity. We used linear and geometric morphometrics to compare measures of body shape, fin length, and head features between and within subspecies of cutthroat trout. Both categories accounted for a significant proportion of the variation between and within the subspecies; however, the larger proportion was explained by subspecific differences, with the greatest morphological divergence between coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) and interior subspecies. Ecotypic categories within each subspecies also explained significant morphological differences: stream populations had longer fins and deeper, more robust bodies than lake populations. The largest ecotypic differences occurred between stream and lake populations of Yellowstone cutthroat trout ( Oncorhynchus clarkii bouvieri ). Given that many cutthroat trout subspecies are of conservation concern, our study offers a better understanding of intraspecific variation existing within the species, providing precautionary evidence of incipient speciation, and a framework of describing phenotypic diversity that is correlated with ecological conditions.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 266–281.     

The stoichiometry of nitrogen and phosphorus spiralling in heterotrophic and autotrophic streams

1. Nutrient spiralling provides a conceptual framework and a whole‐system approach to investigate ecosystem responses to environmental changes. We use spiralling metrics to examine how the coupling of nitrogen and phosphorus uptake varies between streams dominated by either heterotrophic (i.e. bacteria‐dominated) or autotrophic (algal‐dominated) microbial communities. 2. Algae generally exhibit greater capacity to store nutrients than bacteria because of differences in cellular structures. These differences led us to hypothesise that the uptake of N and P in heterotrophic ecosystems should have reduced stoichiometric variation in response to changes in supply N : P compared to autotrophic ecosystems when assimilation dominates nutrient uptake. 3. To test this hypothesis, we used an array of serial nutrient additions in several streams in the South Fork Eel River watershed in Northern California. In one set of experiments, N and P were added alone and simultaneously in separate experiments to two small, heterotrophic streams to assess uptake rates and interactions between nutrient cycles. In a second set of experiments, N and P were added simultaneously at a range of N : P in one heterotrophic and one autotrophic stream to assess differences in uptake responses to changes in supply N : P. 4. Results of these experiments suggest two important conclusions. First, increased N supply significantly shortened P uptake lengths, while P addition had little impact on N uptake in both streams, indicating that uptake of non‐limiting nutrients is tightly coupled to the availability of the limiting element. Second, changes in P uptake and uptake ratios (U_N : U_P) with increased supply N : P supported our hypothesis that heterotrophic streams are more homeostatic in their responses to changes in nutrient supply than autotrophic streams, suggesting that physiological controls on nutrient use scale up to influence ecosystem‐scale patterns in nutrient cycling.     

Adipokinetic hormone content of the corpora cardiaca in gregarious and solitary migratory locusts

Abstract. The adipokinetic hormone (AKH-I and AKH-II) content of the corpora cardiaca from adult males of crowded (gregarious) and isolated (solitary) Locusta migratoria migratorioides (Reiche & Fairmaire) was quantified by reverse-phase high-performance liquid chromatography.Significantly less total hormone was found in the corpora cardiaca of crowded locusts than in those glands of isolated locusts at the age of 12–19 days after fledging.The ratio of AKH-I/AKH-II was higher in crowded than in isolated locusts at this age.From the age of 12–19 days to that of 25–30 days, AKH content increased significantly in the corpora cardiaca of crowded locusts, but no such increase was found in the glands of isolated locusts, and at 25–30 days there were no significant differences in the AKH content of the glands from crowded and isolated locusts.     

Carbon: freshwater plants

δ¹³C values for freshwater aquatic plant matter varies from ?11 to ?50‰ and is not a clear indicator of photosynthetic pathway as in terrestrial plants. Several factors affect δ¹³C of aquatic plant matter. These include: (1) The δ¹³C signature of the source carbon has been observed to range from +1‰ for HCO₃^? derived from limestone to ?30‰ for CO₂ derived from respiration. (2) Some plants assimilate HCO₃^?, which is –7 to –11‰ less negative than CO₂. (3) C₃, C₄, and CAM photosynthetic pathways are present in aquatic plants. (4) Diffusional resistances are orders of magnitude greater in the aquatic environment than in the aerial environment. The greater viscosity of water acts to reduce mixing of the carbon pool in the boundary layer with that of the bulk solution. In effect, many aquatic plants draw from a finite carbon pool, and as in terrestrial plants growing in a closed system, biochemical discrimination is reduced. In standing water, this factor results in most aquatic plants having a δ¹³C value similar to the source carbon. Using Farquhar's equation and other physiological data, it is possible to use δ¹³C values to evaluate various parameters affecting photosynthesis, such as limitations imposed by CO₂ diffusion and carbon source.     

Crassulacean acid metabolism (CAM) in high elevation tropical cactus

Abstract. Several taxa of cacti are distributed in high elevation tropical alpine habitats between 4000–4700 m in central Peru. This region has a marked dry season with soil water potentials as low as – 25 MPa. The barrel type cactus Oroya peruviana and the low ceaspitose Tephrocactus floccosus (both the typical hairy form and a hairless form) all exhibited diurnal fluctuations of malic acid (10–100 μmol/g FW), indicative of CAM photosynthesis. δ³C carbon isotope ratios were – 13 to – 14 suggesting that for these CAM plants the bulk of the net carbon gain is through night-time carbon uptake. This occurs in spite of overnight temperatures below 0°C. CAM activity was observed on nights when air temperature dropped to – 8°C and subepidermal temperatures reached as low as –3°C. In central Peru, the typical form of T. floccosus has a dense covering of long silvery white hairs. Comparisons with an adjacent 'hairless' form showed that the hairy morph maintained a subepidermal temperature several degrees higher during the night. At a site where the 'hairless' morph was rare, the hairy T. floccosus had substantially higher overnight acid accumulation. At another site where the 'hairless' morph was abundant, the hairy T. floccosus had substantially lower acid accumulation relative to the 'hairless' form.     

The effects of dietary nitrogen on reproductive development in the female boll weevil, Anthonomus grandis

ABSTRACT. The role of dietary nitrogen in reproductive development was investigated in the female boll weevil, Anthonomus grandis (Boh.)(Coleoptera: Curculionidae). Artificial diets were employed containing 1.7%, 2.6% and 4.0% N. Each diet was labelled with a ¹⁴C-amino acid mixture and standardized relative to cpm and N per mg of diet dry weight. Egg production, diet consumption, nitrogen consumption and nitrogen utilization were measured by recovering the cpm in the faeces, ovaries plus eggs and the carcass.
Females given the 4% N diet initiated oviposition on day 4 with maximum egg production of 11 eggs/day/female occurring on day 6. Females on the 2.6% N diet also initiated oviposition on day 4, but the time necessary to reach maximum egg production was extended. Egg production by these females eventually equalled the total production of the group on the 4% N diet. This was achieved by consuming more diet per female and dedicating a higher percentage of the absorbed diet to egg formation. With the 1.7% N diet, females showed both a delay and a decrease in total egg production because of reduced feeding and a reduced commitment of consumed nutrients to oöcyte maturation.
Switching dietary nitrogen concentrations after the initiation of oviposition resulted in changes in consumption and reproductive allocation within 48 h.     

Short note Report of diurnal acid metabolism in two aquatic Australian species of Isoetes

Previous studies have demonstrated the presence of crassulacean acid metabolism in the North American submerged aquatic Isoetes howellii (Isoetaceae). Diurnal changes in titratable acidity and malic acid levels indicate the presence of this pathway in two Australian species of Isoetes.