Diffusional conductances to CO2 as a target for increasing photosynthesis and photosynthetic water-use efficiency

A key objective for sustainable agriculture and forestry is to breed plants with both high carbon gain and water-use efficiency (WUE). At the level of leaf physiology, this implies increasing net photosynthesis (A _N) relative to stomatal conductance (g _s). Here, we review evidence for CO₂ diffusional constraints on photosynthesis and WUE. Analyzing past observations for an extensive pool of crop and wild plant species that vary widely in mesophyll conductance to CO₂ (g _m), g _s, and foliage A _N, it was shown that both g _s and g _m limit A _N, although the relative importance of each of the two conductances depends on species and conditions. Based on Fick’s law of diffusion, intrinsic WUE (the ratio A _N/g _s) should correlate on the ratio g _m/g _s, and not g _m itself. Such a correlation is indeed often observed in the data. However, since besides diffusion A _N also depends on photosynthetic capacity (i.e., V _c,max), this relationship is not always sustained. It was shown that only in a very few cases, genotype selection has resulted in simultaneous increases of both A _N and WUE. In fact, such a response has never been observed in genetically modified plants specifically engineered for either reduced g _s or enhanced g _m. Although increasing g _m alone would result in increasing photosynthesis, and potentially increasing WUE, in practice, higher WUE seems to be only achieved when there are no parallel changes in g _s. We conclude that for simultaneous improvement of A _N and WUE, genetic manipulation of g _m should avoid parallel changes in g _s, and we suggest that the appropriate trait for selection for enhanced WUE is increased g _m/g _s.     

Self-Biting in Caged Macaques: Cause, Effect, and Treatment

Injurious self-biting is one of the most serious problems in primate colonies (Niemeyer, Gray, & Stephen, 1996). “Approximately 10% of captive, individually-housed monkeys engage in the disturbing phenomenon of self-injurious behavior (SIB). To date, no adequate explanation or effective therapy has been developed for this disorder ”(Jorgensen, Novak, Kinsey, Tiefenbacher, & Meyer, 1996; cf. Novak, Kinsey, Jorgensen, & Hazen, 1998). In rhesus macaques-the predominant species found in laboratories-the incidence of self-biting may be as high as 14% (recorded in a colony of 188 single-caged males; Jorgensen, Kinsey, & Novak, 1998). Individuals affected with this “behavioral pathology ”(Erwin & Deni, 1979, p. 4) repeatedly bite parts of their own bodies (see Figure 1) while intermittently showing signs of intense excitation such as threatening, trembling, head jerking, and piloerection (Reinhardt, 1999; Tinklepaugh, 1928).     

Bacterial conversion of molasses to acetone and butanol

Summary In cooperation with the company Copersucar (Brazil), several variants of a fermentation system for the continuous production of butanol and acetone from high-test or invert molasses were developed. These fermentation systems involve a relatively economic batch fermentation requiring little investment, using a continuous culture as the inoculation culture, as well as a modern two-stage continuous culture with cell recycling. For example, 13.3 g·1^–1 of solvent (acetone and butanol) are produced with a productivity of 3.3 g·1^–1 ·h^–1 by two-stage continuous molasses fermentation with cell recycling in the second stage. High-test molasses is converted completely into the products. Butanol and acetone production from molasses is economic in Brazil and the construction of a production plant is planned.Offprint requests to: A. S. Afschar     

Microhabitat selection by small mammals in a southern Appalachian fen in the USA

Little ecological information is available on small mammals inhabiting wetlands in the southern Appalachian mountains of the USA. These wetland systems are becoming rare features in southern landscapes due to human activities. We investigated the small mammal fauna and examined the microhabitat associations of the two most abundant species in a southern Appalachian fen. Four species of small mammals were captured: the meadow jumping mouse (Zapus hudsonius), short-tailed shrew ( Blarina brevicauda), white-footed mouse ( Peromyscus leucopus), and golden mouse ( Ochrotomys nuttalli). Peromyscus and Ochrotomys, which were caught in the largest numbers, preferred sites characterized by moderate herbaceous cover and substantial canopy closure. Peromyscus, however, selected areas with greater canopy closure and higher tree densities, suggesting that they are greater habitat specialists than Ochrotomys in this wetland community.     

The production of 2,3-butanediol by fermentation of high test molasses

Summary Klebsiella oxytoca fermented 199 g·l^–1 high test or invert molasses using batch fermentation with substrate shift to produce 95.2–98.6 g 2,3-butanediol·l^–1 and 2,4–4.3 g acetoin·l^–1 with a diol yield of 96–100% of the theoretical value and a diol productivity of 1.0–1.1 g·l^–1·h^–1. Fermentation was performed numerous times with molasses in repeated batch culture with cell recovery. Such repeated batch fermentation, in addition to a high product yield, also showed a very high product concentration. For example, 118 g 2,3-butanediol·l^–1 and 2.3 g acetoin·l^–1 were produced from 280 g·l^–1 of high test molasses. The diol productivity in this fermentation amounted to 2.4 g·l^–1·h^–1 and can undoubtedly be further increased by increasing the cell concentration. Because the Klebsiella cultures ferment 2,3-butanediol at an extremely high rate once the sugar has been consumed, the culture was inhibited completely by the addition of 15 g ethanol·l^–1 and switching off aeration. Offprint requests to: A. S. Afschar     

Integrated production of biodegradable plastic, sugar and ethanol

Poly 3-hydroxybutyric acid (PHB) and related copolymers can be advantageously produced when integrated into a sugarcane mill. In this favorable scenario, the energy necessary for the production process is provided by biomass. Carbon dioxide emissions to the environment are photosynthetically assimilated by the sugarcane crop and wastes are recycled to the cane fields. The polymer can be produced at low cost considering the availability of a low-price carbon source and energy.     

Hybridization between insular endemic and widespread species of Viola in non-disturbed environments assessed by nuclear ribosomal and cpDNA sequences

Viola jaubertiana Marès & Vigin. is a narrow endemic violet of the Balearic Islands, restricted to small, fragmented, and scattered populations living in inaccessible rocky places and calcareous overhangs. V. jaubertiana is entirely glabrous and morphologically very uniform. However, several authors have reported hairy individuals collected at the type locality, suggesting that these rupicolous, pubescent plants are putative hybrids with V. alba Bess. subsp. dehnhardtii (Ten.) W. Becker, a woodland violet growing in the area. Ribosomal ITS sequences of the putative hybrids analysed showed additive species-specific sites of V. alba subsp. dehnhardtii and V. jaubertiana, strongly supporting its hybrid origin from these progenitors. CpDNA sequences of all putative hybrids were uniform, and identical to those present in V. jaubertiana accessions. This suggests that the gene flow between V. alba subsp. dehnhardtii and V. jaubertiana is unidirectional and identifies the endemic V. jaubertiana as the unique ovule donor. The additivity of the ITS sequences, together with the pollen and ovule sterility, suggests that the sampled individuals are primary F₁ hybrids, whereas no trace of introgressive hybridization or hybrid zone has been evidenced by the nuclear and plastid markers used. Judging from herbarium sheets, hybridization between V. alba subsp. dehnhardtii and V. jaubertiana is recurrent and dates back from the XIXth century. Hybrids between these species are not linked to disturbed environments. In fact, they have been always reported in rupicolous habitats, where the maternal species is restricted.     

Extended Newick: it is time for a standard representation of phylogenetic networks

Background  

Phylogenetic trees resulting from molecular phylogenetic analysis are available in Newick format from specialized databases but when it comes to phylogenetic networks, which provide an explicit representation of reticulate evolutionary events such as recombination, hybridization or lateral gene transfer, the lack of a standard format for their representation has hindered the publication of explicit phylogenetic networks in the specialized literature and their incorporation in specialized databases. Two different proposals to represent phylogenetic networks exist: as a single Newick string (where each hybrid node is splitted once for each parent) or as a set of Newick strings (one for each hybrid node plus another one for the phylogenetic network).