Some effects of humidity on the light reaction of photosynthesis in the lichens Cladonia impexa and Collema flaccidium

Luminescence and fluorescence were measured at different relative humidities in the lichen Cladonia impexa Harm. Both parameters showed a constant value at relative humidities lower than 80%: thereafter they increased. Low relative humidity was found to decrease energy transfer from chlorophyll b to chlorophyll a. inhibit electron transport, lower electron holding capacity on the reduced side of photosystem two and impair far-red-induced afterglow, reflecting photophosphorylation. In Collema flaccidium Ach. Ach. energy transfer from the accessory pigments phycocyanin and phycoerythrin to chlorophyll a was only possible at high relative humidity. The results are interpreted as due to conformational changes caused by changed water content in the lichen.     

Decarboxylation and Transport of Auxin in Segments of Sunflower and Cabbage Roots. II. A Chromatographic Study Using IAA-1-14C and IAA-5-3H

The polar movement of IAA has been examined in 5-mm root segments of Brassica oleracea and Helianthus annum. The movement was studied partly with IAA-1-¹⁴C and partly with IAA-5-³H. In both plants a slight acropetal flux of ¹⁴C and IAA-³H was found through the segments. The recovered radioactivity in the agar receiver blocks and in the receiver end of the segments increased as a function of time. A large portion of the applied IAA was converted on the cut surfaces and in the tissues of the segments. Chromatographic analysis indicated different destruction products when estimated by scintillation counting and by spraying with in-dole reagent (DMCA). Chromatograms run in isopropanol: ammonia: water, 8:1:1, yielded three different substances, one spot near the starting line and one near the front, neither of which has been identified. Finally there was a spot with R_f 0.4–0.6, probably representing IAA.     

1:1 Distribution between Induced Mutants and Phenocopies

BY ultraviolet irradiation of germiings of the multicellular alga Ulva mutabilis Føyn, it is possible to obtain chimaeric plants which consist of two morphologically different parts of different genetic constitution, one part wild type and the other mutant^{1, 2}. Other plants found have been identical in appearance to the chimaeras, though the morphologically different parts were both genetically wild type. They should be considered phenocopies of the genetic chimaeras. Surprisingly, the genetical chimaeras and their phenocopies were found in equal numbers. This observation and the previous one that only complete mutations are found after ultraviolet irradiation of Ulva cells¹, can be explained if only one of the two strands in the DNA molecule is genetically conserved.     

The State of Protochlorophyll and Chlorophyll in Corn Roots

The protochlorophyll(ide) present in primary roots of dark-grown corn (Zea mays) seedlings has an in vivo absorption maximum at 634 nm. Red light converts the pigment to chlorophyll(ide) a with an absorption maximum at 675 nm.     

Photosynthetic CO2 fixation in spinach chloroplasts inhibited by pine chloroplasts or extracts of pine chloroplasts

Chloroplasts isolated from pine needles were found to be inactive with respect to CO₂ fixation. Since it was suspected that pine needles may contain substances inhibitory to photosynthesis, studies were carried out using photosynthetically active isolated spinach chloroplasts and chloroplasts isolated from pine needles. When isolated pine chloroplasts were suspended in buffer and were added to isolated spinach chloroplasts they inhibited photosynthetic CO₂ fixation. When the pine chloroplasts were separated from the medium by centrifugation, the separated pine chloroplasts severely inhibited CO₂ fixation by isolated spinach chloroplasts, but the supernatant solution from the pine chloroplasts was not inhibitory. As little as 5% pine chloroplasts (based on chlorophyll content) produced 50% inhibition of CO₂ fixation by the spinach chloroplasts. Studies of fixation of ¹⁴C-labelled CO₂ by spinach chloroplasts were carried out in which after 5 min photosynthesis the pine chloroplasts were added. It was found that the subsequent inhibition of spinach CO₂ fixation was neither due to any effect on the rate of export of photosynthetic metabolites from the chloroplasts to the medium, nor to a direct effect on the RUBP carboxylase reaction. The principal effect was found to be an inhibition of the conversion of fructose-1,6-bisphosphate and sedoheptulose-1,7-bisphosphate to the respective monophosphates and inorganic phosphate. From this finding it was concluded that a principal effect of the inhibition by pine chloroplasts is probably an inhibition either directly or indirectly of the bisphosphatase enzymes in the spinach chloroplasts. Based on its distribution between organic and aqueous acidic or neutral solutions, the inhibitory factor of the pine chloroplasts must be lipophilic. Most of the factor could be transferred to an aqueous phase in a strongly alkaline solution. Following subsequent acidification of the aqueous phase the activity could be completely transferred back into the organic phase. This procedure allowed for separation of the inhibitory factor from most of the pigments and other lipophilic substances present in the pine chloroplasts and yielded a preparation which could be subsequently fractionated by thin layer chromatography. UV absorption was found in two fast moving spots and at the origin. The fastest running spot from the thin layer chromatography plate was found to be the one containing most of the inhibitory activity.     

The Devonian nekton revolution

Klug, C., Kröger, B., Kiessling, W., Mullins, G.L., Servais, T., Frýda, J., Korn, D. & Turner, S. 2009: The Devonian nekton revolution. Lethaia, 10.1111/j.1502‐3931.2009.00206.x Traditional analyses of Early Phanerozoic marine diversity at the genus level show an explosive radiation of marine life until the Late Ordovician, followed by a phase of erratic decline continuing until the end of the Palaeozoic, whereas a more recent analysis extends the duration of this early radiation into the Devonian. This catch‐all approach hides an evolutionary and ecological key event long after the Ordovician radiation: the rapid occupation of the free water column by animals during the Devonian. Here, we explore the timing of the occupation of the water column in the Palaeozoic and test the hypothesis that ecological escalation led to fundamental evolutionary changes in the mid‐Palaeozoic marine water column. According to our analyses, demersal and nektonic modes of life were probably initially driven by competition in the diversity‐saturated benthic habitats together with the availability of abundant planktonic food. Escalatory feedback then promoted the rapid rise of nekton in the Devonian as suggested by the sequence and tempo of water‐column occupation. □Devonian, diversity, ecology, food webs, nekton, plankton, radiation.     

SOME LESSER KNOWN FEATURES OF THE ANCIENT CEPHALOPOD ORDER ELLESMEROCERIDA (NAUTILOIDEA, CEPHALOPODA)

Abstract:  Three specimens of the small breviconic ellesmeroceratid Paradakeoceras minor Flower, 1964 from the Tremadocian of the New York area preserve the annular elevation and muscle scars in moulds of the body chamber. The annular elevation is positioned at the base of the body chamber and is wider on the convex side of the shell than on the concave side. Multiple paired muscle scars can be seen within this annular elevation. A well-preserved body chamber of the breviconic ellesmeroceratid Levisoceras cf. edwardsi Ulrich, Foerste and Miller is described. Its body chamber shows a strong anterior–posterior asymmetry, which is common within the Ellesmeroceratida. The shape of the body chamber and of the soft body attachment structures has led to a reconstruction of an ellesmeroceratid soft body that is organized like a primitive conchiferan mollusc. Based on this reconstruction, a tryblidian cephalopod ancestor is supported. An evolutionary scenario is reconstructed from an ancestral nautiloid that is stretched along the anterior–posterior axis, and has serially arranged shell muscles and a small mantle cavity, towards a modern cephalopod with a dorsal–ventral body orientation, reduced number of shell muscles and a large mantle cavity.     

Use and commercialization of Podocnemis expansa (Schweiger 1812) (Testudines: Podocnemididae) for medicinal purposes in two communities in North of Brazil

The emergence of alternative medicines for AIDS in Asia and Africa was discussed at a satellite symposium and the parallel session on alternative and traditional treatments of the AIDSImpact meeting, held in Marseille, in July 2007. These medicines are heterogeneous, both in their presentation and in their geographic and cultural origin. The sessions focused on the role of these medications in selected resource poor settings in Africa and Asia now that access to anti-retroviral therapy is increasing. The aims of the sessions were to (1) identify the actors involved in the diffusion of these alternative medicines for HIV/AIDS, (2) explore uses and forms, and the way these medicines are given legitimacy, (3) reflect on underlying processes of globalisation and cultural differentiation, and (4) define priority questions for future research in this area. This article presents the insights generated at the meeting, illustrated with some findings from the case studies (Uganda, Senegal, Benin, Burkina Faso, China and Indonesia) that were presented. These case studies reveal the wide range of actors who are involved in the marketing and supply of alternative medicines. Regulatory mechanisms are weak. The efficacy claims of alternative medicines often reinforce a biomedical paradigm for HIV/AIDS, and fit with a healthy living ideology promoted by AIDS care programs and support groups. The AIDSImpact session concluded that more interdisciplinary research is needed on the experience of people living with HIV/AIDS with these alternative medicines, and on the ways in which these products interact (or not) with anti-retroviral therapy at pharmacological as well as psychosocial levels.     

OUGHT WE TO ENHANCE OUR COGNITIVE CAPACITIES?1

Ought we to improve our cognitive capacities beyond the normal human range? It might be a good idea to level out differences between peoples cognitive capacities; and some people's reaching beyond normal capacities may have some good side‐effects on society at large (but also bad side‐effects, of course). But is there any direct gain to be made from having ones cognitive capacities enhanced? Would this as such make our lives go better? No, I argue; or at least there doesn't seem to be any evidence suggesting that it would. And it doesn't matter whether we consider the question from a narrow hedonistic perspective, from a more refined hedonistic perspective, from a desire‐satisfaction view, or from some reasonable objective list view of what makes a life go well. Only an extremely perfectionist – and implausible – view of what makes our lives go well could support any direct value in cognitive enhancement. Finally, our sense of identity gives us no good reasons to enhance even our capacity to remember. So, cognitive enhancement as such would not improve our lives.