Photosynthetic adaptation of two semi-arid species of Gethyllis (Kukumakranka) to drought-and-shade stress

Gethyllis multifolia and Gethyllis villosa are winter-growing, summer-blooming, deciduous and bulbous geophytes that grow naturally in the semi-arid ‘Succulent Karoo Biome’ of South Africa. G. multifolia is threatened in its natural habitat and resides in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’. Previous investigations suggested that G. multifolia is more sensitive to drought stress than G. villosa and that both species adopted certain morphological changes in their leaves during shade stress. Current models indicate that this biome is being exposed to increasingly drier conditions and shading from encroaching indigenous plant species. In this study, the photosynthetic gas exchange responses of both species to drought and shade stresses were investigated and the ‘Vulnerable’ conservation status of G. multifolia. This investigation found that during drought stress G. villosa had a more enhanced photosynthetic performance than G. multifolia which appears not to be related to foliar adaptations such as specific leaf mass (SLM), but to the G. villosa's leaves maintaining their stomatal conductance (Gs), photosynthetic light compensation (LCP) and photon yields. Furthermore, during shade stress G. villosa also had an improved photosynthetic performance by not altering its photosynthetic LCP during reduced light conditions. It can be concluded that G. multifolia has a lower capacity than G. villosa to adapt its photosynthetic apparatus to changing environments such as increasing drought and shaded conditions. This may be a contributing factor to the threatened conservation status of G. multifolia.Web of Scienc

Eco-evolutionary dynamics on deformable fitness landscapes

Conventional approaches to modelling ecological dynamics often do not include evolutionary changes in the genetic makeup of component species and, conversely, conventional approaches to modelling evolutionary changes in the genetic makeup of a population often do not include ecological dynamics. But recently there has been considerable interest in understanding the interaction of evolutionary and ecological dynamics as coupled processes. However, in the context of complex multi-species ecosytems, especially where ecological and evolutionary timescales are similar, it is difficult to identify general organising principles that help us understand the structure and behaviour of complex ecosystems. Here we introduce a simple abstraction of coevolutionary interactions in a multi-species ecosystem. We model non-trophic ecological interactions based on a continuous but low-dimensional trait/niche space, where the location of each species in trait space affects the overlap of its resource utilisation with that of other species. The local depletion of available resources creates, in effect, a deformable fitness landscape that governs how the evolution of one species affects the selective pressures on other species. This enables us to study the coevolution of ecological interactions in an intuitive and easily visualisable manner. We observe that this model can exhibit either of the two behavioural modes discussed in the literature; namely, evolutionary stasis or Red Queen dynamics, i.e., continued evolutionary change. We find that which of these modes is observed depends on the lag or latency between the movement of a species in trait space and its effect on available resources. Specifically, if ecological change is nearly instantaneous compared to evolutionary change, stasis results; but conversely, if evolutionary timescales are closer to ecological timescales, such that resource depletion is not instantaneous on evolutionary timescales, then Red Queen dynamics result. We also observe that in the stasis mode, the overall utilisation of resources by the ecosystem is relatively efficient, with diverse species utilising different niches, whereas in the Red Queen mode the organisation of the ecosystem is such that species tend to clump together competing for overlapping resources. These models thereby suggest some basic conditions that influence the organisation of inter-species interactions and the balance of individual and collective adaptation in ecosystems, and likewise they also suggest factors that might be useful in engineering artificial coevolution

Comparative antioxidant-capacity and -content of leaves, bulbs, roots, flowers and fruit of Gethyllis multifolia L. Bolus and G. villosa Thunb. species

The total polyphenol, oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP), radical cation scavenging ability, flavonol and flavanone contents were measured in the leaves, bulbs, roots, flowers and fruit (dry weight) of two natural populations of Gethyllis multifolia (Kukumakranka) and Gethyllis villosa. The flowers and fruit of G. multifolia and G. villosa showed higher, and in some cases significantly (P < 0.05) higher antioxidant activities when compared to the leaves, bulbs and roots. This, however, was not true for the flavanone content in both species. The total polyphenol content in the fruits of G. multifolia (21.54 mg GAE/g) and G. villosa (27.64 mg GAE/g) were found to be in agreement with those of raisins (28.30 mg GAE/g), blueberries (24 mg GAE/g) and strawberries (15.40 mg GAE/g). The FRAP values of G. multifolia flowers (76.66 μmole AAE/g) and fruit (91.51 μmole AAE/g) were found to be significantly (P < 0.05) higher than those of the other plant parts (16.76 to 39.08 μmol AAE/g). On the other hand, the flowers (590.23 μmol TE/g) and fruit (741.16 μmol TE/g) of G. villosa revealed a significantly (P < 0.05) higher ORAC when compared to the other plant parts (251.25 to 410.60 μmol TE/g). A strong correlation was evident in the fruit of both species between the total polyphenols and FRAP (r = 0.95), ORAC (r = 0.95) and flavonol content (r = 0.79). © 2011 Elsevier B.V. All rights reserved.Article in Pres

Effects of magmatic processes on the potential Yucca Mountain repository: Field and computational studies

Assessing the risk of future magmatic activity at a potential Yucca Mountain radioactive waste repository requires, in addition to event probabilities, some knowledge of the consequences of such activity. Magmatic consequences are divided into an eruptive component, which pertains to the possibility of radioactive waste being erupted onto the surface of Yucca Mountain, and a subsurface component, which occurs whether there is an accompanying eruption or not. The subsurface component pertains to a suite of processes such as hydrothermal activity, changes in country rock properties, and long term alteration of the hydrologic flow field which change the waste isolation system. This paper is the second in a series describing progress on studies of the effects of magmatic activity. We describe initial results of field analog studies at small volume basaltic centers where detailed measurements are being conducted of the amount of wall rock debris that can be erupted as a function of depth in the volcanic plumbing system. Constraints from field evidence of wall rock entrainment mechanisms are also discussed. Evidence is described for a mechanism of producing subhorizontal sills versus subvertical dikes, an issue that is important for assessing subsurface effects. Finally, new modeling techniques, which are being developed in order to capture the three dimensional complexities of real geologic situations in subsurface effects, are described

A Randomized Trial Comparing the Specific Carbohydrate Diet to a Mediterranean Diet in Adults with Crohn’s Disease

Background & Aims This study compared the effectiveness of the Specific Carbohydrate Diet (SCD) to the Mediterranean Diet (MD) as treatment for Crohn’s disease (CD) with mild to moderate symptoms. Methods Adult patients with CD and with mild-moderate symptoms were randomly assigned 1:1 to consume the MD or SCD for 12 weeks. For the first 6-weeks, participants received prepared meals and snacks according to their assigned diet. After 6-weeks, participants were instructed to follow the diet independently. The primary outcome was symptomatic remission at week 6. Key secondary outcomes at week 6 included: fecal calprotectin (FC) response (FC 50% among those with baseline FC >250 μg/g) and C-Reactive Protein (CRP) response (high-sensitivity CRP (hsCRP) 50% reduction from baseline among those with hsCRP >5mg/L). Results 194 patients were randomized, and 191 were included in the efficacy analyses. The percentage of participants who achieved symptomatic remission at week 6 was not superior with SCD (SCD 46.5%, MD 43.5%; P = .77). FC response was achieved in 8/23 participants (34.8%) with SCD and 4/13 participants (30.8%) with MD (P = .83). CRP response was achieved in 2/37 participants (5.4%) with SCD and 1/28 participant (3.6%) with MD (P = .68). Conclusions SCD was not superior to MD to achieve symptomatic remission, FC response and CRP response. CRP response was uncommon. Given these results, the greater ease of following the MD, and other health benefits associated with MD, the MD may be preferred to the SCD for most patients with CD with mild to moderate symptoms