Sex ratios under asymmetrical local mate competition in the parasitoid wasp Nasonia vitripennis

Sex ratio theory has proved remarkably useful in testing theadaptive nature of animal behavior. A particularly productivearea in this respect is Hamilton's theory of local mate competition(LMC), which has been extended in numerous directions to includegreater biological realism, allowing more detailed tests inspecific organisms. We have presented one such extension, termedasymmetrical LMC, which occurs when egg laying by females ona patch is asynchronous, and emerging males do not disperse,resulting in the extent of LMC on a patch varying over time.Our aim here is to test whether the parasitoid wasp Nasoniavitripennis responds to variation in the degree of asymmetricalLMC. Specifically, we show that females adjust their offspringsex ratios in response to (1) variation in the amount of asynchronyin emergence between broods on a patch and (2) the number andproportion of previously parasitized hosts on the patch. Ourresults provide qualitative support for the predictions of theory,suggesting new levels of complexity in the sex ratio behaviorof this much-studied organism. However, our results do not alwaysprovide quantitative support for theory, suggesting furthercomplexities that must be clarified.     

The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca

To investigate the potential for and constraints on the evolution of compensatory ability, we performed a greenhouse experiment using Asclepias syriaca in which foliar damage and soil nutrient concentration were manipulated. Under low nutrient conditions, significant genetic variation was detected for allocation patterns and for compensatory ability. Furthermore, resource allocation to storage was positively, genetically correlated both with compensatory ability and biomass when damaged, the last two being positively, genetically correlated with each other. Thus, in the low nutrient environment, compensatory ability via resource allocation to storage provided greater biomass when damaged. A negative genetic correlation between compensatory ability and plant biomass when undamaged suggests that this mechanism entailed an allocation cost, which would constrain the evolution of greater compensatory ability when nutrients are limited. Under high nutrient conditions, neither compensatory ability nor allocation patterns predicted biomass when damaged, even though genetic variation in compensatory ability existed. Instead, plant biomass when undamaged predicted biomass when damaged. The differences in outcomes between the two nutrient treatments highlight the importance of considering the possible range of environmental conditions that a genotype may experience. Furthermore, traits that conferred compensatory ability did not necessarily contribute to biomass when damaged, demonstrating that it is critical to examine both compensatory ability and biomass when damaged to determine whether selection by herbivores can favor the evolution of increased compensation. Received: 2 April 1999 / Accepted: 21 September 1999     

Evaluating effect of arbuscular mycorrhizal fungal consortia and Azotobacter chroococcum in improving biomass yield of Jatropha curcas

This study was conducted to study the long-term impact of bioinoculants, Azotobacter chroococcum and arbuscular mycorrhizal fungi (AMF) on growth and biomass yield of Jatropha curcas grown in nursery and in field conditions. The experiment was set up in a randomized block design, and the following treatments was designed (T₁ = control, T₂ = Azotobacter, T₃ = inoculation with AMF, and T₄ = inoculation with Azotobacter + AMF). Data on various growth attributes (shoot height and shoot diameter) and biochemical parameters [leaf relative water content (LRWC), sugars, protein, and photosynthetic pigments] were recorded up to 6 months in the nursery and in the field (18 months). Results pertaining to morpho-physiological traits showed Azotobacter and AMF consortia increase shoot height, shoot diameter, LRWC, sugars, proteins, and photosynthetic pigments over control under nursery conditions. Besides enhancing the plant growth, these bioinoculants helped in better establishment of Jatropha plants under field conditions. A significant improvement in the shoot height, shoot diameter, fruit yield/plant, and seed yield (g)/plant was evident in 18-month-old Jatropha plants under field conditions when Azotobacter and AMF were co-inoculated. This work supports the application of bioinoculants for establishment of Jatropha curcas in semi-arid regions.     

Effects of global environmental change on carbon partitioning in vegetative plants of Triticum aestivum and closely related Aegilops species

The use of fossil fuel is predicted to cause an increase of the atmospheric CO₂ concentration, which will affect the global pattern of temperature and precipitation. It is therefore essential to incorporate effects of temperature and water supply on carbon partitioning of plants to predict effects of elevated [CO₂] on growth and yield of Triticum aestivum. Although earlier papers have emphasized that elevated [CO₂] favours investment of biomass in roots relative to that in leaves, it has now become clear that these are indirect effects, due to the more rapid depletion of nutrients in the root environment as a consequence of enhanced growth. Broadly generalized, the effect of temperature on biomass allocation in the vegetative stage is that the relative investment of biomass in roots is lowest at a certain optimum temperature and increases at both higher and lower temperatures. This is found not only when the temperature of the entire plant is varied, but also when only root temperature is changed whilst shoot temperature is kept constant. Effects of temperature on the allocation pattern can be explained largely by the effect of root temperature on the roots' capacity to transport water. Effects of a shortage in water supply on carbon partitioning are unambiguous: roots receive relatively more carbon. The pattern of biomass allocation in the vegetative stage and variation in water-use efficiency are prime factors determining a plant's potential for early growth and yield in different environments. In a comparison of a range of T. aestivum cultivars, a high water-use efficiency at the plant level correlates positively with a large investment in both leaf and root biomass, a low stomatal conductance and a large investment in photosynthetic capacity. We also present evidence that a lower investment of biomass in roots is not only associated with lower respiratory costs for root growth, but also with lower specific costs for ion uptake. We suggest the combination of a number of traits in future wheat cultivars, i.e. a high investment of biomass in leaves, which have a low stomatal conductance and a high photosynthetic capacity, and a low investment of biomass in roots, which have low respiratory costs. Such cultivars are considered highly appropriate in a future world, especially in the dryer regions. Although variation for the desired traits already exists among wheat cultivars, it is much larger among wild Aegilops species, which can readily be crossed with T. aestivum. Such wild relatives may be exploited to develop new wheat cultivars well-adapted to changed climatic conditions.     

Studies of biosorption of Pb2+, Cd2+ and Cu2+ from aqueous solutions using Adansonia digitata root powders

The potentials of Adansonia digitata root powders (ADRP) for adsorption of Pb²⁺, Cd²⁺ and Cu²⁺ from aqueous solutions was investigated. Physico-chemical analysis of the adsorbent (ADRP) shows that hydroxyl, carbonyl and amino groups were predominant on the surface of the adsorbent. Scanning Electron Microscope (SEM) image revealed its high porosity and irregular pores in the adsorbent while the Energy Dispersive X-ray Spectrum showed the major element with 53.0% Nitrogen, 23.8% carbon, 9.1% calcium, 7.5% potassium and 6.6% magnesium present. The found optimal conditions were: initial concentration of the metal ions = 0.5 mg/L, pH = 5, contact time = 90 min, adsorbent dose = 0.4 g and particle size = 32 µm. Freundlich isotherm showed good fit for the adsorption of Pb²⁺, Cd²⁺ and Cu²⁺. Dubinin-Radushkevich isotherm revealed that the adsorption processes were physisorption Cd(II) and Cu(II) but chemisorption with respect to Pb(II) ions. The kinetics and thermodynamic studies showed that Pseudo-second order and chemisorptions provided the best fit to the experimental data of Pb (II) ions only. Batch desorption result show that desorption in the acidic media for the metal ions were more rapid and over 90% of the metal ions were recovered from the biomass.     

Environmental and genetic control of crassulacean acid metabolism in two crassulacean species and an F1 hybrid with differing biomass δ13C values

Abstract The growth, biomass δ¹³C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F₁ hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ¹³C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ¹³C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψ_leaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ¹³C values than did the plants watered only weekly.