The masculinity paradox: facial masculinity and beardedness interact to determine women's ratings of men's facial attractiveness

In many species, male secondary sexual traits have evolved via female choice as they confer indirect (i.e. genetic) benefits or direct benefits such as enhanced fertility or survival. In humans, the role of men's characteristically masculine androgen‐dependent facial traits in determining men's attractiveness has presented an enduring paradox in studies of human mate preferences. Male‐typical facial features such as a pronounced brow ridge and a more robust jawline may signal underlying health, whereas beards may signal men's age and masculine social dominance. However, masculine faces are judged as more attractive for short‐term relationships over less masculine faces, whereas beards are judged as more attractive than clean‐shaven faces for long‐term relationships. Why such divergent effects occur between preferences for two sexually dimorphic traits remains unresolved. In this study, we used computer graphic manipulation to morph male faces varying in facial hair from clean‐shaven, light stubble, heavy stubble and full beards to appear more (+25% and +50%) or less (?25% and ?50%) masculine. Women (N = 8520) were assigned to treatments wherein they rated these stimuli for physical attractiveness in general, for a short‐term liaison or a long‐term relationship. Results showed a significant interaction between beardedness and masculinity on attractiveness ratings. Masculinized and, to an even greater extent, feminized faces were less attractive than unmanipulated faces when all were clean‐shaven, and stubble and beards dampened the polarizing effects of extreme masculinity and femininity. Relationship context also had effects on ratings, with facial hair enhancing long‐term, and not short‐term, attractiveness. Effects of facial masculinization appear to have been due to small differences in the relative attractiveness of each masculinity level under the three treatment conditions and not to any change in the order of their attractiveness. Our findings suggest that beardedness may be attractive when judging long‐term relationships as a signal of intrasexual formidability and the potential to provide direct benefits to females. More generally, our results hint at a divergence of signalling function, which may result in a subtle trade‐off in women's preferences, for two highly sexually dimorphic androgen‐dependent facial traits.     

Exogenous auxin affects ascorbate metabolism in roots of tomato seedlings

Ascorbate levels and redox states, as well as the activities of the enzymes of ascorbate metabolism, were analyzed in roots of tomato seedlings during the culture on a medium supplemented with auxin and compared to the control cultured on an auxin-free medium. Biochemical parameters were determined separately in the distal part of the root where the inhibitory effect of auxin on root elongation growth is observed and in the proximal half on the organ which reacts to auxin treatment with increased lateral root proliferation. ASC peroxidase activity was found to be stimulated by auxin treatment in the lateral-root forming part of the root. This effect was not observed in the distal part of the organ. On the other hand, ASC oxidase activity was raised by auxin exclusively in the distal part of the root. An inhibitory effect of auxin supplementation to the medium on ASC—reducing enzymes was observed. The dehydroascorbate reductase activity was found to be inhibited by auxin only in the proximal part, while the activity of monodehydroascorbate reductase in both, the proximal and distal parts of the root. Ascorbate content increased in roots during culture irrespective of the presence of auxin. However, auxin treatment resulted in higher DHA levels and more significant participation of DHA in the total ascorbate pool when compared to the control grown on the auxin-free medium. Similar to auxin, adding DHA to the culture medium stimulated lateral root formation and inhibited primary root elongation. In contrast to DHA, ASC treatment affected significantly neither lateral root formation nor primary root growth and partly reversed the stimulatory effect of IAA on root formation and the inhibitory effect on root elongation. These results suggest that auxin induced changes in ascorbate metabolism may be involved in developmental reactions in tomato roots.     

Water uptake by roots of maize and sunflower affects the radial transport of abscisic acid and its concentration in the xylem

The radial movement of cis-abscisic acid (ABA) has been investigated in young excised roots of Zea mays L. and Helianthus annuus L. which were grown hydroponically. In addition to the symplastic path, ABA was largely translocated across the root apoplast by solvent drag with the water in the transpiration stream. On the apoplastic path ABA may even cross the endodermis. Depending on the ABA concentration of the medium (range: 5–500 nM) and in the root apoplast, the solvent-drag component of the flow of ABA counteracted the dilution of ABA in the xylem caused by transpirational water flow. Acidification of the rhizosphere and of the root apoplast increased the apoplastic transport component. In sunflower, the apoplastic flow of ABA was significantly weaker than in maize roots. This was also indicated by the larger apparent reflection coefficient (σ_ABA) of sunflower roots for ABA (sunflower: σ_ABA = 0.97 ± 0.02, n = 6 roots; maize: σ_ABA = 0.68 ± 0.06, n = 6 roots; ±SD). For both species, σ_ABA was smaller than unity. Root reflection coefficients were affected by factors such as pH, ABA concentration of the medium, and by the suction force applied to excised root systems. Due to the complex composite structure of the permeation barrier in the root, the reflection coefficient estimated from solvent drag is also complex. Since unstirred layers affected the absolute value of the reflection coefficient, σ_ABA has been termed `apparent'. It is concluded that the pH and ABA concentration of the soil solution as well as the transpiration rate (suction force) modify the intensity of the root-to-shoot signal which is influenced by an apoplastic bypass flow of ABA. The latter may be substantially affected by the existence of Casparian bands in the exodermis, which were lacking in the roots studied in this paper. Received: 25 February 1998 / Accepted: 16 July 1998     

Arsenic-induced root growth inhibition in mung bean (<Emphasis Type="Italic">Phaseolus aureus</Emphasis> Roxb.) is due to oxidative stress resulting from enhanced lipid peroxidation

Arsenic (As) toxicity and its biochemical effects have been mostly evaluated in ferns and a few higher plants. In this study, we investigated the effect of As (10.0 and 50.0 μM) on seedling growth, root anatomy, lipid peroxidation (malondialdehyde and conjugated dienes), electrolyte leakage, H₂O₂ content, root oxidizability and the activities of antioxidant enzymes in mung bean (Phaseolus aureus Roxb.). Arsenic significantly enhanced lipid peroxidation (by 52% at 50.0 μM As), electrolyte leakage and oxidizability in roots. However, there was no significant change in H₂O₂ content. Arsenic toxicity was associated with an increase in the activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX) and glutathione reductase (GR). In response to 50.0 μM As, the activities of SOD and GR increased by over 60% and 90%, respectively. At 10.0 μM As, the activity of ascorbate peroxidase (APX) increased by 83%, whereas at 50.0 μM it declined significantly. The catalase (CAT) activity, on the other hand, decreased in response to As exposure, and it corresponded to the observed decrease in H₂O₂ content. We conclude that As causes a reduction in root elongation by inducing an oxidative stress that is related to enhanced lipid peroxidation, but not to H₂O₂ accumulation.     

Status of Selected Heavy Metal Distribution in Scalp Hair of Traffic Control Personnel Exposed to Vehicular Emissions

Scalp hair samples of traffic control personnel (n = 71, ages between 25 to 45 years) were analyzed for 11 selected metals by using an Inductively Coupled Argon Plasma Atomic Emission (ICP-AE) technique using nitric acid–perchloric acid based wet digestion method. The observed order of mean concentrations (μ g/g, dry weight) of the metals, in washed hair samples, was: Ca > Mg > Zn > Fe > Pb > Cu > Ni > Mn > Cr > Cd > Co, with corresponding metal levels at 1042.2, 182.4, 169.7, 13.6, 12.4, 11.1, 2.7, 1.9, 1.9, 0.8, and 0.7 μ g/g, respectively. Most of the unwashed samples exhibited 10–15% higher metal levels compared with those in washed samples. A positive metal-to-metal correlation (p < 0.01) was observed for the metal pairs: Ca-Mg (r = 0.737), Pb-Cr (r = 0.441), and Cu-Zn (0.385). Principal Component Analysis (PCA) extracted 6 factors as metals origin using varimax normalized rotation commutatively representing more than 76% of the total variance. Cluster Analysis (CA) showed five strong clusters of selected metals in the hair of the subjects: Age-Exposure, Ca-Mg, Cd-Fe-Mn, Pb-Cr, and Cu-Zn. The results of the current study were compared with those for two other occupationally exposed groups, metal arc welders and autodrivers, using published literature values. The traffic controllers in our study generally, with the exception of Cu, exhibited lower levels of metals in hair samples than did autodrivers and arc welders.     

A study of body hair density and distribution in normal women

The distribution and density of terminal hair growth have been studied in 19 different body regions in 100 normal women of fertile age and 25 normal postmenopausal women. In accordance with earlier investigations an age-dependent variation in hair growth pattern was observed. None of the women in either group had terminal hair growth on the cheek, and on the breast region hair was limited to a small circumareolar area. Whereas facial terminal hair growth appeared to be less common than that reported in earlier studies of women from other countries, the frequency of terminal hair in other regions was found to be significantly higher in the Norwegian women. No difference in hair growth pattern between blondes and brunettes could be detected.     

Lorentzian model of roots for understory yellow birch and sugar maple saplings

Total 66 small (<50m(2)), 24 medium (101-200m(2)) and 36 large (201-500m(2)) canopy gaps at the three sites of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh) forests were established in southern Québec, Canada. Half of the gaps were covered by 8x8m(2) shading cloths to mimic a closed canopy. From these gaps, 46 understory yellow birch and 46 sugar maple saplings with different tree ages and sizes were sampled. Single- and multi-variable linear and nonlinear models of root biomass and traits (root surface area, volume, length and endings) were developed and examined. Lorentzian model as a multi-variable nonlinear model was firstly applied to the simulations using both base diameter and height, and performed the best fit to total root biomass in both species with the highest correlation coefficients (R(2)=0.96 and 0.98) and smallest root mean squared deviations (RMSD=7.85 and 7.02) among all the examined models. The model also accurately simulated small fine root (2.0mm in diameter), coarse fine root (>2.0-5.0mm) and coarse root (>5.0mm) biomass (R(2)=0.87-0.99; RMSD=2.24-6.41), and the root traits (R(2)=0.71-0.99; RMSD=0.19-19.38). The study showed yellow birch roots were longer, larger, had more endings (tips) and grew faster than sugar maple roots. The root traits were largely distributed to small fine roots, sharply decreased from small fine roots to coarse fine roots, the fewest in coarse roots except for root volume. When trees were large, coarse root biomass increased more rapidly than fine root biomass, but vise versa when the trees were small.     

Soil microorganisms control plant ectoparasitic nematodes in natural coastal foredunes

Belowground herbivores can exert important controls on the composition of natural plant communities. Until now, relatively few studies have investigated which factors may control the abundance of belowground herbivores. In Dutch coastal foredunes, the root-feeding nematode Tylenchorhynchus ventralis is capable of reducing the performance of the dominant grass Ammophila arenaria (Marram grass). However, field surveys show that populations of this nematode usually are controlled to nondamaging densities, but the control mechanism is unknown. In the present study, we first established that T. ventralis populations are top-down controlled by soil biota. Then, selective removal of soil fauna suggested that soil microorganisms play an important role in controlling T. ventralis. This result was confirmed by an experiment where selective inoculation of microarthropods, nematodes and microbes together with T. ventralis into sterilized dune soil resulted in nematode control when microbes were present. Adding nematodes had some effect, whereas microarthropods did not have a significant effect on T. ventralis. Our results have important implications for the appreciation of herbivore controls in natural soils. Soil food web models assume that herbivorous nematodes are controlled by predaceous invertebrates, whereas many biological control studies focus on managing nematode abundance by soil microorganisms. We propose that soil microorganisms play a more important role than do carnivorous soil invertebrates in the top-down control of herbivorous ectoparasitic nematodes in natural ecosystems. This is opposite to many studies on factors controlling root-feeding insects, which are supposed to be controlled by carnivorous invertebrates, parasitoids, or entomopathogenic nematodes. Our conclusion is that the ectoparasitic nematode T. ventralis is potentially able to limit productivity of the dune grass A. arenaria but that soil organisms, mostly microorganisms, usually prevent the development of growth-reducing population densities.