Sex determination and optimal development in the Moorish gecko,Tarentola mauritanica

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.     

A comparison of the wood anatomy of 11 species from two cerrado habitats (cerrado s.s. and adjacent gallery forest)

A comparative study of the secondary xylem (wood) anatomy of 11 species (38 specimens) occurring in cerrado s.s. and the adjacent gallery forest (both cerrado s.l. habitat) was made with the aim of identifying the anatomical characteristics of ecological value and correlating them with the environmental conditions. The anatomical features that vary, in general, between the two habitats are: growth ring distinctness (well or poorly defined); tyloses and deposits (more abundant in cerrado specimens); gelatinous fibres (more evident in cerrado specimens and in different patterns between habitats); variation in paratracheal and banded parenchyma (more abundant in cerrado); and more cells per parenchyma strand in cerrado. In general, gallery forest specimens have wider vessels, fewer vessels per square millimetre and larger intervessel pits, indicating more efficient water conduction, whereas cerrado s.s. specimens are the opposite, with low vulnerability and mesomorphy indices, demonstrating greater safety under conditions of water stress. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ?? , ??–??.     

Effects of a 50 Hz magnetic field on Dictyostelium discoideum (Protista)

Some studies have demonstrated that a few biological systems are affected by weak, extremely low frequency (ELF) electromagnetic fields (EMFs), lower than 10 mT. However, to date there is scanty evidence of this effect on Protists in the literature. Due to their peculiarity as single-cell eukaryotic organisms, Protists respond directly to environmental stimuli, thus appearing as very suitable experimental systems. Recently, we showed the presence of propionylcholinesterase (PrChE) activity in single-cell amoebae of Dictyostelium discoideum. This enzyme activity was assumed to be involved in cell-cell and cell-environment interactions, as its inhibition affects cell aggregation and differentiation. In this work, we have exposed single-cell amoebae of D. discoideum to an ELF-EMF of about 200 microT, 50 Hz, for 3 h or 24 h at 21 degrees C. A delay in the early phase of the differentiation was observed in 3 h exposed cells, and a significant decrease in the fission rate appeared in 24 h exposed cells. The PrChE activity was significantly lower in 3 h exposed cells than in the controls, whereas 24 h exposed cells exhibited an increase in this enzyme activity. However, such effects appeared to be transient, as the fission rate and PrChE activity values returned to the respective control values after a 24 h stay under standard conditions.     

Reproductive structures and systematics of Buxaceae

Buxaceae belong to a grade of families near the base of eudicots. Flowers of these families are characterized by a variable number and arrangement of floral organs. In this study, the anthetic structure of the gynoecium and androecium of representatives of all genera of Buxaceae were comparatively studied, and observations on the flowering processes and pollination biology were made. Styloceras and Notobuxus were studied in detail for the first time. Various features of the morphological analysis support our earlier molecular phylogenetic study. Shared reproductive characters among Sarcococca , Pachysandra and Styloceras are the occurrence of two (rarely three) carpels, the lack of interstylar nectaries, a micropyle formed by both integuments, attractive stamens in male flowers, and fleshy fruits. In addition, Styloceras and Pachysandra share a secondary partition in the ovary. Notobuxus does not seem to be clearly distinct from Buxus . Both have a similar inflorescence and perianth structure; female flowers have three carpels, interstylar nectaries, micropyles formed by the inner integument, rudimentary arils, and they develop into capsular fruits; in male flowers stamens are sessile and the central pistillode is lacking in some species. Thus, it is questionable to justify a separation of Buxus and Notobuxus at genus level. The results further strongly support the placement of Buxaceae among basal eudicots.  © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 193–228.     

Intrinsic and environmental response pathways that regulate root system architecture

Root system development is an important agronomic trait. The right architecture in a given environment allows plants to survive periods of water of nutrient deficit, and compete effectively for resources. Root systems also provide an optimal system for studying developmental plasticity, a characteristic feature of plant growth. This review proposes a framework for describing the pathways regulating the development of complex structures such as root systems: intrinsic pathways determine the characteristic architecture of the root system in a given plant species, and define the limits for plasticity in that species. Response pathways co-ordinate environmental cues with development by modulating intrinsic pathways. The current literature describing the regulation of root system development is summarized here within this framework. Regulatory pathways are also organized based on their specific developmental effect in the root system. All the pathways affect lateral root formation, but some specifically target initiation of the lateral root, while others target the development and activation of the lateral root primordium, or the elongation of the lateral root. Finally, we discuss emerging approaches for understanding the regulation of root system architecture.     

热带滨海植物红厚壳的抗逆生物学特性

为了解红厚壳(Calophyllum inophyllum)的抗逆特性,对西沙群岛自然生长的红厚壳叶片的形态解剖、生理生态、以及叶片和适生土壤的元素含量进行了研究。结果表明,红厚壳是阳生性植物,其上表皮厚,海绵组织发达且栅栏组织排列紧密,气孔排列松散且密度小(24.40 mm~(-2)),有利于叶片保水抵御干旱。叶片的叶绿素a、b含量低(分别为0.87和0.43 mg g~(-1)),表明红厚壳具适应强光环境的能力。叶片的MDA含量低(13.46 nmol g~(-1)),PRO含量高(127.89μg g~(-1)),SOD活性高(149.42 U g~(-1)),总抗氧化能力高(388.60 U g~(-1)),显示红厚壳能通过提高自身的抗氧化能力抵御膜脂过氧化伤害。红厚壳自然生长的珊瑚岛土壤较为贫瘠、营养元素含量低,但红厚壳植株体内具有较高的营养元素含量,表明红厚壳营养元素利用率高,对于贫瘠土壤具有很好的适应能力。因此,红厚壳具有较高的抗氧化胁迫能力和耐受干旱的能力,适宜生长在热带珊瑚岛等土壤贫瘠的生境,可以作为热带珊瑚岛防风固沙和植被恢复的工具种。     

Muscular anatomy of a whipspider, Phrynus longipes (Pocock) (Arachnida: Amblypygi), and its evolutionary significance

Skeletal muscles in the whipspider Phrynus longipes are surveyed and compared with those of other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of the arachnids. Representatives of 115 muscle groups are described and illustrated, and their possible functions are proposed. Principal results of this analysis include new functional models for the operation of the pharyngeal and sternocoxal mechanisms in Amblypygi and a greatly expanded list of apparently unique synapomorphies supporting the monophyly of Pedipalpi (= Amblypygi, Schizomida, Thelyphonida).     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.