New branched Porolithon species (Corallinales,Rhodophyta) from the Great Barrier Reef,Coral Sea,and Lord Howe Island

Porolithon is one of the most ecologically important genera of tropical and subtropical crustose (non-geniculate) coralline algae growing abundantly along the shallow margins of coral reefs and functioning to cement reef frameworks. Thalli of branched, fruticose Porolithon specimens from the Indo-Pacific Ocean traditionally have been called P. gardineri, while massive, columnar forms have been called P. craspedium. Sequence comparisons of the rbcL gene both from type specimens of P. gardineri and P. craspedium and from field-collected specimens demonstrate that neither species is present in east Australia and instead resolve into four unique genetic lineages. Porolithon howensis sp. nov. forms columnar protuberances and loosely attached margins and occurs predominantly at Lord Howe Island; P. lobulatum sp. nov. has fruticose to clavate forms and free margins that are lobed and occurs in the Coral Sea and on the Great Barrier Reef (GBR); P. parvulum sp. nov. has short (<2 cm), unbranched protuberances and attached margins and is restricted to the central and southern GBR; and P. pinnaculum sp. nov. has a mountain-like, columnar morphology and occurs on oceanic Coral Sea reefs. A rbcL gene sequence of the isotype of P. castellum demonstrates it is a different species from other columnar species. In addition to the diagnostic rbcL and psbA marker sequences, the four new species may be distinguished by a combination of features including thallus growth form, margin shape (attached or unattached), and medullary system (coaxial or plumose). Porolithon species, because of their ecological importance and sensitivity to ocean acidification, need urgent documentation of their taxonomic diversity.     

The biology of triploid fish

This review deals with major areas of triploidy research in fish. It includes not only methods for induction and detection of triploidy but also the impact of triploidy on morphology, anatomy, growth, haematology, energetics, behaviour, endocrinology and gonads in various species of fish, studied so far. The future prospects of research on triploid fish are discussed inviting researchers with diverse areas of interest in fish biology.     

Morpho-anatomical, physiological and biochemical adjustments in response to root zone salinity stress and high solar radiation in two Mediterranean evergreen shrubs, Myrtus communis and Pistacia lentiscus

Salt- and light-induced changes in morpho-anatomical, physiological and biochemical traits were analysed in Myrtus communis and Pistacia lentiscus with a view to explaining their ecological distribution in the Mediterranean basin. In plants exposed to 20 or 100% solar radiation and supplied with 0 or 200 mm NaCl, measurements were conducted for ionic and water relations and photosynthetic performance, leaf morpho-anatomical and optical properties and tissue-specific accumulation of tannins and flavonoids. Net carbon gain and photosystem II (PSII) efficiency decreased less in P. lentiscus than in M. communis when exposed to salinity stress, the former having a superior ability to use Na(+) and Cl(-) for osmotic adjustment. Morpho-anatomical traits also allowed P. lentiscus to protect sensitive targets in the leaf from the combined action of salinity stress and high solar radiation to a greater degree than M. communis. Salt and light-induced increases in carbon allocated to polyphenols, particularly to flavonoids, were greater in M. communis than in P. lentiscus, and appeared to be related to leaf oxidative damage. Our data may conclusively explain the negligible distribution of M. communis in open Mediterranean areas suffering from salinity stress, and suggest a key antioxidant function of flavonoids in response to different stressful conditions.     

Floral development in the tribe Cedreleae (Meliaceae, sub-family Swietenioideae): Cedrela and Toona

BACKGROUND AND AIMS: Floral development of Cedrela and Toona, the genera comprising the basal tribe Cedreleae of the sub-family Swietenioideae of Meliaceae, is described. The focus was on three endangered, ecologically and economically important species: Cedrela fissilis, Cedrela odorata and Toona ciliata. The aims of the study were to characterize the patterns of floral development in the tribe and to establish apomorphic and plesiomorphic floral characters in relation to other taxa within the family based on the current molecular phylogeny of Meliaceae. METHODS: A detailed floral structural and developmental study was completed using both scanning electron microscopy and visualization of microtome sections with a light microscope. KEY RESULTS: Twelve floral developmental stages were identified. The initial development of the pentamerous flowers of both Toona and Cedrela is strikingly similar. The morphological differences observed between them are due to differential patterns of organ elongation and adnation/connation occurring late in development. Additionally, the formation of functionally male and female flowers was found to occur at specific positions within the inflorescence. CONCLUSIONS: Due to the basal position of the tribe Cedreleae in the phylogeny of Meliaceae, functionally either male or female pentamerous flowers and the presence of (at least partially) free stamens may be considered plesiomorphic traits within the family. In contrast, sympetaly and the absence of nectaries in Cedrela species are synapomorphies.     

Salinity stress constrains photosynthesis in Fraxinus ornus more when growing in partial shading than in full sunlight: consequences for the antioxidant defence system

Background and Aims

A major challenge in plant ecophysiology is understanding the effects of multiple sub-optimal environmental conditions on plant performance. In most Mediterranean areas soil salinity builds up during the summer because of low availability of soil water coupled with hot temperatures. Although sunlight and soil salinity may strongly interact in determining a plant''s performance, this has received relatively little attention.

Methods

Two-year-old seedlings of Fraxinus ornus were grown outdoors in pots during a Mediterranean summer in either 45 % (shaded plants) or 100 % (sun plants) sunlight irradiance and were supplied with either deionized water or deionized water plus 75 mm NaCl. Morpho-anatomical traits, water and ionic relations, gas exchange and photosystem II performance, concentrations of individual carotenoids, activity of antioxidant enzymes, concentrations of ascorbic acid and individual polyphenols were measured in leaves. Leaf oxidative stress and damage were estimated by in vivo analysis of stable free radicals and ultrastructural analyses.

Key Results

Leaf concentrations of potentially toxic ions did not markedly differ in shaded or sun plants in response to salinity. Leaves of sun plants displayed superior water use efficiency compared with leaves of shaded plants, irrespective of salinity treatment, and had both better stomatal control and higher CO₂ carboxylation efficiency than leaves of shaded plants. In the salt-treated groups, the adverse effects of excess midday irradiance were greater in shade than in sun plants. The activity of enzymes responsible for detoxifying hydrogen peroxide decreased in shaded plants and increased in sun plants as a result of salinity stress. In contrast, the activity of guaiacol peroxidase and the concentration of phenylpropanoids increased steeply in response to salinity in shaded plants but were unaffected in sun plants.

Conclusions

It is concluded that salinity may constrain the performance of plants growing under partial shading more severely than that of plants growing under full sun during summer. The results suggest co-ordination within the antioxidant defence network aimed at detoxifying salt-induced generation of reactive oxygen species.     

DNA Sequencing of Type Material Reveals Pneophyllum marlothii comb. nov. from South Africa and P. discoideum comb. nov. (Chamberlainoideae,Corallinales, Rhodophyta) from Argentina

A partial rbcL sequence from the type material of Spongites discoideus from southern Argentina showed that it was distinct from rbcL sequences of South African specimens to which that name had been applied based on morpho-anatomy. A partial rbcL sequence from an original syntype specimen, herein designated the lectotype, of Lithophyllum marlothii, type locality Camps Bay, Western Cape Province, South Africa, was identical to rbcL sequences of South African field-collected specimens assigned to S. discoideus. Based on phylogenetic analyses of rbcL and/or psbA sequences, both of these species belong in Pneophyllum and are transferred there as P. discoideum comb. nov. and P. marlothii comb. nov. The two species exhibit a distinct type of development where thick, secondary, monomerous disks are produced from thin, primary, dimerous crusts. Whether this type of development represents an example of convergent evolution or is characteristic of a clade of species within Pneophyllum remains to be resolved.