Differential Response of Various Tissues4Asparagus officinalis to Sodium Chloride

Tolerance of Asparagus officinalis tissues of different levelsof organization to 0–2% NaCl was studied in a tissue culturesystem. The following tissues (organs) were examined: friablecallus with no organogenesis, compact callus exhibiting organogenesis,one-bud shoot segments, and plantlets. Growth of friable callus,the less organized tissue, was progressively inhibited by risingconcentrations of NaCl, whereas growth of compact callus wassomewhat less sensitive. NaCl at concentrations of 1% or highercaused an increase in the mortality of one-bud shoot segmentsand inhibited growth. Concentrations up to 2% NaCl did not causeany mortality of plantlets, the most organized tissue tested;root production declined progressively in response to salinitywhile shoot growth was inhibited only at 2% NaCl. Moderate concentrationsof NaCl (0.5–1.0%) stimulated growth and induced phyllocoidproduction in both shoot segments and plantlets. With increasedNaCl there was a massive uptake of sodium and chloride, principallyinto the shoots, while uptake and accumulation of potassiumdecreased somewhat in shoots, but not in roots and rhizomes.Rooted and unrooted plantlets exhibited similar levels of tolerance.It is, therefore, inferred that salt tolerance of asparagusin culture is dependent on tissue organization. Key words: Asparagus officinalis, salt tolerance, callus, shoot segment, plantlet     

Effects of goat pastoralism on ecosystem carbon storage in semiarid thicket,Eastern Cape,South Africa

Abstract Intensive pastoralism with goats transforms semiarid thicket in the Eastern Cape, South Africa from a dense vegetation of tall shrubs to an open landscape dominated by ephemeral grasses and forbs. Approx. 800 000 ha of thicket (which prior to the introduction of goats had a closed canopy and a Portulacaria afra Jacq. component) have been transformed in this manner. Ecosystem C storage in intact thicket and loss of C due to transformation were quantified. Carbon storage in intact thicket was surprisingly high for a semiarid region, with an average of 76 t C ha^?1 in living biomass and surface litter and 133 t C ha^?1 in soils to a depth of 30 cm. Exceptional C accumulation in thicket may be a result of P. afra dominance. This succulent shrub switches between C₃ and CAM photosynthesis, produces large quantities of leaf litter (approx. 450 g m^?2 year^?1) and shades the soil densely. Transformed thicket had approx. 35% less soil C to a depth of 10 cm and approx. 75% less biomass C than intact thicket. Restoration of transformed thicket landscapes could consequently recoup more than 80 t C ha^?1.     

Evidence of widespread effects of ozone on crops and (semi‐)natural vegetation in Europe (1990–2006) in relation to AOT40‐ and flux‐based risk maps

Records of effects of ambient ozone pollution on vegetation have been compiled for Europe for the years 1990–2006. Sources include scientific papers, conference proceedings, reports to research funders, records of confirmed ozone injury symptoms and an international biomonitoring experiment coordinated by the ICP Vegetation. The latter involved ozone‐sensitive (NC‐S) and ozone‐resistant (NC‐R) biotypes of white clover (Trifolium repens L.) grown according to a common protocol and monitored for ozone injury and biomass differences in 17 European countries, from 1996 to 2006. Effects were separated into visible injury or growth/yield reduction. Of the 644 records of visible injury, 39% were for crops (27 species), 38.1% were for (semi‐) natural vegetation (95 species) and 22.9% were for shrubs (49 species). Owing to inconsistencies in reporting effort from year to year it was not possible to determine geographical or temporal trends in the data. Nevertheless, this study has shown effects in ambient air in 18 European countries from Sweden in the north to Greece in the south. These effects data were superimposed on AOT40 (accumulated ozone concentrations over 40 ppb) and POD3_gen (modelled accumulated stomatal flux over a threshold of 3 nmol m^?2 s^?1) maps generated by the EMEP Eulerian model (50 km × 50 km grid) that were parameterized for a generic crop based on wheat and NC‐S/NC‐R white clover. Many effects were found in areas where the AOT40 (crops) was below the critical level of 3 ppm h. In contrast, the majority of effects were detected in grid squares where POD3_gen (crops) were in the mid‐high range (>12 mmol m^?2). Overall, maps based on POD3_gen provided better fit to the effects data than those based on AOT40, with the POD3_gen model for clover fitting the clover effects data better than that for a generic crop.     

T. R. R. Stebbing:A bibliography with biographic notes

T. R. R. Stebbing (1835–1926), a specialist on the systematics of amphipod Crustacea, was raised in London in a literary family and studied classics, law and history at Oxford. After his ordination as a priest in 1859 he was a schoolmaster, then, after he married, a private tutor at Torquay. About 1863 he read Darwin's Origin of species and was convinced by it; by 1868 he had become a naturalist and systematist. In 1877 he moved to Tunbridge Wells where he spent the rest of his life studying Crustacea, active in scientific societies, and writing essays and reviews.
Stebbing's Darwinism was not particularly original, though he marshalled some good examples from the invertebrates to indicate the importance of variation within and between species. He regarded natural selection as a directing force by which God's plan for organisms was being worked out, and credited it with the origin of language, morality and religion. In taxonomic practice, Stebbing advocated priority of names, simple rules of transliteration and gender, and publication of new names only in a few easily-accessible journals. After the publication of the Regies internationales de la nomenclature zoologique in 1905 his writings on taxonomic practice were confined to minor issues.
A bibliography of Stebbing's 242 publications concerned with carcinology, Darwinism, nomenclature and miscellaneous subjects has been compiled.     

Azetidine-2-carboxylic Acid and Lily Pollen Tube Elongation

Azetidine-2-carboxylic acid (AZC), which occurs naturally inLiliaceous plants, is reported to be a proline (pro) analoguePlant cell walls contain ‘extensin’, which is richin hydroxyproline (hyp). Peptidyl hyp arises through hydroxylationof peptidyl pro followed by glycosylation (arabinose attachment)of hyp Because AZC replaces peptidyl prolyl residues, it maybe a useful tool for evaluating the significance of hyp-o-arabinoselinkages in cell elongation. Therefore, we determined the effectof AZC on [¹⁴C]pro uptake, incorporation and conversion to wall-bound[¹⁴C]hyp in relation to elongation of lily pollen tubes whosewalls consist, in part, of hyp-containing glycopeptides TheAZC suppressed pollen germination 9–42 per cent (1–10mM) and subsequent tube elongation 40–54 per cent (0·1–1mM without affecting respiration In contrast, similar hyp concentrationswere without effect on tube elongation Whereas uptake of [¹⁴C]prowas 16·5–6·2 per cent of the control at0·1–1 mM AZC, [¹⁴C]leucine uptake was 85–25per cent of the control. Light microscope radioautography revealedfewer silver grains over tubes elongated in 0·1–1mM AZC than in its absence. Incorporation of [¹⁴C]pro into tnchloroaceticacid (TCA)-precipitable cytoplasm was reduced by only 10 percent at 0·01–1 mM but 43 per cent at 10 mM AZCGel filtration of cytoplasm from pollen germinated without AZCbut with [¹⁴C]pro resulted in labelled void volume (V) and threeretarded peaks (RI–III) Incorporation into V and RI wasinhibited at both 0·01 and 1 mM AZC These AZC concentrationsreduced conversion of [¹⁴C]pro to wall-bound hyp by 20 percent However, total incorporation of [¹⁴C]pro into salt-water-purifiedwall fractions was suppressed 47–53 per cent (0·1–1mM AZC). Lilium longiflorum, lily, hydroxyproline, proline, azetidine-2-carboxylic acid, pollen, pollen tube elongation