Tumulduria incomperta and the case for Tommotian trilobites

The enigmatic fossil Tumulduria incomperta Missanhevsky 1969 from the basal Tommotian Stage at 'Dvortsy' on the Aldan River, Siberian Platform, is reinvestigated in light of the report (Fedorov et al. 1979, Dokl. AN SSSR 249) of trilobite remains from the same beds. Comparisons of these supposed trilobites with old and new collections from 'Dvortsy' leave no doubt that they are identical to Tumulduria incomperta. Tumulduria is represented by phosphatic plates with a crude bilateral symmetry, consisting of a central longitudinal rounded ridge flanked by flat lateral portions. They are built of growth lamellae overlapping each other along the axis of symmetry. The surface carries prominent transverse folds and lamellar terminations. There is considerable morphological variation, and the similarity of some specimens to trilobites is only superficial. Tumulduria is interpreted as a bilaterally symmetrical metazoan with a dorsal protective plate; it probably represents a short-lived group that left no descendants.     

Within-lake patterns in depth penetration of emergent vegetation

SUMMARY. 1. Within-lake relations of wave exposure (WE), and substratum softness (cone penetration depth; CPD) and organic content (loss on ignition; LOI), to water depth penetration of the emergent vegetation (DPE) was investigated in seven eutrophic lakes in southern Sweden, ranging in area from 1 to 46km².
2. There was a positive relationship between WE and DPE within lakes. This relationship, however, only occurred for sites with relatively soft substrata, for which CPD and LOI were negatively related to both WE and DPE.
3. Analysis of aerial photographs revealed that expansion of the emergent vegetation towards open water, or recession from open water, was not related to wave exposure or water depth, except in one lake where expansion mainly occurred at high exposures.
4. For relatively static vegetation on soft substrata, regressions with CPD°.⁵ explained 62–88% of the within-lake variation of DPE. These regressions did not differ among lakes. Expanding and recessing vegetation were significantly dislocated towards shallower and deeper water, respectively, than predicted from the regression models for static vegetation.
5. Phragmites australis dominated at the lakeward edge of the emergent vegetation, followed in frequency by Typha angustifolia . More broad-leaved species were generally restricted to shallow water and very soft substrata.
6. The results suggest that changes in the distribution of emergent vegetation in moderately wave exposed eutrophic lakes can be predicted largely from substratum character and water depth.     

Influence of submergence on growth of seedlings of Scirpus lacustris and Phragmites australis

• 1 Seeds of Scirpus lacustris and Phragmites australis were germinated in early June, and twenty-four seedlings of each species were subsequently exposed to submerged conditions (eight seedlings at each of the water depths 0.2, 0.4 and 0.8m), in outdoor 500–1 tanks in southern Sweden. Weight and shoot length of the plants were measured in September.
• 2 The Phragmites seedlings did not show any significant growth when submerged. The Scirpus seedlings, however, developed submerged leaves and exhibited considerable submerged growth. One Scirpus plant, in shallow water (0.2m), had developed an aerial shoot by September. Shoot length of the remaining (submerged) Scirpus plants was positively related to plant weight within water depth treatments, and was higher, in relation to plant weight, in deeper water. Mean weight in September of the submerged Scirpus plants decreased with increased water depth.
• 3 In south Swedish lakes with a lowered water table, Scirpus often occupies large areas on the lakeward side of the reed belt, which is generally dominated by Phragmites. The differences between the two species, in performance of submerged seedlings, suggest that this zonation may be created through successful submerged seedling establishment of Scirpus on the lakeward side of Phragmites.

     

Response of small birch plants (Betula pendula Roth.) to elevated CO2 and nitrogen supply

Small birch plants were grown for up to 80 d in a climate chamber at varied relative addition rates of nitrogen in culture solution, and at ambient (350 μmol mol^-1) or elevated (700 μmol mol^-1) concentrations of CO₂. The relative addition rate of nitrogen controlled relative growth rate accurately and independently of CO₂ concentration at sub-optimum levels. During free access to nutrients, relative growth rate was higher at elevated CO₂. Higher values of relative growth rate and net assimilation rate were associated with higher values of plant N-concentration. At all N-supply rates, elevated CO₂ resulted in higher values of net assimilation rate, whereas leaf weight ratio was independent of CO₂. Specific leaf area (and leaf area ratio) was less at higher CO₂ and at lower rates of N-supply. Lower values of specific leaf area were partly because of starch accumulation. Nitrogen productivity (growth rate per unit plant nitrogen) was higher at elevated CO₂. At sub-optimal N-supply, the higher net assimilation rate at elevated CO₂ was offset by a lower leaf area ratio. Carbon dioxide did not affect root/shoot ratio, but a higher fraction of plant dry weight was found in roots at lower N-supply. In the treatment with lowest N-supply, five times as much root length was produced per amount of plant nitrogen in comparison with optimum plants. The specific fine root length at all N-supplies was greater at elevated CO₂. These responses of the root system to lower N-supply and elevated CO₂ may have a considerable bearing on the acquisition of nutrients in depleted soils at elevated CO₂. The advantage of maintaining steady-state nutrition in small plants while investigating the effects of elevated CO₂ on growth is emphasized.     

Early needle senescence and thinning of the crown structure of Picea abies as induced by chronic SO2 pollution. II. Field data basis, model results and tolerance limits

Field data on the sulphur and cation budget of growing Norway spruce canopies (Picea abies [L.] Karst.) are summarized. They are used to test a spruce decline model capable of quantifying effects of chronic SO₂ pollution on spruce forests. At ambient SO₂ concentrations, acute SO₂ damage is rare, but exposure to polluted air produces reversible thinning of the canopy structure with a half-time of a few years. Canopy thinning in the spruce decline model is highest (i) at elevated SO₂ pollution, (ii) in the mountains, (iii) at unfertilized sites with poor K⁺, Mg²⁺ or Zn²⁺ supply, (iv) at low spruce litter decomposition rates, and (v) acidic, shallow soils at high annual precipitation rates in the field and vice versa. Model application using field data from Würzburg (moderate SO₂ pollution, alkaline soils, no spruce decline) and from the Erzgebirge (extreme SO₂ pollution, acidic soils in the mountains, massive spruce decline) predicts canopy thinning by 2–11% in Würzburg and by 45–70% in the Erzgebirge. The model also predicts different SO₂-tolerance limits for Norway spruce depending on the site elevation and on the nutritional status of the needles. If needle loss of more than 25% (damage class 2) is taken to indicate ‘real damage’ exceeding natural variances, then for optimum soil conditions SO₂ tolerance limits range from (27.3 ± 7.4) μg m^?3 to (62.6 ± 16.5) μg m^?3. For shallow and acidic soils, SO₂ tolerance limits range from (22.0 ± 5.5) μg m^?3 to (37.4 ± 7.5) μ m^?3. These tolerance limits, which are calculated on an ecophysiological data basis for Norway spruce are close to epidemiological SO₂-toIerance limits as recommended by the IUFRO, UN-ECE and WHO. The observed statistical regression slope of the plot (damaged spruce trees vs. SO₂-pollution) in west Germany is confirmed by modelling (6% error). Model application to other forest trees allows deduction of the observed sequence of SO₂-sensitivity: Abies > Picea > Pinus > Fagus > Quercus. Thus, acute phytotoxicity of SO₂ seems not to be involved in ‘forest decline’. Chronic SO₂-pollution induces massive canopy thinning of Abies alba and Picea abies only at unfavourable sites, where natural stress factors and secondary effects of SO₂pollution act together to produce tree decline.     

The cap-shaped Cambrian fossil Maikhanella and the relationship between coeloscleritophorans and molluscs

The recent discovery of large shells. growing by accretion, in the scleritome of the coeloscleritophoran Ha lkieria Poulsen, 1967, prompts the reconsideration of a number of cap-shaped shells in the Lower Cambrian. The scaly shells of Maikhanella Zhegallo, 1982. from Mongolia provide a good starting point, mce they occur together with spicules of siphogonuchitid type and appear to be composed of merged spicules. The shells are phosphatired and consist of two main elements: spicules, typically filled with phosphate. and an intermediate matrix. The associated loose spicules belong to forms that have served as the basis for erection of the genera Siphogonuchites Qian. 1977, and Lopochites Qian, 1977. Maikhanella is prohdbly a junior synonym of one or both of the latter two genera, but taxonomic revision is suspended until the type material of these siphogonuchitid genera has been restudied. and all three genera are left as sciotaxa. Various cap-shaped shells and plates in the Chinese Meishucunian are reinterpreted as shells belonging to coeloscleritophornn scleritoines. Maikhanella shells were formed through the embedding of spicules in secondary calcareous shell zubstance. The skeletogenesis has several similarities with that of molluscs, and together with the polyplacophoran-like features of the Halkieria scleritome this forces a reconsideration of the phylogenetic relationships between coeloscleritophorans and molluscs     

Varietal variation in uptake and utilization of potassium (rubidium) in high-salt seedlings of barley

Seedlings of eleven varieties of barley (Hordeum vulgare L.) showed differences in utilization of K⁺ from a full nutrient solution containing 3.0 mM K⁺. The K⁺ content of both roots and shoots was proportional to the fresh weights and dry weights after a week in the nutrient solution. The K⁺ use-efficiency ratio, which indicates the efficiency of nutrient utilization (mg dry weight produced per mg K⁺ absorbed), differed significantly among the varieties. There was no correlation between influx of Rb⁺ and the content of K⁺. It is suggested that there are wide varietal differences in such genetically-determined properties as ion influx and efflux and net ion transport to the shoot. Further-more, the influx of Rb⁺ was closely linked to transpiration, probably due to a variety-specific non-metabolic part of Rb⁺ influx. Varietal differences in influx of Rb⁺ were more pronounced in high-K⁺ roots than in low-K⁺ roots with maximum rate of Rb⁺ uptake, but the rank of varieties was the same in each case. – Criteria for the selection of K⁺ use-efficient varieties of barley are discussed.     

Inhibition and Requirement of Natural Stimulator for Cambial Xylem Production in Isolated Stem Segments of Pinus silvestris

Formation of xylem in sterile culture of isolated pine stem segments supplied with synthetic media continues only for 4–6 weeks. The stem segments originally do not contain an eluable inhibitor affecting elongation in the test of pine hypocotyl sections. After 4 weeks inhibition is detected. Supplying the medium with a methanolic extract from the cambial region of pine stem prolongs xylem production up to 15 weeks. IAA interacts synergistically with a natural stimulator of cambial activity.