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The study aimed to compare the dentine wear of primary and permanent human and bovine teeth because of erosion/abrasion and evaluate if bovine dentine is an appropriate substitute for human dentine in further erosion/abrasions tests. Dentine samples from deciduous molars and human third molars as well as from calves’ and cattle’s lower incisors were prepared and baseline surface profiles were recorded. Each day all samples were demineralized in 1% citric acid, tooth brushed with 100 brushing strokes with toothpaste slurry and stored in artificial saliva for the rest of the day. This cycle was run for 20 days. Afterwards, new surface profiles were recorded and dentine wear was calculated by a customized computer program. Dentine wear because of erosion/abrasion was not statistically, significantly different for human third molars and cattle’s lower incisors ( P = 0·7002). The dentine wear because of erosion/abrasion of deciduous molars and calves’ lower incisors was significantly different ( P < 0·0000). No statistically significant difference in the dentine wear of human third molars and cattle’s lower incisors was observed, so that the use of cattle’s lower incisors as substitute for adult human teeth for further investigations in erosion/abrasion studies could be accepted. [ABSTRACT FROM AUTHOR]

Question: Can above-ground biomass of naturally growing Alhagi sparsifolia shrubs be estimated non-destructively? Location: Qira oasis (37° 01′ N, 80° 48′ E, 1365 m a.s.l.) at the southern fringe of the Taklamakan desert, Xinjiang, NW China. Methods: Two methods were compared to estimate aboveground biomass (AGB) of Alhagi. At first shrub AGB was estimated by manual ground measurements (called ‘allometric approach’) of length, width and height of 50 individuals. Subsequently regression equations were established between calculated shrub canopy volume and shrub AGB (r² = 0.96). These equations were used to calculate AGB from manual ground measurements in 20 sample plots within the Alhagi field. Secondly, kite-based colour aerial photography coupled with the use of a Geographic Information System (called ‘GIS approach’) was tested. First and second order polynomial regressions between AGB data of the 50 individual shrubs and their respective canopy area allowed to automatically calculate the AGB of all remaining shrubs covered by the photograph (r² = 0.92 to 0.96). The use of non-linear AGB regression equations required an automatised separation of shrubs growing solitary or in clumps. Separation criteria were the size and shape of shrub canopies. Results: The allometric approach was more reliable but also more time-consuming than the GIS-based approach. The latter led to an overestimation of Alhagi dry matter in densely vegetated areas. However, this systematic error decreased with increasing size of the surveyed area. Future research in this field should focus on improvements of AGB estimates in areas of high shrub density. [ABSTRACT FROM AUTHOR]

The hypothesis that water relations and growth of phreatophytic Tamarix ramosissima Ledeb. and Populus euphratica Oliv. on dunes of varying height in an extremely arid Chinese desert depend on vertical distance to a permanent water table was tested. Shoot diameter growth of P. euphratica was inversely correlated with groundwater depth (GD) of 7 to 23 m (adj. R² = 0.69, P = 0.025); growth of T. ramosissima varied independent of GD between 5 and 24 m (P = 0.385). Pre-dawn (pd) and midday (md) water potentials were lower in T. ramosissima (minimum pd — 1.25 MPa, md -3.6 MPa at 24 m GD) than in P. euphratica (minimum pd -0.9 MPa, md -3.05 MPa at 23 m GD) and did not indicate physiologically significant drought stress for either species. Midday water potentials of P. euphratica closely corresponded to GD throughout the growing season, but those of T. ramosissima did not. In both species, stomatal conductance was significantly correlated with leaf water potential (P. euphratica: adj. R² = 0.84, P < 0.0001; T. ramosissima: adj. R² = 0.64, P = 0.011) and with leaf-specific hydraulic conductance (P. euphratica: adj. R² = 0.79, P = 0.001; T. ramosissima: adj. R² = 0.56, P = 0.019); the three variables decreased with increasing GD in P. euphratica. Stomatal conductance of P. euphratica was more strongly reduced (> 50% between -2 and -3 MPa) in response to decreasing leaf water potential than that of T. ramosissima (30% between -2 and -3 MPa). Tolerance of lower leaf water potentials due to higher concentrations of leaf osmotically active substances partially explains why leaf conductance, and probably leaf carbon gain and growth, of T. ramosissima was less severely affected by GD. Additionally, the complex below-ground structure of large clonal T. ramosissima shrub systems probably introduces variability into the assumed relationship of xylem path length with GD. [ABSTRACT FROM AUTHOR]

Phytosiderophore (PS) release occurs under both iron and zinc deficiencies in representative Poaceac and has been speculated to be a general adaptive response to enhance the acquisition of micronutrient metals. We tested this hypothesis within an on-going study of the role of micronutrient metal nutrition for patterns of spontaneous vegetation in relation to soil pH and carbonate content. Hordelymus europaeus (L.) Harz, a negative grass species commonly found on soils rich in CaCO3 in Western Central Europe. was subjected lo deficiencies of Fe, Zn, Mn arid Cu using chelator-buffered nutrient solutions. PS release rates were determined at 3 5 d intervals during onset and development of deficiency symptoms. Plant dry matter yields and nutrient concentrations, measured at three time points were used to construct growth curves for calculation of PS release per unit root mass. In comparison with trace metal-sufficient control plants, dry matter production was markedly reduced in the Fe, Zn, Mn and Cu-deficiency treatments, with final relative yields of 6. 11. 15 and 31 % respectively. The phytosiderophore produced under Fe- and Cu-deficiency treatments was identified, using HPLC, as desoxymugineic acid. The highest rate of PS release (18 μmol g ¹ root d. wt in 2 h) was measured in the Fe-deficiency treatment, and there was substantial release in the Cu-deficiency treatment (725 μmol g ¹ root d. wt in 2 h) .No PS release above control levels (2.6 μmol g ¹ root d. wt in 2 h) was observed in the Zn- or Mn-deficiency treatments (1.5 and 26 μmol g ¹ root d. wt in 2 h, respectively). It remains to be clarified whether PS release in response to Cu deficiency is a primary reaction to the deficiency, or is caused by a chain of events similar to that observed in Zn-deficient wheat, which involves internal Fe deficiency. Our results suggest that PS release in the native plant species H. europaeus is a specific response to Fe and Cu deficiency arid is not significantly induced in response to deficiencies of Zn and Mn. Induction of the PS mechanism in different plant species might he more diverse than previously thought. [ABSTRACT FROM AUTHOR]