The effects of capture, net retention and preservation upon lengths of larval and juvenile bass, Dicentrarchus labrax (L.)

Relationships between live and preserved lengths of larval and juvenile bass, Dicentrarchus labrax , subjected to simulated capture, net retention and preservation were investigated. Bass larvae and juveniles shrank during the period of net retention following death. Preserved lengths of larvae, but not of juveniles, decreased significantly when increased periods of net retention preceded preservation. The time which larvae or juveniles remained in 4% formaldehyde in distilled water buffered with 3gl⁻¹ sodium acetate trihydrate or in 70% ethanol in distilled water neutralized with 1gl⁻¹ calcium carbonate powder, had no significant effect upon preserved length. Appropriate data were pooled to calculate transformation factors for estimating live from preserved length. Shrinkage phenomena, and their effects, are discussed. It is suggested that larval bass captured and preserved during standard ichthyoplankton surveys are unsuitable for determination of live length.     

The Effect of Leaf Age on Gas Exchange and Malate Accumulation in C3-CAM Plant Marrubium Frivaldszkyanum (Lamiaceae)

For the first time the expression of C₃ and CAM in the leaves of different age of Marrubium frivaldszkyanum Boiss, is reported. With increasing leaf age a typical C₃ photosynthesis pattern and high transpiration rate were found. In older leaves a shift to CAM occurred and the 24-h transpiration water loss decreased. A correlation was established between leaf area and accumulation of malate. Water loss at early stages of leaf expansion may be connected with the shift to CAM and the water economy of the whole plant.     

Modeling productivity of a salt marsh

A model of primary productivity in a salt marsh is developed and compared to a regression analysis study of data showing dependence of growth on growing season, mean tidal height, and average monthly temperatures for several grass species.     

Aluminium modulation of the photosynthetic carbon reduction cycle in Zea mays

Two-weeks-old maize (Zea mays L. cv. XL-72.3) plants were submitted to Al concentrations of 0-81 g m-3 for 20 d, after which the A1 concentration-dependent effects on CO2 uptake by the mesophyll tissue and subsequent CO2 assimilation in the photosynthetic carbon reduction cycle of bundle sheath cells were investigated. The net photosynthetic rate (PN) and stomatal conductance (gs) increased continuously up to 27 g m-3 Al, whereas the intercellular CO2 concentration showed minimum values with the 27 g m-3 Al treatment. Moreover, the starch and saccharide concentrations, and fructose-1,6-bisphosphatase did not change significantly with increasing Al concentrations. The photosynthetic electron transport rates along with photosystems 2 and 1 started falling from 9 g m-3 Al onwards, while thylakoid acyl lipid composition did not show a clear pattern. With the Al concentration at 81 g m-3, NADP-malate dehydrogenase activity decreased to minimum values, whereas the opposite occurred with those of pyruvate dikinase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase. Thus in vivo Al concentrations modulate the photosynthetic reduction cycle, possibly by interacting with the carbon flow rate exported to the cytosol. Although the inhibition of NADP-malate dehydrogenase activity might limit pyruvate dikinase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase activities, in vivo the balance between phosphoenolpyruvate production and its carboxylation remains unaffected.