To study the involvement of NAD(H) in the activation of respiration after wounding of potato tubers, redox ratios of free cytoplasmic NAD have been determined via the pyruvate/lactate and the oxaloacetate/malate couple. These ratios change after wounding of intact tubers parallel to those of the far more oxidized total extractable NAD(H) pool. In wounded tuber tissue a positive correlation is observed between the redox state of NAD and the respiration rate. Temperature acclimatization of the tubers before wounding delays the establishment of that correlation.

Sucrose density gradient centrifugation of homogenates from dormant or differentiating potato tuber tissue (Solanum tuberosum L. cv. Bintje) showed an increase during differentiation of peroxisomes (s. d. 1.25-1.26), mitochondria (s. d. 1.19-1.20) and acid phosphatase-containing membrane fractions (s.d. 1.18-1.24). The organelles were identified by markerenzyme distribution and by electronmicroscopy of the pooled fractions.

Enzyme cytochemistry demonstrated catalase and peroxidase activity in cells of potato tubers (Solanum tuberosum cv. Bintje); catalase was localized in peroxisomes and peroxidase in the cell walls and Golgi bodies.

The coenzyme-specificity of lactate dehydrogenase, malate dehydrogenase and malic enzyme from the potato tuber (Solanum tuberosum cv. Bintje) has been studied, since in different plant tissues the three enzymes are described to exhibit activity with both NAD and NADP.

After mechanical injury of potato tubers (Solanum tuberosum L. var. Bintje) the levels of NAD+, NADH, NADP+ and NADPH were determined in extracts of the tuber tissue and its mitochondrial fraction. The incubation periods after wounding varied from five hours to three days.

1.1. The Cu uptake by Lymnaea stagnalis, from Na-containing solutions of ⋍2 × 10+3 M Na and 5× 10−5 M CuSO4 causes in the kidney losses of Na and Cl of ⋍30 per cent parallel to an increase in Cu content of ⋍40 per cent.2.2. The water content in the kidney increased after Cu treatment.3.3. The Na losses in the kidney were explained by inhibition of active Na reabsorption.4.4. The concentration of Br increased after Cu treatment.5.5. The increased water content in the kidney was explained by increased water influx from body-fluids and less effective Na exchange.

1. 1. The Cu uptake by Lymnaea stagnalis , from Na-containing solutions of ⋍2 × 10 +3 M Na and 5× 10 −5 M CuSO 4 causes in the kidney losses of Na and Cl of ⋍30 per cent parallel to an increase in Cu content of ⋍40 per cent. 2. 2. The water content in the kidney increased after Cu treatment. 3. 3. The Na losses in the kidney were explained by inhibition of active Na reabsorption. 4. 4. The concentration of Br increased after Cu treatment. 5. 5. The increased water content in the kidney was explained by increased water influx from body-fluids and less effective Na exchange.

1.1. Al, Au, Br, Cl, Cu, K, Mg, Mn, Mo, Na, Sb, Sr, Sn, V and Zn were demonstrated in parts of the gonadal system of Lymnaea stagnalis. Except for Sr and Al these elements were also present in the kidney.2.2. Several organs seem to possess a specific elemental composition. Al is present in large quantities in the eggs, Br in the pars contorta and Mn in the albumen gland.3.3. The eggs capsule contains relatively low quantities of Mg and Mn. In the albumen gland Mg was not detectable. This phenomenon is correlated with the galactose-glucose metabolism in this organ.4.4. The kidney, eggs, egg capsule and ovotestis contain low quantities of Mn.5.5. The Na/Cl ratio varies per tissue.