Leachate toxicity assessment by responses of algae Nitellopsis obtusa membrane ATPase and cell resting potential, and with Daphtoxkit F magna test.

A microscale bioassay based on 50% inhibition of K(+), Mg(2+)-ATPase activity in a microsomal fraction isolated from Nitellopsis obtusa cells was developed. Compared to that for a plasma membrane fraction purified in a sucrose gradient, the preparation procedure for a microsomal fraction is less time consuming and the yield is substantially higher. Characteristics of the microsomal preparation proved to be similar to those of the highly purified plasma membrane preparation (Manusadzianas et al., 2002), at least for heavy metals. Sensitivity to CuSO(4) of the frozen (-8 degrees C) microsomal fraction [49 +/- 17 (SD) microM; n = 8] did not significantly differ from that of the freshly isolated one (52 +/- 30, n = 8), at least for 40 days. Toxicity of leachate water from Kairiai (northern Lithuania) solid waste landfill was assessed by taking samples from various points including temporary reservoirs and analyzing them immediately after spillage (summer 2002) and after storage for almost 2 years at 4 degrees C-6 degrees C. Two tests with the macrophytic alga Nitellopsis obtusa (Charatox, 45-min EC(50) of resting potential depolarization, and ATPase assay, IC(50) of membrane ATPase activity) and one test with the crustacean Daphnia magna (Daphtoxkit F, 48-h 50% immobilization) tests were used. In general, all three tests showed successively decreasing values of landfill leachate toxicity with an increasing degree of dilution with surface waters. The possibility of employing preserved algal preparations on demand in test batteries seems to be promising, especially in emergencies.

Plant gravitropic response.

The gravitropic response of plants to a change in the gravity vector may be divided. in the phase of induction and expression. During the induction phase the amyloplasts, due to their greater density than the cytoplasmic density, shift their position in less than a minute. During this shift there is an interaction with the endoplasmic reticulum, although a role of actin-like proteins of the cytoskeleton may also be involved in this process. The endoplasmatic reticulum maintains a store of sequestered calcium through the action of an ATP-dependent calcium uptake mediated by the Ca2+, Mg(2+)-ATPase system present in the membrane of this organelle. The interaction of the amyloplast with the endoplasmic reticulum leads to the release of free calcium ions from the endoplasmic store. The increased free Ca2+ level in the cytoplasm may modify the activities of certain enzymes and receptor proteins. The gravitropic induction phase is completed when the lateral polarization of the tissues has taken place. These tissues contain information about changes in direction of the IAA transport system and in competition of the IAA-receptor system for the phytohormone. This information is fixed in "memory" and its expression is achieved when the lateral gradient of IAA concentration and of the activity of the IAA-receptor protein complexes is formed in the horizontally oriented plant organ. Flows of IAA and calcium ions in opposite directions may lead to the expression of laterally differentiated growth.