Analysis of the electronic asymmetry of the primary electron donor of photosystem I of <i>Spirodela oligorrhiza</i> by photo-CIDNP solid-state NMR

The electron donor in photosystem I, the chlorophyll dimer P700, is studied by photo-CIDNP (photochemically induced dynamic nuclear polarization) MAS (magic-angle spinning) NMR on selectively 13C and uniformly 15N labeled PSI core preparations (PSI-100) obtained from the aquatic plant duckweed (Spirodela oligorrhiza). Light-induced signals originate from the isotope labelled nuclei of the cofactors involved in the spin-correlated radical pair forming upon light excitation. Signals are assigned to the two donor cofactors (Chl a and Chl a') and the two acceptor cofactors (both Chl a). Light induced signals originating from both donor and acceptor cofactors demonstrate that electron transfer occurs through both branches of cofactors in the pseudo-C2 symmetric Reaction Center (RC). The experimental results supported by quantum chemical calculations indicate that this functional symmetry occurs in PSI despite similarly sized chemical-shift differences between cofactors of PSI and the functionally asymmetric special-pair donor of the bacterial RC of Rhodobacter sphaeroides. This contributes to converging evidence that local differences in time-averaged electronic ground-state properties, over the donor are of little importance for functional symmetry breaking across photosynthetic RC species.

Molecular forms of phosphatase and ribonuclease in phosphate deficient and N,N-dimethylmorpholinium chloride treated Spirodela oligorrhiza (Lemnaceae)

Soluble, membrane bound, and extracellular phosphatases (EC 3.1.3.2 and 3.1.3.1) of control, N,N-dimethylmorphołinłum chloride (DMMC) treated, and phosphate deficient (-P) axenic <i>Spirodela oligorrhiza</i> plants were analysed by Sephadex G-150 gel filtration. Soluble, acid enzymes of control plants were separated into two molecular forms with apparent MW ≥ 400 000 and 85 000. Phosphatase with MW 34 000 replaced the latter isoenzyme in the presence of DMMC. Two alkaline enzymes with apparent MW 210 000 and 36 000 were detected in -P plants. Triton X-100 solubilized a number of acid and alkaline phosphatases from membrane material. DMMC caused the appearance of two membrane bound enzymes (MW 48 000 and 14 000) which were not detected in the control. Senescimg control and DMMC treated plants released an acid phosphatase (MW 48 000; pH optimum 5.2) into the nutrient medium. -P plants released, in addition ,an alkaline phosphatase (MW 170,000; pH optimum 7.8-8.2). Ribonucleases (EC 2.7.7.17.) with apparent MW 31000 and 28 000 daltons were induced by DMMC and -P, respectively.

The growth-retarding effect of daminozide in Spirodela oligorrhiza (Kurz) Hegelm., and its reversal by gibberellin

Butanedioic acid mono-(2,2 dimethylhydrazide) (daminozide), in a concentration of 10^-3 M retarded growth of <em>Spirodela oligorrhiza</em> and increased chlorophyll and protein content in the fronds. Gibberellin A₃ and benzylaminopurine partially alleviated the symptoms of daminozide action.

Preliminary estimation of physiological activity of 9-amine-9-fluorenephosphonic acid derivatives

The physiological activity of twenty one 9-amine-9-fluorenephosphonic acid derivatives was tested. The compounds were synthesized by the Wrocław Technical University. <i>Spirodela oligorrhiza</i> was used as the test plant. There was tested the inhibiting influence of these compounds on the growth of <i>Spirodela</i> and synergism with the herbicide "mecoprop". Ethyl esters substituted at the nitrogen atom with buthyl and heptyl group appeared to be most active. Their concentration of 0.5-1.5 × 10^-5 M inhibited the growth of <i>Spirodela</i> by 50%. Most of the 9-amine-9-fluorenephosphonic acid derivatives tested with different substitutes showed a strong synergism with the herbicide "mecoprop". An addition of these compounds to sublethal solution of the herbicide killed <i>Spirodela</i> within 10-20 houres.

An evaluation of the physiological activity of 9-amine-9-fluorenephosphonic acid derivatives

The physiological activity of eleven 9-amine-9-fluorenephosphonic acid derivatives, synthesized at the Wrocław Polytechnic, was examined. The test plant was <i>Spirodela oligorrhiza</i>. The effect of these compounds on the increase of the dry matter of this plant was tested in eight-day experiments. The activity of the compounds was varied. The most toxic were nos. 2, 4, 9, 8, 5 and 6 which were lethal in low concentrations. Somewhat less toxic were nos. 7, 10 and 11; nos. 1 and 3 were the least toxic.