Tadeusz Baszyński

Differences in sensitivity of the photosynthetic apparatus in Cd-stressed runner bean plants in relation to their age

Abstract Cadmium effects depending on the time of its action and growth stage/age of Phaseolus coccineus were investigated. Three groups of plants at different growth stages of their primary leaves were treated with 25 μ M CdSO 4 . The photosynthetic activities and selected growth parameters of these plants were measured on days 4, 8 and 12 of the metal action and compared with their age-adequate controls. The responses of plants depended on the age of plants and time of Cd action. The younger the Cd-treated plants the bigger the changes in growth parameters observed but photosynthetic activity was almost unchanged during Cd action. With the age of plants their sensitivity to Cd increased and it was more related to the functioning of the photosynthetic apparatus than to the growth parameters. In the oldest Cd-treated plants the lowest activity of photosystem II was accompanied by disruption of the thylakoid membranes in comparison with control. A sensitivity of the photosynthetic apparatus in young Cd-treated plants is discussed with regard to the metal action causing free fatty acids or feedback inhibition of electron flow, while in older plants with regard to changes resembling plant senescence.

Characteristics of the Photosynthetic Apparatus of Copper Non-tolerant Spinach Exposed to Excess Copper

Summary Individual spinach plants ( Spinacia oleracea L., c.v. Matador) sensitive to excess copper were grown on a nutrient medium containing toxic amounts of the metal, and the characteristics of its photosynthetic apparatus were examined. In chloroplasts isolated from Cu-treated plants the accumulation of plastid pigments and lipoquinones was lower than in controls and it decreased with the increase of copper toxicity. The loss of photochemical activity of photosystem I and photosystem II was observed at the late stage of leaf degradation (the leaves turned yellow). The loss of photosystem II activity was faster than that of photosystem I. Consequently, changes in chlorophyll distribution of light harvesting chlorophyll-protein complexes were observed. The CPa level, being the presumable reaction center of photosystem II, decreased significantly. The fine structure of chloroplasts revealed degradation of grana stacks and stroma lamellae depending on the stage of their degeneration, an increase in the number and size of plastoglobuli and intrathylakoidal inclusions. The results obtained have been discussed with regard to direct or indirect effects of copper in chloroplasts of plants sensitive to excess copper.

In vivo response of photosynthetic apparatus of Phaseolus vulgaris L. to nickel toxicity

Summary We investigated the effect of in vivo Ni 2+ toxicity on the photosynthetic system of primary bean leaves ( Phaseolus vulgaris L. cv. Slowianka). The leaf area, chlorophyll and total carotenoid content showed a distinct decrease strictly related to the metal concentration in the nutrient medium and to the period of treatment. An analysis of the parameters of chlorophyll a fluorescence fast phase of induction kinetics revealed the lack of Ni 2+ effect of the primary photochemical processes in photosystem II. The measurements of photosynthetic electron transport under heavy metal influence, both in vivo and in vitro , and comparison with the results obtained from the analysis of the slow phase of the Kautsky curve allow us to postulate an indirect effect of nickel on photosystems related to the disturbances caused by the metal in the Calvin cycle reactions and down-regulation or even feedback inhibition of electron transport by the excessive amounts of ATP and NADPH accumulated due to non-efficient dark reactions.

Photosynthetic Apparatus of Spinach Exposed to Excess Copper

Summary The photosynthetic apparatus of spinach (Spinacia oleracea L. var. Matador) grown in sandy soil containing excess amounts of copper was investigated. In chloroplasts isolated from the leaves of copper-treated spinach the synthesis of plastid pigments and lipoquinones was slightly higher than in the controls, relative to the increase of copper content in the soil. Under experimental conditions the growth rate of roots was decreased but that of leaves and stems was almost unaffected. Photosystem II activity as measured by 2,6-dichlorophenolindophenol photoreduction was not influenced, but photosystem I activity measured in terms of O2 uptake and NADP photoreduction were slightly enhanced due to copper concentration. This increase was related to plastocyanin synthesis, the content of which was also dependent, to some extent, on the amounts of copper in the growth medium of the spinach. Among chlorophyll-protein complexes only CP1 depended on excess copper. Results obtained are discussed with regard to the tolerance of spinach exposed to high concentrations of the metal.

Age-dependent response of maize leaf segments to cadmium treatment: Effect on chlorophyll fluorescence and phytochelatin accumulation

The relationship between the age of leaf tissue and response of the photosynthetic apparatus and phytochelatin accumulation to Cd treatment was studied. Studies were carried out with seedlings of Zea mays L. cv. Hidosil grown in the presence of 100-200 mumol/L Cd for 14 days under low light conditions. The third leaf was divided into 3 segments of equal length differing in the stage of tissue maturity and used for measurements of chlorophyll content, chlorophyll fluorescence, glutathione and phytochelatin content and Cd accumulation. A close relationship between the age of leaf tissue and response of the photosynthetic apparatus to Cd was shown. Cadmium (200 mumol/L) reduced photochemical processes more in older than younger leaf segments as seen in the Chl fluorescence parameters Fv/F0, and t1/2, while the chlorophyll fluorescence decrease ratio (Rfd) was inhibited more strongly in younger ones. Fv/Fm was slightly affected. Cd-induced enhancement of GSH content was correlated with higher phytochelatin accumulation to a greater extent in younger than in older leaf segments. Phytochelatin level corresponded to changes of photochemical processes in older leaves. The peptide thiol:Cd molar ratio for the phytochelatins varied depending on Cd concentration and age of leaf segments. The protective role of phytochelatins for the photosynthetic apparatus is discussed.

Chlorophyll fluorescence in primary leaves of excess Cu-treated runner bean plants depends on their growth stages and the duration of Cu-action

Summary The functioning of the photosynthetic apparatus of runner bean plants (Phaseolus coccineus L., cv. Piekny Jaś) treated with excess Cu (20mgL−1 in the form of CuSO4 · 5H2O) at 5 successive growth stages of their primary leaves was studied. Chlorophyll fluorescence measurements were made on intact leaves or thylakoid membranes isolated from them after different times of Cu action from 3 to 12 days. It was shown that the plants exposed to copper at the intensive and intermediate growth stages were characterized by a lack of changes in the primary PS II photochemical processes. However, a simultaneous a potential quantum efficiency decrease was observed, pointing to intensified energy dissipation processes, as well as to a decrease of the vitality index values Rfd(except plants treated at the beginning of growth). The highest sensitivity of the photosynthetic apparatus to excess Cu occurred in the plants treated at advanced leaf growth stages. The presented data suggest that the observed fast decrease of photosynthetic efficency resulted from Cu-induced PSII complex destabilization connected with an inhibition of its donor side and the primary photochemical processes. At the same time as the inhibition of the electron flow through PSII a certain increase of the reduced QA pool occurred, pointing to a considerable weakening of reoxidation processes of the PSII acceptor side, possibly due to an inhibition of the Calvin cycle by Cu ions.

Different susceptibility of runner bean plants to excess copper as a function of the growth stages of primary leaves

Summary Runner bean plants ( Phaseolus coccineus L., cv. Piekny Jaś) grown hydroponically in Knop solution were treated with excess Cu (20mgL −1 in the form of CuSO 4 · 5H 2 O) at three different growth stages of primary leaves, and after 3–12 days of Cu action, respectively, their growth parameters and plastid pigment content were investigated. Moreover, photosynthetic O 2 evolution of chloroplasts isolated from plants treated with excess Cu at the different growth stages 10 days after the treatment was compared. The plants treated with Cu at the intensive leaf growth stage were characterized by fast and strong growth (measured as leaf area), a fresh weight decrease and a simultaneously increased chlorophyll content in comparison with the control, indicating some inhibition of elongation processes. Relatively smaller changes in growth parameters that were correlated with some modifications of the specific leaf area (calculated per fresh weight), leaf density and pigment composition were observed in the plants treated with Cu at an intermediate growth stage. However, at a longer exposure to Cu there occurred a tendency of Chl a/b and Chl/Car ratios to decrease. These changes, depending on the time of Cu action, were much more distinct in the plants treated with Cu at the stationary growth stage of primary leaves. A simultaneous decrease in leaf tissue density and enhanced specific leaf area, which contributes to an enlarged area for water loss, correlated with chlorophyll content reduction, indicated that a leaf senescence increase was presumably a consequence of water deficiency. In the plants treated with Cu at this stage of leaf growth, photosynthetic O 2 evolution decreased significantly.

The effect of copper deficiency on the photosynthetic apparatus of higher plants

Summary The effect of copper deficiency on the photochemical reactions, plastid pigments and lipoquinones of oat and spinach chloroplasts was investigated. The synthesis of all thylakoid prenyl lipids as well as of chlorophylls was lower during copper deficiency. The inhibition was observed to a different degree for the individual lipids. The formation of plastoquinones (C45-chain) was much more strongly inhibited than that of phytol derivatives and carotenoids. The rates of photosynthesis, expressed as O2 evolved per leaf area, were lower in the deficient than in the control plants. On the basis of chlorophyll, the O2-evolution was slightly higher in deficient plants. The Photosystem I activity of deficient chloroplasts measured in terms of O2-uptake and the photoreduction of NADP from water was much lower than that of the control ones. Cyclic photophosphorylation was inhibited to the same degree. Photosystem II activity was affected to a lesser extent. Plastocyanin and total copper content in deficient chloroplasts decreased over 50% in comparison with control chloroplasts. The effect of copper deficiency on electron transport was discussed with regard to the plastocyanin content of the chloroplasts.

Calcium modifies Cd effect on runner bean plants

The effect of different Ca concentrations in the growth medium on the toxicity of 25 mu M CdSO4 was studied in runner bean plants (var. Piekny Jas) at two different growth stages of primary leaves. ...

Changes in acyl lipid and fatty acid composition in thylakoids of copper non-tolerant spinach exposed to excess copper

Summary The effect of toxic concentrations of Cu on acyl lipid and fatty acid composition in thylakoid membranes of non-tolerant spinach plants exposed to excess Cu was investigated. In Cu-treated plants a decrease in acyl lipid content and changes in its molar distribution were found. Thylakoid lipid degradation was accompanied by changes in fatty acid composition, especially that of 18:3, 16:1 and 16: 0. The obtained results are discussed in terms of the indirect effect of long term action of excess Cu on the thylakoid membrane structure and decrease of its photochemical activities.