Ferenc Láng

Effects of Pb and Cd on Cucumber Depending on the Fe-Complex in the Culture Solution

Summary Modifying effects of EDTA and citrate as Fe(III)-complexes on Pb-and Cd-toxicity were investigated with cucumber ( Cucumis sativus L.) grown in culture solution. Pb and Cd were applied in lO μM concentration. Pb and Cd inhibited the growth of plants with Fe-citrate but with Fe-EDTA only Cd did. Chlorophyll content of Cd-treated plants-independently on the Fe-complex-was very low similarly to the iron deficient plants. Pb is proved to inhibit the chlorophyll accumulation only in plants supplied with Fe-citrate. Photosynthetic activity of 6-week-old plants was characterized by in vivo CO 2 fixation. The highest activities were observed in the middle (third-fourth) leaf storeys, and decreased in the lower and higher leaf storeys. Cd caused more than 50 % inhibition of the photosynthetic activity when applied with Fe-EDTA. With Fe-citrate, the inhibition exceeded 90 %. The photosynthetic activities in the Pb-treated plants were not significantly different from the control plants. The amount of chlorophyll containing complexes, especially that of PS I was highly affected by Cd particularly in the lower leaves. The results correlate with 59 Fe translocation into the shoot. Fe translocation was stimulated by Pb in the presence of Fe-EDTA but it was inhibited in the presence of Fe-citrate. Cd completely inhibited Fe translocation from the root to the shoot with both chelators. It is concluded that strong iron deficiency has a great but not exclusive role in the observed symptoms, and that the quality of the chelator strongly influences the effects of these polluting metals.

Apparatus and Method for Rapid Determination of Photosynthetic CO2 Fixation of Leaves

Summary A simple apparatus and a rapid and sensitive isotope method for determination of photosynthetic CO2 fixation of seedlings, whole leaves or leaf segments is described. The apparatus consists of two main parts: the 14CO2 evolving system and a closed illuminated glass chamber for 14CO2 fixation. The samples are introduced into the glass chamber through a Hg-blockade without ceasing the closeness of the inner gas space. The apparatus is very useful in cases when rapid determination of CO2 fixation in great number of samples is needed.

Stability of sunflower 2S albumins and LTP to physiologically relevant in vitro gastrointestinal digestion

In order for a protein to elicit a systemic allergic response it must reach the circulatory system through the intestinal mucosa as a sufficiently large fragment with adequate structural integrity. Sunflower LTP and 2S albumins (SFA8 and three mixed fractions of Alb1 and Alb2) were digested in simulated gastric fluid (SGF) for 2h and the conditions were then changed to mimic the intestinal environment for a further 2h digestion. The effects of phosphatidylcholine (PC) and emulsification on the digestibility of the proteins were investigated. PC protected all of the proteins studied against both gastric and intestinal digestive enzymes but to different extents. Emulsification of SFA8 resulted in strong protection against digestion, which was further enhanced by the presence of PC in the SGF. These results highlight the importance of considering real food structures such as emulsified systems and also the gastrointestinal environment that proteins are exposed to once consumed when assessing allergenicity.

Structural stability and surface activity of sunflower 2S albumins and nonspecific lipid transfer protein

The structural and interfacial properties of five different fractions of sunflower ( Helianthus annuus L.) seed storage proteins were studied. The fractions comprised lipid transfer protein (LTP), the methionine-rich 2S albumin SFA8 (sunflower albumin 8), and three mixtures of non-methionine-rich 2S albumins called Alb1 and Alb2 proteins (sunflower albumins 1 and 2). Heating affected all of the proteins studied, with SFA8 and LTP becoming more surface active than the native proteins after heating and cooling. LTP appeared to be less thermostable than homologous LTPs from other plant species. SFA8 generated the greatest elastic modulus and formed the most stable emulsions, whereas LTP showed poorer emulsification properties. The mixed 2S albumin fractions showed moderate levels of surface activity but had the poorest emulsification properties among the proteins studied.

Organization of Thylakoid Membranes in Low-Light Grown Maize Seedlings. Effect of Lincomycin Treatment

Summary Etiolated maize seedlings were greened under extreme low-light intensity (25 lux). Pigment content, chlorophyll-protein composition, polypeptide pattern, photochemical activity and ultrastructure of mesophyll chloroplasts were studied. It was found that mainly chlorophyll a protein complexes were formed. The amount of light-harvesting chlorophyll-protein complexes and grana stacks were strongly reduced. The light intensity dependence of photochemical activities of these plastids referred to the presence of photosystems I and II of smaller size. After lincomycin treatment (inhibiting the synthesis of reaction centers and inner antennae) stabilization of light-harvesting chlorophyll a/b complexes of photosystems I and II were allowed. The role of the light regime and chlorophyll accumulation in the assembly and stabilization of light-harvesting chlorophyll-protein complexes is discussed.

Fluorescence Spectroscopy of Iron-Deficient Plants

Iron deficient cucumber (Cucumis sativus L.) plants and such differently supplied with iron were studied by low-temperature fluorescence emission and excitation spectroscopy. Iron deficiency caused a relative decrease and a blue-shift of the 733 nm emission and a decrease or disappearance of the 700 and 707-710 nm excitation bands which are considered to belong to chlorophyll forms of PSI. The process of iron uptake was observed after readdition of iron to previously iron-stressed plants. Iron-deficient plants (with green cotyledon) were treated with the chelator EDTA which treatment resulted in a small increase of the chlorophyll content but the fluorescence spectra of these plants differed from those of plants supplied with iron: they had blue-shifted maxima. The data presented show that fluorescence spectroscopy is a very sensitive and suitable method for studying iron deficiency, observing - indirectly - iron uptake and its utilization in plants.

Influence of Cd and Pb on the Ion Content, Growth and Photosynthesis in Cucumber

The high toxicity of Cd and Pb for plant metabolism is well known (1). Inhibition of growth (2) and metabolic processes including photosynthesis (3), nitrate assimilation (4), protective mechanisms (5), and disturbances of ion- (6) and water balance (7) of plants have been described. Their effect can be considerably modified by the composition of the culture solution (6) and the developmental stage of the plants (2). Photosynthesis was shown to be influenced at the level of chlorophyll synthesis (8), electron transport (3) and activity of Calvin cycle enzymes (9). Though the effects of heavy metals on photosynthesis have been intensively studied, their basic impact is still debated (3). We investigated the effects of Cd and Pb on the photosynthetic processes in relation to metal and water content in the sensitive cucumber plants in order to find specific factors correlating with the inhibition of the examined processes. Plants were treated in young and more developed stage to understand the differences in the toxic effects of heavy metals between developing and mature plants and leaves.

Time Course of the Appearance of Cd Effects on Photosynthetically Competent Poplar Leaves

Cd effects on photosynthetic performance of the third leaf of hydroponically cultured poplar (Populus glauca var. Kopeczkii) plants were followed during a 2-week treatment with 10 μM Cd(NO3)2. Growth and chlorophyll concentration were reduced by about 20%. Chlorophyll a/b ratio was strongly lowered due to the stronger reduction in the amount of photosystem I than that of lightharvesting complex II. A delayed and fast decrease in the transcript levels of lhca1 and lhca2–4 genes, respectively, and a transient increase in those of lhca5 and lil1 were detected by quantitative RTPCR. Actual quantum efficiency of photosystem II did not change in spite of an early (after second day) decrease in stomatal conductance and CO2 fixation probably due to the increased photorespiration rate (elevated glycolate oxidase activity). Decline in ascorbate peroxidase activity resulted in a moderately higher malondialdehyde level in leaves. In conclusion, decreased stomatal conductance/CO2 fixation and thylakoid reorganization were the first detectable symptoms of Cd treatment in photosynthetically competent leaves.

Effect of combined stress on the O2 scavenging enzyme activities in bean and poplar leaves

Wounding, Drought, Elicitation, Catalase, Peroxidase The activity of O2-scavenging enzymes in bean leaves in different positions and poplar leaves in different leaf storeys was investigated. The effects of wounding, elicitation and drought and the combination of these treatments at various levels were studied. Distal bean leaves showed higher responsiveness than those opposite the treated leaves. Poplar leaves above the treated ones proved to be more active than those in lower storeys. A comparison of the interaction of different stress treatments revealed both synergistic and antagonistic effects on the oxidant-generating rate and anti-oxidant synthesis of damaged and non-damaged plant tissues

Effect of Cd and Pb on Photosynthesis in Cucumber

Heavy metal pollution strongly affects plant metabolism including photosynthesis. The effects of Cd and Pb (10 δM) on photosynthetic apparatus were investigated at different leaf storeys of hydroponically cultured (4 δM Fe chelated with either EDTA or citrate) cucumber plants. Cd given from the fourth-leaf stage of plants retarded their growth, particularly that of roots and reduced the amount of all pigment containing complexes in thylakoids, the PSII core being a little more resistant. The organization of treated thylakoids seemed to be very similar to that of iron deficient plants. Pb caused similar but moderate changes. EDTA exerted a protective effect. Fluorescence induction parameter Fv/Fm showed a slight change. However, severe inhibition of CO2 fixation was observed at all leaf storeys.