Eugeniusz Parys

The effect of lead on photosynthesis and respiration in detached leaves and in mesophyll protoplasts of Pisum sativum

Photosynthesis and transpiration rate of detached leaves of pea (Pisum sativum L. cv. Iłowiecki) exposed to solution of Pb(NO3)2 at 1 or 5 mmol·dm−3 concentrations were inhibited. The higher concentration of this toxicant decreased photosynthesis and transpiration rates 2 and 3 times respectively, and increased respiration by about 20 %, as measured after 24 hours of treatment. Similarly to Pb(NO3)2, glyceraldehyde solution, an inhibitor of phosphoribulokinase, at 50 mmol·dm−3 concentration decreased the rates of photosynthesis and transpiration during introduction into pea leaves. The rate of dark respiration, however, remained unchanged during 2 hours of experiment.The potential photochemical efficiency of PS II (Fv/Fm) and the activity of Rubisco (EC 4.1.1.39) at 5 mmol·dm−3 of Pb(NO3)2 were lowered by 10 % and 20 % respectively, after 24 hours. Neither changes in the activity of PEPC (EC 4.1.1.31) or protein and pigment contents were noted in Pb-treated leaves. The photosynthetic activity of protoplasts isolated from leaves treated for 24 or 48 hours with Pb(NO3)2 at 5 mmol·dm−3 concentration was decreased 10 % or 25 %, whereas, the rate of dark respiration was stimulated by about 40 % and 75 %, respectively. The content of abscisic acid, a hormone responsible for stomatal closure, in detached pea leaves treated for 24 h with 5 mmol·dm−3 of Pb(NO3)2 solution was increased by about 3 times; a longer (48h) treatment led to further increase (by about 7 times) in the amount of this hormone. The results of our experiments provide evidences that CO2 fixation in detached pea leaves, at least up to 24 hours of Pb(NO3)2 treatment, was restricted mainly by stomatal closure.

Effect of coumarin and xanthotoxin on mitochondrial structure, oxygen uptake, and succinate dehydrogenase activity in onion root cells.

At concentrations in which they occur on the plant surface and retard mitosis, coumarin and xanthotoxin lowered uptake of oxygen (by 60 and 30%, respectively) by meristematic cells ofAllium cepa root tips. They caused changes in the structure of the mitochondrial matrix to become dense, and protrusions of mitochondrial membranes were visible parallelling their hypertrophy, indicating alteration in the structure and physiology of these organelles. Coumarin and, to a lesser extent, xanthotoxin increased succinate dehydrogenase production in mitochondria and also in the cytoplasm, indicating changes in membrane permeability. Changes in oxygen uptake and mitochondrial structure, in addition to the retardation of mitosis, may be the reason these compounds act as allelochemicals after they have been removed from the plant surface and reach the root meristem.

Relationship between postillumination burst of CO2 and enhancement of respiration in tall fescue leaves

The postillumination burst (PIB) of CO2 and light-enhanced dark respiration (LEDR) depending on oxygen concentration, temperature, respiratory substrates and photorespiratory inhibitor aminoacetonitrile (AAN) were investigated in detached leaves of tall fescue (Festuca arundinacea) using a closed circuit system with an infrared gas analyzer. No PIB was observed in 1 % O2 under temperature over the range from 15 °C to 35 °C. The rate of LEDR was about twice as low in 1 % O2 as that in 21 and 50 % O2 under all temperatures applied. The PIB was absent and LEDR decreased at 21 % O2 following illumination of leaves for 1 hour at 1 % O2. When 200 mM glycine or malate solutions were introduced into the leaves of tall fescue, the magnitudes of PIB increased by about 60 and 40 % and rate of LEDR by about 70 % and 40 %, respectively. Pyruvate and succinate were less effective in promotion of PIB and LEDR. AAN had a small stimulatory effect on PIB and LEDR (about 20 % and 10 %, respectively). The dependences between magnitudes of PIB and rates of LEDR were highly correlated (r=0.94). The results presented indicate that atmospheric concentration of oxygen during the period of photosynthesis of tall fescue leaves was necessary not only for occurrence of PIB and LEDR but also for production of substrate(s) (glycine and/or malate) for these phenomena.

The Toxicity of Lead to Photosynthesis and Respiration in Detached Pea and Maize Leaves

Lead or cadmium introduced into mature leaves of C3 or C4 plants caused inhibition of photosynthesis (Pn) and stimulation of respiration (R) (1.2,3). According to current knowledge the inhibition of photosynthesis by heavy metals results from inactivation of key photosynthetic enzymes, i. e. RuBPC and PEPC (4) as well as from limitation of the reaction steps of the Calvin cycle (5). but not by interaction with photochemical reactions located on the thylakoid membranes. The increase of the rate of respiration (3) usually noted with Pb or Cd is not well understood. The aim of our work was to compare the sensitivity of C3 and C4 plants in relation to photosynthetic and respiratory activities in lead treated plants.

The effect of light quality and gibberellic acid (GA3) on photosynthesis and respiration rates of pea seedlings.

CO2 exchange were measured on pea seedlings (Pisum sativum L. var. Bördi) cultivated from seeds imbibed either in water (C-plants) or in gibberellic acid (GA3) at the concentration of 25 μg/1 (GA-plants), and then grown under 17 W/m2 blue light (B-plants) or 11 W/m2 red light (R-plants).When measured under the same light conditions as during growth the net photosynthesis (APS) rate in B-plants was about twice higher than that in R-plants. Dark respiration (DR) rate was 70% higher in B- than in R-plants. Red light retarded the development of photosynthetic activity, but GA3 suppressed this effect. The hormone enhanced net photosynthesis and dark respiration to the same extent.When measured under saturating white light net photosynthesis rate of C-plants was also two times higher in B-plants than in R-plants. Growth conditions had only a slight effect on the APS of GA-plants under white light. APS rates of GA-plants grown under red light were higher under white light than those of C-plants, but lower than those of plants grown under blue light.We assume that blue light induced formation of plants that were adapted to higher light intensity: red light had an opposite effect, whereas gibberellic acid induced formation of plants that were adapted to medium light intensity.

Mechanical Isolation of Bundle Sheath Cell Strands and Thylakoids from Leaves of C4 Grasses

Bundle sheath (BS) strand cells and BS thylakoids from C4 plants represent a unique system for various studies using a combination of physiological, biochemical, and molecular approaches. We have developed procedures for mechanical disruption of leaf tissues in order to isolate metabolically active bundle sheath strand cells and thylakoids practically free from cross-contamination coming from mesophyll cells. The procedures are described in detail together with useful practical suggestions. Using mechanical disruption we have shown the supramolecular organization of the dimeric LHCII-PSII in BS thylakoids of maize.

Light-enhanced dark respiration in leaves and mesophyll protoplasts of pea in relation to photorespiration, respiration and some metabolites content

The respiration rate of leaves and mesophyll protoplasts of pea (Pisum sativum L.), from plants which were previously kept in darkness for 24 h was doubled following a period of photosynthesis at ambient level of O2 (21 %), whereas the low level of O2 (1 % and 4 % for leaves and protoplasts, respectively) reduced this light-enhanced dark respiration (LEDR) to the rate as noted before the illumination. Similarly to respiration rate, the oxygen at used concentrations had no effect on the ATP/ADP ratio in the dark-treated leaves. However, the ATP/ADP ratio in leaves photosynthesizing at 21 % O2 was higher (up to 40 %, dependence on CO2 concentration in the range 40–1600 1 dm−3) than in those photosynthesizing at 1 % O2 or darkened at air (21 % O2). Also, at 1 % O2 the accumulation of malate was suppressed (by about 40 %), to a value noted for leaves darkened at 21 % O2. The dark-treatment of leaves reduced the ability of isolated mitochondria to oxidize glycine (by about twofold) and succinate, but not malate. Mitochondria from both the light- and dark-treated leaves did not differ in qualitative composition of free amino acids, however, there were significant quantitative differences especially with respect to aspartate, alanine, glutamate and major intermediates of the photorespiratory pathway (glycine, serine). Our results suggest that accumulation of photorespiratory and respiratory metabolites in pea leaves during photosynthesis at 1 % O2 is reduced, hence the suppression of postillumination respiration rate.

Influence of 1,10-phenanthroline, a photodynamic herbicide, on the ultrastructure of mesophyll cells and photosynthetic activity in greening pea seedlings

Abstract We have examined the ultrastructure of mesophyll cells and photosynthetic activity induced by a photodynamic herbicide, 1,10-phenanthroline (Phe), in greening pea seedlings. Greening pea seedlings treated in darkness and subsequently illuminated were resistant to low doses (2 mM) of Phe. Pea plants treated with 10 or 20 mM Phe were susceptible to light, CO2 evolution in Phe-treated plants proceeded at a much higher rate than the rate of CO2 uptake. Net photosynthesis rate (Pn) was extremely low in Phe-treated plants. Ultrastructure of mesophyll cells was the same in control, Phe 10 and Phe 20 plants before transfer of plants to light. Differences between control and Phe-treated plants became visible after 4 hr of illumination and increased during 9 hr of illumination. This difference was manifested in thylakoid swelling, dilation of endoplasmic reticulum (ER) cisternae, degeneration of internal mitochondrial membranes and disruption of chloroplast envelopes. There were starch grains in control but not in Phe-treated plant mesophyll cells. A standard photoinhibition mechanism might explain the destruction caused by phenanthroline and subsequent illumination. In the present paper we suggest another possible mechanism, also based on chelating properties of Phe, which could directly cause membrane depolarization and thus change membrane permeability. One of these mechanisms might explain the structural and functional effects of Phe action.

The Release of CO2 from Tall Fescue Leaves Following Photosynthesis under Photorespiratory and Non-Photorespiratory Conditions

The two main transient phenomena in the course of CO2 evolution can be recorded when leaf of C, plant photosynthesizing in air is suddenly darkened. The first represents the postillumination burst of CO2 (PIB), a phenomenon originally described by Decker (1) from that the existence of photorespiration was first deduced. After that follows a period of increased respiration, a phenomenon termed light-enhanced dark respiration (LEDR) (2). Generally similar sensitivity of PIB and enhanced respiration to oxygen observed in tall fescue leaves (3) suggests the contribution of photorespiratory substrates. However, the solution of bicarbonate introduced into these leaves greatly enhanced both phenomena under photorespiratory conditions. The promotion of LEDR by bicarbonate have also been observed in mesophyll protoplasts of pea (4). Information on the effect of temperature on the transient CO2 exchange phenomena under various O2 concentrations is limited. Only the response of PIB to temperature at 21% O2 has been studied (5). The purpose of the present study was to examine of how a temperature affects PIB and enhanced respiration in tall fescue leaves under photorespiratory (21 and 50% O2) and non-photorespiratory (1% O2) conditions.

Gibberellin-like activity in pea seedlings during growth under red, blue and white light

The influence of blue, red and white light and gibberellic acid (GA3) on gibberellin-like activity in tissue extracts of leaves, stems and roots was investigated during growth of pea seedlings (Pisum salivum L. cv. Bördi). Higher GA-like activity was found in leaves and stems of pea plants that were growing in blue light than in those under red or white light. Patterns of change of activity were different in leaves, stems and roots, and in GA3-treated plants.