The mechanism of the NH4 ion oscillatory transport across the excitable cell membrane

This paper presents results on typical oscillations of the membrane potential induced by the excitation of the cell membrane by different concentrations of the NH4Cl solution. The existence of four classes of oscillations of the membrane potential and several different single and local impulses rhythmically occurring were determined. It is known that the oscillatory processes of the membrane potential are in direct dependence on oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane. A hypothesis on a possible mechanism of oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane is also presented

Photosynthetic pigments and phytochemical activity of photosynthetic apparatus of maize (Zea mays L.) leaves under the effect of thiamethoxam

In the last decade, neonicotinoid insecticides have been actively used to protect plants from pests. Moreover, their effect on the plants, in particular on the state of photosynthetic pig-ments, has been studied paucity. In the present work, it was shown for the first time that treatment of maize (Zea maysL.) leaves with a thiamethoxam (TMX) insecticide leads to a decrease in the functional activity of photosystem II and a decrease in the energyzation of thylakoid membranes. In addition, the effect of thiamethoxam depends on the genotype of maize. The aim of the work was to study the effect of thiamethoxam pesticide on photosynthetic pigments and the photochemical activi-ty of the photosynthetic apparatus of maize leaves of two genotypes. The experiments were carried out in 2018-2019.The object of the study was samples of maize leaves of the inbred line zppl 225 and hybrid zp 341 with high rates of germination, grain quality and yield (Institut za kukuruz “Zemun Polje”, Belgrade, Serbia). The seeds were germinated until the roots appeared (length not less than 5mm),after which they were planted in the soil (vermiculite:chernozem mixture, 1:1) and grown under 16-hour daylight at a constant temperature of 25 С. When the third trueleaf appeared (more than 4 cm in length), the plants were sprayed with a TMX solution at a concentration of 0.2 mg/l. Plants grown under similar conditions without TMX spraying were used as controls. The measurements were carried out when the fifth true leaf reached a size of 12-14 cm.The content of photosynthetic pigments (chlorophyll a, b and carotenoids) was determined spectrophotometrically in 100% acetone extract and calculated using the Holm-Wetstein formula. A change in the confor-mation of carotenoid molecules was recorded by Raman spectroscopy.Light-induced kinetics of prompt fluorescence (PF), delayed fluorescence (DF) and modulated reflection at = 820 nm (MR) were recorded simultaneously using a multifunctional plant efficiency analyzer M-PEA-2 (Hansatech Instruments, Great Britain). PF induction curves (OJIP curves) were analyzed using a standard JIP-test. It was found that in the phase of the fifth true leaf, in the inbred line zppl 225, the chlorophyll content in the presence of TMX decreased from 0.74 to 0.61 mg/g: the amount of chlorophyll a decreased by 17 %, chlorophyll b by 24 %. In contrast, no changes in pigment composition were detected in the leaves of the zp 341 hybrid when exposed to TMX. The OJIP curves of the control and TMX-treated leaves had a typical curve with characteristic O-J, J-I, and I-P phases, which re-flected the processes of sequential reduction of carriers in the electron transport chain of photosyn-thesis (ETC) between two photosystems. The effect of the pesticide onthe leaves of two maize geno-types was manifested in a decrease in the functional state of photosystem II, determined by the fluo-rescence parameter (PIABS), which was obtained based on the analysis of OJIP curves using the JIP-test. Comparison of PIABSin the control and under the influence of TMX revealed statistically sig- 67nificant (p < 0.05) differences: in the leaves of zppl 225 and zp 341 samples treated with TMX, the PIABSparameter decreased by 29 and 24%, respectively. Changes in the fast phase of delayed fluo-rescence, associated with a decrease in the energyzation of the thylakoid membrane upon exposure to TMX, were detected in the leaves of maize. An analysis of the maximum oxidation and reduction rates of P700 (MR kinetics) indicates a decrease in the acceptor pool on the acceptor side of PSI in zppl 225 leaves when exposed to TMX. It was found that the reaction centers (RCs) of PSI zp 341 showed resistance to TMX (no change in the redox transformations of P700). TMX caused changes in the conformation of carotenoid molecules, but did not change their content in the leaf. The pro-posed combination of methods for prompt fluorescence, delayed fluorescence, modulated reflection at = 820 nm and Raman spectroscopy can be the basis for the formation of an effective technology for the diagnosis of early defects of photosynthetic pigments when pesticides enter an intact plant

Variable mechanisms of action of lithium during generating of membrane potential oscilations across the excitable membrane of the Nitela cell

This study presents results on variable mechanisms of lithium transport processes during generating of membrane potential oscillations across the very excitable membrane of the Nittela cell. Generating of several classes of oscillations, single and local impulses of the membrane potential, were presented in dependence on effects of a high LiCl concentration (10 mM), with which the cell membrane is very excited. Results on membrane potential oscillations are presented, and then some of oscillogram parameters were displayed. The assertion is that oscillations of the membrane potential are caused by total oscillatory transport processes: Li+, K+, Na+ and Cl-across the very excitable cell membrane. The paper presents the hypothesis on mechanisms of oscillatory transport processes of ions (Li, Na, K and Cl) expressed over different classes of oscillations, single and local impulses of the membrane potential across the excitable membrane of the Nittela cell

Dynamics of generating transients of delayed fluorescence induction signal and photosynthetic antennas: A possible relationship: Mathematical modeling approach

A mathematical model was developed for resolved temporal transients of experimentally recorded delayed fluorescence (DF) induction signal. During an intermittent light regime, antennas of the photosynthetic apparatus were treated as targets, repeatedly hit by potentially absorbable photons within a series of consecutive light flashes. Formulas were derived for the number of antennas, cumulatively hit by a specific number of photons, as function of the flash serial number (time). Model parameters included: number of absorbable photons in one flash, antenna sizes and numbers. A series of induction curves were analyzed, obtained from a ZeamaysL. leaf segment and differing in the previous dark period (td). Each curve, consisting of the two most prominent DF transients (C and D), was fitted with several model types, differing in the number of absorbed photons. For both transients, the best fitting result was achieved when DF induction was linked to the second absorbed photon. As expected, model parameters related to antenna sizes showed weaker dependence on td than those referring to antenna numbers. With restrictions applied in this model, the two DF induction transients may be related to two classes of photosynthetic antennas. Their different sizes may have a predominant influence on the efficiency of photon absorption, and possibly time-dependent appearance of DF transients

Photosynthetic properties of elite erect leaf maize inbred lines and their contribution to seed production improvement

A hypothesis that elite erect leaf maize inbred lines are characterized by properties of an efficient photo-model and that as such are very desirable in increasing the number of plants per unit area (plant density) in the process of seed production has been confirmed in the present study. The properties of the observed elite erect leaf maize inbred lines were based on the effects and characteristics of thermal processes of delayed chlorophyll fluorescence occurring in their thylakoid membranes. The temperature dependence of the delayed chlorophyll fluorescence intensity, the Arrhenius plot for the determination of phase transitions (critical temperatures) and activation energy are the principal parameters of the thermal processes. Based on the obtained results on photosynthetic properties it was also possible to estimate the tolerance and adaptation of elite erect leaf maize inbred lines to high temperatures and drought

Photosynthetic properties of erect leaf maize inbred lines as the efficient photo-model in breeding and seed production

The initial idea of this study was a hypothesis that erect leaf maize inbred lines were characterized by properties of an efficient photo-model and that as such were very desirable in increasing the number of plants per area unit (plant density) in the process of contemporary selection and seed production. The application of a non-invasive bioluminescence-photosynthetic method, suitable for the efficiency estimation of the photo-model, verified the hypothesis. Obtained photosynthetic properties of observed erect leaf maize inbred lines were based on the effects and characteristics of thermal processes of delayed chlorophyll fluorescence occurring in their thylakoid membranes. The temperature dependence of the delayed chlorophyll fluorescence intensity phase transitions (critical temperatures) in the thylakoid membranes and activation energy are the principal parameters of the thermal processes. Based on obtained photosynthetic properties it is possible to select erect leaf maize inbred lines that are resistant and tolerant to high and very high temperatures, as well as, to drought. They could be good and efficient photo-models wherewith

Significant biophysical and genetic properties of maize inbred lines and hybrids with erect top leaves

This study confirms the hypothesis that there are elite maize inbred lines and hybrids with erect top leaves, which have a dominant property of an efficient photosynthetic and fluorescent model that is successfully used in modern breeding programmes and the production hybrid seed and commercial maize. This statement is supported by the displayed results on the erect top leaves, the dynamics of grain dry-down during the maturation period and photosynthetic and florescence parameters: the temperature dependence of the delayed chlorophyll fluorescence intensity, the Arrhenius criterion for the determination of critical temperatures (phase transition temperatures) and the activation energies. The presented results show that properties of observed maize inbreds and their hybrids are based on the nature of conformational and functional changes that occur in their thylakoid membranes and other chemical tissues structures of grain and intact leaves, as well as, on positive effects in maize breeding. Moreover, other relevant significant breeding and seed production properties (commercial maize quality over grain structure, physical and chemical parameters) of maize inbred lines and their hybrids were analyzed in the present study

Structural properties of maize hybrids established by infrared spectra

This paper discusses the application of the infrared (IR) spectroscopy method for determination of structural properties of maize hybrid grains. The IR spectrum of maize grain has been registered in the following hybrids: ZP 341, ZP 434 and ZP 505. The existence of spectral bands varying in both number and intensity, as well as their shape, frequency and kinetics have been determined. They have been determined by valence oscillations and deformation oscillations of the following organic compounds: alkanes, alkenes, alkynes, amides, alcohols, ethers, carboxylic acids, esters and aldehydes and ketones, characteristic for biogenic compounds such as carbohydrates, proteins and lipids. In this way, possible changes in the grain structure of observed maize hybrids could be detected

Genetic, chemical, and physical predispositions of new maize inbred lines and hybrids with efficient photosynthesis

This study confirmed our hypothesis that new maize inbred lines and hybrids derived from them had a dominant property of an efficient photosynthetic model. This property is successfully used in breeding programmes, modern technologies of the seed, and commercial maize production. This statement is supported by the results displayed on the erect position of the top leaves of new maize inbred lines and photosynthetic and florescence parameters: the change of the delayed chlorophyll fluorescence intensity during its course and dynamics, the Arrhenius criterion for the determination of critical temperatures (phase transition temperatures) and the activation energies, as a measure of conformational changes in chloroplasts and the thylakoid membrane. Furthermore, a grain structure including its physical and chemical parameters of new maize inbred lines and hybrids was analysed in the present study. In addition, relevant breeding, seed production and technological traits, properties and parameters of new maize inbred lines and maize hybrids were observed in the present study. The overall presented results show that properties of new inbred lines and maize hybrids are based on the nature of conformational and functional changes that occur in their chloroplasts and thylakoid membranes, as well as, on progressive effects in modern breeding, contemporary hybrid seed production, and the commercial maize production. [Projekat Ministarstva nauke Republike Srbije, br. 03E211, 03E22, 142025, TR-20003, TR-20007, TR-20014