N.L. Loseva

A differential photomicrocalorimetric method for investigating the rate of energy storage in plants

Abstract This paper describes the equipment and method for the direct measurement of the quantity and rate of light-induced changes in plants. The photomicrocalorimetric method can be used for the investigation of energetics in photosynthesis and other photobiological processes in higher plants, algae and microorganisms. The rate of energy storage of Chlorella cells and a number of agricultural plants under optimal and extreme conditions have been determined.

The effect of melafen on the growth and energy processes in the plant cell.

During the past years, significant success has been reached in understanding the role of phytohormones in life of plants, their metabolism, and molecular mechanism of their action [1, 2]. Because the use of phytohormones in practice is economically disadvantageous, the synthetic preparations that at ultralow concentrations can trigger physiological and genetic programs, thereby leading to the intensification of key physiological processes, have been intensively sought.

Heat production of root cells upon the dissipation of ion gradients on plasma membrane

The dissipation of ion gradients across plasma membranes contributes to the heat production by live cells. The aim of the present research is to determine the dependence of the rate of heat production by plant tissues on ion balance shifts, supposing a priori that the shifts are the beginning mechanism in adaptation to various stresses. Excised wheat roots subjected to prolonged incubation in different solutions served as objects for investigation. Two ion transporters (K + /H + -transporter nigericin and Ca 2+ -ionophore A23187) shifted the ion homeostasis and induced distinct changes in the energy metabolism of plant tissues. Nigericin, which considerably increased the plasmalemma conductivity for protons and potassium, enhanced production of heat by root cells throughout the exposure. Prolonged incubation with A23187 was required to display its ion-transporting properties which were accompanied by a rise in the rate of heat release. The high rate of heat release and respiration in root cells exposed to ion transporters is a reflection of the ion-gradient dissipation and the increased energy expenditure for the activation of ATPase systems necessary for the restoration of ionophore-disturbed ion homeostasis.

Aspects of the energetic balance of plant cells under different salt conditions

Abstract Aspects of the intracellular energetic balance were studied in assimilating cells of Chlorella , grown in a medium with different concentrations of NaCl. The responses depending on salt concentration were revealed by a microcalorimetric method. The lower concentrations of NaCl (450 mM) induced an increase in the heat production by Chlorella . Under higher salt concentration (550 mM), a sharp increase in heat production took place. This was probably connected with the cell destruction. In explaining the results, the protective mechanisms of Chlorella connected with energy redistribution under different salt conditions, are emphasized.

Direct and indirect calorimetric studies of stress responses of chlorella cells to infection with the mycoplasma, Acholeplasma laidlawii

Loseva, N. L., Gordon, L. K., Minibayeva, F. V., Alyabyev, A. J., Chernov, V. M., Chernova, O. A., Andreyeva, I. N., Rachimova, G. G., Tribunskih, V. I., Estrina, R. I., Gogolev, J. B., Kemp, R. B. (2002). Direct and indirect calorimetric studies of stress responses of chlorella cells to infection with the mycoplasma, Acholeplasma laidlawii. Thermochimica Acta, 390, (1-2), 39-46 Sponsorship: INTAS project, Ref. no.: 99-01390

The effect of high temperature and salt on the metabolic heat rate of Chlorella cells

The metabolic heat rate of plants is an integral indicator of the state of the organism. The metabolic heat rate reflects changes in all the anabolic and catabolic processes in plant cells between optimal and extreme conditions. The present studies determined the effects of extreme temperatures (45°C) and high NaCl concentrations (450 mM) on the rate of heat evolution by Chlorella cells. At first, the rate of heat production increases as compared with the control; thereafter it decreases to a steady-state value which is lower than that of the the control. The decrease in metabolic rate may be connected with changes in metabolic processes associated with adaptation of the organism to stress condition.

A comparative study of the effect of melaphene and kinetin on growth and energy processes in the plant cell.

Earlier, when studying the responses of plants to treatment with certain types of chemicals, we found that melaphene, the melamine salt of bis(methylol)phosphinic acid, at ultralow concentrations exhibits regulatory activity [1]. Studies of the effect of melaphene on the regulation of growth and development of the unicellular alga Chlorella , as well as on the rate of photosynthesis, respiration, and metabolic heat emission as an index of energy status of cells, showed that melaphene had the greatest effect at concentrations of 3 × 10 –9 –3 × 10 –10 å [1]. These results and published data allowed us to conclude that the effect of melaphene on energy processes and metabolism in plants is similar to the effect of phytohormones of the cytokinin series [2].

The energetic stress response of the microalgal Chlorella vulgaris to the mycoplasma, Acholeplasma laidlawii as a model system for plant–pathogen interaction

Loseva, N. L., Alyabyev, A. J., Gordon, L. K., Andreyeva, I. N., Kolesnikov, O. P., Ponomareva, A. A., Chernov, V. M., Kemp, R .B. (2003). The energetic stress response of the microalgal Chlorella vulgaris to the mycoplasma, Acholeplasma laidlawii as a model system for plant-pathogen interaction. Thermochimica Acta, 397, (1-2), 37-47. Sponsorship: INTAS Grant no. 99-1390

Effect of NaNO2, a donor of nitric oxide, on the energy metabolism of plant cells

39 Nitric oxide (NO) has been demonstrated to have a wide spectrum of biochemical effects [1]. NO is one of the messengers involved in the regulation of both intraand intersignaling in plants [2]. NO has also cytotoxic and cytostatic properties along with the regulatory functions [1]. In addition, NO is known to effectively regulate plant respiration owing to its high affinity to a number of enzymes participating in glycolysis and mitochondrial oxidation [3, 4].

Carnosine Modulates Oxygen Consumption and Heat Production by Wheat Root Cells

Today, it becomes more and more apparent that early responses of cells to exposure to various agents include the proton entry into them [1, 2]. Acidification of the cytoplasm results in a drop of the pH gradient on the plasmalemma. The removal of excess protons from the cytoplasm and the restoration of pH gradient are energy-consuming processes [3]. Subsequent activation of proton ATPase reflects the triggering of the biophysical pH-buffering system. However, cells also have a biochemical pH-buffering system. Biochemical pHstabilization of cells is determined by pH-dependent metabolic reactions of organic acids, resulting from the release and binding of free carboxylic acids [4]. The role of biophysical pH-stabilization in plant cells has been considered in many articles [4, 5], whereas the functioning of biochemical pH-stabilization of the cytoplasm has been studied to a lesser extent [6, 7]. In view of this, it was of interest to determine the contribution of the biochemical component of pH-stabilization of the cell to possible prevention of acidification of the cytoplasm and the ratio between the two types of pH-stabilization under the conditions of “proton load” of cells. It is known that dipeptides carnosine and anserine regulate cytoplasmic pH in animal cells [8, 9]. We used carnosine in our studies, because this is a nontoxic natural compound that exhibits proton-acceptor properties [8].