Effects of Cytokinin Preparations on the Stability of the Photosynthetic Apparatus of Two Wheat Cultivars Experiencing Water Deficiency

Carboxylase activity of the key enzyme of carbon metabolism, ribulose-bisphosphate carboxylase/oxygenase (RuBisCO; EC 4.1.1.39), and phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31), as well as the intensity of carbon dioxide photosynthetic assimilation in young seedlings and adult leaves of the wheat Triticum aestivum L. cultivars Mironovskaya 808 (a more tolerant) and Lyutestsens758 (a less tolerant), were compared under conditions of progressive water deficiency. The water stress had more pronounced negative effects on all the studied characteristics of the photosynthetic apparatus of the cultivar Lyutestsens758. Its seedlings were more sensitive to water stress. Compounds with a cytokinin activity (6-benzylaminopurine, thidiazuron, kartolin 2, and kartolin 4) played a protective role, increasing the stability of the photosynthetic apparatus under conditions of water deficiency. Preparations of kartolins displayed the maximum protective effect.     

Effects of Cytokinin Preparations on the Pools of Pigments and Proteins of Wheat Cultivars Differing in Their Tolerance to Water Stress

Contents of chlorophylls, carotenoids, soluble leaf proteins, and the key enzyme of carbon metabolism—ribulose bisphosphate carboxylase/oxygenase (RuBisCO; EC 4.1.1.39)—in young seedlings and adult leaves of the wheat Triticum aestivum L. cultivars Mironovskaya 808 and Lyutescens 758, contrasting in their water stress tolerances, were compared under conditions of normal available water supply, water deficiency, and subsequent rehydration. It was discovered that compounds displaying a cytokinin activity (6-benzylaminopurine, thidiazuron, kartolin-2, and kartolin-4) reduced the decreases in contents of chlorophylls, carotenoids, soluble leaf proteins, and RuBisCO, progressing with development of water stress, as well as contributed to their more rapid recovery. These compounds with cytokinin activity also accelerated restoration of the compounds studied to their initial concentrations during rehydration. The kartolin preparations caused a maximal protective effect. Water stress had a more pronounced negative effect on the cultivar Lyutescens 758. Dehydration resulted in a more extensive destruction of seedlings compared to leaves of adult plants.     

MutL Protein from the Neisseria gonorrhoeae Mismatch Repair System: Interaction with ATP and DNA

Molecular Biology - The mismatch repair system (MMR) ensures the stability of genetic information during DNA replication in almost all organisms. Mismatch repair is initiated after recognition of a...     

Comparative study of the somatic conjugation of chromosomes in the neural ganglia of male and female Drosophila melanogaster D-32

The frequency of somatic conjugation of the 2nd and 3d chromosome pairs has been analysed in male and female neural ganglia from Drosophila melanogaster larvae D-32 line. The frequency of conjugation found for males was 1.5 times lower than for females. On this basis a supposition concerning less duration of homologous conjugation in males has been put forward. It is suggested that it is due to the differences in space arrangement of homologous chromosomes holding their conjugation.     

Protective Role of Kartolin-4 in Wheat Plants Exposed to Soil Draught

Parameters of photosynthesis, heat-resistance, and osmotic pressure of cell exudate of leaves of the drought-sensitive cultivarLyutestsens 758 of wheat, Triticum aestivum, were studied under conditions of normal water supply, soil drought, and subsequent rehydration. The plants preliminarily treated with kartolin-4 were compared to untreated plants. Kartolin-4, a preparation with cytokinin-like activity, partially prevented the drought-induced inhibition of the photosynthetic assimilation of carbon dioxide and carboxylation activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), the key enzyme of carbon metabolism in plants. Upon subsequent rehydration, kartolin-4 stimulated the reparation reactions and facilitated the rapid recovery of normal photosynthetic activity. Kartolin-4 also increased the plant resistance to overheating and water deficiency.     

The spatial reorganization of the perinucleolar area of hematopoietic cells in human leukemias]

The structure of perinucleolar zone in nuclei of peripheral blood hemopoietic cells has been studied. The cells of human patient with chronic lympholeukemia, chronic myeloleukemia, various forms of acute leucosis have been investigated. The phenomenon of radial strings and border structures has been found in these cells. The features have been revealed by visualization of ribonucleoproteides and lipoproteins. The same process takes place in human lymphocytes after 6-24 h of 3-phosphoglyceric aldehyde stimulation in vitro. A comparative study of morphologic peculiarities of hemopoietic cell nucleolar apparatus depending on cell cycle phase has been performed. The action of cytostatics upon the structure of nucleus perinucleolar zone has been investigated.