The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ‘P360’, and ‘PS1313’, respectively. Plants were grown hydroponically and supplied with two nutrient solutions - a nonsalinized control and a salinized solution which contained 40 mmol L-1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the
PN and gs reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na+ and Cl- in the leaf tissue and PN. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and PN. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance., Y. Rouphael ... [et al.]., and Obsahuje bibliografii
Excess solar radiation under hot climate can lead to decline in photosynthetic activity with detrimental effects on growth and yield. The aim of this study was to evaluate the use of a transparent plastic roof as shading for diurnal changes in photosynthetic gas exchange, chlorophyll fluorescence, fruit set and quality of mango (Mangifera indica L.) cv. 'Nam Dok Mai' growth in the field conditions. Fully expanded leaves were examined either shaded by the plastic roof or sunlit under natural conditions. Leaf temperature and leaf-to-air vapour pressure deficit of the shaded leaves measured on the clear day were lowered compared to those of the sunlit leaves. It resulted in increased stomatal conductance and photosynthetic rates of the shaded leaves compared to those of the sunlit leaves, especially from the morning to midday. Furthermore, the reversible decrease of the maximal quantum yield of PSII was more pronounced in the sunlit leaves than that in the shaded ones. Shading increased the total fruit number; the shaded fruits developed better external color than that of the sun-exposed fruits. Our results indicated that shading could maintain the high photosynthetic activity by reducing stomatal limitations for carbon supply and was effective in alleviating the photoinhibitory damage to PSII during bright and clear days with excessive radiation. Finally, shading could increase the number of fruits and improve mango peel color., K. Jutamanee, S. Onnom., and Obsahuje bibliografii
We honor here Hartmut Karl Lichtenthaler, a pioneer of plant physiology, plant biochemistry, plant biophysics, plant molecular biology, and stress physiology. His contributions to the ingenious use of chlorophyll a fluorescence imaging in understanding the physiological processes in leaves stand out. We wish him many happy and productive years of research and educating others., G. Govindjee., and Obsahuje bibliografické odkazy
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) is one of the key enzymes involved in assimilation of CO2 in chloroplasts. Phylloplane microfungi and their metabolites have been reported to affect the physiology of host plants, particularly, their photosynthesis. However, information is lacking on the effect of these microflora on the physiology of chloroplasts. The current study emphasized the impact of two dominant phylloplane fungi, Aspergillus niger and Fusarium oxysporum, on activity of Rubisco in tomato chloroplasts. Ergosterol, which is a component of only fungal cell membranes and is not synthesized by plants, have been demonstrated to elicit activity of Rubisco. In the present study, it was demonstrated through in silico, in vitro, and in vivo approaches. Results demonstrated that the fungal metabolites, which contained ergosterol, could double Rubisco activity. Maximum carboxylation rate of Rubisco increased also in ergosterol-treated plants. Michaelis-Menten constant of Rubisco was also slightly affected. Ergosterol was found also to influence and enhance the binding of CO2 and ribulose-1,5-bisphosphate to Rubisco. Therefore we can postulate that the physiology of the chloroplast is probably influenced by phylloplane microfungi., J. Mitra, P. Narad, P. K. Paul., and Obsahuje bibliografii
Chronic hypoxia results in hypoxic pulmonary hypertension characterized by fibrotization and muscularization of the walls of peripheral pulmonary arteries. This vessel remodeling is accompanied by an increase in the amount of lung mast cells (LMC) and the presence of small collagen cleavage products in the vessel walls. We hypothesize that hypoxia activates LMC, which release matrix metalloproteinases (MMPs) cleaving collagen and starting increased turnover of connective tissue proteins. This study was designed to determine whether in vitro hypoxia stimulates production of MMPs in rat LMC and increases their collagenolytic activity. The LMC were separated on the Percoll gradient and then were divided into two groups and cultivated for 24 h in 21 % O2 + 5 % CO2 or in 10 % O2 + 5 % CO2. Presence of the rat interstitial tissue collagenase (MMP-13) in LMC was visualized by immunohistological staining and confirmed by Western blot analysis. Total MMPs activity and tryptase activity were measured in both cultivation media and cellular extracts. Exposure to hypoxia in vitro increased the amount of cells positively labeled by anti-MMP-13 antibody as well as activities of all measured enzymes. The results therefore support the concept that LMC are an important source of increased collagenolytic activity in chronic hypoxia., H. Maxová, J. Novotná, L. Vajner, H. Tomášová, R. Vytášek, M. Vízek, L. Bačáková, V. Valoušková, T. Eliášová, J. Herget., and Obsahuje bibliografii a bibliografické odkazy
Green photosynthetic stems are often responsible for photosynthesis due to the reduction of leaves in arid and hot climates. We studied the response of PSII activity to high irradiance in the photosynthetic stems of Hexinia polydichotoma in the Taklimakan Desert by analysis of the fast fluorescence transients (OJIP). Leaf clips of a chlorophyll fluorometer were used in conjunction with a sponge with a 4-mm-width groove to prevent light leakage for precise in vivo measurements. High irradiance reduced performance indices, illustrating the photoinhibition of PSII to some extent. However, the decrease in active reaction centers (RC) per PSII absorption area and maximum quantum yield indicated a partial inactivation of RCs and an increase in excitation energy dissipation, resulting in downregulation of photosynthetic excitation pressure. In addition, the increased efficiency of electron transport to PSI acceptors alleviated overexcitation energy pressure on PSII. These mechanisms protected the PSII apparatus as well as PSI against damages from excessive excitation energy. We suggested that H. polydichotoma exhibited rather photoadaptation than photodamage when exposed to high irradiance during the summer in the Taklimakan Desert. The experiment also demonstrated that the modified leaf clip can be used for studying dark adaptation in a photosynthetic stem., L. Li, Z. Zhou, J. Liang, R. Lv., and Obsahuje seznam literatury
The total content of rat liver microsomal cytochrome P450 (CYP) significantly decreased after repeated i.p. administration of the antiviral agent tenofovir ((R)-9-[2-(phosphonomethoxy)propyl] adenine) and tenofovir disoproxil at a daily dose 25 mg/kg, although the content of liver microsomal protein did not change. The decrease of the CYP content was accompanied by concomitant increase of the amount of inactive CYP form, cytochrome P420. This effect was confirmed by a parallel study of the activities of selected CYP forms, CYP2E1 (p-nitrophenol hydroxylation) and CYP1A2 (7-ethoxyresorufin deethylation). The activity (expressed relatively to the protein content) of both CYP forms decreased significantly following the decrease of the total CYP. On the other hand, the CYP2E1 activity expressed relatively to the decreasing total CYP content remained unchanged. However, CYP1A2 activity also decreased when calculated relatively to the total native CYP content indicating lower stability of this form. Semiquantitative RT-PCR showed no significant changes in expression of major rat liver microsomal CYP forms after tenofovir treatment. In conclusion, repeated administration of tenofovir in higher doses led to significant decrease of the relative proportion of active liver microsomal CYPs accompanied by a conversion of these enzymes to the inactive form (CYP420) maintaining the sum of CYP proteins unchanged., E. Anzenbacherová, P. Anzenbacher, Z. Zídek, E. Buchar, E. Kmoníčková, P. Potměšil, J. Nekvindová, A. Veinlichová, A. Holý., and Obsahuje bibliografii a bibliografické odkazy
Parasitic organisms inhabiting the alimentary canal should permanently resist the destructive action of host digestive enzymes. The intestinal parasites were shown to produce specific protease inhibitors protecting them from proteolysis. However, little is known about this adaptive mechanism in cestodes so far, especially for the tapeworms dwelling inside the fish intestines. Here, we explored the ability to inactivate proteolytic enzymes in the fish tapeworm Eubothrium rugosum (Batsch, 1786) (Bothriocephalidea) parasitising the intestine of wild burbot, Lota lota (Linnaeus). The assays were conducted with different concentrations of commercial trypsin and homogenate of intestinal mucosa both being the sources of proteinases. The incubation of live E. rugosum in trypsin solutions of two different concentrations caused a significant decrease in the enzyme activity. The extent of activity reduction was dependent on trypsin concentration. At the same time, the inhibitory effect of the worm incubation medium turned out to be statistically insignificant. These findings suggest partial adsorption of the enzyme to the tegument surface, with its further inactivation. In contrast to the incubation medium, the worm extract suppressed over 80% of trypsin activity and nearly half of the proteolytic activity in the mucosa homogenate. Notably, the inhibitory activity of the tapeworms hardly depended on their size characteristics. Finally, the research has demonstrated secretion of proteinase inhibitor in E. rugosum, which appears to be essential for its survival in enzymatically hostile environment., Galina I. Izvekova, Tatyana V. Frolova, Evgeny I. Izvekov., and Obsahuje bibliografii