Interspecific differences in desiccation tolerance of selected Antarctic lichens: Analysis of photosystem II effectivity and quenching mechanisms

Lichens can survive and cope with unsufficient water supply resulting in low intrathalline relative water content. Under such conditions, photosynthesis is negatively affected by different degree of dehydration. In our study, fully hydrated samples of Xanthoria elegans, Umbilicaria decussata and Usnea aurantiaco-atra were light-acclimated and during following desiccation from a fully hydrated to dry state, steady-state chlorophyll fluorescence (FS), effective quantum yield of photochemical processes in PSII (ФPSII), and nonphotochemical quenching (qN) were measured in response to decreasing relative water content (RWC). The three experimental lichen species showed a high desiccation tolerance. The desiccation-induced decrease in ФPSII was found in X. elegans, U. decussata and U. aurantiaco-atra, at the RWC values below 30%. This is well comparable to the evidence reached in other Arctic / Antarctic lichen species. Interspecific differences in desiccation tolerance of these selected Antarctic lichens, based on the analysis of photosystem II effectivity and quenching mechanisms, were described and discussed

Spectral characteristics of bryophyte carpet and mat subformation showing a vitality-dependent color pattern: Comparison for two distant regions of maritime Antarctica

Spectral characteristics of the bryophyte carpet and mat subformation on Nelson Island (South Shetlands Islands) and Galindez Island (Argentine Islands, Graham Coast) were analyzed using spectral reflectance characteristics. A set of 9 specific reflectance indices were calculated and compared between two locations for the same type of moss vegetation formed by Sanionia georgicouncinata and Warnstorfia spp. The Normalized Difference Vegetation Index (NDVI) is efficient in discriminating between the two contrasting color/ecological moss community classes, i.e. such as less vigorous or dead and vigorous. However, NDVI is not sufficiently sensitive to discriminate intermediate vitality states. Presented data also demonstrates that complementary application of two indices, NDVI and Photochemical Reflectance Index (PRI), can be promising for follow-up studies focused on the determination of the color differences attributed to ecolophysiological state of a moss community. With the same values of NDVI, bryophyte carpet and mat subformation on Galindez Island are characterized by higher values of the OSAVI, which can be used as an indicator for further monitoring

What does critical temperature tell us about the resistance of polar lichens to freezing stress? Applicability of linear cooling method to ecophysiological studies.

Lichens from polar regions are well adapted to low temperature and considered cryoresistant. However, interspecific differences in their cryoresistance exist according to the degree of their adaptation and severity of the environment. In our study, we applied linear cooling technique in order to evaluate the interspecific differences in several lichen species. Thalli segments of Umbilicaria antarctica, Nephroma antarctica, Placopsis contortuplicata and Lasallia pustulata were exposed to the cooling from 20 to –35°C at a constant rate of 2°C min-1. Simultaneously with the cooling, chlorophyll fluorescence parameters evaluating potential (FV/FM) and effective yield of primary photochemical processes in PSII (FPSII) were measured in 30 s interval. Temperature response curves of FV/FM and FPSII formed typical S-curves that were species specific. Critical temperature (cooling point at which FPSII equals 0), was found in a narrow range of –25 to –28°C, suggesting that all experimental lichen species have a high resistance to sub-zero temperatures. The method of linear cooling used in this study has proven its applicability in ecophysiological studies since it is sensitive enough for the evaluation of species-specific differences in cryoresistance. This study describes different parameters that can be derived from the S-curves and discuss their proper use in ecophysiological and stress physiology studies

A study of the osmotic sensitivity of pike (Esox lucius, L., 1758) spermatozoa for the optimization of their cryopreservation

Purpose. The study of the osmotic sensitivity of pike (Esox lucius, L., 1758) spermatozoa. Methodology. The osmotic response of pike spermatozoa was investigated by spectrophotometry method based on the kinetics of light transmission of cells suspensions, which were placed in distilled water and 10–200 mOsm/kg solutions of NaCl . Measurements of light transmittance were carried out using photoelectrocolorimeter KF-77 (ZALIMP, Poland), equipped with a magnetic stirrer and thermostatted sample compartment. The coefficient of permeability of spermatozoa plasma membrane for water molecules (Lp) was determine by approximation of the experimental time dependences of the relative volume by solutions of the equations of modified Kedem-Kachalskyi physical-mathematical model of transmembrane mass transport. The activation energy (Еа) of the substances transfer across the cell membrane was calculated taking into account lnLp(1/T) dependencies. Findings. The characteristic time of water penetration is about 40-50s within 100-200 mOsm/kg range (12 °C). Membrane permeability coefficient of pike spermatozoa for water molecules is 5.43 - 1.15 - 10-15 m3/Ns. The decline in coefficient of membrane permeability for water molecules in the range of 25–10 °C is characterized by the activation energy of water transfer, which is 64±5 kJ/mol, that indicates about water molecules penetration into spermatozoa via a passive diffusion through the lipid bilayer. Hypoosmotic resistance of pike spermatozoa, estimated as time before lysis of 50% cells incubated in distilled water, is 70–110 s (12 °C). Developed approaches also can be used as simple and quick tests of the functional state of cell membranes. Originality. The coefficient of plasma membranes permeability of pike spermatozoa and its temperature dependence were defined for the first time. Practical value. The results are used in the design of media and modes of pike sperm cryopreservation

PERMEABILITY OF STERLET SPERM MEMBRANES (ACIPENSER RUTHENUS L., 1758) FOR WATER MOLECULES

Purpose. The literature analysis of the results cryopreservation of different fish species highlights a variation of many parameters, in particular the sperm survival rate during the freezing and unfreezing process. The survival capability of spermatozoa may be called the main parameter, which indentifies the efficiency of the entire process of low temperature freezing of reproductive products. Therefore, the goal of this work was to investigate and find the causes of different degrees of fish sperm cryoimmunity, in particular that of starlet, which is a valuable of sturgeon (Acipenser) species. We also studies the possibility to find the optimum ways to improve the efficiency of the survival rate of the defrosted spermatozoa of different fish species for their further use to produce viable offspring. Methodology. The determination of sterlet sperm membrane permeability was performed after carrying out all necessary manipulations with brood males which included: prespawning incubation, hormonal stimulation, determination of sperm maturity degree, obtaining the sperm by stripping. The measurement of sperm membrane permeability for water molecules was performed based on the technique, which had been used earlier to measure carp sperm permeability, but taking account the specific peculiarities inherent to sterlet sperm. Findings. Based on the performed measurements, we determined the sterlet sperm membrane permeability for water molecules with the use of photometric method. The received experimental data show the highest degree of sterlet sperm membrane permeability for water molecules as compared to carp sperm membrane permeability. Originality. As a result of this experiment, we determined for the first time the absolute value of sterlet sperm membrane permeability for water molecules with the use of photometric method as well as compared the results with those obtained during our work with the carp sperm. Practical value. The data obtained during the experimental studies can be used in the practice of sperm cryopreservation for improving the efficiency of the sperm different of fish species during the process of low temperature freezing especially for such commercially valuable fish species as sturgens

Індукція вакуолізації в сперматозоїдах чоловіків з олігоастенотератозооспермією після кріоконсервування з гліцерином і полівінілпіролідоном

Background. The two–step method using penetrating cryoprotectant glycerol is a routine for cryopreservation of spermatozoa from men with normal spermatogenesis. However, the use of this freezing method in the case of oligoasthenoteratozoospermia (OAT) leads to additional cells damage and there is a need to search for new effective cryopreservation method. The sperm vacuolization inherent in male gametes plays a negative role, reducing the fertilizing ability of cells. Objective. The aim of the study was to assess the degree of vacuolization induced in human OAT sperm after cryopreservation by a two–stage method using glycerol and polyvinylpyrrolidone (PVP), molecular mass 360000. Methods. The isolated sperm fraction was divided into 3 groups: group I – native spermatozoa, II – spermatozoa cryopreserved by the two–stage method with 10% glycerol, group III – spermatozoa cryopreserved by the two–stage method with 10% PVP. Results. About 5% of spermatozoa contained vacuoles in group I. The number of spermatozoa with one small vacuole increased to (19.68 ± 2.27)% in group II. And in group III the number of cells without vacuoles was comparable with native spermatozoa: 95.59 ± 1.59 and (96.09 ± 2.02)%, respectively. Conclusion. Thus, the use of a penetrating cryoprotectant of glycerol at 10% concentration for two–stage method cryopreservation of human spermatozoa initiates the vacuoles formation while the use of non–penetrating PVP can prevent vacuolization.Актуальность. Двухэтапный метод с использованием проникающего криопротектора глицерина является рутинным для криоконсервирования сперматозоидов мужчин с нормальным сперматогенезом. Однако применение данного способа замораживания в случае олигоастенотератозооспермии (ОАТ) приводит к возникновению дополнительных повреждений клеток и возникает необходимость в поиске новых эффективных способах криоконсервирования. Вакуолизация сперматозоидов, присущая мужским гаметам, играет отрицательную роль, снижая оплодотворяющую способность клеток. Цель. Оценка степени вакуолизации, индуцируемой в ОАТ сперматозоидах человека после криоконсервирования двухэтапным методом с использованием глицерина и поливинилпирролидона (ПВП), молекулярной массой 360000. Методы. Выделенную фракцию сперматозоидов разделяли на 3 группы: группа I – нативные сперматозоиды, II – сперматозоиды, криоконсервированные с 10% раствором глицерина, группа III – криоконсервированные с 10% ПВП. Результаты. В группе I около 5% сперматозоидов содержали вакуоли. В группе II количества сперматозоидов с одной мелкой вакуолью увеличилось до (19,68±2,27)%. А в группе III количество клеток без вакуолей было сравнимо с нативными сперматозоидами: 95,59±1,59 и (96,09±2,02)% соответственно. Заключение. Таким образом, использование проникающего криопротектора глицерина в концентрации 10% для двухэтапного криоконсервирования сперматозоидов человека инициирует образование вакуолей, в то время как применение непроникающего ПВП позволяет предотвратить вакуализацию.Актуальність. Двоетапний метод з використанням проникаючого кріопротектору гліцерину є рутинним для кріоконсервування сперматозоїдів чоловіків з нормальним сперматогенезом. Однак застосування даного способу заморожування у випадку олігоастенотератозоосперміі (ОАТ) призводить до виникнення додаткових ушкоджень клітин і виникає необхідність у пошуку нових ефективних способах кріоконсервування. Вакуолізація сперматозоїдів, притаманна чоловічим гаметам, відіграє негативну роль, знижуючи здатність до запліднення клітин. Мета. Оцінка ступеня вакуолизації, індукованої в ОАТ сперматозоїдах людини після кріоконсервування двохетапним методом з використанням гліцерину та полівінілпіролідону (ПВП), молекулярною масою 360000. Методи. Виділену фракцію сперматозоїдів поділяли на 3 групи: група I – нативні сперматозоїди, II – сперматозоїди, кріоконсервовані з 10% розчином гліцерину, група III – кріоконсервовані з 10% ПВП. Результати. В групі I близько 5% сперматозоїдів містили вакуолі. У групі II кількості сперматозоїдів з однією дрібною вакуоллю збільшилася до (19,68 ± 2,27)%. А в групі III кількість клітин без вакуолей було порівняно з нативними сперматозоїдами: 95,59 ± 1,59 і (96,09 ± 2,02)% відповідно. Підсумок. Таким чином, використання проникаючого кріопротектори гліцерину в концентрації 10% для двоетапного кріоконсервування сперматозоїдів людини ініціює утворення вакуолей, в той час як застосування непроникаючої ПВП дозволяє запобігти вакуалізації

Resistance of Primary Photosynthesis to Photoinhibition in Antarctic Lichen <i>Xanthoria elegans</i>: Photoprotective Mechanisms Activated during a Short Period of High Light Stress

The Antarctic lichen, Xanthoria elegans, in its hydrated state has several physiological mechanisms to cope with high light effects on the photosynthetic processes of its photobionts. We aim to investigate the changes in primary photochemical processes of photosystem II in response to a short-term photoinhibitory treatment. Several chlorophyll a fluorescence techniques: (1) slow Kautsky kinetics supplemented with quenching mechanism analysis; (2) light response curves of photosynthetic electron transport (ETR); and (3) response curves of non-photochemical quenching (NPQ) were used in order to evaluate the phenomenon of photoinhibition of photosynthesis and its consequent recovery. Our findings suggest that X. elegans copes well with short-term high light (HL) stress due to effective photoprotective mechanisms that are activated during the photoinhibitory treatment. The investigations of quenching mechanisms revealed that photoinhibitory quenching (qIt) was a major non-photochemical quenching in HL-treated X. elegans; qIt relaxed rapidly and returned to pre-photoinhibition levels after a 120 min recovery. We conclude that the Antarctic lichen species X. elegans exhibits a high degree of photoinhibition resistance and effective non-photochemical quenching mechanisms. This photoprotective mechanism may help it survive even repeated periods of high light during the early austral summer season, when lichens are moist and physiologically active