Persistence of the Effects of Se-Fertilization in Olive Trees over Time, Monitored with the Cytosolic Ca2+ and with the Germination of Pollen

Selenium (Se) is an important micronutrient for living organisms, since it is involved in several physiological and metabolic processes. Biofortification with Se increases the nutritional and qualitative values of foods in Se-deficient regions and increases tolerance to oxidative stress in olive trees. Many studies have shown that Se, in addition to improving the qualitative and nutritional properties of EVO oil, also improves the plant’s response to abiotic stress. This study addressed this issue by monitoring the effects of Se on cytosolic Ca2+ and on the germination of olive pollen grains in oxidative stress. The olive trees subjected to treatment with Na-selenate in the field produced pollen with a Se content 6–8 times higher than the controls, even after 20 months from the treatment. Moreover, part of the micronutrient was organic in selenium methionine. The higher selenium content did not produce toxic effects in the pollen, rather it antagonized the undesirable effects of oxidative stress in the parameters under study. The persistence of the beneficial effects of selenium observed over time in pollens, in addition to bringing out an undisputed adaptability of olive trees to the micronutrient, suggested the opportunity to reduce the number of treatments in the field.

Artificial medium for in vitro pollen germination of some ornamental Linum species

For the first time components of the nutrient medium were identified for the successful germination of pollen in such ornamental species of the Linum genus as L. grandiflorum, L. hirsutum, L. pubescens and L. thracicum. It was shown that the media with PEG-2000 in concentrations of 20-30% in combination with boric acid and calcium chloride in the concentrations of 200 mg/l ensure germination of Linum pollen up to 40-50%. The addition of sucrose and PEG with higher molecular weight adversely affects the germination of pollen. This will allow anyone to evaluate the quality of flax pollen quickly and efficiently and more successfully implement many genetic and breeding programs.

Spatial and Temporal Distribution of Arabinogalactan Proteins during Larix decidua Mill. Male Gametophyte and Ovule Interaction

The role of ArabinoGalactan Proteins (AGPs) in the sexual reproduction of gymnosperms is not as well documented as that of angiosperms. In earlier studies, we demonstrated that AGPs play important roles during ovule differentiation in Larix decidua Mill. The presented results encouraged us to carry out further studies focused on the functions of these unique glycoproteins during pollen/pollen tube and ovule interactions in Larix. We identified and analyzed the localization of AGPs epitopes by JIM4, JIM8, JIM13 and LM2 antibodies (Abs) in male gametophytes and ovule tissue during pollination, the progamic phase, and after fertilization and in vitro growing pollen tubes. Our results indicated that (1) AGPs recognized by JIM4 Abs play an essential role in the interaction of male gametophytes and ovules because their appearance in ovule cells is induced by physical contact between reproductive partners; (2) after pollination, AGPs are secreted from the pollen cytoplasm into the pollen wall and contact the extracellular matrix of stigmatic tip cells followed by micropylar canal cells; (3) AGPs synthesized in nucellus cells before pollen grain germination are secreted during pollen tube growth into the extracellular matrix, where they can directly interact with male gametophytes; (4) in vitro cultured pollen tube AGPs labeled with LM2 Abs participate in the germination of pollen grain, while AGPs recognized by JIM8 Abs are essential for pollen tube tip growth.

Impact of temperature and air moisture on pollen viability

The environments have a direct impact on formation and functioning of the generative organs in plants. Parameters characterizing viability of pollen grains are closely linked with weather conditions, especially temperature and air moisture. Very often a phase of a beginning of flowering of winter rapeseed (end of March – beginning of April) lasts in unfavourable conditions. In April 2020, we studied influence of the main weather factors (frosts, low moisture) on germination of pollen grains of the varieties Loris, Sarmat and hybrids 40059 × Jesper 16– 132 and 40008 × INRA of winter rapeseed bred in VNIIMK. Pollen viability was determined by B.A. Trankovsky’s method, accounting amount of germinating pollen grains on the artificial nutrient medium, calculating a percentage of germinating pollen grains to their total quantity. We determined optimal concentration of sucrose solution (20%) in a nutrient medium for germination of pollen of winter rapeseed varieties and hybrids. Due to our results, lowered air temperatures (from -0.5 to -1.9 оС) combined with air moisture from 39 to 86% in a period of beginning of crop flowering negatively influenced on germination of pollen grains. Viability of pollen of the varieties Loris and Sarmat was in average 47 and 37%, respectively. Pollen grains of the hybrids (F1 40059 × 52 Jesper 16-132 and F1 40008 × INRA) had less viability – 38 and 21%, respectively, this certifies higher susceptibility of tissues of the reproductive organs to low temperature and moisture.

In vitro germination of pollen grains of three native species from Pampa biome with ornamental potential

The aim of this work was to verify the in vitro germination of pollen grains of Angelonia integerrima L., Campomanesia aurea O. Berg and Sesbania punicea (Cav.) Benth in different culture medium and temperatures. For this purpose, flower buds from which pollen was collected and sprayed on plates containing the three evaluated culture medium: M1 - agar and sucrose; M2 - agar, sucrose and H3BO3; M3 - agar, sucrose, H3BO3, Ca(NO3), MgSO4 and KNO3; and two incubation temperatures (20 °C and 30 °C). Data was subjected to analysis of variance after its transformation to square root and means were compared by Fisher’s test (LSD). For the three species, the temperature of 30 ºC provided the highest percentage of pollen grain germination. For A. integerrima, M1 and M3 promoted the highest germination percentages (40.7 % and 56.5 %, respectively). On the other hand, for C. aurea, M2 provided the highest germination average (43.7 %). At last for S. punicea, M3 was the one that provided the highest average (31.62 %). It was concluded that the evaluated species differ in micronutrient requirements for in vitro germination of pollen grains. The temperature of 30 °C was suitable for all three species.

THE EFFECT OF PHYTOHORMONES AND LIGHT ON THE GERMINATION OF APPLE POLLEN WITH REDUCED VIABILITY

Background. Studying the effect of phytohormones and light on the germination of apple pollen with reduced viability on an artificial nutrient medium is of importance, because it may facilitate an increase in the germination percentage among plant samples promising for breeding after their long-term preservation under low temperatures.Materials and methods. Pollen viability of the apple-tree cultivar ‘Krasnolistnaya’ was measured by germinating it on an artificial nutrient medium containing 10% sucrose solution and 0.8% agar. Drops of a distilled water suspension of pollen with added phytohormones were applied to the surface of the nutrient medium. Pollen was germinated in the dark (24 hours in a thermostat at 21°C) and under light (in an artificial light chamber at 21°C with a photoperiod of 16 hours of light / 8 hours of darkness). Results. Pollen of cv. ‘Krasnolistnaya’ with reduced viability most effectively germinated with the use of gibberellin at a concentration of 1 mg/l and 10 mg/l: the germination percentage was 22.3±0.8% and 21.8±1.3% respectively (сf. 10.9±1.5% in the reference). The most effective combination of phytohormones was gibberellin 10 mg/l + kinetin 10 mg/l – the percentage of germination was 22.8±6.3%; kinetin 1 mg/l + indolylbutyric acid 1 mg/l – the percentage of germination was 17.5±5.9% vs. 10.9±1.5% in the reference.Conclusion. Phytohormones were observed to have a significant effect on the germination of apple pollen with reduced viability. Effective concentrations and combinations of phytohormones that promote the germination of pollen with reduced viability have been identified. Light does not affect the germination of pollen with reduced viability.

Production and in vitro viability of pollen of peach trees grown in subtropical climate

Studies of the production and viability of pollen are very important in breeding programs and for assessing the climatic adaptation of fruit species. The objective of this work was to determine the pollen production per anther and its viability from in vitro germination tests of 16 peach cultivars. The analyses were carried out at the Horticulture Laboratory with vegetable matter from the peach trees in the fruit sector of the Federal Technological University of Paraná, Dois Vizinhos, Paraná State, Brazil. The cultivars used in the research were: Bonão, BR-1, Charme, Chimarrita, Coral, Douradão, Eldorado, Fascínio, Granada, Kampai, Leonense, Marli, Regalo, Riograndense, Rubimel, and Zilli. Pollen production was obtained by counting in a Neubauer chamber. In vitro germination of pollen was obtained after incubation of pollen in culture through a controlled environment (presence of photoperiod and temperature of 25 °C). The experimental design used was completely randomized with four replications. The data were submitted to the Lilliefors normality test and to variance analysis and means comparisons by the Scott-Knott test (a = 0.05). We concluded that the winter conditions of 2016 were better for the development of the buds, which promoted greater production of pollen per anther. The cultivars Douradão, Leonense, Regalo, and Rubimel had the highest rates of pollen viability. The storage of pollen at -20 °C for 60 days reduced its average viability by 42%. Four hours of incubation with photoperiod, is enough to promote the germination of peach pollen.

OsmiR528 regulates rice-pollen intine formation by targeting an uclacyanin to influence flavonoid metabolism

The intine, the inner layer of the pollen wall, is essential for the normal development and germination of pollen. However, the composition and developmental regulation of the intine in rice (Oryza sativa) remain largely unknown. Here, we identify a microRNA, OsmiR528, which regulates the formation of the pollen intine and thus male fertility in rice. Themir528knockout mutant aborted pollen development at the late binucleate pollen stage, significantly decreasing the seed-setting rate. We further demonstrated that OsmiR528 affects pollen development by directly targeting the uclacyanin geneOsUCL23(encoding a member of the plant-specific blue copper protein family of phytocyanins) and regulating intine deposition.OsUCL23overexpression phenocopied themir528mutant. The OsUCL23 protein localized in the prevacuolar compartments (PVCs) and multivesicular bodies (MVBs). We further revealed that OsUCL23 interacts with a member of the proton-dependent oligopeptide transport (POT) family of transporters to regulate various metabolic components, especially flavonoids. We propose a model in which OsmiR528 regulates pollen intine formation by directly targetingOsUCL23and in which OsUCL23 interacts with the POT protein on the PVCs and MVBs to regulate the production of metabolites during pollen development. The study thus reveals the functions of OsmiR528 and an uclacyanin during pollen development.