Flower stages, germination and viability of pollen grains of Annona squamosa L. in tropical conditions

The success in the application of artificial pollination techniques, aspects of floral biology should receive special attention, especially regarding the viability studies of pollen grains. In this sense, two experiments were carried out, aiming to determine the floral stages: floral opening (anthesis), female, male and senescence stages of A. squamosa L flowers under tropical climate conditions, and to evaluate the germination and viability of pollen grains submitted to different storage conditions. In the first experiment, observations and data collection began when flowers were still closed. Readings were taken every two hours for 46 hours until all the flowers reached the senescence stage. For the second, the experimental design was completely randomized, in a 2 x 7 factorial scheme, with 2 storage conditions (environment at 27 ± 2°C and refrigerated at 5 ± 2°C) and 7 pollen grain conditioning times (0, 4, 8, 12, 16, 20 and 24 hours), with 4 repetitions for the analysis of pollen grain germination and 3 repetitions for the analysis of pollen grain viability, and each repetition consisted of one blade. The variables evaluated were percentage of viable and non-viable pollen grains and percentage of germinated and non-germinated pollen grains. For tropical climatic conditions, the flower anthesis (female stage) of the sugar-apple begins at 00:00 h, extending until 12:00h on the same day. The flowers of the tree reach a functionally staminate stage (male stage) from 6 a.m. the next day. Pollen grains stored at room conditions (27 ± 2°C) remain viable for up to 24 hours after collection, showing that storage in a cold environment at low temperatures (5 ± 2°C) is not necessary. Seed pollen grains have a germination percentage of 51.25% when stored under ambient conditions (27 ± 2°C) for up to 4 hours after collection.

Biology of Flowering, Fruit and Viability of Pollen of Varieties and Forms of Quince Cultivated on the Territory of the Nakhchivan Autonomous Republic

The zones of distribution of varieties and forms of quince on the territory of the Nakhchivan Autonomous Republic have been established, phenological observations have been carried out, their flowering and fruiting have been studied. On the territory of the Autonomous Republic, flowering of varieties and forms of quince begins in the second decade of April, depending on the distribution zone, with an average daily temperature of 12–13 °C and lasts 12–13 days, depending on weather conditions. Each flower has 10–12 stamens arranged in one row. The article also studied the viability of pollen in a number of quince varieties. Pollen viability was studied in the varieties Sary, Tursh, Ordubad, Gara and wild forms. Pollen fertility was determined by staining with acetocarmine. Pollen germinates in 2–5–10–15 and 20% glucose solution. Counting of germinated pollen grains was carried out under a microscope. The study showed that of all the experimental varieties, the pollen fertility of the Sary quince and Tursh quince varieties is high (up to 96.6–97.1%). The best medium for the germination of quince pollen is a 10–15% glucose solution. Pollen germination in this solution reaches 47.4–88.0%. In distilled water (control), the germination of quince pollen reached from 9.7% to 35.6% for varieties. Quince pollen remains viable for 31–43 days.

Transcriptome and translatome changes in germinated pollen under heat stress uncover roles of transporter genes involved in pollen tube growth

ABSTRACTPlant reproduction is one key biological process very sensitive to heat stress and, as a consequence, enhanced global warming poses serious threats to food security worldwide. In this work we have used a high-resolution ribosome profiling technology to study how heat affects both the transcriptome and the translatome of Arabidopsis thaliana pollen germinated in vitro. Overall, a high correlation between transcriptional and translational responses to high temperature was found, but specific regulations at the translational level were also present. We show that bona fide heat shock genes are induced by high temperature indicating that in vitro germinated pollen is a suitable system to understand the molecular basis of heat responses. Concurrently heat induced significant down-regulation of key membrane transporters required for pollen tube growth, thus uncovering heat-sensitive targets. We also found that a large subset of the heat-repressed transporters is specifically up-regulated, in a coordinated manner, with canonical heat-shock genes in pollen tubes grown in vitro and semi in vivo, based on published transcriptomes from Arabidopsis thaliana. Ribosome footprints were also detected in gene sequences annotated as non-coding, highlighting the potential for novel translatable genes and translational dynamics.

Factors Influencing Cross Barriers in Interspecific Hybridizations of Water Lily

In interspecific hybridizations of water lily (Nymphaea), the existence of cross barriers makes it difficult to obtain hybrids and seriously influences the utilization of admirable characters from tropical water lilies. To determine the causes, pollen viability, pistil receptivity, and embryo and endosperm development were investigated in three water lily crosses, including Nymphaea odorata ‘Peter Slocum’ × Nymphaea micranthar (PM), ‘Peter Slocum’ × Nymphaea gigantea (PH), and ‘Peter Slocum’ × Nymphaea colorata (PC). The results indicated that the viability of pollen grains was 17.3% for ‘Peter Slocum’, 19.3% for N. colorata, 10.3% for N. micrantha, and 17.6% for N. gigantea. In the self-pollinated ‘Peter Slocum’, the number of germinated pollen grains on stigmas peaked at 12 hours after pollination (HAP), indicating its good pollen germinability. However, only a few pollen grains germinating on the sigma between 2 and 24 HAP in the crosses of PM, PH, and PC. In addition, a high percentage (81.2%) of normal embryos developed to different stages within 20 d after pollination in the self-pollinated ‘Peter Slocum’. But only 3.5% and 3.7% of normal globular embryos were observed in the PC and PM combinations, respectively. Moreover, no normal embryos were observed in the PH cross. At the same time, no seeds were obtained in PM, PC, and PH crosses. The results suggest that prefertilization barriers existed in the PH cross, whereas pre- and postfertilization barriers existed together in the PC and PM crosses. These may be the main causes resulting in the failure of interspecific hybridizations in water lily.

Learning by Doing: Applying the Concept of Pollen Viability in a Horticulture Classroom

Learning by doing plays a critical role in a learner’s conceptual understanding. By actively engaging with a concept, students gain experience and develop an enduring understanding of the concept. The concept of pollen viability is a critical component in the field of plant breeding and can be used to explain various aspects of pollen quality. An inquiry activity was designed to expose undergraduate students in a horticulture course to the concept of pollen viability and its application. The entire class was tasked with collaborating to identify an in vitro germination medium optimized to germinate plumeria (Plumeria rubra) pollen. To determine optimum sucrose and pH concentrations of the medium, student groups were assigned treatments of pollen from two plumeria cultivars that were germinated in Brewbaker and Kwack media of differing sucrose and pH concentrations. Students calculated the percentage of germinated pollen and assessed pollen tube integrity and used these variables as evidence of an optimized medium. Although undergraduates were engaged in authentic research practices during the inquiry activity, lack of time and resources impeded completion of the activity. However, students were exposed to methods and instrumentation directly related to evaluating pollen viability. Moreover, they were exposed to the basic practice of pollen quality assessment that they can use to carry out investigations on pollen fertility. In addition, insight was gained to improve the inquiry activity in the future. Now, well-informed modifications to the inquiry activity can be made to pilot this activity in a formal horticulture laboratory section.

ОСОБЕННОСТИ РАЗВИТИЯ МУЖСКОГО ГАМЕТОФИТА СОСНЫ ОБЫКНОВЕННОЙ PINUS SILVESTRIS L. В УСЛОВИЯХ ГОРОДСКОЙ СРЕДЫ

<p>The peculiarities of the development of the male gametophyte of Pinus silvestris L. in the urban environment were studied. Quality of pollen was evaluated by laboratory experiments through germination at the nutrient medium and by histochemical staining to determine the presence of redox enzymes. It was shown that pollen viability is closely linked to climatic and weather conditions during the period of microsporogenesis and mass pollination. Atmospheric pollution affected the pollen significantly. Low temperatures and high humidity in the background of the weak capacity of self-purification of the atmosphere led to a reduction of the potential pollen viability. The ability of the pollen grains to germinate was reduced, the number of abnormal pollen tubes was increased, and the proportion of cells containing active peroxidase was decreased. We revealed a close positive correlation between the frequency of germinated pollen grains and the presence of active peroxidase, as well as a negative correlation between the percentage of colored pollen and the frequency of pollen tube anomalies, which confirmed the role of peroxidase activity not only in the induction of pollen germination, but also the formation of pollen tubes.<br />A ranking of the urban territory on the strength of unfavorable environmental factors has been carried out. The reaction of male gametophyte of pine allowed us to consider it as a biological indicator of unfavorable ecological situation in the urban environment.</p>

Effect of nickel on pollen germination and pollen tube length in Arabis alpina (Brassicaceae)

In this work we studied and compared the toxic effect of nickel (Ni) on pollen germination and pollen tube length in Arabis alpina L. collected from serpentine and non-serpentine populations distributed in the Rila mountains, Bulgaria. Pollen grains were treated with prepared standard solutions of 100, 300, 500, and 700 μM Ni as NiCl2 in distilled water. A nutritional medium was also used to assess pollen germination. Nickel inhibited pollen germination and pollen tube elongation in both serpentine and non-serpentine plants. The percentage of germinated pollen in serpentine plants treated with Ni was higher than in non-serpentine plants but there was no difference in pollen tube elongation between groups. However, pollen tubes showed abnormalities such as coiling and swelling of the tip, or burst, and varied considerably among the samples. A complete break of pollen tube elongation is due to such abnormalities. Also, decreased pollen fertility in both populations was found. The plants from serpentines were less sensitive to (i.e. more tolerant of) elevated Ni concentrations commonly found in serpentine soils.

In VitroPollen Viability and Pollen Germination in Cherry Laurel (Prunus laurocerasusL.)

Pollen quality is important for growers and breeders. This study was carried out to determinein vitropollen viability and pollen germination in seven genotypes of cherry laurel (Prunus laurocerasusL.). Two pollen viability tests, TTC (2,3,5-triphenyl tetrazolium chloride) and IKI (iodine potassium iodide), were used. Pollen traits of genotypes were studied using anin vitromedium containing 0%, 5%, 10%, 15%, and 20% sucrose to determine the best sucrose concentrations for germination. In the second step, the germinated pollen was counted 1, 4, 6, 10, 12, 24, and 48 hours later until there was no further germination. The viability rates were different according to genotypes and tests used. The IKI and TTC staining tests and pollen germination had low correlation (r2= 0.0614 andr2= 0.0015, resp.). Painted pollen rate was higher and pollen was well-stained with IKI test and pollen viability estimated with TTC staining test was better than that estimated with the IKI staining test. 15% sucrose gave the best germination rates in most of the genotypes. Pollen germination rates were recorded periodically from one hour to 48 hours in 15% sucrose and the results showed that pollen germination rates increased after 6 hours of being placed in culture media.