Pollen Grain Germination Research Articles

Биология цветения, плодоношения и жизнеспособности пыльцы сортов и форм айвы, возделываемых на территории Нахичеванской автономной республики

Abstract. 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.

ZnO nanoparticles effect on pollen grain germination and pollen tube elongation

Plant germ cells, such as pollen grains, can be affected by exposure to metal nanoparticles (NPs) that have diffused into the environment. The germination and tube elongation of pollen grain (Lilium longiflorum) exposed to low-solubility NPs was observed. The germination rate of pollen grain exposed to 100 mg L−1 ZnO NP dispersion decreased significantly from controls and exposure of the other NPs. On the other hand, when pollens were exposed to ionic solutions in which particles were removed from the 100 mg L−1 ZnO NP dispersion, the germination rates were equivalent to those in the control pollens. On the contrary, decrease of the germination rate compared to controls was small in the exposure to ZnCl2 solution, which contained a larger amount of water-soluble Zn2+ than ZnO NP dispersion. From these results, it was concluded that fine ZnO NP may adhere to pollens, due to the cohesive property of nanoparticles, and Zn2+ dissolved at the interface may be continuously absorbed by pollens. When pollen was exposed to ZnO NP, a spot with a high Ca2+ local concentration was observed at the tip of the pollen tube. On the contrary, simultaneous exposure to antagonistic ZnO NP and CaCl2 resulted in no decrease in the germination rate. From the above, it is considered that upon exposure to ZnO NP, cells absorb Zn2+ depending on the specific solubility of ZnO NP. Despite the low solubility of zinc oxide nanoparticle, pollen cell-attached particles inhibited germination and elongation of pollen tube by continuous Zn2+ dissolution from particles and Zn2+ absorption by the cell.

Reproductive biology of East Indian satinwood (Chloroxylon swietenia DC., Rutaceae: Sapindales), a threatened timber-yielding tree

Chloroxylon swietenia DC. (Rutaceae) is widely used in folk medicine and provides a commercial timber. In the present study, phenological events such as flowering and fruiting phenology, pollinator visitation, anthesis, pollen viability, and pollen tube germination tests were analyzed in 11 populations, in Tamil Nadu, India. The number of flowers was recorded as 82.6 ± 1.4 to 162.2 ± 4.2 during flower bud formation and reduced to 25.4 ± 0.5 to 61.8 ± 1.0 at maturity. The number of fruits per twig was 21.0 ± 0.8 to 47.2 ± 0.7 in initial stages and slightly reduced to 16.2 ± 1.8 to 34.6 ± 1.4 at maturation. Sixty-two species of insects were visiting the flowers with bees/ants as effective pollinators. The 2,5-diphenyltetrazolium bromide assay revealed more viable pollen grains in five populations, and fluorescence dye assay revealed maximum viable pollen grains in six populations. In the pollen tube germination test, the 60% sucrose concentration provides significant results, with a high number of germinated pollen grains. Principal component analysis of flowering and fruiting phenology, floral visitors, and pollen viability showed 79.5%, 79.3%, 56.7%, and 41.7% for the first factor, respectively. Our results indicated that C. swietenia depends heavily on pollinators for its reproduction. Hence, there is a need to expand this study to related species which are having agronomic, pharmacological, and economic potential.

Arabidopsis 3-Ketoacyl-CoA Synthase 4 is Essential for Root and Pollen Tube Growth

Very long-chain fatty acids (VLCFAs) are essential precursors of membrane lipids, such as phospholipids and sphingolipids, cuticular waxes, suberins, and Brassica seed oils. The first step of VLCFA synthesis is mediated by 3-ketoacyl-CoA synthase (KCS), which catalyzes the condensation of a C2 unit from malonyl-CoA to acyl-CoA. In the present study, we investigated the role of KCS4 in pollen tube and root growth. KCS4 was predominantly expressed in shoot and root apical meristems, leaf veins, mature and germinated pollen grains, and developing embryos. The fluorescent signals of KCS4 fused with enhanced yellow fluorescent protein (KCS4:eYFP) were detected in the endoplasmic reticulum of tobacco epidermis. KCS4 disruption inhibited pollen tube elongation and root growth, whereas KCS4 promoter-driven KCS4 expression rescued the growth-retarded phenotype to wild type (WT) in kcs4 complementation lines. Root growth assay of WT and kcs4 lines treated with metazachlor and mefluidide, which are specific KCS inhibitors, and fatty acid analysis of their roots and seeds revealed that KCS4 is involved in the elongation of longer than C24 VLCFAs, which are essential for root and pollen tube growth.

In Vitro Germination of Pollen Grains in Pitahaya Species

ABSTRACT The aim of this study was to adjust the basic culture medium for germination of pollen grains for the different species from the genus Hylocereus. Pollen grains from the species Hylocereus polyrhizus Weber and Hylocereus undatus (Haw.) Britton & Rose were withdrawn of anthers from flowers bagged the previous day, before its opening. Then, with a brush, the pollen grains were spread on the surface of Petri dishes containing 20 mL of culture medium. Four experiments were sequentially installed, considering and selecting the best results from the previous experiment to install the next one. Measurements were made on the length of pollen tube under different concentrations of boric acid. Moreover, germination rate readings were performed after 24 h. The pollen viability of species from the genus Hylocereus varies according to species and the pollen germination was influenced by composition and concentration of medium. The culture medium for the germination of pollen grains from H. polyrhizus species must be increased with 100 g L−1 of sucrose, 518 mg L−1 of calcium nitrate and 636 mg L−1 of boric acid, the pH being measured for 5 and the medium solidified with 6 g L−1 of agar. For H. undatus, the medium should be composed of 100 g L−1 of sucrose, 616 mg L−1 of calcium, 619 mg L−1 of boric acid, 6 g L−1 of agar and pH 6. Both species increased the length of pollen tube with the addition of boric acid.

Germination of Pollen Grains of Spathodia companulata P. Beauv in in vitro and in vivo like Condition with the Influence of a Promoter Medium

In vitro, germination is the most commonly used technique in pollen physiology. This provides a simple experiment method to study the pollen germination and pollen tube growth, in the endogenous as well as exogenous conditions. In vivo conditions (endogenous) can also apply to the study of pollen system. In the present investigation, the pollen germination of Spathodia companulata P. Beauv was studied in the different parts of the carpel viz., style, stigma, ovary, style-stigma, style-ovary and whole gynoecium. Spathodia companulata P. Beauv is planted for reforestation schemes, for soil conservation. In India, it is seen that there is a rare formation of fruit and seeds in this plant. Thus for the study of the growth of the plant for cultivation purposes, the growth of the pollen tube was studied which could be one of the reason for the less fruit and seed formation. Pollen tubes were found to be stimulated by those components present in the different selected parts of the carpel.

An Ethylene Over-Producing Mutant of Tomato (<i>Solanum lycopersicum</i>), Epinastic, Exhibits Tolerance to High Temperature Conditions

Above-optimal temperatures reduce yield in many crops, including tomato, largely because of the heat-sensitivity of their reproduction process. A full understanding of heat-stress (HS) response and thermotolerance of tomato reproduction is still lacking. Recently, using external application of the plant hormone ethylene, it was demonstrated that ethylene plays a role in heat-tolerance of tomato pollen (the male reproductive cells). In order to expand our understanding on involvement of ethylene in tomato pollen thermotolerance, we analyzed the response of wild type and ethylene-related tomato mutant plants to HS, at physiological and molecular levels. We report that mild chronic HS conditions highly reduce the number of viable and germinating pollen grains as well as the production of seeded fruits in wild type tomato plants, while no significant reduction was detected/observed in pollen quality, number of seeded fruits and seeds per fruit in plants of the ethylene over-producer mutant epinastic. Our findings suggest that ethylene is involved in thermotolerance of tomato reproduction, pointing to an effect on pollen viability and germination potential, highlighting candidate genes involved in pollen response to HS (like SlHSP17, SlHSP101, SlMBF1) and suggesting directions for further studies.

Влияние температуры и влажности воздуха на жизнеспособность пыльцы рапса озимого

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.

Characteristics of the pollen morphology and viability of Bougainvillea (Nyctaginaceae)

Pollen grains of 92 Bougainvillea genotypes were examined using a light microscope (LM) and scanning electron microscope (SEM) to identify taxonomic characteristics and the relationship between pollen morphology and germination capacity. The shapes of fresh pollen grains of Bougainvillea genotypes are spheroidal to prolate-spheroidal or suboblate after infolding. The sexine of Bougainvillea pollen grains consists of columellae and a reticulate cristatum, with or without microechini. The distribution pattern of the tectum microechini is uniform on the pollen grains within each genotype, yet it is variable among the different genotypes. Pollen with a smooth reticulate cristatum was observed in the genotypes of B. peruviana, while pollen with muri covering the cristatum were found in the genotypes of B. glabra and B. spectabilis. The pollen grains of each Bougainvillea germplasm have a wide range of diameters. The mean diameter of the pollen grains of the diploid genotypes ranged from 22.2 to 32.1 μm, while that of the polyploid genotypes ranged from 26.7 to 40.4 μm. The germinated pollen grains were observed in the diploid and tetraploid genotypes, the pollen germination rate of which was commonly less than 20 %. The size of germinated pollen grains was significantly larger than that of the silent ones, which indicated that the nonuniform distribution of grain size is a key reason for the low germination capacity of Bougainvillea pollen.

Viability of black currant pollen before and after cryopreservation in liquid nitrogen, and its morphological features

Background.Learning about morphological and biological features of pollen is very important to make correct estimations of plant productivity and breeding efficiency.Materials and methods. The viability of black currant pollen was analyzed in 2019 at the Laboratory for Long-Term Storage of Plant Genetic Resources, N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR). Eleven black currant cultivars of various ecogeographic and genetic origin maintained at Pushkin and Pavlovsk Laboratories of VIR served as the material for the research. Pollen viability was tested on an artificial medium with 10% sucrose and 0.8% agar. Morphological studies were carried out using light and confocal laser scanning microscopy at the Palynology Laboratory and the Core Centrum of Cell and Molecular Technologies in Plant Science housed by the Komarov Botanical Institute (BIN).Results and conclusion. The prevailing adverse weather conditions in 2019 produced a negative impact on the process of male generative structure formation. The level of pollen viability, depending on the cultivar, ranged from 17.98 to 58.60%. After exposure to liquid nitrogen (–196°C) for 6 months, the number of germinated pollen grains increased 1.1 to 3.2 times in all the studied cultivars, except one (‘Pozdnyaya poslevoennaya’, k-7652). A palynomorphological study revealed that reduced pollen viability in some cultivars (‘Krasnoyarskaya 1018’, k-7607; ‘Tsema’, k-25900; ‘Pozdnyaya poslevoennaya’, k-7652) was associated with morphological deviations in the sporoderm structure (small pollen grains, exine thickening and formation of verrucate mesoporium surfaces). A low positive correlation was observed between the level of pollen viability and the diameters of the pore (r = 0.43) and pollen grain (r = 0.27). An insignificant negative correlation was apparent between the level of viability and the exine thickness (r = –0.33).

Dasykothon leptomiscus gen. et sp. nov., a fossil flower of possible Lauralean affinity from Myanmar amber

A new fossil angiosperm, Dasykothon leptomiscus, is described from mid-Cretaceous amber deposits in the Hukawng Valley of northwestern Myanmar (Burma). The flower is post-anthesis except for one stamen that retains its pollen. The perianth is slightly irregular and composed of 5 ovate or lance-linear, erect or incurved sepals. The ca. 12 stamens have slender, elongate filaments and dorsifixed, bithecal, longitudinally dehiscent anthers. The superior ovary bears 2 long, curved styles. Germinating pollen grains observed on the stigmas are monoporate and have the peculiar feature of a grooved ridge encircling the grain from pole to pole. This structure is hypothesized to be an evolutionary elaboration of the meridionally syncolpate sulcus found in some members of the Atherospermataceae. The generalized floral morphology of the fossil prevents ready taxonomic assignment to a modern family.

Doubly guaranteed mechanism for pollination and fertilization in Ipomoea purpurea.

Flowers, the reproductive organs of angiosperms, show a high degree of diversity in morphological structure and flowering habit to ensure pollination and fertilization of the plants. Effect of flower movement on pollination and fertilization was investigated in Ipomoea purpurea (Convolvulaceae) in this study. Fluorescence microscopy was used to observe the germination of pollen grains at different temperatures. From 04:00 to 06:00h, the stigma was taller than the filaments, so that self-pollination could not occur, and cross-pollination was carried out by insects. Pollen grains germinated rapidly after falling on the stigma; the pollen tube reached the ovule to complete fertilization after 2-3h. From 07:00 to 09:00h, filaments of two stamens grew rapidly and reached the same height as the stigma, thus allowing self-crossing. But at this time, the ambient temperature was already high and was not conducive to the germination of pollen grains. The corolla closed, forming an inverted bell shape, where the inner microenvironment ensured completion of pollen germination and fertilization. Preferential cross-pollination and delayed self-crossing of I. purpurea provided a doubly guaranteed mechanism for pollination and fertilization, facilitating its adaptation to a high temperature climate.

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.

Intensified pollination and fertilization ameliorate heat injury in rice (Oryza sativa L.) during the flowering stage

Heat induces spikelet sterility during flowering in rice. Spikelet sterility in heat-stressed plants is associated with poor pollination due to insufficient pollen grain deposition and unsatisfactory fertilization from reduced pollen germination on the stigma. Measures aimed at facilitating pollen shedding and pollen germination will help to address the adverse effects of heat stress on spikelet fertility in rice during the flowering stage. Intensified pollination by artificially assisted pollen shedding combined with intensified fertilization by promoting pollen germination through chemical application (pH=8.0, 10 % sucrose, 0.1 mM spermidine, 0.01 % myo-inositol, 0.01 % boric acid, 1 μM 24-epibrassinolide, 1 mM KCl, 1 mM CaNO3, 1 mM CaCl2, 0.03 % casein enzymatic hydrolysate, 0.01 % ferric ammonium citrate, 10 mM γ-aminobutyric acid, and 1–2 drops of Tween 20) increased spikelet fertility significantly compared with that without intensified measures under heat treatments in controlled greenhouse conditions. Intensified pollination increased the percentage of anther dehiscence and the number of pollen grains on the stigma, and the chemical application increased the number of germinated pollen grains on the stigma, thus increasing the spikelet fertility and ultimately the grain yield. In open-field conditions, intensified pollination and fertilization measures increased the spikelet fertility, grain weight and quality significantly under elevated temperatures. The proposed methods of enhancing pollination and fertilization are simple and effective for ameliorating the adverse effects of heat stress on the grain yield and quality in rice. This study provides strategies for sustainable rice production under the high temperatures expected with future global warming.

Foliar application of macro and micronutrients and productivity of oilseed crops: A review

Macro and Micronutrients in oilseeds essential for plant growth, but plants require macro nutrients in large quantity and micronutrients relatively in smaller quantity. Macronutrients include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S). They play major role in protein and starch synthesis, fruit formation, nodulation, pegging, oil synthesis and chlorophyll production. Micronutrients include iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo) and boron (B). They play major role in translocation of photosynthesis, increases seed setting percentage, essential for translocation of sugar, germination of pollen grains, stigma receptivity, amino acid and protein synthesis which ultimately increase the productivity of oilseed crops.

How panicle angle and panicle position in the canopy determine pollination and seed set in rice (Oryza sativa L.)

ABSTRACT We examined the effect of panicle position relative to canopy and of panicle angle on pollination and floret sterility in rice at anthesis in a paddy field. We set panicles of pot-grown rice at the flowering stage either upright (0°) or inclined (30°), either above or at canopy height (Experiment 1) and either beneath or at canopy height (Experiment 2), in three replications each. In Experiment 1 and Experiment 2, panicle inclination at 30° increased the percentage of florets with <20 total pollen grains on the stigma (TP20) by 21% and 27%, increased the percentage of florets with <10 germinated pollen grains on the stigma (GP10) by 21% and 30%, and increased floret sterility by 10% and 26%, respectively. Floret sterility was correlated with GP10 in all trials. GP10 was correlated with TP20. The effect of position on floret sterility was not significant. We conclude that panicle inclination at 30° significantly increased floret sterility even under the canopy condition. Uprightness of panicles should be an important objective in rice breeding and production. Abbreviations TP20, percentage of florets with <20 total pollen grains on the stigma; GP10, percentage of florets with <10 germinated pollen grains on the stigma.

Dependence of pollination and fertilization in rice (Oryza sativa L.) on floret height within the canopy

We examined changes in rice (Oryza sativa L.) floret sterility and pollination as a function of vertical position of florets in the canopy at anthesis in paddy fields to clarify the ideal panicle height. Flowering pot-grown rice plants were placed in the rice canopy at different heights to position their florets at different depths below the canopy surface. The percentage of floret sterility was approximated as Y = 0.000335 X12 + 0.0296 X1 – 0.0451 X2 + 0.0152 X1X2 – 0.0468 (R2 = 0.921), where Y is the logit-transformed floret sterility (%), X1 is floret depth at anthesis (cm), and X2 is wind speed above the canopy (m s–1). The percentage of florets with fewer than 20 pollen grains on the stigma after flowering was approximated well by Y = 0.000554 X12 – 0.235 X22 + 0.5346 (R2 = 0.892), where Y is the logit-transformed percentage. The floret sterility (%) was correlated with the percentage of florets with <10 germinated pollen grains and with the percentage with <20 total pollen grains. Thus, there exists an optimal flowering depth and an ideal panicle position with respect to the canopy surface that stabilizes pollination and fertilization, and the optimal position for fertilization deepens with increasing wind strength.

Ecological fitting is a sufficient driver of tight interactions between sunbirds and ornithophilous plants.

Plant–bird pollination interactions evolved independently on different continents. Specific adaptations can lead to their restriction when potential partners from distant evolutionary trajectories come into contact. Alternatively, these interactions can be enabled by convergent evolution and subsequent ecological fitting.We studied the interactions between New World plants from the genus Heliconia, Asian plants of genus Etlingera and African sunbirds on a local farm in Cameroon. Heliconia spp. evolved together with hummingbirds and Etlingera spp. with spiderhunters —an oriental subgroup of the sunbird family.Sunbirds fed on all studied plants and individual plant species were visited by a different sunbird spectrum. We experimentally documented a higher number of germinated pollen grains in sunbird‐visited flowers of Etlingera spp. For Heliconia spp., this experiment was not successful and pollen tubes were rarely observed, even in hand‐pollinated flowers, where enough pollen was deposited. The analyses of contacts with plant reproductive organs nevertheless confirmed that sunbirds are good pollen vectors for both Heliconia and Etlingera species.Our study demonstrated a high ecological fit between actors of distinct evolutionary history and the general validity of bird‐pollination syndrome. We moreover show that trait matching and niche differentiation are important ecological processes also in semi‐artificial plant‐pollinator systems.

Studies on reproductive organs and morpho-anatomical features of leaf and stem in three traits of Vinca rosea L.

Periwinkle or Vinca rosea L. has medicinal importance with three phenotypes i.e., Pink, Red eye and White. The present investigation distinguishes the three traits i.e., white, pink and red-eyed flower-bearing traits of V. rosea based on morphology, palynology, pollen grain germination and study of anatomical features of leaf, stem and variations in parts of the flower. The results revealed that significant differences were recorded in stomatal frequency, stomatal index, size of the petals, pollen viability and pollen germination. The highest per cent viability appears in pink flower-bearing plants (98.8%) followed by red-eyed flower-bearing plants (34.3%) and White flower-bearing plants (34%). Similarly, the percentage germination of pollen grains is high in pink flower-bearing plants (98.1%) followed by red-eyed flower-bearing plants (33.3%) and white flower-bearing plants (33.3%).

Pollen of Arbutus unedo: Effects of plant growth regulators

Arbutus unedo is a species mainly used for landscaping purposes and lately for honey production. Its antioxidant characteristics have also been a subject of of research interest. The germination of pollen grains freshly collected from flowers was tested in vitro, and 30% sucrose gave the highest pollen germination. Subsequently, three growth regulators belonging to the categories of gibberellins and brassinosteroids [24-epibrassinolide (Ebl) and 22S,23S-homobrassinolide (Hbl)] were added to the growth medium singly or in double combinations (gibberellin + brassinosteroid), and the petri dishes were kept for 24 hours at 26?1?C. The results showed that the highest germination rates were obtained from treatments with 0.01 ppm Hbl (45.47%) and 0.001 ppm Hbl (26.74%). They were followed by treatments with 0.001 ppm Ebl, 25 ppm GA3 and 0.1 ppm Ebl. As the concentration of GA3 increased, the germination rate declined considerably. Statistical analysis of the combined treatments showed that combinations of growth regulators lowered the germination rates compared to their individual application. Moreover, action of the lowest GA3 concentration (25 ppm) best matched the effects of brassinosteroids, and increasing the GA3 concentration in combined treatments did not improve germination. The highest germination was obtained with 0.1 ppm Hbl, followed by all Ebl treatments. Brassinosteroids might be an inducer of pollen germination in plants depending on their type and concentrations. When individually included in the growth medium, the extent of this induction was greater with the homobrassinolide than with the epibrassinolide. Their interactions with gibberellins are shown to be mostly dependent on the concentration of gibberellic acid used. The tested epibrassinolide was more consistent than the homobrassinolide in maintaining higher germination levels. The findings of this study indicate that gathering more information from studies involving other plant species is needed to clarify the role of brassinosteroids in in vitro and in vivo germination.