Onset Of Germination Research Articles

Imaging and Quantitative Analysis of Size and Distribution of Spherical Bodies, e.g. Embryonic Oil Bodies

Oil bodies (OBs) are seed-specific lipid storage organelles that allow the accumulation of neutral lipids that sustain plantlet development after the onset of germination. Using fluorescent dyes and confocal microscopy, we monitored the dynamics of OBs in living Arabidopsis (Arabidopsis thaliana) embryos at different stages of development (Miquel et al., 2014). Image acquisition was followed by a detailed statistical analysis of OB size and distribution during seed development in the four dimensions (x, y, z, and t).

Novel Use of Trinexapac-Ethyl to Study Weed Seed Germination

Understanding seed biology and onset of germination requirements is a key point for designing effective weed management programs. Gibberellins (GAs) are known to play a role in onset of germination of several species. Onset of germination often requires an increase in de novo GA content or an increase in sensitivity to GAs. Reduced germination of seeds incubated in solutions containing compounds that inhibit GA synthesis provide evidence that GAs are required to trigger germination. Trinexapac-ethyl (TE), a GA synthesis inhibitor, is frequently used as a plant growth regulator in crop production. However, to the best of our knowledge, TE has not been used to study the requirement of GAs in onset of germination. Germination studies were conducted using seeds of artichoke thistle and common teasel under a range of TE concentrations (0 to 500 μM TE), a combined solution of 125 μM TE + 100 μM GA3for artichoke, and 250 μM TE + 100 μM GA3for common teasel. Germination tests were conducted at 20/10 C (12-h thermoperiod) in darkness for artichoke and at constant 15 C with 12 h of light for common teasel. Germination of artichoke in 125 μM TE was reduced to 47% when compared with the check (95%), but the combined TE + GA3solution maintained germination at 84%. Germination of common teasel in 250 μM TE was reduced to 10% when compared with the check (91%), and the combined TE + GA3solution increased germination to 63%. These results demonstrate the utility of TE to study the role of GAs in onset of germination. This novel use of TE is a valuable option to study germination requirements of weed species, and therefore contributes to the design of weed management programs.

Effect of gibberellic acid on germination potential in vitro seed Carica quercifolia (St. Hil.). Hieron. (Caricaceae)

The species Carica quercifolia (St. Hil.). Hieron. (Caricaceae), native to the region west of Santa Catarina has ornamental potential and fruitful, however, its seeds have low germination rates. Thus, the objective was to evaluate the effect of gibberellic acid (GA) on seed germination of C. quercifolia in vitro. Initially, the seeds were subjected to an aseptic treatment with sodium hypochlorite and 70% alcohol, then subjected to five different treatments with gibberellic acid (control, 50, 100, 150 and 200 mg.L-1) and subsequently inoculatedinoculated on MS medium. Each treatment had 12 replications and six sub-repetitions. After inoculation, seeds were kept in a germination chamber with a photoperiod of 16 hours (50 mol photons m-² s-¹) and temperature of 26 ± 2 ° C. The onset of germination was observed at day 35 of culture only in treatments with 100 and 200 mg L-1 GA. After 42 days of cultivation, there was low germination rate in both control seeds and seeds treated with GA, and there were no statistically significant differences. The results suggest that the concentrations of GA were used possibly lower, unable to induce the germination C. quercifolia.

Specialization of Oleosins in Oil Body Dynamics during Seed Development in Arabidopsis Seeds

Oil bodies (OBs) are seed-specific lipid storage organelles that allow the accumulation of neutral lipids that sustain plantlet development after the onset of germination. OBs are covered with specific proteins embedded in a single layer of phospholipids. Using fluorescent dyes and confocal microscopy, we monitored the dynamics of OBs in living Arabidopsis (Arabidopsis thaliana) embryos at different stages of development. Analyses were carried out with different genotypes: the wild type and three mutants affected in the accumulation of various oleosins (OLE1, OLE2, and OLE4), three major OB proteins. Image acquisition was followed by a detailed statistical analysis of OB size and distribution during seed development in the four dimensions (x, y, z, and t). Our results indicate that OB size increases sharply during seed maturation, in part by OB fusion, and then decreases until the end of the maturation process. In single, double, and triple mutant backgrounds, the size and spatial distribution of OBs are modified, affecting in turn the total lipid content, which suggests that the oleosins studied have specific functions in the dynamics of lipid accumulation.

Mass Propagation of an epiphytic orchid Acampe papillosa (Lindl.) through in vitro seed germination

A method of in vitro propagation of a medicinally important epiphytic orchid of NBU campus Acampe papillosa has been developed. Three different categories of media (1/2 MS, MS and Knudson C) were used for in vitro asymbiotic seed germination for conservation and commercial uses. Seed germination was observed in all the media without any growth supplement or additives although not efficiently. Seeds showed positive germination response in all the three media but the frequency and onset of germination, protocorm formation and associated morphogenic changes leading to plantlets establishment varied with the nature of additional growth stimulus. Different concentrations and combinations of auxin and cytokinins were used to enhance the germination and seedling development. The different concentration of coconut water (CW) was used as additive supplement in this study and 15% CW showed good germination within 22 days in KnC medium. Various concentrations and combinations of plant growth regulators BAP (1mg l-1 to 4 mg l-1), NAA (0.5 mg l-1 to 2 mg l-1) and IBA (0.5 mg l-1 to 2 mg l-1) were added into the three categories of media as growth stimulants. The induction of PLBs was observed in the absence of any exogenous supply of PGRs, but the addition of BAP (4 mg l-1) with KnC medium improved the shoot growth significantly and enhanced the PLBs development (95% efficiency) with highest shoot length (2.5 cm) after six months of culture. Minimum number of days was required for seedling development (148 days) when cultured into the KnC medium supplement with combinations of BAP (4 mg l-1) and IBA (2 mg l-1). Addition of small quantity of NAA (0.5 mg l-1to 2 mg l-1) was not improved the PLBs or seedling development in compared to BAP and IBA. Rooting was improved by addition of IBA (0.5 mg l-1 to 2 mg l-1) into the media. High rate of rooting efficiency was recorded when combinations of auxin and cytokinin was used. Frequency of rooting (95%) was studied in KnC medium containing BAP (4 mg l-1) and IBA (2 mg l-1). Seedling of 2.5 cm long with 3-4 leaves were transferred to earthen pot containing wood charcoal and coco peat for acclimatization under green house conditions. Hardened plantlets showed significantly high survival rate (81%) after seven months of transfer. Therefore, the present method of micro-propagation could be used successfully to propagate this important orchid for commercial production and conservation purposes.

The role of moist-chilling and thermo-priming on the germination characteristics of white spruce (Picea glauca) seed

The individual and combined effect of moist-chilling and thermo-priming on germination parameters (capacity, speed, lag and dormancy index) were evaluated using seed lots representing British Columbia's five white spruce (Picea glauca) seed planning zones. The combined effect of moist-chilling followed by a 3-day priming at 15 or 20°C, stimulated seed germination across all seed lots. These combined treatments resulted in substantial improvement of all germination parameters including reducing the dormancy index (14 vs. 25). Generally, three days of priming at 20°C yielded a higher percent germination than priming for the same period at 15°C, irrespective of whether or not seeds had received a previous moist-chilling treatment. Thermo-priming alone led to some improvement in germination characteristics such as reducing the time to germination onset (lag) and increasing germination speed. These results indicate that the combined application of moist-chilling and thermo-priming could improve container nursery practices for commercial seedling production of white spruce. The positive combined effect of moist-chilling and thermo-priming on seed germination offer great potential for generalised application to other conifers; however, species-specific treatment adjustment is required.

Effect of high pressure on green pea seeds germination and plantlets development

The aim of this work was to study the impact of high pressure (50 MPa, 10 min) on germination of pea seeds with different imbibition times (0, 12 and 36 h). The parameters analysed were the percentage of germinated seeds, length of roots and stems, number of leaves developed and the weight of young plantlets. Peroxidase (POD), polyphenol oxidase (PPO), pectin methylesterase (PME) and total proteolytic activity were analysed in seeds after the pressure treatment and in leaves after the germination period. Results showed that 50 MPa applied during 10 min retarded the germination onset and inhibited seeds to germinate. The pressure treatment increased and decreased the length of roots and stems, respectively. The number of leaves per germinated seed decreased with the pressure treatment. Enzymatic activities of seeds showed that only total proteolytic activity was significantly reduced by pressure and only for 0 h of imbibition. POD and PPO activities determined in leaves of the plantlets increased with the pressure treatment, while PME activity also increased but only for 12 h of imbibition and total proteolytic activity decreased.

Phytotoxicity induced by Phragmites australis: an assessment of phenotypic and physiological parameters involved in germination process and growth of receptor plant

This study investigated the possible phytotoxicity induced by Phargmites australis on phenotypic and physiological parameters of recipient plants with identification of major inhibitors in the donor plant. This was achieved using aqueous extracts of different organs and root exudates of P. australis in laboratory and greenhouse experiments with Lactuca sativa as the model test plant. The observed reduced liquid imbibition and altered resource mobilization in seeds of L. sativa, in particular an insufficient carbohydrate supply, demonstrated that the onset of germination might be negatively affected by phytotoxicity. Dose-response studies pointed out that oxidative stress through reactive oxygen species production could potentially cause the observed germination and seedling growth reductions. The osmotic effects by mannitol solution on germination as well as growth and physiology at a level of −0.57 and −0.45 bar, respectively, demonstrated that the results from aqueous plant extracts were partially induced by the osmotic potential on and above those levels. Overall, the relative strength of inhibition on measured parameters was the highest in leaf extract, followed by rhizome, root, stem, and inflorescence. Root exudates of P. australis also had negative impacts by reducing germination and growth of plant. High-performance liquid chromatography (HPLC) analysis revealed gallic acid, a potent phytotoxin, as a major compound with an order of leaf >inflorescence>rhizome>root>stem.

Short-term liquid nitrogen storage of wild tomato (Solanum lycopersicum Mill.) seeds modifies the levels of phenolics in 7 day-old seedlings

In this work, we studied the effect of short-term liquid nitrogen storage on the germination and phenolics contents of wild tomato (Solanum lycopersicum Mill.) seeds. After storage in liquid nitrogen for different time periods (0, 7, 14, 21 and 28 days), seeds were retrieved from liquid nitrogen and set to germinate. Both control and cryopreserved seeds displayed about 60% germination without statistically significant differences. No phenotypic changes were observed visually in seedlings recovered from different treatments 7 days after onset of germination. After 7 days, levels of phenolics (free, cell-wall linked and total) were recorded in roots, stems and leaves of seedlings. When seeds were immersed in liquid nitrogen for 7, 14 and 21 days, the levels of cell wall-linked, free and total phenolics decreased significantly in roots and stems, compared to non-cryopreserved controls. However, their concentration generally increased when seeds were immersed in liquid nitrogen for 28 days. In leaves, a similar pattern to that observed in roots and stems was noted with the free phenolics content but cell wall-linked phenolics increased in leaves of seedlings derived from seeds immersed in liquid for 7 or 14 days. Further studies are required to clarify the mechanisms underlying the changes recorded here.

Identification of Barley Breeding Lines Combining Preharvest Sprouting Resistance with “Canadian‐type” Malting Quality

ABSTRACTRapid onset of germination in Canadian malting barley (Hordeum vulgare L.) facilitates production of good quality malt but predisposes barley to preharvest sprouting (PHS). Dormancy can be bred into barley to avoid PHS but some dormancy genes negate the potential for the “Canadian‐type” malt quality associated with a rapid start to germination. The microsatellite marker, GMS001, identified lines with PHS resistance and “Canadian‐type” malt quality in a cross between an Australian cultivar, Baudin, with PHS resistance, and a Canadian malt barley breeding line, TR253, without PHS resistance. The resulting population was grown at three sites over 2 yr with select site/years malted and analyzed for quality. Rapid visco analysis indicated PHS in some barley lines with as little as 11 mm of rain near harvest. The rapid visco analysis results substantiated the importance of the marker on chromosome 5H as breeding lines with the Baudin allele were less susceptible to sprouting, although they exhibited variable malt quality. Lines with the TR253 allele were PHS susceptible but had better and more consistent malt quality. Among the lines with the Baudin allele, five with PHS resistance and consistently good malt quality were identified. Among the lines with the TR253 allele, one showed good PHS resistance and the desirable “Canadian‐type” malt quality. These lines could serve as potential parents of future genotypes combining PHS resistance with good “Canadian‐type” malting potential.

Transcriptional landscape of Aspergillus nigerat breaking of conidial dormancy revealed by RNA-sequencing

BackgroundGenome-wide analysis was performed to assess the transcriptional landscape of germinating A. niger conidia using both next generation RNA-sequencing and GeneChips. The metabolism of storage compounds during conidial germination was also examined and compared to the transcript levels from associated genes.ResultsThe transcriptome of dormant conidia was shown to be highly differentiated from that of germinating conidia and major changes in response to environmental shift occurred within the first hour of germination. The breaking of dormancy was associated with increased transcript levels of genes involved in the biosynthesis of proteins, RNA turnover and respiratory metabolism. Increased transcript levels of genes involved in metabolism of nitrate at the onset of germination implies its use as a source of nitrogen. The transcriptome of dormant conidia contained a significant component of antisense transcripts that changed during germination.ConclusionDormant conidia contained transcripts of genes involved in fermentation, gluconeogenesis and the glyoxylate cycle. The presence of such transcripts in dormant conidia may indicate the generation of energy from non-carbohydrate substrates during starvation-induced conidiation or for maintenance purposes during dormancy. The immediate onset of metabolism of internal storage compounds after the onset of germination, and the presence of transcripts of relevant genes, suggest that conidia are primed for the onset of germination. For some genes, antisense transcription is regulated in the transition from resting conidia to fully active germinants.

The proteome of exudates from germinating Lupinus albus seeds is secreted through a selective dual‐step process and contains proteins involved in plant defence

The general knowledge of defence activity during the first steps of seed germination is still largely incomplete. The present study focused on the proteins released in the exudates of germinating white lupin seeds. During the first 24 h, a release of proteins was observed. Initially (i.e. during the first 12 h), the proteins found in exudates reflected the composition of the seed, indicating a passive extrusion of pre-formed proteins. Subsequently, when the rate of protein release was at its highest, the composition of the released proteome changed drastically. This transition occurred in a short time, indicating that more selective and regulated events, such as secretory processes, took place soon after the onset of germination. The present study considered: (a) the characterization of the proteome accumulated in the germinating medium collected after the appearance of the post-extrusion events; (b) the biosynthetic origin and the modalities that are the basis of protein release outside the seeds; and (c) an assessment of antifungal activity of these exudates. The most represented protein in the exudate was chitinase, which was synthesized de novo. The other proteins are involved in the cellular mechanisms responding to stress events, including biotic ones. This exudate was effectively able to inhibit fungal growth. The results of the present study indicate that seed exudation is a dual-step process that leads to the secretion of selected proteins and thus is not a result of passive leakage. The released proteome is involved in protecting the spermosphere environment and thus may act as first defence against pathogens.

NAD+ Accumulation during Pollen Maturation in Arabidopsis Regulating Onset of Germination

Although the nicotinamide nucleotides NAD(H) and NADP(H) are essential for various metabolic reactions that play major roles in maintenance of cellular homeostasis, the significance of NAD biosynthesis is not well understood. Here, we investigated the dynamics of pollen nicotinamide nucleotides in response to imbibition, a representative germination cue. Metabolic analysis with capillary electrophoresis electrospray ionization mass spectrometry revealed that excess amount of NAD+ is accumulated in freshly harvested dry pollen, whereas it dramatically decreased immediately after contact with water. Importantly, excess of NAD+ impaired pollen tube growth. Moreover, NAD+ accumulation was retained after pollen was imbibed in the presence of NAD+-consuming reaction inhibitors and pollen germination was greatly retarded. Pollen deficient in the nicotinate/nicotinamide mononucleotide adenyltransferase (NMNAT) gene, encoding a key enzyme in NAD biosynthesis, and a lack of NAD+ accumulation in the gametophyte, showed precocious pollen tube germination inside the anther locule and vigorous tube growth under high-humidity conditions. Hence, the accumulation of excess NAD+ is not essential for pollen germination, but instead participates in regulating the timing of germination onset. These results indicate that NAD+ accumulation acts to negatively regulate germination and a decrease in NAD+ plays an important role in metabolic state transition.

Time course gene expression profiling of yeast spore germination reveals a network of transcription factors orchestrating the global response

BackgroundSpore germination of the yeast Saccharomyces cerevisiae is a multi-step developmental path on which dormant spores re-enter the mitotic cell cycle and resume vegetative growth. Upon addition of a fermentable carbon source and nutrients, the outer layers of the protective spore wall are locally degraded, the tightly packed spore gains volume and an elongated shape, and eventually the germinating spore re-enters the cell cycle. The regulatory pathways driving this process are still largely unknown. Here we characterize the global gene expression profiles of germinating spores and identify potential transcriptional regulators of this process with the aim to increase our understanding of the mechanisms that control the transition from cellular dormancy to proliferation.ResultsEmploying detailed gene expression time course data we have analysed the reprogramming of dormant spores during the transition to proliferation stimulated by a rich growth medium or pure glucose. Exit from dormancy results in rapid and global changes consisting of different sequential gene expression subprograms. The regulated genes reflect the transition towards glucose metabolism, the resumption of growth and the release of stress, similar to cells exiting a stationary growth phase. High resolution time course analysis during the onset of germination allowed us to identify a transient up-regulation of genes involved in protein folding and transport. We also identified a network of transcription factors that may be regulating the global response. While the expression outputs following stimulation by rich glucose medium or by glucose alone are qualitatively similar, the response to rich medium is stronger. Moreover, spores sense and react to amino acid starvation within the first 30 min after germination initiation, and this response can be linked to specific transcription factors.ConclusionsResumption of growth in germinating spores is characterized by a highly synchronized temporal organisation of up- and down-regulated genes which reflects the metabolic reshaping of the quickening spores.

Ni2+ effects on Nicotiana tabacum L. pollen germination and pollen tube growth

To investigate the mechanisms of Ni(2+) effects on initiation and maintenance of polar cell growth, we used a well-studied model system-germination of angiosperm pollen grains. In liquid medium tobacco pollen grain forms a long tube, where the growth is restricted to the very tip. Ni(2+) did not prevent the formation of pollen tube initials, but inhibited their subsequent growth with IC(50) = 550 μM. 1 mM Ni(2+) completely blocked the polar growth, but all pollen grains remained viable, their respiration was slightly affected and ROS production did not increase. Addition of Ni(2+) after the onset of germination had a bidirectional effect on the tubes development: there was a considerable amount of extra-long tubes, which appeared to be rapidly growing, but the growth of many tubes was impaired. Studying the localization of possible targets of Ni(2+) influence, we found that they may occur both in the wall and in the cytoplasm, as confirmed by specific staining. Ni(2+) disturbed the segregation of transport vesicles in the tips of these tubes and significantly reduced the relative content of calcium in the aperture area of pollen grains, as measured by X-ray microanalysis. These factors are considered being critical for normal polar cell growth. Ni(2+) also causes the deposition of callose in the tips of the tube initials and the pollen tubes that had stopped their growth. We can assume that Ni(2+)-induced disruption of calcium homeostasis can lead to vesicle traffic impairment and abnormal callose deposition and, consequently, block the polar growth.

Effects of cryopreservation of Phaseolus vulgaris L. seeds on early stages of germination

In this work, we studied the effects of cryopreservation on various parameters of early stages of germination of Phaseolus vulgaris seeds (0, 7 and 14days). Percentages of germination, fresh mass of different plant parts, levels of chlorophyll pigments (a, b, total), malondialdehyde, other aldehydes, phenolics (cell wall-linked, free, and total) and protein were determined. No phenotypic changes were observed visually in seedlings recovered from cryopreserved seeds. However, several significant effects of seed liquid nitrogen exposure were recorded at the biochemical level. There was a significant negative effect of cryopreservation on shoot protein content, which decreased from 3.11mgg(-1) fresh weight for non-cryopreserved controls to 0.44mgg(-1) fresh shoot weight for cryopreserved seeds. On the other hand, cryopreservation significantly increased levels of other aldehydes than malondialdehyde in shoots at day 7, from 56.47μmolg(-1) for non-cryopreserved controls to 253.19μmolg(-1) fresh shoot weight for cryopreserved samples. Liquid nitrogen exposure significantly reduced phenolics contents (free, cell-wall linked, total) in roots at day 7 after onset of germination. In general, roots were more affected by cryostorage compared with other plant parts, while leaves were the least affected. The effects of seed cryopreservation seem to decline progressively along with seedling growth.

Assessment of the loose smut fungi (Ustilago nuda and U. tritici) in tissues of barley and wheat by fluorescence microscopy and real-time PCR

Loose smut fungi of barley and wheat (Ustilago nuda and U. tritici, respectively) colonize the plant without causing obvious disease symptoms before heading. The availability of diagnostic methods to detect and follow the growth of these pathogens in the plant would therefore be highly advantageous for both resistance breeding and the development of effective seed treatments. Using seed lots of barley and wheat highly infected with loose smut, we studied the early establishment of the loose smut pathogens in the plant by fluorescence microscopy. In hand-cut sections stained with the fluorochrome Blankophor®, fungal hyphae were observed to invade the shoot apical meristem and leaf primordia during the first days after the onset of germination. At the first node stage the ear and leaf primordia were generally extensively colonized. Hyphae of U. nuda were also regularly observed in high density in the nodes. A protocol was developed for the specific amplification of U. nuda and U. tritici DNA extracted from infected plant tissue. PCR screening of U nuda in seedlings from infected and healthy seed lots was compared to ELISA, microscopy and ultimately head infection of mature plants derived from tillers of the tested seedlings. The results indicated that a prediction of loose smut infection by real-time PCR is possible at the second leaf stage, and that the assay is equally suited for use with spring and winter varieties of barley and wheat.

Differential responses to somatic embryogenesis of different genotypes of Brazilian oil palm (Elaeis guineensis Jacq.)

To assess the potential of different genotypes of Brazilian oil palm (Elaeis guineensis Jacq.) to somatic embryogenesis and somatic embryo proliferation, mature zygotic embryos of nine commercial genotypes of E. guineensis (BRSC2001, BRSC2328, BRSC2301, BRSC3701, BRSCM1115, BRSC7201, BRSC2528, BRSC2501, and BRSCN1637) were used. Explants were incubated on Murashige and Skoog (MS) supplemented with 450 μM picloram, 3.0 % sucrose, 500 mg l−1 glutamine, and 2.5 g l−1 activated charcoal, and gelled with 2.5 g l−1 Phytagel. After induction, for differentiation and maturation, the embryogenic calli (ECs) were transferred into fresh medium supplemented with 0.6 μM naphthaleneacetic acid (NAA) and 12.30 μM 2-isopentenyladenine (2iP) or 40 μM picloram in combination with 0.3 g l−1 activated charcoal, and 500 mg l−1 glutamine. Somatic embryos were converted into plants on MS medium with macro- and micro-nutrients at half strength, 2 % sucrose, and 2.5 g l−1 activated charcoal, and gelled with 2.5 g l−1 Phytagel. In general, zygotic embryos swelled after 14 days. Primary calli, which were observed in all the genotypes after 45–60 days of culture, eventually progressed to ECs at 90 days. At this time, scanning electron microscopy (SEM) analysis showed cellular differences between compact and friable calli. After 150 days in the induction phase, the ECs with proembryos that were transferred to the medium for differentiation and maturation, differentiated asynchronically into somatic embryos at globular and torpedo stages. The results showed that BRSC2328 and BRSCM1115 had the highest potential for EC formation (90–100 %) and somatic embryo differentiation (40.7 and 52.5 somatic embryos per callus, respectively) when compared to other genotypes. After approximately 90 days of culture on MS basal medium without growth regulators, protrusion of the leaf primordia was observed, characterizing the onset of germination of the somatic embryos into plants.

Frugivory by Taiwan Barbets (Megalaima nuchalis) and the effects of deinhibition and scarification on seed germination

We investigated the frugivory of Taiwan Barbets ( Megalaima nuchalis Gould, 1863) on passage time and germination of 19 species of commonly consumed fruits, distinguished the deinhibition and scarification effects, and tested if complete bird-gut passage increases seed germination. We measured fruit and seed size and seed retention times (SRTs) and examined the germination of intact fruits and pulp-removed and defecated seeds. Germination latency in intact fruits of most species was prolonged, whereas in more non-figs (7/12), the seed germinability increased after ingestion, and nearly all figs germinated by higher proportions after defecation or depulping. Yet, figs revealed major differences from non-figs. SRTs of both non-figs and figs were negatively dependent on fruit size, which was positively correlated to seed size in non-figs only. The germinability was negatively correlated and the germination onset time was positively correlated with SRTs of the last seeds in non-figs, but neither was correlated with SRTs in figs. Most (14/17) species with germination success were enhanced either by deinhibition and scarification, or the fruits hardly germinated but were aided by pulp removal. Deinhibition revealed greater effects than scarification in increasing the germinability and shortening latency, thus aiding, in particular, non-fig seeds with shorter SRTs or that are often culled during feeding.

Frost as a limiting factor for recruitment and establishment of early development stages in an alpine glacier foreland?

AbstractQuestionsHow frost resistant are the early development stages (seeds, seedlings, plantlets and juveniles) of alpine plant species? Do summer frosts impair establishment of plant species typical of different successional stages on a central alpine glacier foreland?LocationRotmoos glacier foreland, Austrian Central Alps (Obergurgl, Tyrol, Austria).MethodsSeeds of 12 species typical of different successional stages were collected in the glacier foreland and either sown directly in the field or in a growth chamber (25/10 °C, 16/8 h) and grown to the investigated development stages. Frost resistance of the early development and adult stages was determined by exposing them to a set of freezing temperatures and assessing viability with the tetrazolium test (LT 50, i.e. 50% of samples being lethally frost damaged).ResultsDry seeds had the highest frost resistance (LT 50: −19 °C), followed by wet seeds after imbibition (LT 50: −8 °C). With the onset of germination, frost resistance decreased rapidly. While germinated seeds tolerated a mean of −3.2 °C, seedlings and juveniles were less frost resistant (LT 50: −2.5 °C). Along the primary succession, seedlings of pioneer species were significantly less frost resistant than early‐ and late‐successional species. However, field grown seedlings, mainly of pioneer species, showed higher frost resistance (mean: −5 °C) than the growth chamber seedlings (mean: −3 °C), indicating that frost hardening (transition from a lower to a higher level of frost resistance) is already possible during these early stages of development.ConclusionsThe low frost resistance during and after germination may not suffice to survive summer frosts and may at least in certain years explain the high seedling mortality rates recognized in the glacier foreland.