Wahlberg’s epauletted fruit bat (<Emphasis Type="Italic">Epomophorus wahlbergi</Emphasis>) as a potential dispersal agent for fleshy-fruited invasive alien plants: effects of handling behaviour on seed germination

The spread of invasive alien plants into natural habitats is of growing global concern. Several studies have investigated the role that avian frugivores play in the dispersal of these seeds and their effects on germination success. Fruit bats have however received little attention as important dispersal agents of invasive alien plants, despite their recognized role as long distance dispersal agents of various native flora. We investigated whether Wahlberg’s epauletted fruit bats, Epomophorus wahlbergi, would positively influence the germination of seeds of invasive alien plants. These fruit bats were fed fruits of four invasive alien plant species—Psidium guajava, Melia azedarach, Eriobotrya japonica, and Morus alba. Epomophorus wahlbergi were able to process more fruit per gram body mass than birds have been observed to do. Spat and de-pulped control seeds had similar germination success and germinated at approximately the same time for most species. While seeds retained in whole fruit had significantly less germination success than spat seeds for all species, except M. azedarach, they mostly germinated at approximately the same time. Epomophorus wahlbergi can swallow small seeds (< 2 mm), while seeds larger than this are generally spat out. Large fruit are usually carried away to feeding roosts where seeds are dropped, thereby dispersing seeds and fruits which are too large for some bird species to ingest. Epomophorus wahlbergi should not be underestimated as dispersers of these invasive alien plants as they consume proportionally large amounts (0.62 ± 0.09 to 0.99 ± 0.11 g.g⁻¹ body mass) of fruit, except for M. azedarach, and positively affect their seed germination rates.     

Seed cryopreservation and micropropagation of the federally threatened species,Price’s potato-bean (Apios priceana B.L. Robins.)

Apios priceana, commonly known as Price’s potato-bean, is a perennial species native to the Southeastern US. Habitat destruction has caused A. priceana to become rare, and it is federally listed as threatened. Protocols developed for in vitro germination, shoot micropropagation, in vitro rooting, shoot establishment in soil, and seed cryopreservation will assist in the safeguarding and conservation of dwindling natural populations. Seeds were germinated in vitro on plant growth regulator (PGR)-free Murashige and Skoog (MS) medium after seed sterilization in H₂O₂ and seed nicking. Greatest shoot multiplication occurred on MS medium with BAP/IBA/GA₃ at 2.22/0.49/1.44 μM with 2.0 g/l Phytagel and pH adjusted to 5.7. Shoots rooted in vitro in MS medium with 3.2 μM IBA. Shoots rooted in vitro rapidly established in greenhouse potting mix, usually showing new growth within 2 wk, with tuber formation by the end of the growing season. Plants transferred to a forest setting in late winter survived, grew throughout the summer, and became dormant in the fall. In small post cryopreservation tests with A. americana and A. priceana seeds, air or desiccant-dried to water contents below 10% but above 2.5%, germination reached 87–90%.

     

Frugivory and Seed Dispersal by Brown Lemurs in a Malagasy Tropical Dry Forest

In the Ankarafantsika tropical dry forest (northwestern Madagascar), the common brown lemur (Eulemur fulvus fulvus) is the largest frugivore and probably the sole disperser of large‐seeded plants (seed diameter > 10 mm). To investigate seed dispersal by this primate, I recorded the feeding activities of a troop; also conducted fecal analyses, germination trials on defecated seeds, and a vegetation survey over 1 yr (beginning Dec 2006). Brown lemurs mostly consumed fruit (68%). The fruit of Vitex beraviensis was the most exploited resource (21% of total feeding time). Among dung samples, 1126 contained intact seeds of 70 plant species, with a median of six seeds and two species per sample. These data indicate that the brown lemur population dispersed approximately 9854 seeds/km²/d. Although the number of annually defecated seeds was overwhelmingly the largest in Grewia triflora, many of the small seeds were often clumped in dung piles. In contrast, large seeds of V. beraviensis occurred in the largest number of dung samples. The rate and time of seed germination in V. beraviensis were improved by passage through brown lemur guts. Therefore, V. beraviensis may readily establish seedlings in sites of brown lemur fecal deposition. Vitex beraviensis and brown lemurs are probably involved in a strong mutualism. Twenty‐three large‐seeded plants were probably dependent on brown lemurs for seed dispersal and some of these species were common trees in the forest. Maintenance of these key plant–animal interactions will probably contribute to the conservation of species diversity and intact regeneration of the Ankarafantsika forest.     

Fire damage on seeds of Calliandra parviflora Benth. (Fabaceae), a facultative seeder in a Brazilian flooding savanna

Optimal sexual reproduction in relation to fire effects varies in Fabaceae species. Calliandra species have a large investment in reproduction. We investigated the consequences of fire during the fruiting period of Calliandra parviflora Benth., by checking fruit exposure to fire, pre-dispersal seed predator infestation, and the effect of fruit burning on germination. We conducted this study in a floodable savanna in central Brazil, where we collected burnt and unburnt fruits. We measured the fruit and seed mass, and counted the number of damaged and undamaged seeds and live larvae per fruit. We analyzed the seed germination percentage from burnt and unburnt fruits. The burnt fruits presented greater mass than the unburnt fruits, despite their seed mass being similar. The number of damaged seeds per fruit was only slightly higher in burnt compared to unburnt fruits (p = 0.047). The number of larvae on pre-dispersal seeds per fruit varied from 0 to 4 and did not differ between burnt and unburnt fruits. The germination percentage of unburnt fruit seeds (mean = 22 ± 17%), was significantly higher than that of burnt fruit (mean = 3.0 ± 2.0%, p < 0.001). Fire during fruiting or pre-dispersion decreases seed germination from 22 to 3%, but it does not hurt vegetative regeneration or resprout capacity of C. parviflora, which is a facultative seeder. Hence, we suggest that C. parviflora has potential for post-fire restoration in floodable open grassy savannas, in the ecotone between Cerrado and Pantanal, because this species may sprout quickly after first post-fire rains.     

<Emphasis Type="Italic">In vitro</Emphasis> germination and micropropagation of <Emphasis Type="Italic">Givotia rottleriformis</Emphasis> Griff.

The propagation of Givotia rottleriformis Griff. is difficult as a result of long seed dormancy associated with poor seed germination. The present study was undertaken to develop a protocol to overcome seed dormancy by culture of zygotic embryo axes and then develop an efficient method for micropropagation of Givotia. Best germination frequency (78.3%) was achieved from mature zygotic embryo axes isolated from acid-scarified fresh seeds when cultured on Murashige and Skoog (MS) medium (half-strength major salts) with 28.9 μM gibberellic acid (GA₃). Efficient plant conversion was achieved by transfer of 10-d-old germinated embryos to MS medium (half-strength major salts) supplemented with 1.2 μM kinetin (KN) and 0.5 μM indole-3-butyric acid (IBA). However, acid scarification of 1-yr-old seeds decreased the germination frequency of zygotic embryo axes in comparison to those obtained from non-acid-scarified seeds which germinated (96.2%) and converted into plants (80.3%) on MS basal (half-strength major salts) medium. Multiple shoot bud induction was achieved by culture of shoot tips derived from in vitro germinated seedlings on MS medium with 0.5 μM thidiazuron for 4 wk, and the shoots elongated after transfer to a secondary medium with 1.2 μM KN. A maximum number of 7.8 shoots per explant with an average shoot length of 3.2 cm was achieved after two subcultures on this medium. The in vitro regenerated shoots rooted (41.5%) on half-strength MS medium with 0.5 μM IBA. The in vitro generated seedlings and micropropagated plants were established in soil with a survival frequency of 70% and 60%, respectively.     

Heat increases germination of water-permeable seeds of obligate-seeding <Emphasis Type="Italic">Darwinia</Emphasis> species (Myrtaceae)

We examined the response of seeds to heat in four geographically restricted and one widespread species of shrubby Darwinia from the fire-prone region of southeastern Australia. These shrubs are killed by fire and rely on seed germination after a fire to maintain populations. We replicated the germination trials across several sites and several fruiting seasons for most species. Seeds had a high level of viability and were largely dispersed in a dormant state, except in D. glaucophylla, where seed dormancy varied significantly across fruiting seasons. The indehiscent fruit of all species readily imbibes moisture when wet and seeds are not considered to be ‘hard-seeded’. All species had increased seed germination in response to a limited range of heating temperatures (generally 80–100°C). Higher temperatures killed increasing proportions of seeds. This pattern was broadly consistent across species, population and seasons, although the proportion of seeds whose germination was promoted by heat varied from high (D. diminuta, D. fascicularis, D. glaucophylla) to moderate (D. biflora, D. procera). Our work highlights the importance of heat as a mechanism for influencing germination in species that are not hard-seeded. Consequently, soil temperatures during a fire should strongly influence post-fire germination levels in Darwinia. The roles of other cues that promote germination, i.e. smoke, seasonal temperatures and their interactions with heat, remain to be investigated.     

The effect of frugivory on postdispersal seed removal and germination in the pantropical forest tree Antiaris toxicaria Leschenault

The quality of seed treatment by frugivores has an effect on seed removal after dispersal, seed germination and tree recruitment. We provide information on postdispersal seed removal, germination and subsequent recruitment in tropical forest tree species Antiaris toxicaria in Ghana. We tested whether postdispersal seed removal and germination rates were differentially affected by the following seed treatments: seeds that were spat out by monkeys with all fruit pulp removed and spitting seeds with fruit pulp partially removed as observed in some birds and bats. We used seeds of intact ripened fruits as control. Frugivore seed treatment and distance from bole affected seed removal patterns, whereas intact seeds were significantly removed from all seed stations. The germination success was greater for seeds that were spat out by monkeys and poor for seeds with fruit pulp partially removed and intact fruits. More recruits were recorded at the edge of the adult A. toxicaria canopy radius. There was weak relationship (r² = 0.042) between the number of recruits and distance away from the adult tree. Results suggest that the subsequent recruitment in tropical forest tree species may be enhanced by some frugivore fruit‐handling behaviour where fruit pulp is removed from the seeds without destroying the seeds.     

Seed weight and germination behavior of the submerged plant Potamogeton pectinatus in the arid zone of northwest China

Variation in seed weight is common within and among plant species, but few studies have attempted to document the pattern of seed weight and germination attributes for aquatic macrophytes at a large scale. This study examined within‐species variation in seed weight and germination attributes and the effects of environmental factors on seed traits of the submerged plant Potamogeton pectinatus in the arid zone of northwest China. Our results showed that the average seed weight was 0.24 g per 100 seeds with a coefficient of variation (CV) of 28.4% among the eight P. pectinatus populations. The total germination fraction of seeds of P. pectinatus was relatively poor, less than 35% in seven P. pectinatus populations, and the lowest germination percentage found was only 2%. There were significant differences in seed weight, time to onset of germination, and total germination fraction among the eight different populations. Hierarchical partitioning analysis showed a strongly positive correlation between seed weight and water temperature and pH. Seed weight and the maternal environmental factors significantly affected both time to initiation of germination and total germination fraction. Our results suggest that (1) seed weight variation in P. pectinatus primarily is the result of temperature variation during fruit development; (2) relatively poor germination fraction suggests that seeds are relatively unimportant in the short‐term survival of populations and that it may be another adaptive trait allowing plants to take place in the right place and at the right time, especially in harsh environment; and (3) variation in seed germination traits should be determined by local environmental and intrinsic factors that interact in a complex fashion.     

The role of frugivorous birds in fruit removal and seed germination of the invasive alien Cotoneaster franchetii in central Argentina

Many invasive plant species have fleshy fruits that are eaten by native frugivorous birds which disperse their seeds and may facilitate their germination, playing an important role in plant invasion success. The fleshy‐fruited shrub Cotoneaster franchetii (Rosaceae) is an important invasive alien in the mountainous regions of central Argentina. To determine the role of avian frugivorous in fruit removal of this species, we conducted a frugivore exclusion experiment including bagged and unbagged branches in 75 plants of C. franchetii. At the end of the dispersal period, we compared the percentage of missing fruits (removed by birds + naturally dropped) in unbagged branches with the percentage of naturally dropped fruits in bagged branches. To assess whether any mechanism acting on seeds during their passage through bird guts (de‐inhibition by pulp removal and/or seed scarification) affects seed germination of this species, we compared percentage and speed of germination among seeds obtained from faeces of the native frugivorous Turdus chiguanco, from manually de‐pulped fruits, and from intact fruits. The percentage of missing fruits per shrub in unbagged branches was significantly higher than the percentage of naturally dropped fruits in bagged branches, suggesting that frugivorous birds play an important role in fruit removal of C. franchetii in the study area. Seeds from bird faeces and from manually de‐pulped fruits germinated in higher percentage and faster than seeds from intact fruits. Germination percentage and speed of seeds from manually de‐pulped fruits were significantly higher than those of gut‐passed seeds. These results indicate that T. chiguanco increases and accelerates seed germination of C. franchetii through pulp removal, but not through seed scarification. Overall, our findings indicate that native frugivorous birds facilitate the dispersal and germination success of C. franchetii, likely playing an important role in its invasion throughout the mountainous region of central Argentina.     

Mechanisms affecting the fate of Prosopis flexuosa (Fabaceae,Mimosoideae) seeds during early secondary dispersal in the Monte Desert,Argentina

Abstract The fate of seeds during secondary dispersal is largely unknown for most species in most ecosystems. This paper deals with sources of seed output of Prosopis flexuosa D.C. (Fabaceae, Mimosoideae) from the surface soil seed‐bank. Prosopis flexuosa is the main tree species in the central Monte Desert, Argentina. In spite of occasional high fruit production, P. flexuosa seeds are not usually found in the soil, suggesting that this species does not form a persistent soil seed‐bank. The magnitude of removal by animals and germination of P. flexuosa seeds was experimentally analysed during the first stage of secondary dispersal (early autumn). The proportion of seeds removed by granivores was assessed by offering different types of diaspores: free seeds, seeds inside intact endocarps, pod segments consisting of 2–3 seeds, and seeds from faeces of one herbivorous hystricognath rodent, the mara (Dolichotis patagonum). The proportion of seeds lost through germination was measured for seeds inside intact endocarps, seeds inside artificially broken endocarps, and free seeds. Removal by ants and mammals is the main factor limiting the formation of a persistent soil seed‐bank of P. flexuosa: >90% of the offered seeds were removed within 24 h of exposure to granivores in three of four treatments. Seeds from the faeces of maras, on the other hand, were less vulnerable to granivory than were other types of diaspores. These results suggest that herbivory might be an indirect mechanism promoting seed longevity in the soil (and likely germination) by discouraging granivore attack. On the other hand, germination did not seem to have an important postdispersal impact on the persistence of P. flexuosa seeds in the soil. Both direct and indirect interactions between vertebrate herbivores and plants may foster P. flexuosa's seed germination in some South American arid zones.     

The role of Rhytidoponera metallica (Hymenoptera,Formicidae) in facilitating post‐fire seed germination of three ant‐dispersed legume species

The fire avoidance hypothesis proposes that a benefit of seed dispersal by ants (myrmecochory) is to protect seeds from being killed during fire and to facilitate post‐fire germination of seeds that require heat shock to break their physical dormancy. The aim of this study was to quantify the effect of fire and seed burial by a predominant seed‐dispersing ant, Rhytidoponera metallica (subfamily: Ectatomminae) on germination levels of three ant‐dispersed legume species (Pultenaea daphnoides, Acacia myrtifolia and Acacia pycnantha). Experimental burial of seeds within aluminium cans at a site prior to being burnt and at an adjacent unburnt site showed that fire increased germination levels, particularly for seeds buried at 1‐ and 2‐cm deep and that overall, germination levels differed among the three plant species. To quantify seed burial depths and post‐fire germination levels facilitated by R. metallica ants, seeds were fed to colonies prior to fire at the burnt and unburnt sites. Of the seeds buried within nests that were recovered, between 45% and 75% occurred within the upper 6 cm of the soil profile, although unexpectedly, greater percentages of seeds were recovered from the upper 0–2 cm of nests in the unburnt site compared with nests in the burnt site. Germination levels of buried seeds associated with R. metallica nests ranged from 21.2% to 29.5% in the burnt site compared with 3.1–14.8% in the unburnt site. While increased seed germination levels were associated with R. metallica nests following fire, most seeds were buried at depths below those where optimal temperatures for breaking seed dormancy occurred during the fire. We suggest that R. metallica ants may provide fire avoidance benefits to myrmecochorous seeds by burying them at a range of depths within a potential germination zone defined by intra‐ and inter‐fire variation in levels of soil heating.     

Germination studies on three critically endangered endemic angiosperm species of the Kashmir Himalaya,India

The critically endangered and perennial alpine endemic angiosperms, namely, Aquilegia nivalis, Lagotis cashmeriana and Meconopsis latifolia inhabit such habitats in the Kashmir Himalaya that are characterised by short growing season and heavy snow cover for about 3–4 months during winter season. The seeds of these species under natural conditions experience a long period of pre-chilling during winter prior to their germination in following spring season. Taking cue from such a requirement, present study investigated the effect of chilling and exogenous application of growth hormones, NO₃ ⁻ and NH₄ ⁺ on total percent germination of otherwise deep-dormant seeds of these species, under alternate light/dark and continuous dark light regimes. Prolonged pre-chilling followed by treatment of seeds with different doses of GA₃ had a pronounced stimulatory effect on the total germination percentage in all the three species. In fact, highest germination percentage in A. nivalis was recorded only when pre-chilled seeds were treated with 1.5 mM GA₃ under alternate light/dark conditions. Likewise, germination of pre-chilled seeds of L. cashmeriana with ruptured seed coats was improved when treated with various concentrations of GA₃. Seed germination in M. latifolia was also favourably influenced by treatment of pre-chilled seeds with GA₃ or nitrogen applied either as NO₃ ⁻ or as NH₄ ⁺ under alternate light/dark conditions. Treatment of seeds with kinetin (6-furfuryl-aminopurine) had no significant influence on germination percentage in any of the three species. Thus, prolonged chilling of seeds followed by their treatment with GA₃ under alternate light/dark conditions are the requirements necessary for seed germination in these species.     

Variation in dormancy and germination in three co-occurring perennial forest herbs

Mesic deciduous forest herbs often disperse seed with morphophysiological dormancy (MPD) that prevents germination during unfavorable periods for seedling survival. However, for seeds of some species with MPD, seasonal separation of root and shoot emergence and variation in dormancy levels can complicate interpretation of seedling emergence timing in the field. We tested whether dormancy-break and germination requirements differed among co-occurring perennial forest herbs, Actaea racemosa, Hydrastis canadensis, and Sanguinaria canadensis, which are wild-harvested for their medicinal properties and known to have MPD. Seeds of all species exhibited a summer → autumn → winter requirement for seedling emergence in spring. However, species differed in seed-bank persistence due to variation in primary dormancy levels and stratification requirement of seeds. A. racemosa and H. canadensis can form short-term persistent seed bank, whereas S. canadensis can form a long-term persistent seed-bank, regardless of whether elaiosomes were removed from seeds prior to burial. A. racemosa seeds are dispersed in autumn with weak physiological dormancy, as seeds germinated to high rates at 15/6°C after 8 weeks. In contrast, most seeds of the summer dispersed species, H. canadensis and S. canadensis, require summer temperatures to overcome physiological dormancy. Consequently, seedling emergence is reduced and delayed by 1 year if seeds are not sown immediately following the period of natural dispersal. Seedling emergence was much lower in the field than in controlled conditions for all species, especially in the small-seeded A. racemosa. Interspecific variation in dormancy levels and germination traits must be considered when establishing populations for conservation purposes and in understanding recruitment limitation in perennial forest herbs.     

Endozoochorous dispersal of forest seeds by carnivorous mammals in Sierra Fría,Aguascalientes, Mexico

Some carnivorous mammals ingest fruit and disperse seeds of forest plant species capable of colonizing disturbed areas in ecosystems. The objective of the present study was to evaluate the dissemination of Arctostaphylos pungens and Juniperus deppeana seeds by the gray fox (Urocyon cinereoargenteus), coyote (Canis latrans), and other carnivores in the Protected Natural Area Sierra Fría, in Aguascalientes, Mexico. Scat collection was undertaken via transects using the direct search method, while the seasonal phenology of A. pungens and J. deppeana was evaluated by recording flower and fruit abundance on both the plant and the surrounding forest floor ground. Seed viability was assessed by optical densitometry via X‐ray and a germination test. It was found that the gray fox, coyote, ringtail (Bassariscus astutus), and bobcat (Lynx rufus) disseminated seeds of A. pungens (212 ± 48.9 seeds/scat) and J. deppeana (23.6 ± 4.9 seeds/scat), since a large proportion of the collected scat of these species contained seeds (28/30 = 93.33%, 12/43 = 27.9%, 6/12 = 50% and 7/25 = 28% respectively). The gray fox, coyote, ringtail, and bobcat presented an average of seed dispersion of both plant species of 185.4 ± 228.7, 4.0 ± 20.0, 12.1 ± 30.4, and 0.8 ± 1.5 per scat; the seed proportions in the gray fox, coyote, ringtail, and bobcat were 89.6/10.4%, 82.3/17.7%, 90.4/9.6%, and 38.1/61.9% for A. pungens and J. deppeana, respectively. The phenology indicated a finding related to the greater abundance of ripe fruit in autumn and winter (p < .01). This coincided with the greater abundance of seeds found in scats during these seasons. Endozoochory and diploendozoochory enhanced the viability and germination of the seeds (p > .05), except in those of A. pungens dispersed by coyote. These results suggest that carnivores, particularly the gray fox, the coyote, and the bobcat, play an important role in forest seed dissemination, and thus forest regeneration, by making both a quantitative and qualitative contribution to the dispersal of the two pioneer species under study.     

Increasing the germination percentage of a declining native orchid (Himantoglossum adriaticum) by pollen transfer and outbreeding between populations

• The declining native orchid Himantoglossum adriaticum H. Baumann is a European endemic of priority interest (92/43/ EEC, Annex II). Northern Italian populations of H. adriaticum are small and isolated, with depressed seed set. Given the important implications for plant population conservation, we tested the hypothesis that artificial pollen transfer (hand‐pollination) and outbreeding between populations increases fruit set and seed germination percentage.
• The background fruit set and in vitro germination rates were determined for ten reference populations. An artificial cross‐pollination experiment included (a) pollen transfer from one large population to two small and isolated populations; (b) pollen transfer between two small but not isolated populations; (c) within‐population pollen transfer (control). All seeds were sown on a modified Malmgren's medium and cultured in a controlled environment. Germination percentage was compared using a Kruskal‐Wallis anova .
• The background fruit set (mean = 18%) and germination (<5%) rates were consistently low across populations. Fruit set after hand‐pollination was consistently 100%. Pollen transfer from the largest population to smaller populations resulted in an increase in total germination ranging from 0.9% to 2.9%. The largest increase in germination occurred between small‐sized and less isolated populations (from 1.7% to 5.1%).
• The results of pollen transfer between the small populations are particularly encouraging, as the mean increase in germination was almost four times that of the control. Outbreeding can be considered a valuable tool to increase genetic flow and germination in natural populations, limit the accumulation of detrimental effects on fitness driven by repeated breeding with closely‐related individuals, thereby increasing the possibility of conservation of rare or endangered species.

     

Production of arachidonic acid and dihomo-γ-linolenic acid from glycerol by oil-producing filamentous fungi, Mortierella in the ARS culture collection

The filamentous fungi of the genus Mortierella are known to produce arachidonic acid from glucose, and the species alpina is currently used in industrial production of arachidonic acid in Japan. In anticipation of a large excess of the co-product glycerol from the national biodiesel program, we are trying to find new uses for bioglycerin. We screened 12 Mortierella species: M. alpina NRRL 6302, M. claussenii NRRL 2760, M. elongata NRRL 5246, M. epigama NRRL 5512, M. humilis NRRL 6369, M. hygrophila NRRL 2591, M. minutissima NRRL 6462, M. multidivaricata NRRL 6456, M. nantahalensis NRRL 5216, M. parvispora NRRL 2941, M. sepedonioides NRRL 6425, and M. zychae NRRL 2592 for their production of arachidonic acid (AA) and dihomo-γ-linolenic acid (DGLA) from glycerol. With glucose as substrate all of the strains tested produced AA and DGLA. The total fatty acid content of 125 mg/g cell dry weight (CDW) and fatty acid composition for AA (19.63%) and DGLA (5.95%) in the mycelia of M. alpina grown on glucose were comparable with those reported by Takeno et al. (Appl Environ Microbiol 71:5124–5128, 2005). With glycerol as substrate all species tested grew on glycerol and produced AA and DGLA except M. nantahalensis NRRL 5216, which could not grow on glycerol. The amount of AA and DGLA produced were comparable with those obtained with glucose-grown mycelia. The top five AA producers (mg AA/CDW) from glycerol were in the following order: M. parvispora > M. claussenii > M. alpina > M. zychae > M. minutissima. The top five dry mycelia weights were: M. zychae > M. epigama > M. hygrophila > M. humilis > M. minutissima. The top five species for total fatty acids production (mg /g CDW) were: M. claussenii > M. parvispora > M. minutissima > M. hygrophila > M. maltidivaricata. We selected two species, M. alpina and M. zychae for further studies with glycerol substrate. Their optimum production conditions were determined. Time course studies showed that the maximum cell growth and AA production for both species were at 6 days of incubation. Therefore, glycerol can be considered for industrial use in the production of AA and DGLA.     

Imbibition phases and germination response of Mimosa bimucronata (Fabaceae: Mimosoideae) to water submersion

Mimosa bimucronata is a pioneering tree that occurs predominantly in moist lowlands, floodplains and on margins of rivers and lakes in Latin America. The effect of submergence on seed germination in M. bimucronata was firstly studied. Patterns of water absorption by M. bimucronata seeds were investigated thereafter to assess the imbibition phases of scarified and unscarified seeds. The germination percentage was significantly higher in scarified than in unscarified seeds, and the velocity of seed germination also increased considerably in scarified seeds. Submergence duration did not significantly affect germination percentages of scarified and unscarified seeds. Therefore, seed viability after submersion suggests that M. bimucronata may display hydrochorous dispersal and also that seeds are able to germinate successfully in areas with frequent seasonal flooding. With respect to imbibition phases, phase II was very short or even absent for scarified and unscarified seeds; therefore, a plateau, where water absorption by seeds is established, was not observed. Finally, we verified that the passage from phase I to III was very tenuous and took a long time in seeds without scarification.