Frugivory and the effects of ingestion by bats on the seed germination of three pioneering plants

The dispersion and seedling establishment of pioneering plants can be favoured by the presence of frugivorous bats because the bats usually improve seed germination after ingestion. Although seed germinability is known to vary greatly after ingestion by different bats, the relative contribution of each bat species to seed germination within plant communities is poorly understood. In this study, we first determined the fauna of frugivorous bats in a semideciduous seasonal forest remnant in southern Brazil and subsequently identified the plant species of the seeds passed through their guts. Second, the germination performance (i.e., germination percentage and speed) of the seeds of three pioneering plants (Piper aduncum, Piper hispidinervum and Solanum granuloso-leprosum) ingested by the most abundant bats was compared with that of the non-ingested seeds (seeds collected from fruits). Additionally, the effects on seed germination of different bat species were compared. During one year, five species of frugivorous bats were caught, and the seeds of eleven identifiable plant species (not counting those of undetermined species) were found in their faeces. We found that the germination performance of the seeds of Piper species was significantly enhanced after ingestion by bats, whereas S. granuloso-leprosum seeds had neutral or reduced germinability when seeds in faeces were compared with pulp-removed seeds. Our results revealed that the bat species that were captured exerted different effects upon seed germination; such a disparity is expected to result in different rates of early establishment of these pioneer plants in tropical forests, most likely affecting forest composition and structure, particularly during the initial stages of succession.     

Changes in polyamine concentration during seed germination

Phaseolus mungo seeds 0 to 10 days after germination contained putrescine, spermidine, spermine, cadaverine, agmatine and tyramine. The rate of biosynthesis of total polyamines, proteins and RNA in the developing seeds follows similar profiles, reaching maxima 3 hr from germination. Putrescine, cadaverine, spermidine, spermine and agmatine were the major amines found in Pisum sativum 0–7 days after germination. RNA and proteins seem to follow the same pattern as polyamines during the first 12 hr in the developing pea seeds. RNA reaches a peak at 15 hr and polyamines and proteins peak 24 hr after germination. A rise to total polyamine concentration was also observed in seeds of Tragopogon porrifolius, Zea mays and Triticum aestivum 2–12 hr after germination.     

Does passage time through the lizard Podarcis lilfordi’s guts affect germination performance in the plant Withania frutescens?

I tested predictions of the hypothesis that a longer seed passage time through the gut of the lizard Podarcis lilfordi enhances germination performance in the plant Withania frutescens. I compared germination success and germination time between seeds that were ingested by lizards and control seeds that were not. I also explored relationships between natural variation in seed passage time and germination performance. Germination success did not differ between ingested (63 %) and non-ingested seeds (56 %); there was no significant relationship between germinability and retention time. Germination time did not differ between ingested and non-ingested seeds, and was unrelated to retention time. Hence, I found no support for the hypothesis that prolonged retention times should improve germination performance. In addition, this is a pilot study stressing the importance of reptiles as seed dispersers, at least in certain habitats.     

Submergence Tolerance and Germination Dynamics of Roegneria nutans Seeds in Water-Level Fluctuation Zones with Different Water Rhythms in the Three Gorges Reservoir

The Three Gorges Dam features two water-level fluctuation zones (WLFZs): the preupland drawdown zone (PU-DZ) and the preriparian drawdown zone (PR-DZ). To investigate the vegetation potential of Roegneria nutans in WLFZs, we compared the submergence tolerance and germination dynamics in the natural riparian zone (NRZ), PU-DZ and PR-DZ. We found that the NRZ seeds maintained an 81.3% intactness rate and >91% germination rate. The final seed germination rate and germination dynamics were consistent with those of the controls. Meanwhile, the PU-DZ seeds submerged at 5 m, 10 m, 15 m, and 20 m exhibited intactness rates of 70.5%, 79.95%, 40.75%, and 39.87%, respectively, and >75% germination. Furthermore, the PR-DZ seeds exhibited intactness rates of 22.44%, 61.13%, 81.87%, and 15.36% at 5 m, 10 m, 15 m, and 17 m, respectively, and 80% germination. The germination rates of the intact seeds submerged >10 m were >80%. Finally, the intact seeds germinated quickly in all WLFZs. The high proportion of intact seeds, rapid germination capacity, and high germination rate permit R. nutans seeds to adapt to the complicated water rhythms of the PU-DZ and PR-DZ and indicate the potential for their use in vegetation restoration and recovery. Thus, perennial seeds can be used for vegetation restoration in the WLFZs of large reservoirs and in other regions with water rhythms similar to the Three Gorges Reservoir.     

The role of fleshy pericarp in seed germination and dispersal under flooded conditions in three wetland forest species

In flooded habitats, inundations affect important forest regeneration processes, such as seed dispersal and germination. The main seed dispersal mechanism used by species in Austral South American temperate swamp and riparian forests is endozoochory, which releases seeds from the fleshy pericarp. Endozoochory could be favorable or unfavorable in wetland habitats, since this mechanism exposes seeds directly to water and can, in some cases, be detrimental to germination. In this study, we studied whether or not the fleshy pericarp favors germination after the flooding period's end. Furthermore, we quantified if the number of days which the fruit was found to be floating related to its germination success. We used the seeds of three common fleshy fruit species of flooded habitats from southern Chile, the trees Luma apiculata and Rhaphithamnus spinosus, and the vine Luzuriaga radicans. We simulated flooding periods of 7, 15, 30 and 45 days submerging seeds, with and without pericarps, in water. We found that the pericarp's presence significantly increased Luma's germination success and significantly decreased that of Luzuriaga. The germination of Rhaphithamnus was low after periods of flooding in both seed treatments, with no significant differences found between them. The fruits could float for an average of one to four weeks, depending on the species, which did not relate to their germination success. These results show that germination was affected by the presence of fleshy pericarps in flooded conditions and furthermore, that flotation allows for hydrochory from one week to one month. We suggest that in swamp forests multiple seed dispersal mechanisms are advantageous, especially for fleshy-fruited species.     

Suitable water temperature for seed storage of Zostera japonica for subtropical seagrass bed restoration

Restoration of Zostera japonica is needed. Laboratory culture experiments to know the germination characteristics might be helpful for implementation of actual restoration. As a part of germination experiments, we explored suitable water temperature for long-term storage of Z. japonica seeds. This work was based on earlier reports of Zostera marina, which presumably has similar physiological properties to Z. japonica. This study consisted of two experiments: (1) preservation experiments to investigate the fate of stored Z. japonica seeds and (2) germination experiments to investigate the germination potential of the stored seeds. The results of the preservation experiments suggested that seed condition, that is, germinated, degraded, unstable, stable, etc., showed variations between the seeds stored at 4 and 23 °C. The majority of the seeds stored at 4 °C were germinated, while those at 23 °C seemed to be degraded, presumably by bacteria and mold. The germination experiments suggested high germination potential of seeds stored at 4 °C even after 302 days had elapsed. In conclusion, including previously reported results on Z. marina, low temperature was suitable for the preservation of seeds to maintain germination potential.     

How significant are endophytic fungi in bromeliad seeds and seedlings? Effects on germination,survival and performance of two epiphytic plant species

In bromeliads, nothing is known about the associations fungi form with seeds and seedling roots. We investigated whether fungal associations occur in the seeds and seedling roots of two epiphytic Aechmea species, and we explored whether substrate and fungal associations contribute to seed germination, and seedling survival and performance after the first month of growth. We found a total of 21 genera and 77 species of endophytic fungi in the seeds and seedlings for both Aechmea species by Illumina MiSeq sequencing. The fungal associations in seeds were found in the majority of corresponding seedlings, suggesting that fungi are transmitted vertically. Substrate quality modulated the germination and growth of seedlings, and beneficial endophytic fungi were not particularly crucial for germination but contributed positively to survival and growth. Overall, this study provides the first evidence of an endophytic fungal community in both the seeds and seedlings of two epiphytic bromeliads species that subsequently benefit plant growth.     

Light limitation and litter of an invasive clonal plant,Wedelia trilobata,inhibit its seedling recruitment

Background and Aims

Invasive clonal plants have two reproduction patterns, namely sexual and vegetative propagation. However, seedling recruitment of invasive clonal plants can decline as the invasion process proceeds. For example, although the invasive clonal Wedelia trilobata (Asteraceae) produces numerous seeds, few seedlings emerge under its dense population canopy in the field. In this study it is hypothesized that light limitation and the presence of a thick layer of its own litter may be the primary factors causing the failure of seedling recruitment for this invasive weed in the field.

Methods

A field survey was conducted to determine the allocation of resources to sexual reproduction and seedling recruitment in W. trilobata. Seed germination was also determined in the field. Effects of light and W. trilobata leaf extracts on seed germination and seedling growth were tested in the laboratory.

Key Results

Wedelia trilobata blooms profusely and produces copious viable seeds in the field. However, seedlings of W. trilobata were not detected under mother ramets and few emerged seedlings were found in the bare ground near to populations. In laboratory experiments, low light significantly inhibited seed germination. Leaf extracts also decreased seed germination and inhibited seedling growth, and significant interactions were found between low light and leaf extracts on seed germination. However, seeds were found to germinate in an invaded field after removal of the W. trilobata plant canopy.

Conclusions

The results indicate that lack of light and the presence of its own litter might be two major factors responsible for the low numbers of W. trilobata seedlings found in the field. New populations will establish from seeds once the limiting factors are eliminated, and seeds can be the agents of long-distance dispersal; therefore, prevention of seed production remains an important component in controlling the spread of this invasive clonal plant.     

The novel ethylene antagonist, 3-cyclopropyl-1-enyl-propanoic acid sodium salt (CPAS), increases grain yield in wheat by delaying leaf senescence

Orchid is a major floral crop around the world and Dendrobium hybrids are considered to be one of the most popular orchids. In vitro germination of hybrid seeds is a common practice among orchid growers, however, in many cross pollinations the embryos may not develop to maturity, leading to poor seed germination. The effect of seed maturity and sucrose concentration were investigated via asymbiotic germination of nobile Dendrobium hybrids. Capsules were harvested from two hybrids (Den. Lucky Girl × Den. Second Love ‘Kirameki’ and Den. Lucky Girl × Den. Hamana Lake ‘Kumi’) and one selfing of Den. Second Love ‘Kirameki’ at 2, 3, 4, and 5 months after pollination and immature seeds were taken. Immature seeds from 3- to 5-month old capsules could be successfully germinated on Hyponex based medium. Immature seeds from 4-month old capsules showed greatest germination rate of tested treatments, whereas 3-month old immature seeds showed the least germination. After 6 weeks of in vitro culture, protocorms derived from embryos developed on every concentration of sucrose, but germination was greater at lower concentrations. Greater concentration of sucrose decreased normal-developed protocorms.     

Germination stimulation in wild oats (Avena fatua L.) by synthetic strigol analogs and gibberellic acid

At concentrations of 0.01–1 mM, five synthetic multiring analogs of strigol were effective germination stimulants of intact and dehulled wild oat (Avena fatua L.) seeds. The effect was concentration-dependent and equaled or exceeded that produced by equimolar gibberellic acid (GA₃). The most effective strigol analog treatments induced 55–80% germination within 7 days in intact wild oat seeds and resulted in 63–86% germination and normal seedling growth over 14 days. Intact wild oat controls germinated 14% after 14 days. The stimulation of wild oat germination by these synthetic strigol analogs demonstrates that these compounds, initially developed as germination stimulants for the seeds of the parasitic weed, witchweed (Striga asiatica L. Kuntz.), have bioregulatory activity in dormant seeds of monocots, as well as dicots. None of the compounds tested significantly affected the germination of nondormant cultivated oat seeds (Avena sativa L.). The commonly used dispersal agent, Tween 20 (0.1%), was found to inhibit germination of cultivated oats, alone and in the presence of 2% acetone.     

栎属7种植物种子的发芽抑制物质研究

运用系统溶剂法和生物测定法,以栎属7种植物种子为材料,研究了其种皮、胚(胚及周围部分子叶)和子叶(远离胚端2/3子叶)1.0 g/mL和0.5 g/mL浓度甲醇等浸提液以及各有机相对白菜种子萌发的影响。结果表明:栓皮栎、锐齿栎、蒙古栎、沼生栎和麻栎甲醇浸提液均能显著降低白菜种子发芽率、根长和苗高,且对发芽率的抑制作用逐渐降低;夏栎和房山栎甲醇浸提液对白菜种子发芽率没有显著影响,但对根长和苗高有一定的抑制作用;种子不同部位甲醇浸提液的抑制作用表现为胚>子叶>种皮,且甲醇高浓度浸提液的抑制作用大于低浓度的抑制作用;甲醇相对白菜种子发芽率、苗高或根长的抑制作用最强,其次是乙酸乙酯相,其它溶剂相萃取液的抑制作用不明显。栎属种子甲醇浸提液及各有机相对白菜种子苗高和根长的抑制作用强于对发芽率的影响,说明栎属种子中所含抑制物质主要是限制自身根和芽的生长,可能是造成延迟萌发和出苗不整齐的原因。     

The effect of growth retardants on phytochrome-induced lettuce seed germination

Experiments were carried out to explore the involvement of the plant hormone gibberellin (GA) in the light-induced germination of lettuce seeds. Three growth retardants known to be inhibitors of GA biosynthesis were tested for their effect on red-light-induced germination. Chlormequat chloride (CCC) and AMO-1618 had no effect, but ancymidol was strongly inhibitory. Moreover, the inhibition caused by ancymidol was completely overcome by GA₃. CCC and AMO-1618 inhibit the formation ofent-kaurene, while ancymidol blocks the oxidation ofent-kaurene toent-kaurenoic acid. Ancymidol also was found to inhibit GA-induced dark germination of lettuce seeds, and this inhibition was partially reversed by higher levels of GA. Therefore, the results suggest two possibilities for the relationship between phytochrome and GA in this system: first, the rate-limiting step in the germination of light-sensitive lettuce seeds, that which is regulated by phytochrome, is the oxidation ofent-kaurene toent-kaurenoic acid. Alternatively, red-light treatment may result in the release of active GAlike substances which, in turn, induce germination. In either case the results presented here support the view that phytochrome exerts its effect on lettuce seed germination by means of GA rather than via an independent pathway.     

Seed flotation and germination of salt marsh plants: The effects of stratification, salinity, and/or inundation regime

We examined the effects of cold stratification and salinity on seed flotation of eight salt marsh species. Four of the eight species were tested for germination success under different stratification, salinity, and flooding conditions. Species were separated into two groups, four species received wet stratification and four dry stratification and fresh seeds of all species were tested for flotation and germination. Fresh seeds of seven out of eight species had flotation times independent of salinity, six of which had average flotation times of at least 50 d. Seeds of Spartina alterniflora and Spartina patens had the shortest flotation times, averaging 24 and 26 d, respectively. Following wet stratification, the flotation time of S. alterniflora seeds in higher salinity water (15 and 36 ppt) was reduced by over 75% and germination declined by more than 90%. Wet stratification reduced the flotation time of Distichlis spicata seeds in fresh water but increased seed germination from 2 to 16% in a fluctuating inundation regime. Fresh seeds of Iva frutescens and S. alternflora were capable of germination and therefore are non-dormant during dispersal. Fresh seeds of I. frutescens had similar germination to dry stratified seeds ranging 25-30%. Salinity reduced seed germination for all species except for S. alterniflora. A fluctuating inundation regime was important for seed germination of the low marsh species and for germination following cold stratification. The conditions that resulted in seeds sinking faster were similar to the conditions that resulted in higher germination for two of four species.     

Differential germination behaviour in seeds of the Indian arid zone

Seed germination studies of a number of Indian arid zone species were conducted and the seeds were classified into groups on the basis of germination behaviour. Results of seed germination were also compared with those of old seed collections. Most of the seeds studied showed some form of dormancy, the hard seed coatedness being the most common. InBorreria articularis, germination inhibitors were found. Seeds of different years required different duration of acid scarification for maximum germination and these differences have been attributed to rainfall and other such environmental conditions in those years.     

Temperature and water requirements for germination and effects of discontinuous hydration on germinated seed survival in Tillandsia recurvata L.

Tillandsia recurvata is an epiphytic bromeliad with a wide distribution in the Americas; however, little is known about the development of its post-seminal adaptations for survival in epiphytic environments. The purpose of this study was to define the temperature and water requirements for the germination of T. recurvata seeds. The absence of radicle emergence in T. recurvata seeds resulted in 2?stages of germination: swollen with broken seed coat (stage-1) and chlorophyllic embryos (stage-2). The effects of partial or discontinuous hydration on germinated seed survival were also assessed. The seeds were collected in a semi-arid shrubland of Mexico City. We explored: (1) whether water vapour can provide a sufficient water source for germination; (2) the temperature required for germination stage-1 and the optimal and critical osmotic potentials for germination in both germination stages; (3) the effect of seed incubation at different osmotic potentials that undergo subsequent dehydration on their survival in stage-2; and (4) the loss of dehydration tolerance during early post-seminal development. In addition, an image of T. recurvata seed anatomy was obtained to illustrate its structures. Germination stage-1 of T. recurvata seeds is rather similar across the tested temperature range. The seeds required to be in contact with liquid water to germinate. The interval of osmotic potential facilitating both germination stages was from 0 to ?0.6?MPa. Although germinated seeds displayed dehydration tolerance, this tolerance decreased in germination stage-2. The osmotic potential during germination affected the tolerance of the chlorophyllic embryos (stage-2) to subsequent dehydration.     

Polyamines, IAA and ABA during germination in two recalcitrant seeds: Araucaria angustifolia (Gymnosperm) and Ocotea odorifera (Angiosperm)

Background and Aims

Plant growth regulators play an important role in seed germination. However, much of the current knowledge about their function during seed germination was obtained using orthodox seeds as model systems, and there is a paucity of information about the role of plant growth regulators during germination of recalcitrant seeds. In the present work, two endangered woody species with recalcitrant seeds, Araucaria angustifolia (Gymnosperm) and Ocotea odorifera (Angiosperm), native to the Atlantic Rain Forest, Brazil, were used to study the mobilization of polyamines (PAs), indole-acetic acid (IAA) and abscisic acid (ABA) during seed germination.

Methods

Data were sampled from embryos of O. odorifera and embryos and megagametophytes of A. angustifolia throughout the germination process. Biochemical analyses were carried out in HPLC.

Key Results

During seed germination, an increase in the (Spd + Spm) : Put ratio was recorded in embryos in both species. An increase in IAA and PA levels was also observed during seed germination in both embryos, while ABA levels showed a decrease in O. odorifera and an increase in A. angustifolia embryos throughout the period studied.

Conclusions

The (Spd + Spm) : Put ratio could be used as a marker for germination completion. The increase in IAA levels, prior to germination, could be associated with variations in PA content. The ABA mobilization observed in the embryos could represent a greater resistance to this hormone in recalcitrant seeds, in comparison to orthodox seeds, opening a new perspective for studies on the effects of this regulator in recalcitrant seeds. The gymnosperm seed, though without a connective tissue between megagametophyte and embryo, seems to be able to maintain communication between the tissues, based on the likely transport of plant growth regulators.     

Do Conditions During Dormancy Influence Germination of Suaeda maritima?

Background and Aims

Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2–3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination.

Methods

Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination.

Key Results

A temperature of about 15 °C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry.

Conclusions

The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 °C and the salinity is reduced.Key words: Suaeda maritima, germination, pre-treatment, salinity, temperature     

Germination of dimorphic seeds of the desert annual halophyte Suaeda aralocaspica (Chenopodiaceae), a C4 plant without Kranz anatomy

Background and Aims

Suaeda aralocaspica is a C₄ summer annual halophyte without Kranz anatomy that is restricted to the deserts of central Asia. It produces two distinct types of seeds that differ in colour, shape and size. The primary aims of the present study were to compare the dormancy and germination characteristics of dimorphic seeds of S. aralocaspica and to develop a conceptual model of their dynamics.

Methods

Temperatures simulating those in the natural habitat of S. aralocaspica were used to test for primary dormancy and germination behaviour of fresh brown and black seeds. The effects of cold stratification, gibberellic acid, seed coat scarification, seed coat removal and dry storage on dormancy breaking were tested in black seeds. Germination percentage and recovery responses of brown seeds, non-treated black seeds and 8-week cold-stratified black seeds to salt stress were tested.

Key Results

Brown seeds were non-dormant, whereas black seeds had non-deep Type 2 physiological dormancy (PD). Germination percentage and rate of germination of brown seeds and of variously pretreated black seeds were significantly higher than those of non-pretreated black seeds. Exposure of seeds to various salinities had significant effects on germination, germination recovery and induction into secondary dormancy. A conceptual model is presented that ties these results together and puts them into an ecological context.

Conclusions

The two seed morphs of S. aralocaspica exhibit distinct differences in dormancy and germination characteristics. Suaeda aralocaspica is the first cold desert halophyte for which non-deep Type 2 PD has been documented.Key words: Borszczowia, cold desert halophyte, physiological seed dormancy, seed germination, Suaeda     

Impacts of Host Trees and Sowing Conditions on Germination Success and a Simple Ex Situ Approach to Generate Symbiotic Seedlings of a Rare Epiphytic Orchid Endemic to Hainan Island,China

For species relying on seeds for population regeneration, knowledge on seed germination behaviors in relation to environmental factors is critical in designing species recovery strategy. Dendrobium sinense is an orchid endemic to Hainan Island of China and listed as Endangered by the IUCN Redlist. It reproduces primarily via seeds in its natural habitat. However, how germination is impacted by major environmental factors is poorly known. This study aimed to examine germination success of D. sinense seeds using two approaches, i.e. in situ and ex situ, using host tree barks as germination media. The latter was intended to generate symbiotic seedlings in a simple and economic approach which could be used for reintroduction efforts. In addition, three factors of in situ symbiotic seed germination success, including different sowing time, location (distance from an adult plant), and host tree were investigated. Our results showed that seeds sown ex situ and in situ in July had the highest rates of germination. Seed germination was significantly higher ex situ using bark as medium than in situ. Seeds sown directly on Rhododendron moulmainense, the most common host tree, with naturally occurring conspecific orchids had the highest rate of germination. In contrast, ex situ seeds sown on the bark of Cyclobalanopsis blakeii, a non-host species, had the highest rate of seed germination. In situ a positive correlation was found between the seed germination rate and the distance of the seeds from the adult D. sinense. Based on these results, it is likely seedling recruitments are determined by host tree species, the presence of and the distance from an adult conspecific orchid, which imply the importance of the mycorrhizal fungi, which were not reported here. This study provided important information on the optimal environmental conditions for population augmentation and reintroduction, which can be used as part of the species recovery strategy.     

The ecology of germination and reproduction of less frequent and vanishing species of the Czechoslovak flora I.Alyssum saxatile L.

Lhotská M. (1988): The ecology of germination and reproduction of less frequent and vanishing species of the Czechoslovak flora I.Alyssum saxatile L.—Folia Geobot. Phytotax., Praha, 23: 321–324.—The conditions of germination of both fresh and stratified seeds ofAlyssum saxatile were investigated in the laboratory at 13 various temperature values. The temperature of 15/25°C was found to be optimum. In stratified seeds germination was accelerated, and the range of range of temperatures suitable for germination became wider. Seeds sown out after ripening sprouted in the first half of June, and by autumn they developed rather robust rosettes.