Germination Ecology Research Articles

Comparative germination ecology and seedling growth of two Ibero-Levantine endemic species belonging to the Silene mollissima aggregate (Caryophyllaceae)

The present study was focused on the seed germination and seedling growth of Silene mollissima and S. hifacensis, endemics of the Mediterranean Ibero-Levantine biogeographic province, in order to better understand what environmental factors (e.g. temperature, salinity) influence their ecology and rarity causing their narrow distribution.Inter- and intra-specific variability in the responses to light (12h light/12h dark) and darkness, constant and alternating temperatures, salinity tolerance and germination recovery after washing seeds with distilled water were evaluated. Moreover, the biomass production and the growth rate during the early stages of seedling development were measured at several temperatures.Seeds of the two species were non-dormant and light did not affect their germination. For both species, germination was high at the lowest tested temperatures, while at the highest temperatures inter-specific differences were observed. Seeds of the two species were able to germinate up to 250mM NaCl, furthermore the highest germination occurred in the non-saline control and decreased with increasing salinity. Independently from the tested temperature, S. mollissima and S. hifacensis seeds totally recovered their germination after the NaCl exposure. For both S. mollissima populations the increasing temperature promoted the seedling dry weight and the growth rate, while this pattern was observed only for one S. hifacensis population. This study highlighted that although these species have different needs during their seed germination, they share several common traits in same critical phases of their life cycle. From the ecological viewpoint, our results are consistent with field germination from autumn until spring for S. mollissima and limited to the autumn–winter months for S. hifacensis, when soil moisture is high and salinity levels are low due to the seasonal washout by rainfall. These findings may partially explain the limited distribution of the two species, although further investigation would be needed.

Influence of aerial seed banks on germination response in three desert plant species

Aims To determine if the germination response of desert plant species to a period of aerial storage in field conditions (i.e. mature seeds that remain attached to the parent plant) is comparable to seeds harvested at maturity and stored in ambient laboratory conditions, to better understand the role of aerial seed bank in the germination ecology of desert plants, using one annual and two perennial species. Methods Seeds of three desert plants (Anastatica hierochuntica, Blepharis ciliaris and Scrophularia deserti) that matured in June 2014, were collected from wild plants in June and November 2014, and germinated under two photoperiods (0, 12 hours light) and three thermoperiods (night/day temperatures of 15/25, 20/30 and 25/35 degrees C). Important Findings Seeds of B. ciliaris and S. deserti had significantly higher germination percentages when harvested and stored for five months, compared to being stored in the aerial seed bank. Germination percentages of these two species increased with decreasing temperature and in the presence of light. These results indicate that these species use a combination of aerial and soil seed banks to maintain a percentage of viable seeds through favourable germination periods. Germination percentages of A. hierochuntica were high under all tested circumstances, indicating that this species relies mainly on the aerial seed bank to maintain a percentage of viable seeds through favourable germination periods. This study shows that the population survival strategies of an aerial seed bank are species-specific. These results have practical implications for conservation and habitat restoration for these species, and also for their propagation since early collection of mature fruits and ex situ storage will result in greater germination percentages of some species.

Germination Ecology and Seed Dispersal of a Critically Endangered Plant: A Case Study of Pomaderris vacciniifolia (Round-Leaf Pomaderris).

Change in ecosystem disturbance regimes from human land-use poses a worldwide problem for management of rare species. Two important types of disturbance influencing the persistence of species in Australian ecosystems are habitat fragmentation and fire. In this study, seed dispersal and the germination ecology of Pomaderris vacciniifolia—a critically endangered, rare endemic Australian shrub—were examined to identify likely influences of fire and fragmentation on the decline of populations. The response of seed germination to simulated effects of wildfire and canopy openings was investigated, as was the unaided dispersal capability of seeds from parent plants. A significant increase in germination rate was observed following 100°C heat treatment to seeds, while smoke and light exposure had little influence. Seed imbibition was strongly influenced by heat treatment. The findings indicate a likely positive post-fire germination response, with implications for recruitment success determined by moisture availability following fire. Unaided seed dispersal was limited, which partly explains the apparent decline of populations. Understanding disturbance requirements for threatened species, and subsequent management of landscapes for disturbance, will aid conservation of rare species throughout the world.

Role of ethylene in germination and seedling growth of littleseed canarygrass (Phalaris minor Retz.)

Littleseed canarygrass is a major weed of wheat in rice–wheat cropping system of North-West India. The present study was conducted to study the role of ethylene in germination ecology and seedling growth of littleseed canarygrass and wheat using cobalt chloride (inhibitor of ethylene synthesis) and ethephon (ethylene source). Cobalt chloride at concentrations ≥0.1 mM caused significant reduction in germination (%), germination index and increased the mean germination time of littleseed canarygrass, whereas wheat seeds exhibited significant decrease in germination (%) at cobalt chloride concentrations ≥0.5 mM. Cobalt chloride at higher concentrations significantly reduced the seedling growth of littleseed canarygrass and wheat with more pronounced effect on root length as compared to shoot length. It also significantly increased the membrane leakage and soluble sugar content of seedlings of both species with concomitant decrease in chlorophyll and protein content. Ethephon at 0.1 and 1 mM concentrations significantly increased the germination (%), speed of germination with concomitant decrease in mean germination time as compared to control. Ethephon concentrations 0.1 and 1 mM had no effect on membrane leakage, total soluble sugars and protein content but increased the chlorophyll content in seedlings of both species. Seed dormancy of littleseed canarygrass induced by higher concentrations of cobalt chloride, i.e., 2.5 and 5 mM could also be overcome by treatment with 1 mM ethephon, confirming the role of ethylene in germination of this weed.

The germination ecology of Helonias bullata L. (swamp pink) with respect to dry, saturated, and flooded conditions

Poor sexual recruitment is a major conservation concern for the rare obligate wetland plant Helonias bullata L. (swamp pink). Helonias predominately occurs in forested wetlands amongst hummock-hollow topography where water levels fluctuate spatially and temporally, creating a wide variety of moisture microsite conditions for germination. To determine how moisture conditions affect the germination response of Helonias seeds, germination percentages and rates were compared after seeds were exposed to dry, saturated (stream margin), and flooded (floating and submerged) conditions in a growth chamber and field for 1–35 days. Helonias final germination percentages were greater than 50% after exposure of all conditions, except dry conditions in the growth chamber. Moisture availability at the time of seed arrival was the main factor that influenced the germination of Helonias. Helonias seeds exposed to saturated and flooded conditions germinated within a short time frame (10-30days). Rapid germination may be important for Helonias plants in forested wetlands where variable moisture conditions can create a narrow window for regeneration. For both the growth chamber and field experiment, final germination percentages were significantly higher (p<0.05) for floating seeds compared to those kept dry. Water likely serves as an important dispersal mechanism for Helonias seeds since they exhibit high floating capability and germinability relative to the length of time spent in the water.

Plant-derived smoke and temperature effects on seed germination of five Helianthemum (Cistaceae)

Plant-derived smoke promotes germination in Mediterranean-like environments, but its effect is unclear in the Mediterranean Cistaceae. This article investigates the role of smoke in the comparative germination ecology of five Helianthemum taxa. Laboratory germination experiments were conducted using seeds collected in the field and stored in a seed bank. All seeds were mechanically scarified prior to testing. Various pre-treatments with smoke solutions and gibberellins were applied, and seeds were incubated in three germination temperature regimes (30/20°C, 22/12°C, 14/4°C). In H. cantabricum, H. nummularium, H. oelandicum and H. urrielense germination was very high at the three temperatures, and no effect of smoke was detected. In H. tinetense germination was generally poor and a significant effect of smoke was found, but the effect size was small. The thermal niche of Helianthemum appears to follow an opportunistic strategy, being limited only by physical dormancy at the time of dispersal. H. tinetense follows a more conservative strategy, with physiological dormancy retarding germination. In the Mediterranean basin and surrounding areas, smoke appears to be one of a multitude of environmental signals controlling germination. The smoke effect might be more relevant in certain species such as H. tinetense.

Germination Ecology of Herbicide-Resistant Population of Littleseed Canarygrass from North–Western India

ABSTRACTLittleseed canarygrass (Phalaris minor Retz.) is a most dominant weed of wheat (Triticum aestivum L.) in the north-western states of India. Little information is available on germination of littleseed canarygrass and wheat under similar ecological conditions. The present study was conducted under controlled conditions to study germination ecology of littleseed canarygrass population possessing multiple-herbicide resistance, along with wheat. Germination of littleseed canarygrass and wheat was independent of light. Optimum temperature for germination of littleseed canarygrass and wheat was 20°C. Germination of both species was completely inhibited at osmotic potentials lower than −0.4 MPa. Seeds of littleseed canarygrass and wheat were able to germinate even at NaCl concentration of 200 mM, with complete inhibition at 300 mM. Germination of both species was favored in a pH range of 5–8. Moisture, salinity, and pH stresses significantly reduced the speed of germination, with a concomitant increase in mean germination time, thus exposing seedlings to longer periods of less favorable conditions. This information should help in predicting potential distribution of littleseed canarygrass to new areas and also assist in formulating effective weed-management strategies for the future.

Role of the lens in controlling physical dormancy break and germination of Delonix regia (Fabaceae: Caesalpinioideae).

Physical dormancy occurs in all three subfamilies of Fabaceae, namely Mimosoideae, Papilionoideae and Caesalpinioideae, making it one of the largest plant families in terms of number of species with physical dormancy. However, little is known about the water gap structure and germination ecology of species in Caesalpinioideae. Freshly collected seeds of Delonix regia (Caesalpinioideae) did not imbibe water, thus they had physical dormancy. Both dry heat and wet heat were effective in breaking dormancy, however, longer duration was required at 80°C and shorter duration at 90°C. Seeds buried in the field for 2years germinated to 21% and 42% after the first and second summer, respectively, compared with 3% germination in seeds at the time of maturity. Seeds incubated at 15/60°C in the laboratory (mimicking summer conditions) for 3months supported this conclusion, as dormancy was relieved in 18% and 24% of seeds stored dry and watered intermediately, respectively. All the dormancy breaking treatments resulted in lifting of palisade layers in the lens region to form a circular lid-like opening, i.e. water gap (Type II simple). Blocking experiments confirmed that water entered only through the lens and no secondary water entry point was observed. No apparent changes in morphology/anatomy of the hilum region were noted in dormant and non-dormant (water permeable) seeds. These results suggest that summer temperatures could open the lens in a proportion of seeds every year and that germination occurs during the subsequent wet season in the tropics.

Host influence on germination and reproduction of the facultative hemi‐parasitic weed Rhamphicarpa fistulosa

AbstractRice Vampireweed, Rhamphicarpa fistulosa, was a minor parasitic weed until recently when rice cultivation in sub‐Saharan Africa was expanded into marginal wetlands, that are the parasite's natural habitat. Unlike most of the parasitic weeds, R. fistulosa is facultative, meaning that the parasite is able to complete its life cycle without a host. However, when not connected to a host plant, its biomass and seed production is lower. Because very little is known regarding the germination ecology of the parasite, the main objective of our study was to identify the cues that favour germination. We hypothesised that, first, being a wetland species, germination of R. fistulosa is stimulated by light and high soil moisture. Second, we hypothesised that if host plant presence increases its reproductive output then a germination stimulatory effect from host presence is likely to have developed. A Petri‐dish and pot experiment showed that light and completely saturated soils were a requirement for germination, demonstrating that germination requirements of R. fistulosa are typical of species that grow in environments with fluctuating water levels. A pot experiment in which five infestation levels of R. fistulosa were installed in the absence and presence of a rice plant, showed that host plant presence resulted in a 3.7 times higher seed production rate and a 15% larger average seed size. Despite this reproductive advantage, a pot experiment with three rice cultivars, selected because of their difference in strigolactone production, showed that host plant presence, regardless of the development stage, did not influence the emergence rate of R. fistulosa. In a follow‐up study, the germination stimulation effect of root exudates collected from the same three rice cultivars and a treatment consisting of an artificial germination stimulant (GR24) was compared with a treatment consisting of plain water. In these treatments, seeds of R. fistulosa were compared with seeds of the obligate parasite Striga hermonthica. Germination of S. hermonthica was strongly advanced by the presence of root exudates and GR24 but was completely absent in water, whereas germination of R. fistulosa in all treatments was similar to that in plain water. The absence of a host recognition mechanism at the germination stage suggests that the regulation of germination through light and soil moisture is near optimal. Our finding might also indicate that for this facultative parasitic plant species, a more opportunistic germination strategy is superior. Implications of the findings for management of R. fistulosa in rice cultivation are discussed.

Germination ecology of wild living walls for sustainable vertical garden in urban environment

Germination characteristics of 10 xerophytic species, widespread in the Mediterranean were studied. A variety of seed treatments were explored to overcome the seed dormancy, including scarification and stratification. Only in Convolvulus cantabrica dormancy was shown to be physical, since it could be removed by seed coat scarification. Several species showed light-dependent germination, possibly related to the fact that in their micro-environment of incubation they are exposed to minimum seed burial. Emergence tests in peat-perlite substrate were carried out in order to verify the optimal burial conditions for seed propagation. This inhibition was found to be inversely related to the low unit weight of seed. Species with minute seeds, such as Erigeron karviskianus and Phagnalon rupestris, had the best performance of germination without burial, while the larger ones such as C.cantabrica and Centranthus ruber, had the best performance at 6 and 4mm of sowing, respectively.

Perspectives in restoration: storage and pretreatments of seeds for better germination of Sudanian savanna-woodland species

Insufficient knowledge of the germination ecology of local species is one of the main constraints to restoration of degraded rural lands. We tested seeds from fourteen Sudanian savanna species targeted for restoration for their response to two different pretreatments (conventional and prolonged acid pretreatments) and two different storage conditions (ambient room conditions and refrigerator at 4 °C). For 6 of the studied species, longer soaking in sulphuric acid significantly improved germination rates and also reduced the germination time of some species. Storage condition, in general did not affect germination rates except for two species where cool storage depressed germination. The practical implication is that, for the species tested, when mature seeds are collected for plantation in the upcoming rainy season, there is no need to invest in infrastructure and energy for storing in cold conditions. The study also revealed that in general when seeds are stored in ambient conditions from the time of collection up to seeding time, although germination rate does not increase, germination time is shortened and this could be of great interest in synchronizing germination in real field conditions.

Germination ecology of nutraceutical herbs for agronomic perspectives

Abstract The growing need for nutraceutical foods has elicited increasing interest in the herbs traditionally used for ethnobotanical purposes. Their richness in antioxidants inspired this research, which is aimed at cultivating them as crops. Sixteen wild species of crucial interest as food were studied in term of seed propagation. The frequent dormancy was reduced or removed by physical, or physiological seed treatments in laboratory experiments in Petri dishes. However, their direct field sowing, in spring and autumn, did not show the same performance in spite of the efficacy of the treatments. This specially occurs in the case of species with very small seeds suggesting a burial involvement of this soil-mediated inhibition. This inhibition was markedly lower after greenhouse sowing in a soft substrate (peat–pearlite) confirming the hypothesis that the soil acts (via hypoxia) as a crucial obstacle to germination. The study of the emergence reduction by a slight burial (1 cm), compared to unburied germination, allowed to evaluate, for each species, the burial-mediated inhibition. After the 1000 seed weight measurement a relation between these two parameters (burial inhibition and seed weight) was fitted. A polynomial regression confirmed the inverse relationship between seed weight and burial-mediated inhibition showing the remarkable burial-intolerance of very small seeds. Consequently the greenhouse sowing in substrate appears the most suitable agronomic strategy overall for food herbs characterized by little seeds. Critical issues are discussed regarding these weeds becoming real nutraceutical crops.

Exceptional preservation of tiny embryos documents seed dormancy in early angiosperms.

The rapid diversification of angiosperms through the Early Cretaceous period, between about 130-100 million years ago, initiated fundamental changes in the composition of terrestrial vegetation and is increasingly well understood on the basis of a wealth of palaeobotanical discoveries over the past four decades and their integration with improved knowledge of living angiosperms. Prevailing hypotheses, based on evidence both from living and from fossil plants, emphasize that the earliest angiosperms were plants of small stature with rapid life cycles that exploited disturbed habitats in open, or perhaps understorey, conditions. However, direct palaeontogical data relevant to understanding the seed biology and germination ecology of Early Cretaceous angiosperms are sparse. Here we report the discovery of embryos and their associated nutrient storage tissues in exceptionally well-preserved angiosperm seeds from the Early Cretaceous. Synchrotron radiation X-ray tomographic microscopy of the fossil embryos from many taxa reveals that all were tiny at the time of dispersal. These results support hypotheses based on extant plants that tiny embryos and seed dormancy are basic for angiosperms as a whole. The minute size of the fossil embryos, and the modest nutrient storage tissues dictated by the overall small seed size, is also consistent with the interpretation that many early angiosperms were opportunistic, early successional colonizers of disturbance-prone habitats.

Germination ecology of the endemic Iberian daffodil Narcissus radinganorum (Amaryllidaceae). Dormancy induction by cold stratification or desiccation in late stages of embryo growth

Aim of study: We studied the germination ecology of a threatened daffodil in order to develop a protocol to produce plants ex-situ from seeds, a key tool for population reinforcement.Area of study: Experiments were carried out both outdoors and in the laboratory in Albacete (Spain).Material and methods: Embryo length, radicle and shoot emergence were analyzed to determine the level of morphophysiological dormancy (MPD). Effects on germination of cold stratification or desiccation in late stages of embryo growth were also studied.Main results: Mean embryo length in fresh seeds was 1.36 mm, needing to grow up to 2.20 mm to be able to germinate. In the laboratory, embryo growth occurred during warm stratification (28/14, 25/10ºC), and then radicle emerged when temperatures went down (15/4ºC in darkness). Phenology study in outdoors conditions revealed that embryo grew during summer-early autumn, short time after seed dispersal in nature (i.e., May); radicle emerged in autumn. The shoot however did not emerge until late winter-early spring, because it was physiologically dormant and required a cold (5ºC) period of 30 days to break dormancy. Early cold temperatures interrupted the embryo growth and induced dormancy in seeds whose embryo had grown 30% with respect to the initial length. Desiccation in seeds whose embryo had grown 30% did not induce dormancy, but did it when the embryo growth reached 70%.Research highlights: Seeds of Narcissus radinganorum have deep simple epicotyl MPD.Key words: dormancy break; radicle emergence; shoot emergence; epicotyl MPD; phenology; secondary dormancy.

Seed Germination Ecology of Doveweed (Murdannia nudiflora)and Its Implication for Management in Dry-Seeded Rice

This study was conducted in the laboratory and screenhouse to determine the effects of temperature, light, osmotic stress, salt stress, burial depth, use of crop residues as mulch, depth of flooding, and use of POST herbicides on the emergence, survival, and growth of doveweed. In the light/dark regime, germination was higher at alternating day/night temperatures of 35/25 C (95%) than at 30/20 C (72%), and no germination occurred at 25/15 C. Light strongly influenced germination (95%) and dark completely inhibited germination. No germination occurred at an osmotic potential of −0.8 MPa and a salt concentration of 150 mM and above. The highest germination (91%) was observed from the seeds sown on the soil surface and emergence decreased by 78, 86, and 92% when burial depths were increased to 0.5, 1, and 2 cm, respectively. No seedlings emerged from seeds buried at depths of more than 2 cm. The use of rice residues as mulch significantly reduced the emergence and growth of doveweed seedlings. The amount of residue required to suppress 50% of the maximum biomass was 2.5 t ha−1. Flooding had a more pronounced effect on seedling biomass than seedling emergence. Biomass was reduced by 78, 92, and 96% when flooding depths increased from 0 to 2, 4, and 6 cm, respectively, for the seeds placed on the soil surface, whereas for the seeds buried at 0.5 cm, these values were 78, 100, and 100%. Bentazon (100 g ha−1) and bispyribac-sodium (30 g ha−1) provided 100% control of doveweed when applied at the three-leaf stage. Doveweed control was less than 31% with glyphosate rates up to 2,000 g ha−1. The application of 2,4-D (500 g ha−1) provided 100% control of doveweed even when applied at the seven-leaf stage. The information from this study could help in developing more sustainable and effective integrated weed management strategies for the control of this weed and weeds with similar response in dry-seeded rice systems.

Seeds: ecology, biogeography, and evolution of dormancy and germination

Introduction. Ecologically Meaningful Germination Studies. Types of Seed Dormancy. Germination Ecology of Seeds with Nondeep Physiological Dormancy. Germination Ecology of Seeds with Morphophysiological Dormancy. Germination Ecology of Seeds with Physical Dormancy. Germination Ecology of Seeds in the Persistent Seed Bank. Causes of Within-Species Variations in Seed Dormancy and Germination Characteristics. A Geographical Perspective on Germination Ecology: Tropical and Subtropical Zones. A Geographical Perspective on Germination Ecology: Temperate and Arctic Zones. Germination Ecology of Plants with Specialized Life Cycles and/or Habitats. Biogeographical and Evolutionary Aspects of Seed Dormancy. Subject Index.

A new seed coat water-impermeability mechanism in Chaetostoma armatum (Melastomataceae): evolutionary and biogeographical implications of physiophysical dormancy

AbstractDetermining the phylogenetic and biogeographic distribution of physical dormancy remains a major challenge in germination ecology. Here, our goal was to describe a novel water-impermeable seed coat mechanism causing physical dormancy (PY) in the seeds of Chaetostoma armatum (Melastomataceae). Although seed coat permeability tests indicated a significant increase in seed weight after soaking in distilled water, anatomical and dye-tracking analyses showed that both water and dyes penetrated the seed coat but not the embryo, which remained in a dry state. The water and dye penetrated the lumen of the exotestal cells, which have a thin outer periclinal face and thickened secondary walls with U-shaped phenolic compounds. Because of this structure, water and dye do not penetrate the inner periclinal face of the exotestal cells, indicating PY. Puncturing the seeds increased germination more than tenfold compared to that of the control, but GA3 did not increase germination further. A significant fraction of the seeds did not germinate after puncturing, indicating that embryos are also physiologically dormant (PD). This paper constitutes the first report of the water-impermeable seed coat in the Myrtales and the first report of physiophysical (PD+PY) dormancy in a shrub from a tropical montane area.

Does smoke promote seed germination in 10 Interior West Penstemon species?

Recent research has shown that exposing seeds to smoke stimulates germination for a multitude of plant species, including several species in the genus Penstemon (Scrophulariaceae). I evaluated whether smoke, either alone or followed by 10 wk of stratification (moist prechilling), influenced germination for 10 Penstemon species native to the Interior West of North America. Seeds were collected from 3 to 9 wild populations per species, with each population serving as a replicate for that species in the experimental design. I found that percent germination increased in response to smoke for 3 species, Penstemon secundiflorus Benth., P. strictus Benth., and P. unilateralis Rydb., with smoke-exposed seeds exhibiting 1.9-, 2.5-, and 1.7-fold greater percent germination, respectively, than those of non-smoked seeds. Increased germination in P. unilateralis was only observed for seeds that had also been stratified, while increased germination for P. secundiflorus and P. strictus was observed for both stratified and non-stratified seeds. I also found that percent germination was stimulated by stratification for 6 species, P. auriberbis Pennell, P. eriantherus Pursh, P. glaber Pursh, P. rydbergii A. Nelson, P. secundiflorus , and P. strictus . Penstemon auriberbis, P. eriantherus , and P. secundiflorus were the most responsive, with percent germination increasing 63.4-, 10.6-, and 9.7-fold, respectively, following stratification. These findings improve our understanding of the role of smoke, as well as the role of stratification, in Penstemon germination ecology and should be of use to those who wish to propagate Penstemon species for restoration, horticultural, research, and other purposes.

Annual dormancy cycles in buried seeds of shrub species: germination ecology of Sideritis serrata (Labiatae).

The germination ecology of Sideritis serrata was investigated in order to improve ex-situ propagation techniques and management of their habitat. Specifically, we analysed: (i) influence of temperature, light conditions and seed age on germination patterns; (ii) phenology of germination; (iii) germinative response of buried seeds to seasonal temperature changes; (iv) temperature requirements for induction and breaking of secondary dormancy; (v) ability to form persistent soil seed banks; and (vi) seed bank dynamics. Freshly matured seeds showed conditional physiological dormancy, germinating at low and cool temperatures but not at high ones (28/14 and 32/18 °C). Germination ability increased with time of dry storage, suggesting the existence of non-deep physiological dormancy. Under unheated shade-house conditions, germination was concentrated in the first autumn. S. serrata seeds buried and exposed to natural seasonal temperature variations in the shade-house, exhibited an annual conditional dormancy/non-dormancy cycle, coming out of conditional dormancy in summer and re-entering it in winter. Non-dormant seeds were clearly induced into dormancy when stratified at 5 or 15/4 °C for 8 weeks. Dormant seeds, stratified at 28/14 or 32/18 °C for 16 weeks, became non-dormant if they were subsequently incubated over a temperature range from 15/4 to 32/18 °C. S. serrata is able to form small persistent soil seed banks. The maximum seed life span in the soil was 4 years, decreasing with burial depth. This is the second report of an annual conditional dormancy/non-dormancy cycle in seeds of shrub species.

Strong potential for endozoochory by waterfowl in a rare, ephemeral wetland plant species, Astragalus contortuplicatus (Fabaceae)

It was proposed previously that passive dispersal by migratory aquatic birds explain the widespread distribution of many wetland organisms. Several experimental studies have shown that many widespread wetland plant species can be readily dispersed within the guts of Anatidae. However, it is unclear whether plants with a more restricted distribution are able to disperse via waterbirds. This paper addresses the dispersal ability and germination ecology of the little-known Hungarian milkvetch &lt;em&gt;Astragalus contortuplicatus&lt;/em&gt;, which occurs on banks of continental rivers and has a limited and unpredictable distribution. To test whether limited capacity for endozoochory by waterfowl could explain the sporadic appearance of this species, we force-fed ten captive mallards (&lt;em&gt;Anas platyrhynchos&lt;/em&gt;) with 100 milkvetch seeds each. Droppings were collected for up to 45 h after feeding. Intact and viable seeds were found in the droppings of each mallard, and altogether 24.7% of seeds fed were recovered intact. The proportion of retrieved seeds that germinated (27.0%) was significantly higher than that of untreated control seeds (0.5%), but significantly lower than that of mechanically scarified seeds (96.0%). Retrieved seeds that germinated developed into healthy mature plants. Given the average flight velocity of mallards, seeds of &lt;em&gt;A. contortuplicatus&lt;/em&gt; may travel up to 1600 km inside the digestive tract of migrating individuals. Our results suggest that avian vectors may be more important for the dispersal of rare higher plants (especially those with a hard seed-coat) than hitherto considered. Moreover, they suggest that rarity does not necessarily indicate limited dispersal ability, and may instead be explained by specific habitat requirements.