Characterization of As(III) oxidizing <Emphasis Type="Italic">Achromobacter</Emphasis> sp. strain N2: effects on arsenic toxicity and translocation in rice

Achromobacter sp. strain N2 was isolated from a pyrite-cinder-contaminated soil and presented plant growth promoting traits (ACC deaminase activity, production of indole-3-acetic and jasmonic acids, siderophores secretion, and phosphate solubilization) and arsenic transformation abilities. Achromobacter sp. strain N2 was resistant to different metals and metalloids, including arsenate (100 mM) and arsenite (5 mM). The strain was resistant to ionic stressors (i.e., arsenate and NaCl), whereas bacterial growth was impaired by osmotic stress. Strain N2 was able to oxidize 1.0 mmol L^?1 of arsenite to arsenate in 72 h. This evidence was supported by the retrieval of an arsenite oxidase AioA gene highly homologous to arsenite oxidases of Achromobacter and Alcaligenes species. Rice seeds of Oryza sativa (var. Loto) were bio-primed with ACCD-induced and non-induced cells in order to evaluate the effect of inoculation on rice seedlings growth and arsenic uptake. The bacterization with ACCD-induced cells significantly improved seed germination and seedling heights if compared with the seeds inoculated with non-induced cells and non-primed seeds. Enhanced arsenic uptake was evidenced in the presence of ACCD-induced cells, suggesting a role of ACCD activity on the mitigation of the toxicity of arsenic accumulated by the plant. This kind of responses should be taken into account when proposing PGP strains for improving plant growth in arsenic-rich soils.     

Role of Endogenous Growth Regulators in Seed Dormancy of Avena fatua: I. Short Chain Fatty Acids

The hypothesis that endogenous short chain fatty acids (C 6-C 10) are important in maintaining seeds of wild oat (Avena fatua L.) in the dormant state by acting as natural germination inhibitors (Berrie, Buller, Don, Parker, 1979 Plant Physiol 63: 758-764) was investigated. When germination of nondormant seeds was inhibited by treatment with short chain fatty acids, the seeds did not revert to a similar biochemical and physiological state as exhibited by dormant seeds. First, nonanoic acid-induced inhibition of seed germination was not reversed by hormone treatments which normally break dormancy in wild oat seeds. Second, nondormant seeds treated with short chain fatty acids maintained similar relative proportions of the pentose phosphate pathway and the Embden-Meyerhoff-Parnas pathway for respiratory glucose metabolism as that found in the nondormant controls. Seeds imbibed in the presence of nonanoic acid lost more amino acids and proteins into the imbibition solution than did the untreated controls, suggesting membrane damage had occurred. Inasmuch as increasing concentrations of nonanoic acid also progressively reduced the growth of the coleoptile and roots of intact seedlings until all growth ceased and no germination occurred, the inhibition of seed germination could be due to a nonspecific inhibition of growth of the embryo, perhaps because of disruption of membrane structure and function. Finally, no correlation between endogenous levels of short chain fatty acids in seeds or isolated embryonic axes and seed dormancy could be demonstrated.     

Relative toxicity of arsenite and arsenate on germination and early seedling growth of rice (Oryza sativa L.)

Elevated soil arsenic levels resulting from long-term use of arsenic contaminated ground for irrigation in Bangladesh may inhibit seed germination and seedling establishment of rice, the country's main food crop. A germination study on rice seeds and a short-term toxicity experiment with different concentrations of arsenite and arsenate on rice seedlings were conducted. Percent germination over control decreased significantly with increasing concentrations of arsenite and arsenate. Arsenite was found to be more toxic than arsenate for rice seed germination. There were varietal differences among the test varieties in response to arsenite and arsenate exposure. The performance of the dry season variety Purbachi was the best among the varieties. Germination of Purbachi was not inhibited at all up to 4 mg l^–1 arsenite and 8 mg l^–1 arsenate treatment. Root tolerance index (RTI) and relative shoot height (RSH) for rice seedlings decreased with increasing concentrations of arsenite and arsenate. Reduction of RTI caused by arsenate was higher than that of arsenite. In general, dry season varieties have more tolerance to arsenite or arsenate than the wet season varieties.     

Scatter Hoarding of Seeds Confers Survival Advantages and Disadvantages to Large-Seeded Tropical Plants at Different Life Stages

Scatter hoarding of seeds by animals contributes significantly to forest-level processes, including plant recruitment and forest community composition. However, the potential positive and negative effects of caching on seed survival, germination success, and seedling survival have rarely been assessed through experimental studies. Here, I tested the hypothesis that seed burial mimicking caches made by scatter hoarding Central American agoutis (Dasyprocta punctate) enhances seed survival, germination, and growth by protecting seeds from seed predators and providing favorable microhabitats for germination. In a series of experiments, I used simulated agouti seed caches to assess how hoarding affects seed predation by ground-dwelling invertebrates and vertebrates for four plant species. I tracked germination and seedling growth of intact and beetle-infested seeds and, using exclosures, monitored the effects of mammals on seedling survival through time. All experiments were conducted over three years in a lowland wet forest in Costa Rica. The majority of hoarded palm seeds escaped predation by both invertebrates and vertebrates while exposed seeds suffered high levels of infestation and removal. Hoarding had no effect on infestation rates of D. panamensis, but burial negatively affected germination success by preventing endocarp dehiscence. Non-infested palm seeds had higher germination success and produced larger seedlings than infested seeds. Seedlings of A. alatum and I. deltoidea suffered high mortality by seed-eating mammals. Hoarding protected most seeds from predators and enhanced germination success (except for D. panamensis) and seedling growth, although mammals killed many seedlings of two plant species; all seedling deaths were due to seed removal from the plant base. Using experimental caches, this study shows that scatter hoarding is beneficial to most seeds and may positively affect plant propagation in tropical forests, although tradeoffs in seed survival do exist.     

Seed Dormancy,Seedling Establishment and Dynamics of the Soil Seed Bank of Stipa bungeana (Poaceae) on the Loess Plateau of Northwestern China

Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls), chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma) had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening), gibberellin (GA₃) and potassium nitrate (KNO₃) significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively.     

黄瓜种子及其萌发期的化感作用研究

以大白菜、萝卜、番茄和黄瓜种子为受体,采用实验室培养皿种子发芽生物测试法研究了黄瓜种子浸提液、种子萌发、胚根和芽苗分泌物、芽苗腐解物和芽苗浸提液的化感效应。结果表明:(1)黄瓜种子浸提液对大白菜、萝卜、番茄和黄瓜种子萌发均有化感抑制作用,即黄瓜种子内含有某些化感抑制物质。(2)在水浸提过的黄瓜种子萌发过程中,它不仅对其近邻套种的大白菜、萝卜和番茄种子萌发产生化感抑制作用,而且其胚根和芽苗分泌物对后茬播种的4种蔬菜种子发芽也表现出不同程度的化感抑制作用;黄瓜芽苗腐解物和芽苗水浸提液也对各受体蔬菜种子发芽与生长产生不同程度的化感抑制作用,且随着腐解芽苗量的增加或浸提液浓度的升高,各受体蔬菜种子的发芽指标值、化感效应指数值和综合效应值随之降低。(3)黄瓜种子浸提液及芽苗各器官的化感物质对黄瓜种子的萌发与生长产生了自毒作用,且黄瓜芽苗腐解物、芽苗浸提液、胚根及芽苗分泌物对受体黄瓜的自毒作用均为最大。研究发现,黄瓜种子浸提液、种子萌发时期以及芽苗各器官的化感物质主要是通过抑制受体胚根的生长而起化感抑制作用,即受体蔬菜种子胚根对化感效应最为敏感;因黄瓜种子及萌发期释放化感物质的途径有所不同,导致受体大白菜、萝卜、黄瓜和番茄的化感响应也不相同;在黄瓜种子萌发和芽苗生长的早期,化感物质即开始在芽苗体内进行合成与积累,一部分可通过胚根和芽苗分泌途径释放到环境中,另一部分可通过芽苗腐解途径释放化感物质,并对受体蔬菜种子萌发与生长表现出较强的化感抑制作用。     

果肉和埋土深度对新疆野杏种子萌发与幼苗生长的影响

为探明新疆野杏（Armeniaca vulgaris）种子萌发与幼苗生长对果肉和埋土深度的响应,以期为新疆野杏的天然更新与实生苗培育提供理论参考。通过2种果皮结构（有果肉和无果肉）的种子在不同埋土深度（地表至18.0 cm的14个梯度）对新疆野杏种子萌发和幼苗生长进行研究,旨在揭示果皮结构和埋土深度对新疆野杏种子萌发与成苗能力的影响。结果表明：果肉和埋土深度显著影响野杏种子的萌发、幼苗生长与质量（P<0.05）。埋土深度<3.0 cm不利于成苗,埋土深度>6.0 cm时,萌发能力与幼苗生长量随埋土深度的增加而降低,3.0～6.0cm为适宜埋土深度。无果肉种子萌发优于有果肉种子,萌发率、萌发指数、成苗率、活力指数分别增长了37.18%、3.88%、37.18%、26.59%,幼苗高、基径、叶片数量、根冠比、幼苗质量指数分别增长了36.99%、7.48%、68.69%、20.61%、14.29%,其萌发能力与幼苗生长量显著高于有果肉种子（P<0.05）。有无果肉种子的萌发和幼苗生长指标与埋土深度呈显著负相关（P<0.05）。研究结果表明,无果肉处理对新疆野杏种...     

侧柏不同器官水提取物对油松种子萌发和幼苗生长的他感效应

研究了侧柏（Platycladus orientalis）根、枝、叶、果实不同浓度水提取物及枝叶挥发油对油松种子萌发和幼苗生长的他感效应。结果表明：侧柏各器官及挥发油都含有化感物质,均对油松种子萌发及幼苗生长表现出“高抑低促”效应,而且低浓度时的促进作用明显强于高浓度时的抑制作用。与对照相比,在浓度为2 mg·mL^-1时,侧柏根水提取物对油松幼苗根长和鲜重的促进能力最强,其根长和鲜重分别比对照提高了79.78%和376.60%;侧柏叶水提取物对油松幼苗苗高促进能力最强,比对照提高了102.41%;侧柏枝水提取物对油松种子发芽的促进能力最强,发芽率比对照提高了65.63%。而在浓度为30 mg·mL^-1时,除了侧柏根和枝水提取物对油松种子萌发（87.50%）和鲜重（85.11%）表现出明显的抑制作用外,其它提取物对油松幼苗根长和苗高生长的抑制作用均不明显。侧柏枝叶挥发油对油松种子萌发,幼苗生长均表现为促进作用,特别对油松种子萌发具有显著的促进作用,其促进率达70.37%。说明侧柏和油松混交,可能有利于油松树木生长及生产力的提高。     

The effects of shrub patch sizes on the colonization of pioneer plants on the volcano Mount Koma,northern Japan

Vegetation recovery on Mount Koma, Hokkaido, Japan, has been slow after the catastrophic eruption in 1929, due to undeveloped soil and limited plant colonization. Nowadays, the seedling establishment is supported mostly by a nurse plant, Salix reinii forming shrub patches, facilitates the plant colonization. Although the effects of shrub patches should differ with patch sizes, the size effects have not been examined well. To examine the size effects, seed-sowing experiments were conducted on two common pioneer herbaceous species, Miscanthus sinensis and Polygonum sachalinense, in the field. The seed germination and seedling survival were monitored by the seeds sown into S. reinii patches (0.97 m²–4.12 m² in area) for 4 months during snow-free periods. Microenvironments altered by the patches were measured. Lab-experiments were performed to characterize the seed germination and seedling growth.Larger patches decreased light intensity and temperature more and increased litter and water content. The large patches promoted the seed germination of the two species. Interspecific interactions, examined by a seed mixture experiment, showed that the interaction increased the seed germination on M. sinensis and decreased that on P. sachalinense. On the lab-experiments at three temperatures (15, 20 and 25 °C), M. sinensis seeds germinated more at higher temperatures and obtained higher seedlings biomass. P. sachalinense germinated the seeds more at 20 °C and grew faster at lower temperatures. The total biomass of the two species was reduced by shade that intercepted 50% of light intensity. The seed germination and seedling growth of these two species became higher on litter with 2 cm in depth than on no litter. Soil water supported seed germination when the seeds of these two species were mixed while the water reduced the growth of P. sachalinense seedlings. Therefore, the dry soils were suitable for their growths. In all the treatments, P. sachalinense seedlings showed higher mortalities than M. sinensis.In conclusion, the large patches facilitated more to the colonization of pioneer plants via seed germination and growth. Large patches acted as a nursery supporting the natural regeneration in the disturbed area by improving litter accumulation, maintaining soil water, reducing strong light and/or protecting from heat.     

Reversal of (±) -Abscisin II Induced Inhibition of Lettuce Seed Germination and Seedling Growth by Kinetin

Observations have been made on the effect of synthetic, (±)-abscisin II (dormin), alone and in combination with gibberellin, kinetin and indoleacetic acid, on seed germination and seedling growth of two strains of lettuce, cv. Attraktion and cv. Hohlblättriger Butter. (±)-Abscisin II inhibited seed germination and seedling growth in both strains. The inhibitory effect of abscisin II on seed germination as well as seedling growth was completely overcome by kinetin in both dark and light. Gibberellic acid, on the other hand, proved ineffective in exerting its influence on seed germination in presence of abscisin II but affected subsequent seedling growth as usual. Indoleacetic acid was found to be least potent in reversing abscisin II caused inhibition of seed germination and seedling growtb. It is concluded, that like its effect on certain other naturally occurring inhibitors of seed germination, kinetin can effectively undo the inhibitory effects of abscisin II in these growth processes.     

Water-soluble phenolic compounds in the coat control germination and peroxidase reactivation in <Emphasis Type="Italic">Triticum aestivum</Emphasis> seeds

In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid equivalent g⁻¹ dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1% H₂O₂ reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H₂O₂ pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated. Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation.     

Priming effects on seed germination in Tecoma stans (Bignoniaceae) and Cordia megalantha (Boraginaceae), two tropical deciduous tree species

Successful revegetation necessarily requires the establishment of a vegetation cover and one of the challenges for this is the scarce knowledge about germination and seedling establishment of wild tree species. Priming treatments (seed hydration during a specific time followed by seed dehydration) could be an alternative germination pre-treatment to improve plant establishment. Natural priming (via seed burial) promotes rapid and synchronous germination as well as the mobilisation of storage reserves; consequently, it increases seedling vigour. These metabolic and physiological responses are similar to those occurring as a result of the laboratory seed priming treatments (osmopriming and matrix priming) applied successfully to agricultural species. In order to know if natural priming had a positive effect on germination of tropical species we tested the effects of natural priming on imbibition kinetics, germination parameters (mean germination time, lag time and germination rate and percentage) and reserve mobilisation in the seeds of two tree species from a tropical deciduous forest in south-eastern México: Tecoma stans (L Juss. Ex Kunth) and Cordia megalantha (S.F Blake). The wood of both trees are useful for furniture and T. stans is a pioneer tree that promotes soil retention in disturbed areas. We also compared the effect of natural priming with that of laboratory matrix priming (both in soil). Matrix priming improved germination of both studied species. Natural priming promoted the mobilisation of proteins and increased the amount of free amino acids and of lipid degradation in T. stans but not in C. megalantha. Our results suggest that the application of priming via the burial of seeds is an easy and inexpensive technique that can improve seed germination and seedling establishment of tropical trees with potential use in reforestation and restoration practices.     

Mechanisms regulating seedling emergence of orchardgrass (Dactylis glomerata L.) and western wheatgrass (Pascopyrum smithii [Rydb.] L.): Dormancy change,seed fate and seeding date

Seed germination and seedling emergence of ‘Arctic’ and ‘Lineta’ orchardgrass (Dactylis glomerata L.) and ‘Walsh’ and ‘LC9078a’ western wheatgrass (Pascopyrum smithii [Rydb.] L.) were studied both in the field and laboratory. Four seeding dates were conducted each year over 2 years and seedling emergence and seed fate in the soil were monitored. The effects of alternating temperature and light on germination were quantified and correlated with seedling emergence from soil and in the field. Orchardgrass seeds were less dormant than western wheatgrass as indicated by the disparity in germination percentage between constant and alternating temperatures. Seed germination percentage was usually higher than seedling emergence in the field for orchardgrass but lower for western wheatgrass, and temperature was not responsible for the difference. Exposing orchardgrass seeds to light during germination check helped break dormancy in orchardgrass when temperature was unfavorable (low and/or constant temperatures), while favorable temperatures (optimal, alternating temperatures) conditions overcame the inhibiting effect of light in western wheatgrass. The final seedling emergence of orchardgrass was either similar among the four seeding dates or decreased slightly from early May to early June. For western wheatgrass, however, final seedling emergence increased with seeding dates from early to late May and decreased in early June. Soil temperatures of the first 2 weeks after seeding increased from the early May to late May and then decreased. These temperatures were below or near the optimal temperatures for western wheatgrass seeds to release dormancy and germinate. Germination of the previously buried seeds indicated that orchardgrass and western wheatgrass had the potential for a high germination percentage under field conditions for all seeding dates. While soil temperatures close to the optimal temperature for dormancy breaking and germination promoted germination of orchardgrass, the same conditions could cause deterioration of seeds if they failed to germinate. For western wheatgrass, deeper dormancy reduced seed mortality.     

Fatty acid beta-oxidation in germinating Arabidopsis seeds is supported by peroxisomal hydroxypyruvate reductase when malate dehydrogenase is absent

Peroxisomal malate dehydrogenase (PMDH) oxidises NADH produced by fatty acid beta-oxidation during seed germination and seedling growth. Arabidopsis thaliana beta-oxidation mutants exhibit seed dormancy or impaired seed germination and failure of seedlings to degrade triacylglycerol (TAG), but the pmdh1 pmdh2 null mutant germinates readily and degrades TAG slowly during seedling growth. We reasoned that in the pmdh1 pmdh2 mutant an alternative means of oxidising NADH operates to allow a slow rate of beta-oxidation, such as NADH and NAD⁺ transport across the peroxisomal membrane or activity of another peroxisomal oxido-reductase. Here we show that peroxisomal hydroxypyruvate reductase (HPR) is present in germinating seeds and although knocking out HPR has little effect on germination and early seedling growth, when knocked out in combination with PMDH it exacerbates the pmdh1 pmdh2 phenotype. It greatly increases the proportion of dormant seeds and reduces the rate of seed germination. Seedlings have increased sucrose dependence and resistance to 2,4-dichlorophenoxybutyric acid (2,4-DB), and slower rate of TAG breakdown. When PMDH is absent, malate is lower in amount in germinating seeds and when HPR is also absent, serine (the immediate precursor of hydroxypyruvate) is much higher. These results indicate that HPR can oxidise NADH at sufficient rate in the absence of PMDH to support beta-oxidation and hence seed germination. We conclude that while HPR normally plays little role in seed germination our results support the growing body of evidence that peroxisomal NADH cannot be exported to the cytosol for oxidation but is oxidised by resident oxido-reductases.     

Effect of Methyl Jasmonate on the Germination and the Degradation of Storage Reserve in Rice Seed

The effects of methyl jasmonate (MeJA, Nippon Zeon Co., Ltd, Tokyo, Japan) on germination and the degradation of storage reserve in rice （Oryza sativa L.） seeds were studied. There were dual effects of MeJA on seed germination and seedling growth of rice, low concentration of MeJA promoted germination and seedling growth whereas high concentration of MeJA inhibited germination and seedling growth. The optimal concentration of promotion was 5×10-7 mol/L. The acid phosphatase activity, α-amylase activity, degradation of starch and salt-soluble proteins were affected same as germination by MeJA. MeJA inhibited the degradation of glutelins, the higher the concentration, the higher the extent of inhibition above 5×10-7 mol/L.The results showed that either promotion or inhibition of germination by MeJA was very close to the effect on the activity of α-amylase. The mechanisms between abscisic acid and MeJA affection on seed germination and seedling growth were compared.     

Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus

Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.     

In situ seed baiting to isolate germination-enhancing fungi for an epiphytic orchid,Dendrobium aphyllum (Orchidaceae)

Orchid conservation efforts, using seeds and species-specific fungi that support seed germination, require the isolation, identification, and germination enhancement testing of symbiotic fungi. However, few studies have focused on developing such techniques for the epiphytes that constitute the majority of orchids. In this study, conducted in Xishuangbanna Tropical Botanical Garden, Yunnan, China, we used seeds of Dendrobium aphyllum, a locally endangered and medicinally valuable epiphytic orchid, to attract germination promoting fungi. Of the two fungi isolated from seed baiting, Tulasnella spp. and Trichoderma spp., Tulasnella, enhanced seed germination by 13.6 %, protocorm formation by 85.7 %, and seedling development by 45.2 % (all P?Epulorhiza, another seed germination promoting fungi isolated from Cymbidium mannii, also enhanced seed germination (6.5 %; P?P?Trichoderma suppressed seed germination by 26.4 % (P?Tulasnella was the only treatment that produced seedlings. Light increased seed imbibition, protocorm formation, and two-leaved seed development of Tulasnella inoculated seeds (P?Tulasnella be introduced for facilitating D. aphyllum seed germination at the protocorm formation stage and that light be provided for increasing germination as well as further seedling development. Our findings suggest that in situ seed baiting can be used to isolate seed germination-enhancing fungi for the development of seedling production for conservation and reintroduction efforts of epiphytic orchids such as D. aphyllum.     

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.     

Effects of increased nitrogen deposition and precipitation on seed and seedling production of Potentilla tanacetifolia in a temperate steppe ecosystem

Background

The responses of plant seeds and seedlings to changing atmospheric nitrogen (N) deposition and precipitation regimes determine plant population dynamics and community composition under global change.

Methodology/Principal Findings

In a temperate steppe in northern China, seeds of P. tanacetifolia were collected from a field-based experiment with N addition and increased precipitation to measure changes in their traits (production, mass, germination). Seedlings germinated from those seeds were grown in a greenhouse to examine the effects of improved N and water availability in maternal and offspring environments on seedling growth. Maternal N-addition stimulated seed production, but it suppressed seed mass, germination rate and seedling biomass of P. tanacetifolia. Maternal N-addition also enhanced responses of seedlings to N and water addition in the offspring environment. Maternal increased-precipitation stimulated seed production, but it had no effect on seed mass and germination rate. Maternal increased-precipitation enhanced seedling growth when grown under similar conditions, whereas seedling responses to offspring N- and water-addition were suppressed by maternal increased-precipitation. Both offspring N-addition and increased-precipitation stimulated growth of seedlings germinated from seeds collected from the maternal control environment without either N or water addition. Our observations indicate that both maternal and offspring environments can influence seedling growth of P. tanacetifolia with consequent impacts on the future population dynamics of this species in the study area.

Conclusion/Significance

The findings highlight the importance of the maternal effects on seed and seedling production as well as responses of offspring to changing environmental drivers in mechanistic understanding and projecting of plant population dynamics under global change.