Seed germination for an annual form of Zostera marina from the sea of Cortez,Mexico

Seed of Zostera marina L. collected at Punta Chueca, Sonora, that was germinated in artificial seawater under growth chamber conditions was less affected by salinity than by temperature. Mean germination was higher for seed collected on reproductive shoots in situ (43%) than for seed collected in fresh beach debris (17%), but no germination was recorded for seed collected in dried beach debris. Mean germination for seed kept at either 15 or 35‰ salinity was approximately equal. Earliest germination was recorded in late April 1980, two weeks after collection, and germination continued through March 1981 at 18–20°C, conditions which are comparable to winter water temperatures in Canal del Infiernillo. Germination was inhibited at 28–32°C, temperatures that are near summer water conditions. The germination responses reflect the adaptive strategies of an annual population to habitat conditions near the southern limit of the species.     

Field studies on seed germination and seedling development in Zostera marina L.

Seeds of Zostera marina L. were collected in July 1978 and July 1979 and planted within two weeks in sediment-filled containers in shallow water at Northwest Creek, New York. The containers were retrieved at periodic intervals over the next 12 months and the seeds and seedlings examined. Between 76 and 93% of the recovered seeds germinated; primarily during October–December, 3–4 months after release. Seedling growth and development occurred during the autumn and spring, but not in winter. A progressive loss of seedlings was observed during the winter and spring, however, and none survived past May.Three stages of seedling development were distinguished. Stage 1 represented germination including emergence and straightening of the cotyledon. Stage 2 seedlings exhibited continued growth of the cotyledon and variable, but often extensive, elongation (2–50 mm) of the axial hypocotyl. The plumule remained undeveloped (length ? 3 mm), and there were no hairs on the basal hypocotyl. Stage 3 seedlings showed the same range in axial hypocotyl length, but they were distinguished by the onset of plumule growth and hypocotyl hair formation.     

The role of seedlings and seed bank viability in the recovery of Chesapeake Bay,USA, <Emphasis Type="Italic">Zostera marina</Emphasis> populations following a large-scale decline

The objective of this study was to quantify the spatial and temporal recolonization characteristics of Zostera marina beds in the lower Chesapeake Bay following large scale declines in the late summer of 2005. Transects were established and monitored monthly for changes in eelgrass abundance at three sites (two downriver, one upriver) in the York River from April–October 2006 and 2007. Measurements included percent bottom cover, above ground biomass, shoot density, shoot origin (seedling or vegetative), seed bank abundance and seed viability. During 2006, the eelgrass beds at all sites recovered with seedlings providing the largest proportion of the total shoot abundance. This trend shifted in 2007 and surviving vegetative shoots were the dominant component of shoot standing crop. A second consecutive decline related to low light conditions occurred during the summer of 2006 in the upriver site and recovery there was minimal in 2007. These results highlight that after a single die off event, seed germination with subsequent seedling growth is the principal method for revegetation in lower Chesapeake Bay Z. marina beds. However, no viable seeds remain in the seed bank during this first year of recovery and shoots produced by the seedling growth do not flower and produce seeds until their second year of growth. Therefore the seed-bank density is low and is not immediately replenished. This suggests that the resiliency of perennial Chesapeake Bay Z. marina populations to repeated disturbances is restricted and repeated annual stress may result in much longer term bed loss.     

An Effective Method for Collecting and Storing Seeds from Zostera marina (Eelgrass) in the Yellow Sea,China

The coast of the Yellow Sea in China, like many other temperate coastal zones, has been experiencing a dramatic decline in the abundance of seagrass. Intensive efforts have been made to restore seagrass communities along the coast to restore the function of the coastal ecosystem. Transplanting adult Zostera marina shoots is labor‐intensive, time‐consuming, expensive, and detrimental to donor beds; thus, restoring seagrass communities through the use of seeds is highly valued in current, large‐scale restoration trials. In this study, an effective method for collecting, processing, and storing Z. marina seeds was developed. From 2009 to 2013, respectively, 122,000, 421,000, 364,000, 1,041,000, and 1,091,000 seeds were successfully collected. Two‐way analysis of variance (ANOVA) showed the interaction between salinity and temperature significantly affected the cumulative germination rate (CGR) (p < 0.01) during the storage period and the viability (p < 0.01) of seeds after storage. The germination rate after storage was significantly affected by salinity and temperature (p < 0.01). The highest viability (89.8 ± 1.0%) and germination rate (75.6 ± 4.5%) were found among seeds stored at 4°C and a salinity of 44.5 psu for 7 months. The cost for planting 1 ha of sea bottom with Z. marina seeds ranged from $2,613 to $80,900 depending on the seeding density and seed loss during storage. The average cost per Z. marina seed in this study was $0.00586.     

Growing Zostera marina (eelgrass) from Seeds in Land‐Based Culture Systems for Use in Restoration Projects

The use of aquaculture systems to grow the seagrass Zostera marina (eelgrass) from seeds for restoration projects was evaluated through laboratory and mesocosm studies. Along the mid‐Atlantic coast of North America Z. marina seeds are shed from late spring through early summer, but seeds typically do not begin to germinate until the late fall. Fall is the optimal season to plant both seeds and shoots in this region. We conducted studies to determine if Z. marina seeds can be induced to germinate in the summer and seedlings grown in mesocosms to a size sufficiently large enough for out‐planting in the fall. Seeds in soil‐less culture germinated in the summer when held at 14°C, with percent germination increasing with lower salinities. Cold storage (4°C) of seeds prior to planting in sediments enhanced germination and seedling survival. Growth rates of seedlings were significantly higher in nutrient enriched estuarine sediments. Results from preliminary studies were used in designing a large‐scale culture project in which 15,000 shoots were grown and out‐planted into the Potomac River estuary in the Chesapeake Bay and compared with an equal number of transplanted shoots. These studies demonstrate that growing Z. marina from seeds is an alternative approach to harvesting plants from donor beds when vegetative shoots are required for restoration projects.     

THE EFFECT OF SEED DIMORPHISM ON THE GERMINATION AND SURVIVAL OF SALICORNIA EUROPAEA L. POPULATIONS

Seed dimorphism influenced the germination behavior of Salicornia europaea L., with small seeds being more dormant and less salt tolerant than large seeds. All of the large less dormant seeds of S. europaea germinated prior to May, and all seedlings produced after this time were from small seeds. A persistent seed bank was maintained by the small dormant seeds. Survivorship was relatively constant during the normal germination season, but increasing salinity stress at any time during the spring reduces the chance of seedling survival. Little germination occurred from July through September because of the high surface soil salinities during this period.     

Desiccation,Moisture Content and Germination of Zostera marina L. Seed

Zostera marina is the only seagrass species whose seeds have been successfully used in large‐scale restoration. Although progress has been made in refining Z. marina restoration protocols, additional information on Z. marina seed physiology is necessary as the science of seagrass restoration evolves. We tested the germination rates of Z. marina seeds under different relative humidities and temperatures for different periods of time. Z. marina seed moisture content (MC) and germination rates were also tested when seeds were exposed to a temperature of 25°C and relative humidity of 50%. Z. marina seeds suffered higher mortality when exposed to lower relative humidity and higher temperature for longer period of exposure time. A significant negative correlation was detected between seed germination rate and MC. Z. marina seeds are sensitive to desiccation exposure and long periods of exposure to air should be prevented to minimize seed mortality when seeds are used in restoration projects.     

A butenolide, isolated from smoke, can overcome the detrimental effects of extreme temperatures during tomato seed germination

The butenolide, 3-methyl-2H-furo[2, 3-c]pyran-2-one, is an highly active compound isolated from plant-derived smoke. This compound is known to stimulate seed germination in a wide range of plants akin to smoke or aqueous extracts of smoke. The present study attempted to elucidate the role of the butenolide in overcoming detrimental effects of low and high temperatures on tomato seed germination and seedling growth. The germination percentage followed a parabolic curve for temperatures ranging from 10 to 40°C, with 25°C being the optimum for all treatments. Control seeds showed radicle emergence at two extreme temperatures (10 and 40°C) and seedlings failed to develop further, even upon prolonged incubation. By comparison the butenolide-treated seeds grew into phenotypically normal seedlings at these non-optimum temperatures. The smoke–water-treated seeds had an intermediate response as only a fraction of germinated seed developed into normal seedlings. Seedling vigour indices as well as seedling weight were significantly higher (p ≤ 0.05) for butenolide-treated seeds at all temperatures. Furthermore, seedlings developed in the presence of the butenolide had about a 1:1 correspondence between root and shoot length. Butenolide-treated seeds grew better than the control seeds in the temperature shift experiments. A gradual decline in the vigour index values was recorded with an increased duration of incubation at the extreme temperatures. Results of the present study are very important from an horticultural point of view as they indicate the potential use of the butenolide compound in restoring normal seed germination and seedling establishment in tomato below and above optimum temperatures.     

Salinity and waterlogging tolerance of some populations of Melaleuca ericifolia Smith

Seed germination of Melaleuca ericifolia (swamp paperbark) is delayed by submergence in water but the final percentage germination after removing seeds from water is unaffected; some seeds will germinate and the cotyledons emerge whilst submerged. Germination is totally inhibited at salinities of 14% and a population which naturally occurs adjacent to coastal saltmarsh was inhibited more by salinities of 6–12% than two other populations from freshwater habitats. Seedling growth may be increased by water-logging conditions and the degree of response differs for different seed sources. Inundation stimulates root growth and new roots are thick and aerenchymatous. Root systems in the field run horizontally and are shallow, apparently being restricted by clay at depth. All populations studied showed a similar seedling growth-response to salinity treatments; growth declined at salinities ≤ 13% and was severely restricted at 21%, although no seedlings died after 48 days’exposure to the latter treatment.     

Altitudinal variations in germination and growth responses ofReynoutria japonica populations on Mt Fuji to a controlled thermal environment

The authors examined altitudinal variations in the thermal responses of seed germination and seedling growth inReynoutria japonica (=Polygonum cuspidatum) under controlled environmental conditions. Seed populations were collected from different altitudes on Mt Fuji in Japan. The mean seed weight of the upland populations (above 1500 m) was significantly (1.5-fold) heavier than that of the lowland populations (below 1400 m). Under the lowest temperature regime of 15/10°C (day/night) the upland populations showed a significantly higher percentage and speed of germination than the lowland populations; this was not significant under higher temperature regimes. These results indicate that the germination traits of the upland populations on Mt Fuji are favorable for colonization in their cold habitats (low temperature and short growing season). Growth and shoot development were compared between the seedlings grown from seeds collected at altitudes of 700 and 2420 m. The upland seedlings showed a significantly larger biomass and leaf area than the lowland seedlings at 15°C, but there was no difference at 25°C. The difference in biomass at 15°C was attributed to the difference in seed weight. The upland seedlings produced a significantly larger number of branches with smaller and more numerous leaves at both 15°C and 25°C. these developmental traits of the upland seedlings were considered to represent the adaptation of the life form to upland environments. It was concluded that theR. japonica populations along an altitudinal gradient on Mt Fuji can be classified into two ecotypes, whose distribution border lies at an altitude of about 1400–1500m. In this study, the seed weight and germination traits of twoR. japonica seed populations collected in Chiba Prefecture were briefly compared with those of the lowland populations on Mt Fuji.     

Morphological characteristics of annual Zostera marina shoots at various germination temperatures

The timing of the transition from seed, seedlings and development into flowering is paramount importance in annual-type Zostera marina, because flowering is the first step of sexual reproduction. A majority of plants use environmental cues to regulate the transition to their developmental stages because plants must flower synchronously for successful outcrossing and must complete their sexual reproduction under favorable external conditions. The morphological characteristics (seeds and lateral shoot production, branch number, and inflorescence length) of reproductive shoots of Z. marina L. were examined in outdoor mesocosms to better understand the reproductive strategies of annual populations. Seeds in the germination experiment were divided into two groups: those exposed to cold (7 °C; vernalized group) and those left untreated (25-21 °C; non-vernalized group). All 600 seeds (300 from each group) were cultured for 2 months at 7, 10, 15, 20, and 25 °C in an indoor incubator. In the vernalized group, the germination rates were almost significantly higher than in the non-vernalized group. However, germination rates were not significantly affected by germination temperature. In outdoor mesocosms, production of vegetative shoots was observed in plants germinated at 15 and 20 °C in the vernalized group and at 10, 15 and 20 °C in the non-vernalized group. The highest number of vegetative shoots produced (35) was observed in plants germinated at 20 °C in the vernalized group, whereas seeds of either group failed to produce vegetative shoots when germinated at a low temperature (7 °C).In the flowering phase, the number of branches per shoot in the vernalized group was significantly higher than in the non-vernalized group. The total number of spadices on the 1st branches of plants in the vernalized group (germination at 20 °C) was significantly lower than that in the non-vernalized group at the same germination temperature. The total number of spadices per reproductive shoot in the vernalized group (germination at 10 °C) was also higher than in the non-vernalized group. Thus, both low temperature (vernalization) and seed germination temperature have implications for the sexual and asexual propagation of annual Z. marina populations.     

Effects of Salinity and Nutrient Addition on Mangrove Excoecaria agallocha

Effects of salinity on seed germination and growth of young (1 month old) and old (2-year old) seedlings of Excoecaria agallocha were investigated. Combined effects of salinity and nutrient level were also examined on old seedlings. Seed germination was best at 0 and 5 psu salinity. 15 psu salinity significantly delayed root initiation and decreased final establishment rate. All seeds failed to establish at 25 psu salinity. Young seedlings performed best at 0 and 5 psu, but growth was stunned at 15 psu, and all seedlings died within 90 days at 25 psu. Old seedlings grew best at salinities below 5 psu and they survived the whole cultivation at 25 psu. This indicated that E. agallocha increased salt tolerance over time. Gas exchange was significantly compromised by salinities above 15 psu but evidently promoted by high nutrient. Proline accumulated considerably at high nutrient, and its contents increased from 0 to 15 psu but decreased at 25 psu salinity. Lipid peroxidation was aggravated by increasing salinity beyond 15 psu but markedly alleviated by nutrient addition. These responses indicated that E. agallocha was intolerant to high salinity but it can be greatly enhanced by nutrient addition.     

Effect of salinity on germination,seedling emergence,seedling growth and ion accumulation of a euhalophyte Suaeda salsa in an intertidal zone and on saline inland

The effect of salinity on germination, seedling emergence, seedling growth and ion accumulation of a euhalophyte Suaeda salsa L. in an intertidal zone and on saline inland were investigated. Brown seeds of S. salsa were heavier and better developed than black seeds in both the intertidal zone and on saline inland. The brown seeds/black seeds ratio for S. salsa in the intertidal zone was much higher than that for S. salsa on saline inland. More germinated seeds grew as seedlings under high salinity for S. salsa from the intertidal zone than S. salsa on saline inland; high salinity decreased the shoot length more severely for S. salsa from saline inland than for S. salsa from the intertidal zone; the seedling growth at a range of NaCl, measured either as shoot length or shoot dry weight, for S. salsa from the intertidal zone was lower than that of S. salsa from saline inland. In conclusion, for S. salsa from the intertidal zone there appears to be selection for slower growth and producing more brown seeds. The establishment of populations of S. salsa in different saline environments depends on the responses of seed germination, seedling emergence and seedling growth to salinity. These characteristics may determine the natural distributions of S. salsa populations in different saline environments.     

The Use of Abscisic Acid to Synchronize Carrot Seed Germination Prior to Fluid Drilling

Abscisic acid (ABA) was used as a reversible block to the progressof carrot seed germination in a practical seed treatment. Pre-treatingseeds with 10^–4M ABA solution at 15 °C for 12 d gave93% germination of viable seeds on subsequent transfer to waterbefore radicle lengths became too long for fluid drilling. Thiscompared with only 31 % without pre-treatment ABA pretreatment significantly increased the synchrony of carrotseed germination and did not affect final percentage germinationor early seedling growth rates. Seedling emergence from ABA-treatedgerminating seeds was earlier and more uniform than from untreatedgerminating seeds and seedlings from both these treatments emergedbefore those from ungerminated seeds Daucus carota L., carrot, germination, seed treatment, fluid drilling, abscisic acid, radicle extension     

Large‐Scale Zostera marina (eelgrass) Restoration in Chesapeake Bay,Maryland, USA. Part I: A Comparison of Techniques and Associated Costs

The Chesapeake Bay, like many other temperate estuaries, has exhibited dramatic declines in the abundance of submerged aquatic vegetation (SAV) during the later half of the twentieth century. Because of the functions SAV serve in maintaining a healthy estuarine ecosystem, SAV restoration has become an important component of Chesapeake Bay restoration. Specifically, recent water quality improvements in areas from which populations of Zostera marina (eelgrass) have been extirpated have suggested that Z. marina restoration could succeed. Early restoration efforts involved transplanting Z. marina plants from healthy source beds to restoration locations, but this was labor intensive, time consuming, expensive, and potentially detrimental to donor beds. This multi‐year project investigated new techniques for large‐scale Z. marina seed collection and processing and compared two seed dispersal methods to evaluate cost effectiveness. Tens of millions of mature Z. marina seeds were collected through snorkeling, SCUBA, or with a mechanical harvester. Seed storage conditions and processing techniques were manipulated in order to maximize seed yield. Seeds were dispersed using two methods: spring seed buoys and fall seed broadcasts. Our costs for planting 1 ha of bottom with Z. marina seeds ranged from $6,674 to $165,699 depending on seeding density and dispersal method used. The average cost per Z. marina seed was $0.17. Interannual variations in seed collection yield and seed viability after summer storage had great impact on final costs. Our results suggest that the use of seeds for large‐scale Z. marina restoration offers a competitive advantage to more traditional transplanting methods.     

Seed Germination and Seedling Development in Cyclamen persicum

Cyclamen persicum Mill, seeds germinate in a narrow range oftemperature and germination is strongly inhibited by continuousirradiation with white light. The thermal optimum is approx.15 °C in both darkness and light. Seed germination is alsovery sensitive to oxygen deprivation and this sensitivity ismore pronounced at 20 °C than at the optimum 15 °C.Very immature seeds cannot germinate at any temperature, butgerminability increases during seed maturation Seedling development is unusual since seed reserves are usedimmediately for tuber formation. Tuberization is optimal at15–20 °C in light and in darkness. Supra-optimal temperatures(25–30 °C) or hypoxia inhibit tuber formation andlead to very elongated tubers These results allow the producers to improve the productionof homogeneous populations of cyclamen seedlings Wheat seeds, Triticum aestwum L., acetylcholinesterase, electrophoresis, germination, assay     

Effects of seed mass on seedling success in Artocarpus heterophyllus L., a tropical tree species of north-east India

I examined the effects of seed mass on performance of seedlings of Artocarpus heterophyllus L. (Moraceae), a large evergreen late successional shade-tolerant tree species in three contrasting light conditions. Seed mass varied many fold from 1.5 to 14 g in A. heterophyllus. Germination and germination time showed a significant correlation with seed mass. Germination differed significantly among three light regimes (50%, 25% and 3%). Seed mass and light level significantly affected seedling survival. The seedlings that emerged from large seeds survived better than those from small seeds under all light regimes. Survival of seedlings was maximum in 25% light regime for all seed mass classes but did not differ significantly from that at 50% light regime. Survival was significantly lower in 3% light as compared to 50% and 25% light regimes. Seedling vigor (expressed in terms of seedling height, leaf area and dry weight) was also significantly affected by seed mass and light regimes. Seedlings that emerged from larger seeds and grew under 50% light regime produced the heaviest seedlings, while those resulting from smaller seeds and grown under 3% light regime produced the lightest seedlings. Resprouting capacity of seedlings after clipping was significantly affected by seed mass and light regime. Seedlings emerging from larger seeds were capable of resprouting several times successively. Resprouting was more pronounced under 50% and 25% light regimes as compared to 3% light. Success of A. heterophyllus regeneration appears to be regulated by an interactive effect of seed mass and light regime.     

Waterfowl grazing in autumn enhances spring seedling recruitment of intertidal Zostera noltii

Feeding pits dug by waterfowl in Zostera noltii meadows are thought to promote seedling recruitment by accumulating seeds and enhancing germination. We tested the latter hypothesis by creating a series of “treatment pits” (resembling natural feeding pits) in the center and at the edge of two meadows near the Island of Sylt (Germany). Seedling density was monitored from the autumn seed set until the following spring. Seedling density (mean, SE) in treatment pits was significantly higher (4.4, 5.3) than in manipulated (2.4, 1.9) and unmanipulated controls (1.4, 0.4), as well as significantly higher in center (2.8, 0.5) relative to edge (2.5, 1.1) locations. Results confirm a facilitating effect of waterfowl grazing on seedling recruitment in spring due to seed accumulation in feeding pits in autumn. The mechanism could provide a valuable tool for the conservation of intertidal Z. noltii meadows in the Wadden Sea.     

Effects of seed dispersal on Juniperus communis recruitment on a Mediterranean mountain

Abstract. The recruitment of the relict shrub Juniperus communis on a mountain in SE Spain was studied during the period 1994–1998. The main objective was to determine both the quantitative and qualitative effects of bird dispersal on seedling establishment. Seed removal by birds, seed rain, post‐dispersal seed predation, germination, and seedling emergence and survival were analysed in different microhabitats. Birds removed 53 ‐ 89% of the seeds produced by plants. Seed rain was spatially irregular as most seeds accumulated near stones used by birds as perches and below mother plants while a few seeds were dropped in wet meadows and open ground areas. Post‐dispersal seed predation by rodents affected < 10% of dispersed seeds but varied significantly among microhabitats. Only 3.6 ‐ 5.5% of dispersed seeds appeared viable, as many seeds had aborted or showed wasp damage. Seeds germinated in the second and third springs after sowing, reaching a germination percentage of 36%. Seedling emergence was concentrated in wet meadows. Seedling mortality was high (75–80%), but significantly lower in wet meadows, the only microhabitat where seedlings could escape from summer drought, the main mortality cause. Seed abortion, germination and seedling mortality proved to be the main regeneration constraints of J. communis on Mediterranean mountains. Birds exerted a strong demographic effect, although their qualitative effect was limited by abiotic factors which caused the pattern of seed rain to differ from the final pattern of recruitment between microhabitats.     

Comparative ecology of seedling recruitment in an oligotrophic wet meadow

Abstract. For the regeneration niche to contribute to the maintenance of species diversity interspecific differences in sensitivity of seedling recruitment to environmental conditions is assumed. We experimentally tested differences between meadow species for the response of seed germination to chilling, and sensitivity of seedling recruitment to microscale heterogeneity. We also compared the dynamics of seedling recruitment in gaps. Seed germination was tested in standard laboratory germination tests, comparing control seeds with seeds chilled at +4 °C, and at –14°C for one month. Species responses varied from significant increases in germinability after chilling (e.g. Cirsium palustre, Betonica officinalis, Angelica sylvestris) to significant decreases (e.g. Hieracium umbellatum, Succisa pratensis, Selinum carvifolia). In some species, chilling at + 4 °C has a similar effect to chilling at –14 °C, in others the effect of chilling at + 4°C was intermediate, and in some, there was no effect of chilling at + 4°C, but an effect of chilling at –14°C. Different chilling temperatures also affect timing and speed of seed germination under greenhouse conditions. The dynamics of seed germination under field conditions was studied by sowing seeds into artificially created gaps and following their germination, both where the seedlings were removed after emergence and where they were not removed. Species differ in their germination dynamics: they all start late April, but then differentiate from an abrupt maximum and early finish of germination (in the second half of May), to prolonged germination without a marked maximum. Seedling removal increased the total number of germinated seeds, with a marked density dependence at this stage. Seeds were also sown into plots with treatments (1) gaps, sod stripped, above-ground vegetation removed; (2) mown, moss layer removed; (3) mown; (4) untouched control. Seedling emergence was monitored for 3 yr. Seedling recruitment decreased from treatments (1) to (4), but sensitivity differed between species. With increasing seed weight, the difference between gaps and other treatments decreased. The results show that there are considerable differences in seedling recruitment sensitivity between species.