Number Of Viable Seeds Research Articles

Water level drawdown induces a legacy effect on the seed bank and retains sediment chemistry in a eutrophic clay wetland

The lack of extreme water level fluctuations in managed, non-peat forming wetland ecosystems can result in decreased productivity through the loss of heterogeneity of these ecosystems. Stochastic disruption, such as a water level drawdown, can effectively reverse this effect and return the wetland to a more productive state, associated with higher biodiversity through new vegetation development. Yet, aside from the effect on vegetation dynamics, little is known about longer-term effects (30 years) of a water level drawdown, hereafter referred to as legacy effects, and how this may impact future water level drawdowns.Here, we aim to unravel the legacy effects of a water level drawdown, stand alone and along a water level gradient, on seed bank properties and nutrient availability in a eutrophic clay wetland. To identify these, we studied the hydrologically managed nature reserve Oostvaardersplassen in the Netherlands. Here, one section was subjected to a multi-year water level drawdown and another section was kept inundated. We determined seed bank properties in both areas, spatially and along a soil elevation gradient (20 cm). Nutrient availability was measured by taking sediment samples along the water level gradient and through experimental manipulation of the water level in an indoor mesocosm experiment.Germination was higher in locations with a water level drawdown history, especially at relatively high elevations. Additionally, the proportion of pioneer species in the seed bank was higher in the water level drawdown area. Overall, nutrient concentrations were higher compared to other aquatic systems. Nutrient availability was higher in the inundated area and did not respond to the water level gradient. We conclude that 30 years after an induced water level drawdown there is no depletion of nutrients, while we still observe a legacy effect in the number of viable seeds in the seed bank.

Contribution of yield structure elements to the winter wheat productivity formation at different moisture availability

The current paper has presented the experimental results of estimating the influence of moisture availability on productivity and yield structure elements of the winter wheat varieties. There have been studied 11 winter common wheat varieties of a semi-intensive type developed in the FSBSI “ARC “Donskoy”. The purpose of the study was to determine the influence of different soil moisture levels on the yield and its structural elements of winter wheat. The varieties were tested in laboratory conditions by simulating soil drought (sucrose solution was with an osmotic pressure of 16 atmospheres), as well as on a vegetation plot “zasushnik” with optimal and insufficient moisture. When determining potential drought resistance based on the ‘seed germination’ indicator, the studied varieties were divided into three resistance groups. The varieties ‘Ayuta’ (83.3 %) and ‘Volnitsa’ (82.1 %) were highly drought-resistant, which significantly exceeded the standard variety ‘Don 107’ (70.3 %) (НСР05 ± 6.0 %). The estimation of varieties in contrasting moisture conditions made it possible to identify stable yield traits, such as ‘length of a head’, ‘number of grains per main head’ and ‘grain weight per main head’, and ‘1000-grain weight’. High depression values under drought conditions were established according to ‘number of productive stems’, ‘length of a head’ and ‘1000-grain weight’ (6.5; 7.0; 12.0 %, respectively). There has been found a correlation between the laboratory and vegetation estimation of the trial. The correlation coefficient between resistance to lack of moisture in soil (number of viable seeds) and a depression degree of yield indicators (‘number of productive stems’, ‘length of a head’, ‘number of grains per main head’, ‘grain weight per main head’, ‘1000-grain weight’) ranged from 0.32 to 0.98. There have been identified the varieties ‘Zhavoronok’, ‘Polina’, ‘Premiera’ and ‘Podarok Krymu’, combining laboratory drought resistance with a complex of productivity traits.

Pollination of Richea dracophylla (Ericaceae) and the role of the nocturnal ant Notoncus hickmani (Formicinae)

AbstractOur observation of large numbers of ants Notoncus hickmani (Formicinae) on the flowers of a Tasmanian endemic shrub Richea dracophyllum (Ericacea) during the night in winter prompted us to carry out a more extensive study of pollination of R. dracophyllum at two sites. Terminal panicles bear inflorescences of 300+ flowers whose petals are fused into calyptrae covering the reproductive organs, and the calyptrae must be removed before pollination can occur. To exclude birds, we placed mesh bags over some inflorescences. Inflorescences with exclusion bags had a high proportion of retained calyptra and the numbers of viable seeds were greatly reduced. We found R. dracophyllum to have a very long flowering period (more than 6 months) and a range of floral visitors, including honey‐eaters (Meliphagidae) and flying insects. At one site we observed large numbers (up to 100) of N. hickmani on inflorescences between dusk and midnight during winter at air temperatures down to 2.5°C. They fed on nectar from flowers that had lost their calyptra where they were exposed to pollen from the anthers and scanning electron microscopy showed high numbers of pollen grains being carried on the ants. The feeding behaviour of these ants would facilitate pollination between adjacent flowers (geitonogamy). Smaller numbers of dolichoderine ants (Iridomyrmex bicknelli?) were observed during the daytime in spring but mainly fed under partially detached calyptrae where they had little exposure to pollen. We suggest that R. dracophylla is pollinated by a range of species and functional groups—birds, flying insects and ants, and that the pollinating species will vary during the year and between sites, although insects depend on birds to remove the calyptrae. Ant pollination is rare, nocturnal ant pollination is extremely rare, and pollination by nocturnal cryophilic ants has not been documented previously.

Small floral patches are resistant reservoirs of wild floral visitor insects and the pollination service in agricultural landscapes

Small floral patches that coexist with crops in agricultural landscapes can function as biodiversity reservoirs. However, the influence of the landscape context and agricultural management on the capacity of these small green infrastructures to support diversity is poorly understood. Here, we evaluate the effect of landscape simplification, agricultural intensification in the neighbourhood, and quality of the floral habitats on the success of these patches to support flower-visiting insect communities as well as the pollination service they provide.To this aim, we sampled floral patches located in 18 paired olive farms with contrasting herb cover management (intensive vs. low-intensity), distributed along a wide gradient of landscape complexity at the regional scale of South Spain. We conducted surveys of flower-visiting insects in 36 multi-floral stands and 36 mono-floral stands of Sinapis alba Linnaeus (1753) within these floral patches. Mono-floral stands were used to evaluate variations in the pollination service through number of viable seeds and seed set.Results revealed that the abundance and diversity of flower-visiting insects respond to the quality of the floral patch (diversity of flowers) but not to landscape context nor agricultural management around it. Moreover, the pollination service was similar and high (seed set ca. 100 %) in all floral patches regardless of their context.Our findings highlight the importance of even small floral patches that function as reservoirs of diversity of flower-visiting insects and the pollination service. They also show the high resistance of these patches to agricultural intensification and simplification in olive grove landscapes.

Flowering capacity and botanical seed production of sweet potato genotypes

ABSTRACT The identification of genotypes with greater capacity for flowering and seed production is crucial for greater efficiency in the genetic improvement of the sweet potato crop. Thus, the objective of this work was to evaluate the flowering capacity and the production of botanical seeds in sweet potato genotypes. The work was carried out in the municipality of Lavras, located in the southern region of Minas Gerais, Brazil. Twenty-two sweet potato genotypes belonging to the germplasm bank of the Federal University of Lavras (UFLA) were evaluated. The characteristics evaluated were the flowering period (days), the number of viable seeds, the total weight of viable seeds, the weight of 1000 seeds and the percentage of germination. The obtained data were analyzed by means of descriptive statistics, study of correlations and analysis of main components. The sweet potato genotypes evaluated showed a high capacity for flowering and production of botanical seeds. Flowering usually starts 125 days after planting and extends on average for 72 days. Considering future recombination to promote flowering capacity, seed production and greater germination, genotypes BD-05, BD-26 and BD-44 should be prioritized.

Особенности плодоношения некоторых сортов Clematis L. коллекции Никитского ботанического сада

The article presents the results of studying the fruiting in 9 clematis cultivars under the conditions of the southern coast of Crimea. Morphometric characteristics of seeds, their weight and germination capacity are given. Potential and real seed production was assessed. It was found that the studied cultivars are characterized with high potential seed production, on average from 38.1 to 116.9 ovules per fruit, but relatively low real seed production, on average from 1.3 to 8.3 seeds per fruit. Among the studied cultivars, the largest number of viable seeds formed per plant was noted in 4 cultivars: ‘Jan Pawel II’, ‘Ramona’, ‘Elegia’ and ‘Juulii’. These cultivars are recommended for use in breeding works as maternal parental forms.

Influence of high temperature on the reproductive biology of dry edible bean (Phaseolus vulgaris L.)

ABSTRACT: The aim of this study was to investigate the effect of heat stress on 12 bean genotypes through the analysis of their reproductive biology in terms of flowering, pollen viability, meiotic behavior, and production. Plants were grown in a climate chamber at 25-20 °C (day and night) and at a high temperature treatment 37-26 °C (day and night) from the vegetative (V4) development stage to physiological maturity. The experimental design was 2 × 12 factorial arrangement with six replications and the factors consisted of heat treatments and genotypes. In three replications, the number of newly opened flowers was checked daily. At physiological maturity, the following traits were evaluated: percentage of pod set, number of pods, number of viable seeds, number of aborted seeds, 100 seed weight, and seed yield (g per plant). The other three replications were used to collect flowers to create slides to study viability of the pollen grain and analyze the meiotic behavior. The heat treatment factor significantly affected the following traits: total number of pollen grains, number of flowers, number of pods, pod set, number of viable seeds, 100 seed weight, and seed yield. The raised temperature reduced these variables, except for percentage of pod set, and increased meiotic irregularities. The mean values regarding seed yield were 16.39 g per plant for the control treatment and 7.46 g per plant under high temperature. IAC Imperador, FT Nobre, Perola, BRS Estilo, and IAC Diplomata stood out for higher bean seed yield under increased temperature.

Потенційна забур’яненість ґрунту залежно від його обробітку за вирощування гречки посівної в Прикарпатті України

An actual problem in modern agriculture is the development of weed control measures in crops. The number of weeds, in turn, depends on the number of viable seeds in the soil. Therefore, the purpose of the study was to determine the effect of different variants of primary and pre-sowing tillage on the content and distribution of physically complete weed seeds in the 0–30 cm layer of soil, as well as its germination and productivity of sowing buckwheat. The research was conducted in the conditions of the Carpathian State Agricultural Research Station of NAAS and the Laboratory of the Department of Agriculture and Herbology of NULES of Ukraine during 2015–2017. According to the results of both experiments, variants of chiseling by 20–22 cm, disking by 10–12 cm and 6–8 cm led to the placement of the bulk of weed seeds – 43–56 % in the upper 0–10 cm soil layer, which subsequently allows you to choose the optimal system of pre-sowing tillage. These variants of basic tillage in combination with the second variant of pre-sowing provided the highest level of germination of weed seeds (+ 250–288 % to control). The highest crop yield (3.61 t/ha) in both experiments was recorded for the combination chiseling of soil on 20–22 cm and pre-sowing, which included of early spring harrowing, harrowing with heavy tooth-boring harrows (as weed germination) and pre-sowing cultivation to the depth of sowing.

Assessing the Impact of Lumbricid Earthworms on Forest Seeds in Northeastern Ohio

This study examines the capacity of two nonnative lumbricid earthworms, Lumbricus terrestris and L. rubellus, to ingest and digest the seeds of herbaceous plants and affect their distribution in forest soils of northeastern Ohio. A survey of earthworms in a forested area of Cleveland Metroparks revealed Lumbricus was the most common and widely distributed earthworm genus, although Aporrectodea and Octolasion were also well represented. A total of 120 soil samples taken adjacent to earthworm sampling plots and placed in a growth chamber yielded a total of 35 germinations. The germinations occurred primarily in the upper 8 cm of the soil profile, suggesting limited redistribution of seeds by earthworms. Growth chamber feeding trials using seeds ranging in size from approximately 2 to 5 mm maximum linear dimension revealed that both species of earthworm will consume and digest seeds that measure up to between 3 and 4 mm. Lumbricus terrestris consistently ingested and digested more than twice as many seeds as did the substantially smaller L. rubellus. Comparisons of the germination rates of seeds egested by the earthworms with rates for seeds that were not ingested showed no impact on germination due to egestion, suggesting ingestion and subsequent egestion of seeds by lumbricid earthworms does not enhance germination. By ingesting and digesting seeds, L. rubellus and L. terrestris should reduce the number of viable seeds in the soil and, thereby, contribute to changes in forest vegetation.

Deciphering the role of reproductive investment, pollination success and predispersal seed predation on reproductive output in Juniperus thurifera

ABSTRACTBackground: Plant reproductive output is determined by a complex set of factors including resource availability, pollination success and pre-dispersal predation. Disentangling the relative contribution of each factor is critical to underpin the factors determining plant fitness.Aims: To unravel the relative contributions of initial reproductive effort, pollination success and pre-dispersal seed predation to plant reproductive success in the fleshy-fruited, wind-pollinated Juniperus thurifera.Methods: We conducted an experiment including pollen addition and pesticide application on 40 female juniper trees for 20 months. Flower production was used as a proxy for resource levels.Results: Main fruit loss occurs in early stages of fruit development. Initial flower number affected fruit and seed set by (a) increasing the rate of fruit formation and the number of viable seeds within fruits and (b) modifying the incidence of low-mobile predators through a satiation effect. Pollination did not limit fruit set, although hand pollinated fruits had more viable seeds. Pre-dispersal seed predation by different arthropods was critical in defining final fruit set.Conclusions: Fruit set in J. thurifera was determined by the interaction of initial reproductive effort and pre-dispersal seed predation. Pollination was not a limiting factor in this relatively dense juniper forests during a year of high flower production.

Seed germinability and longevity influences regeneration of Acacia gerrardii

Acacia gerrardii is the only native tree species of the Kuwaiti desert ecosystem. However, anthropogenic disturbances and harsh arid climate have contributed towards the disappearance of this keystone species from its habitat. In this study, effects of different seed pretreatments to break dormancy, water entry pathway, and ecology (seasonal timing) of dormancy loss and germination of A. gerrardii were investigated. Effects of mechanical scarification, hot water treatment (30 s, 1, 2, and 5 min), and concentrated acid scarification (10, 20, and 30 min) on germination percentage and rate (time to 50% germination and final germination) were also examined. Pretreatment with mechanical scarification produced the highest germination in the least time and 20 °C, 40% RH with 12 h of light (2370 Lux) were found to provide the best germination environment. Seeds were rapidly aged at 60% RH and 45 or 50 °C to determine longevity, and the results were analyzed using probit analysis. Times taken for viability of A. gerrardii seeds aged at 45 and 50 °C to fall to 50% (p50) were 38.6 and 9.3 days, respectively, and therefore the seeds can be considered to have medium longevity. Experiments to find the water entry pathway in A. gerrardii indicated that the micropyle region was the primary point of water entry into the seed. Seed burial experiments indicated that though seed retention decreased over time, there was no significant decrease in number of viable seeds after 31 weeks. The findings of this study are important to nursery managers, seed banks, and those involved in conservation and restoration activities.

Мінливість кількісних ознак Hibiscus syriacus L. в умовах м. Запоріжжя

Мінливість кількісних ознак Hibiscus syriacus L. в умовах м. Запоріжжя

Tomato Reproductive Success Is Equally Affected by Herbivores That Induce or That Suppress Defenses.

Herbivory induces plant defenses. These responses are often costly, yet enable plants under attack to reach a higher fitness than they would have reached without these defenses. Spider mites (Tetranychus ssp.) are polyphagous plant-pests. While most strains of the species Tetranychus urticae induce defenses at the expense of their performance, the species Tetranychus evansi suppresses plant defenses and thereby maintains a high performance. Most data indicate that suppression is a mite-adaptive trait. Suppression is characterized by a massive down-regulation of plant gene-expression compared to plants infested with defense-inducing mites as well as compared to control plants, albeit to a lesser extent. Therefore, we hypothesized that suppression may also benefit a plant since the resources saved during down-regulation could be used to increase reproduction. To test this hypothesis, we compared fruit and viable seed production of uninfested tomato plants with that of plants infested with defense-inducing or defense-suppressing mites. Mite-infested plants produced fruits faster than control plants albeit in lower total amounts. The T. evansi-infested plants produced the lowest number of fruits. However, the number of viable seeds was equal across treatments at the end of the experiment. Nonetheless, at this stage control plants were still alive and productive and therefore reach a higher lifetime fitness than mite-infested plants. Our results indicate that plants have plastic control over reproduction and can speed up fruit- and seed production when conditions are unfavorable. Moreover, we showed that although suppressed plants are less productive in terms of fruit production than induced plants, their lifetime fitness was equal under laboratory conditions. However, under natural conditions the fitness of plants such as tomato will also depend on the efficiency of seed dispersal by animals. Hence, we argue that the fitness of induced plants in the field may be promoted more by their higher fruit production relative to that of their suppressed counterparts.

Seed Biology of the Weed Maryland Meadowbeauty (Rhexia mariana L.) in Blueberry (Vaccinium spp.)

ABSTRACTStudies were conducted at three locations across the North Carolina coastal plain region to determine sexual reproductive potential, seedbank density, frequency of seed dormancy, and effect of temperature on Maryland meadowbeauty seed germination. Seed capsule density ranged from 500 per m2 to 1124 per m2 across locations. Each capsule contained an average of 74 seeds. Seeds germinated only in the 35/20 °C temperature regime, which represents the hottest month (August) of the growing season in southeastern North Carolina. Total number of germinated seeds differed across locations and ranged from 30% to 57%. The percent (average) of viable (66) and nonviable (26) meadowbeauty seeds was not different across locations. Relative germination and seed dormancy percentages were calculated based on the number of viable seeds. The percent relative germination and seed dormancy were different across locations and ranged from 47% to 86% and 14% to 55%, respectively. The highest number of germination resulted from 90 days of stratification. On average, 27 seeds germinated among soil samples, which is equivalent to 989 seeds per m2. The data indicate that the populations of meadowbeauty in blueberry fields have the potential to sexually reproduce and contribute 5 × 106 to 1.1 × 107 seed capsules/ha and 3.7 × 108 to 8.3 × 108 seeds/ha of infestation. Freshly mature seeds can germinate and contribute 1.79 × 108 to 7.14 × 108 seedlings/ha in the year the seeds are produced and 5.18 × 107 to 4.4 × 108 seeds/ha can be dormant and incorporated into the seed bank on an annual basis. Approximately 9.89 × 106 seeds/ha are dormant and viable in the soil and have the potential to germinate following adequate stratification.

Seed Production and Control of Sicklepod (Senna obtusifolia) and Pitted Morningglory (Ipomoea lacunosa) with 2,4-D, Dicamba, and Glyphosate Combinations

Sicklepod and pitted morningglory are two of the most important weed species in row-crop production in the southeastern United States. The upcoming introduction of soybean and cotton varieties resistant to 2,4-D and dicamba will increase the reliance on these auxinic herbicides. However, it is not clear how these herbicides will affect sicklepod and pitted morningglory control. Field experiments were conducted in 2013 and 2014 in Jay, FL to determine whether 2,4-D (560 and 1,120 g ae ha−1), dicamba (420 and 840 g ae ha−1), and glyphosate (1,060 g ae ha−1) alone or in combination applied when weed shoots were 11 (early POST [EPOST]) and 22 (late POST [LPOST]) cm long effectively control and prevent seed production of sicklepod and pitted morningglory. LPOST provided more effective control of sicklepod than EPOST. This was attributed to emergence of sicklepod seedlings after the EPOST application. When glyphosate was tank mixed with 2,4-D or dicamba, sicklepod control was higher (78 to 89% and 87 to 98% in 2013 and 2014, respectively) than for single-herbicide treatments (45 to 77% and 38 to 80% in 2013 and 2014, respectively) 6 wk after treatment (WAT). Pitted morningglory control was not affected by application timing, and 2,4-D provided 91 to 100% 6 WAT, which was equivalent to treatments with tank mixtures containing glyphosate. Dicamba applied at 420 g ha−1had the lowest pitted morningglory control (44 to 70% and 82 to 86% in 2013 and 2014, respectively). Sicklepod and pitted morningglory plants that survived and recovered from herbicide treatments produced the same number of viable seeds as nontreated plants in most treatments. The results of the present study indicated that the use of 2,4-D and dicamba alone will not provide adequate extended control of sicklepod, and the use of tank mixtures that combine auxinic herbicides with glyphosate or other POST herbicides will be necessary to manage sicklepod adequately in 2,4-D- or dicamba-resistant soybean and cotton. Because sicklepod plants that survived a single herbicide application are capable of producing abundant viable seeds, integrated approaches that include PRE herbicides and sequential POST control options may be necessary to ensure weed seed bank reductions.

Composition of Soil Seed Banks in Relation to Four Different Land Use Patterns in Tropical Moist Forest Lands of Southwest Lowlands, Sri Lanka

The soil seed bank comprises all viable seeds in the soil. Seed banks have been defined as the collections of seeds that can remain dormant in the surface soil until their germination is triggered by an environmental change. Natural forests in the tropics have been and continue to be subjected to natural and human induced disturbances, which have resulted in their degradation or complete destruction. In places where the sites are left without further interference, the processes of succession that will ultimately lead to re-vegetation of the sites may be initiated. In such cases, soil seed banks serve as one of the major sources of plant re-growth. This study was conducted to document the species composition of soil seed banks in four different landuses and to make a comparison between them. Those are natural forest area in Sinharaja Forest Reserve towards Pitakele, Kekilla fernland, Pine plantations and tea lands in Pitakele village. Three sites from each landuse were randomly selected for the study and ten soil samples were randomly collected from ten different locations in each site and mixed to make a composite. The number of viable seeds in each soil sample was estimated through germination trials. A total of 1,673 seeds germinated from the soil seed banks of the 12 sites. Most of the tree species were observed in soil seed banks in natural forest and Pine plantations while seeds of herbaceous and graminoid species dominated the soil seed banks of the tea lands and Kekilla fernlands. Natural forest supported the lowest species diversity (Shannon index: H‟1.37) in soil seed banks compared to other land uses. Pine lands (Shannon index: H‟2.22) and Tea lands (Shannon index: H‟1.58) had higher species diversity followed by Kekilla fernland (Shannon index: H‟1.47). Keywords: Soil seed bank, Landuse pattern, Southwest lowlands

Puzzling out the reproductive biology of the endangered cat’s head rockrose (Helianthemum caput-felis, Cistaceae)

Helianthemum caput-felis is an endangered plant species growing in fragmented habitats in the western Mediterranean basin. Reproductive traits, breeding system and pollinator assemblage were studied in its largest known (mainland) European population to improve knowledge on the reproductive biology of the species. Hand-pollination experiments were carried out to determine the breeding system. Generalized linear mixed models (GLMM) were fitted to the data to evaluate the effect of treatment on fruit set and number of viable seeds per fruit. We also investigated the composition of the pollinator assemblage by direct observations, and studied their pollen load. Results were then compared to previous studies conducted in an island population. In the studied population, H. caput-felis is partially self-compatible, but mostly an outbreeder species, since outcrossed flowers produced many more fruits and seeds than self-pollinated ones. Conversely, pollination treatments did not affect reproductive output in the island population. We also found several differences between island and mainland composition of floral visitors, as it was expected. The study of pollen loads revealed that insects were mostly visiting H. caput-felis. Despite the low capacity to produce fruits with self-pollination, H. caput-felis presented no reproductive limitations in its main inland population. Reproductive characteristics along with differences among populations should be taken into account for adequate management and conservation practices.

Impact of herbivory on mile-a-minute weed (Persicaria perfoliata) seed production and viability

The monophagous weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) has been introduced into North America as a biological control agent for the invasive vine mile-a-minute weed, Persicaria perfoliata (L.) H. Gross. This weevil has been shown to reduce the percent cover of mile-a-minute and the number of seed clusters produced, as well as altering the phenology of seed production. However, prior work has not examined the potential impact of the weevil on seed viability and numbers of seeds per cluster. When both adult and larval weevils fed on whole plants in the greenhouse, seed production and fruit maturation were delayed and both the total number of seeds and number of seeds per cluster were reduced. Overall, weevils in greenhouse cages reduced the reproductive potential of P. perfoliata by 35%. When adult weevils were confined on developing seed clusters in the field, the number of seeds produced per cluster, the weight of seeds produced, and seed viability all decreased. Overall, the number of viable seeds per cluster was reduced by 37% in the presence of adult weevils. Taken together, these findings demonstrate that this biological control agent can have important impacts on the reproductive potential of its target weed through mechanisms that have not previously been shown.

Sources and doses of nitrogen in the production of sunflower plants irrigated with saline water

ABSTRACT The cultivation of sunflower allows its use as bio-fuel and alternative forage. It is a viable alternative in the semiarid regions. Current study evaluates the effect of saline water use, sources and doses of nitrogen fertilization on the production of sunflower in the experiment conducted in drainage lysimeters between May and August 2012, under protected conditions, at Pombal - PB Brazil. The experiment consisted of a randomized block design, with a 2 x 3 x 4 factorial arrangement and three replications. The treatments consisted of two levels of electrical conductivity of water - ECw (0.3 and 3.0 dS m-1), three sources of nitrogen (urea, ammonium sulfate and calcium nitrate) and four levels of N (40, 80, 120 and 160% of recommended dose - 100 mg kg-1, for trials in pots). Dry mass of chapter (DMC), mass of achenes (MAc), the number of viable seeds (MVS), total number of seeds (TNS) and internal (DCI) and external (DCE) diameter of chapter. Irrigation with water of ECw=3.0 dS m-1 negatively affected all variable evaluated. Doses of N 104 and 160% of recommended dose for trials in pots, resulted in the highest DMC, TNS, DCE and DCI. N sources and the interaction between factors did not affect significantly any of the variable evaluated.

Population structure, seed loads and flowering phenology in three common (Melaleuca styphelioides, M. thymifolia, M. nodosa) and one rare (M. deanei) Melaleuca (Myrtaceae) species of the Sydney region

Melaleuca deanei F.Muell. is listed under state and national protection legislation occurring as small, disjunct populations restricted to the Central Coast botanical district of New South Wales. This paper reports on the population structure, reproductive output and phenology of large and small field populations of M. deanei, compared with three common congeneric species in the area, namely, Melaleuca nodosa (Sol. ex Gaertn.) Sm., Melaleuca thymifolia Sm. and Melaleuca styphelioides Sm. Both M. deanei and M. styphelioides had few seedlings per population at the sites studied. Results indicated that seedling recruitment is rare and would appear to require specific conditions. In addition, M. deanei had a low incidence of flowering within the small populations, significantly fewer fruiting plants per population and significantly lower numbers of viable seeds per square metre, most likely compounding its limited recruitment. Flowering, when it occurred in M. deanei, was from mid to late October through to late November–early December with increased flowering in response to fire and along road edges. Further study is needed to determine reproductive success at the individual-plant level, the breeding system and recruitment requirements of these species.