Optimum Germination Research Articles

Optimization of In Vitro Germination, Viability Tests and Storage of Paeonia ostii Pollen.

Paeonia ostii is an important woody oil crop mainly cross-pollinated. However, the low yield has become an important factor restricting the industrial development of P. ostii. Cross-pollination has become one of the important measures to increase the seed yield. Therefore, conservation of pollen with high vitality is crucial to ensure successful pollination of P. ostii. In this study, we found an effective methodological system to assess the viability, ability to germinate, and optimal storage conditions of P. ostii pollen grains. The optimal medium in vitro was 50 g/L sucrose, 100 mg/L boric acid, 50 g/L PEG6000, 100 mg/L potassium nitrate, 300 mg/L calcium nitrate, and 200 mg/L magnesium sulfate at pH 5.4. Optimal germination condition in vitro was achieved at 25 °C for 120 min, allowing easy observation of the germination percentage and length of the pollen tubes. In addition, the viability of pollen grains was assessed by comparing nine staining methods. Among them, MTT, TTC, benzidine-H2O2, and FDA were effective to distinguish between viable and non-viable pollen, and the results of the FDA staining method were similar to the pollen germination percentage in vitro. After evaluation of pollen storage, thawing and rehydration experiments showed that thawing at 4 °C for 30 min and rehydration at 25 °C for 30 min increased the germination percentage of pollen grains stored at low temperatures. The low-temperature storage experiments showed that 4 °C was suitable for short-term storage of P. ostii pollen grains, while -80 °C was suitable for long-term storage. This is the first report on the in vitro germination, viability tests, and storage of P. ostii pollen grains, which will provide useful information for P. ostii germplasm conservation and artificial pollination.

Germination of tartary buckwheat at various light strengths to enhance flavonoid content and scale-up of the process using smart-farm systems

This study evaluated the relationship between light strength and bioactive compounds in Tartary buckwheat sprouts during germination and growth to establish smart-farm conditions for the mass production of sprouts. Tartary buckwheat (Fagopyrum tataricum Gaertner) was used in this study because of its high bioactive compound content. Tartary buckwheat sprouts were germinated and grown under different light intensities. The contents of rutin and other flavonoids increased at light intensities up to 6,000 lux. The total flavonoid and polyphenol contents and antioxidant activity were highest at 10,000 lux. However, the anti-glycemic and anti-cholesterol activities displayed different trends to that of the flavonoid content. Nevertheless, 6,000 lux was determined to be the optimal condition for flavonoid content. However, the light intensity of the smart-farm system is much lower, and the humidity is not controlled. Therefore, a 6,000 lux light intensity is not feasible at the industrial scale. The optimal germination conditions that did not affect the flavonoid contents were re-established for the scale-up of Tartary buckwheat sprout production using the smart-farm system considering the yield, productivity, and prevention of fungal contamination. These were 600 g Tartary buckwheat per germination plate, a 5° slope, and no chlorine sterilization at 200 lux light intensity.

Ethephon promotes isoflavone accumulation in germinating soybeans by its acceleration of isoflavone biosynthetic pathway

Soybeans have medicinal value and are an oil crop with medicinal and food properties. The present work investigated two aspects of isoflavone accumulation in soybean. First, germination conditions for exogenous-ethephon-mediated accumulation of isoflavone were optimised through response surface methodology. Second, various influences of ethephon on the growth of germinating soybeans and isoflavone metabolism were investigated. The findings of the research led to the conclusion that exogenous ethephon treatment effectively facilitated the enrichment of isoflavones in soybeans during germination. Optimal germination conditions were obtained through a response surface optimization test, which yielded the following criteria: a germination time of 4.2 d, an ethephon concentration of 102.6 μM, and a germination temperature of 30.2 °C. The maximum isoflavone content was 544.53 μg/sprout FW. Relative to the control, the addition of ethephon significantly inhibited sprout growth. Exogenous ethephon treatment led to the phenomenon that peroxidase, superoxide dismutase, and catalase activities and their gene expression increased significantly in germinating soybeans. Meanwhile, the expression of genes related to ethylene synthetase increase under the effect of ethephon promoting ethylene synthesis. Ethylene multiplied the total flavonoid content of soybean sprouts relying on the increase in activity and gene expression of crucial isoflavone biosynthesis-related enzymes (phenylalanine ammonia-lyase and 4-coumarate coenzyme A ligase) during germination.

Seed Priming Improves Enzymatic and Biochemical Performances of Rice During Seed Germination under Low and High Temperatures

As an abiotic stress, adverse germination temperatures cause serious disruptions in physiological and biochemical processes involved in seed germination. Using a factorial experiment, we examined the effects of different seed priming treatments on enzymatic and biochemical performances of rice seed germination under different temperatures. Each of the rice genotypes (Hashemi, Sadry-domsefid, IRON-70-7053-7 and NORIN-22) was primed with hydro-hardening, KCl, CaCl2 and ascorbic acid (AsA) and without a priming agent as a control at low (15 ºC), optimum (25 ºC) and high (35 ºC) germination temperatures. The results showed that the enzymatic and biochemical performances of all the rice genotypes were affected by the seed priming agents, especially under the low germination temperature. At 15 ºC, seed priming with AsA was found to be the best agent for the activities of amylase, α-amylase, catalase (CAT), peroxidase (POX), ascorbate peroxidase (APOX) and superoxide dismutase (SOD) as well as the content of soluble sugars in the NORIN-22 genotype, and for protease activity and soluble protein content in the IRON-70-7053-7 genotype. SOD at the low germination temperature and CAT, POX and protease at the optimum and high germination temperatures were the most important enzymes in occurrence of germination potential in terms of seedling length, vigor index, normal seedling rate and germination rate. Under the priming agents, the highest changes in normal seedling rate were observed at the low and optimum germination temperatures by AsA priming in the Hashemi and NORIN-22 genotypes, and at the high germination temperature under KCl priming in the Hashemi genotype.

The effect of different priming methods in breaking seed dormancy in date palm (Phoenix dactylifera L.)

Seed dormancy is a phenomenon that prevents seeds from growing during adverse conditions. A number of factors may be responsible for this phenomenon, but one very common reason is the hardness of the seed coat as in the case of Date palm. This research was conducted to determine the effect of different priming methods on the rate of germination of date palm seeds. The treatments include cold water, hot water, H2SO4 and control in a cross randomized design. For the cold water treatment seeds were soaked for either 24, 48 or 72 hours; for the hot water treatment they were soaked for either 5, 10, or 15 minutes; and for the acid treatment they were soaked in 25 %, 50 % or 100 % of H2SO4 for 5 minutes. Twenty (20) seeds were selected for each treatment to carry out the germination experiment using moist absorbent paper. Data for germination rate was collected at 1, 2 and 3 weeks after planting (WAP). An optimal germination rate of 83% was observed at 3 WAP for the hot water treatment for 5 minutes. From this research, it can be concluded that priming generally increased the rate of germination of date palm seeds.

An improved multi-objective brainstorming algorithm with the application of rapeseed germination characteristics optimization

As one of the most important raw materials for daily edible oil, the annual production and quality of oilseed rape have a great impact on the daily lives of people and the development of the country. The germination quality of rapeseed directly affects the future yield and quality of oilseed rape, and seed germination vigor (SGV) and chlorophyll content (CC) are important factors affecting the quality of rapeseed germination. It is very necessary to make the rapeseeds have optimal germination characteristics and seed germination vigor at the early stage of germination by controlling the combination of each decision variable at the segmented harvest. The two objectives are coupled with each other to form a complex multi-objective optimization problem, which is important in the current research field of the rapeseed problem. To solve this problem, a modified brainstorming optimization algorithm based on OPTICS clustering, named MOPCBSO, is proposed in this study. The algorithm uses optics clustering as a new clustering method, chaotic mutation as a new updating method for individuals, and introduces an elite strategy and a tracking strategy. 19 benchmark test functions and nonparametric tests are adopted to examine the performance of the MOPCBSO compared with other optimization algorithms. The results show that the proposed algorithm has significant advantages over other algorithms in terms of convergence and comprehensiveness, demonstrating the effectiveness of the algorithm improvement. To optimize rapeseed germination characteristics, mathematical models are built, in which, cut-down time, after-ripening time and stubble height are selected as decision variables, while chlorophyll concentration and seed germination vigor in seeds as the target characteristics. The data of oliseed rape field trials were collected from 2020 to 2021 in Huanggang City, Hubei Province. Finally, the optimal solution for the germination characteristics of rapeseeds was obtained by the MOPCBSO, which provided an effective basis for the subsequent rapeseed production experiments.

Germination Ecology of African Lovegrass (Eragrostis curvula) and Herbicide Options for Its Control

African lovegrass (Eragrostis curvula) is one of the invasive perennial grasses that continues to disturb natural ecosystems globally. Experiments were conducted in southeast Queensland, Australia, to evaluate the effects of temperature, salt stress, water stress, burial depth, and sorghum crop residue load on the emergence and efficacy of postemergence herbicides on two populations (Clifton and Crows Nest) of E. curvula. The optimal germination temperature regimes for E. curvula were 30/20 and 35/25 °C, but seeds did not germinate at temperatures commonly occurring in the Queensland winter (15/5 °C). Total darkness inhibited germination by 79%, indicating that the shade cover effect would reduce germination of E. curvula. The Clifton population tolerated a higher concentration of sodium chloride (160 mM) and osmotic potential (−0.8 MPa). Under both salt and water stress, germination was 31% and 20% greater in the Clifton population than in Crows Nest, respectively, suggesting that the Clifton population is more tolerant to salt and drought stress. The maximum germination was obtained for the surface seeds while emergence declined with increased burial depth up to 4 cm. No seedlings emerged from the 8 cm depth. The addition of sorghum residue amounts up to 8 Mg ha−1 to the soil surface inhibited emergence compared to the no-residue treatment, suggesting that retention of heavy cereal residue will further delay or restrict emergence. Several postemergence herbicides were found to be effective in controlling E. curvula at an early stage. Information from this study will further compliment earlier studies on the targeted management of E. curvula populations.

Germination of the exotic Calotropis procera (Aiton) W.T. (Apocynaceae) in Mexico

Background: Seed germination strategies are important for exotic species to identify the factors that control seed germination and establishment.
 Questions and /or Hypotheses: Temperature and light germination requirements for seeds of Calotropis procera do not change neither in its native regions nor in lands where it is exotic. Calotropis procera show germination traits that may increase their probability of colonization.
 Studied species: Calotropis procera is a perennial plant native to some desertic areas in Asia and Africa and now naturalized in America.
 Study site and dates: Mature fruits were collected in Oaxaca in September 2019 to test germination parameters. The last experiment was conducted in September 2021.
 Methods: We determined the effect of different temperatures, photoblastic response, and loss of viability of seeds kept at laboratory conditions for two years. We performed several sowings under controlled conditions and achieved germinability, t50 and the time to germinate.
 Results: Seeds were non-dormant, neutral photoblastic and did not lose viability after two years of dry storage. Temperature affected germinability and t50. Optimum germination temperature was 30 °C with no germination above 40 °C.
 Conclusions: Germination requirements of seeds of Calotropis procera studied were similar to those reported worldwide. Though seed germination was affected by maximum mean temperatures, seeds germinated fast and at high percentages under a wide range of temperatures, which together with other attributes, may confer C. procera great chances for successful colonization.

Effect of Salinity and Temperature on Seed Germination of Atriplex halimus L. (halimus and schweinfurthii subspecies) Harvested in Western Algerian Region

Background: Temperature and salinity effects on the germination and seedling growth of two subspecies of Atriplex halimus were studied in order to select the best one for the rehabilitation of degraded lands at risk of desertification. Methods: Influence of salinity levels (0, 100, 200, 300 and 400 mM) and temperature (15, 20, 25, 30 and 35°C) on seed germination of two subspecies of Atriplex halimus, halimus and Schwein furthii, were assessed. Results showed optimal germination at NaCl concentration of 100 mM that decreases above 200 mM for both subspecies. In sp Schwein furthii the germination capacity is higher at NaCl concentration of 100 mM and temperatures varying between 20 and 30°C. Result: High doses of salt (300 and 400 mM) strongly decrease the number of seeds germinated at all temperature regimes. In contrast, at temperatures between 30 and 35°C, seed germination appears to be strongly affected in sphalimus. Salinity levels of 300 and 400 mM with temperatures of 15, 20 and 35°C, reduce germination and increase mean germination time. The presence of 100 mM of NaCl in the culture medium sometimes appears to be beneficial for the growth of the seedlings. However, at high doses of salt (300 and 400 mM), length, fresh and the dry weight of the seedlings are reduced.

Effect of optimized germination technology on polyphenol content and hypoglycemic activity of mung bean.

The study aimed to investigate the effect of germination conditions on the content of polyphenol extract in mung bean and to further investigate the effect of polyphenol extract in germinated mung bean on diabetic mice. Through single factor experiment and response surface experiment, the effects of soaking temperature, soaking time, germination temperature, germination time and soaking liquid CaCl2 concentration on the polyphenol content of mung bean were analyzed. The optimal germination conditions of mung bean were determined as soaking temperature 25°C, soaking time 11 h, germination temperature 28°C, germination time 3 days and CaCl2 concentration 2 mM. Under these conditions, the content of polyphenol extract in germinated mung bean was 4.878 ± 0.30 mg/g, which was 3.07 times higher than that in ungerminated mung bean. The structure and content of purified polyphenols in germinated mung bean were determined by HPLC-MS/MS. Quinic acid, Quercetin, Rutin, Vitexin, Isovitexin and other substances were identified, and the content of polyphenols was 65.19%. In addition, through the in vivo and in vitro hypoglycemic activity experimental study of germinated mung bean polyphenols extract, the results showed that germinated mung bean polyphenols had an in vitro inhibitory effect on α-glucosidase, IC50 was 44.45 mg/ml. In vitro inhibitory activity was stronger after digestion. Polyphenol extract can significantly reduce blood sugar and improve insulin resistance in Type 2 diabetic mice (T2DM). According to the results, germination treatment is an effective way to increase the content of polyphenols in mung bean, and the polyphenols extract has hypoglycemic activity.

Effects of Rice Straw Steam-explosion Spent Liquor on the Growth of Cabbage Seedlings

The direct use of spent liquor from pulping and papermaking engineering, which is abundant in active organic matter, can avoid resource wastage and environmental pollution. In this study, the effects of soaking solution and filtrate from steam-exploded rice straw on seed germination and the early development of cabbage were investigated. The results have shown that soaking solution and filtrate stimulated early cabbage growth at low concentrations. Optimal germination potential and the rate of soaking solution-treated cabbage seeds increased by 8% and 5%, respectively; meanwhile, that of the filtrate-treated cabbage seeds increased by 11% and 5%, respectively. Promotion of root growth by steam-exploded rice straw spent liquor was expressed in lateral root multiplication. The fresh weight of cabbage seedlings treated with the soaking solution/filtrate increased by more than 50% and the dry weight over 20%. Comparatively, the stimulation of filtrate on seed germination and early development of cabbage is superior to that of the soaking solution. Steam-exploded rice straw spent liquor is rich in bioactive lignin and oligosaccharides, which makes it a promising biostimulant for promoting crop growth.

Effect of Pre-sowing Seed Treatments and Synthetic Polymer Coating on Seed Quality and Storability in Redgram (Cajanus cajan. L.)

Successful agriculture depends on high-quality seed, which is a fundamental and important ingredient. Under unfavourable environmental conditions like drought, pre-sowing seed treatment such as seed coating and seed priming could boost the seed germination and seedling vigour. The coating agents often include plant growth regulators, micro-fertilizers, pesticides, and insecticides. The present investigation was carried out to assess the impact of seed treatment and polymer coating on seed quality parameters of pigeon pea cv PRG 176 during 2018 to 2021 at Seed Research and Technology Centre, Rajendranagar, Hyderabad. The trail was laid out in randomized block design with four replications. Freshly harvested redgram variety Ujwala Seeds were treated for Seed hardening with ZnSO4 @100ppm + Seed coating with Polymer 3ml/kg + Bavistin 2g/kg + Imidacloprid 1ml/kg + Pseudomonas fluorescens 10 g/kg + Rhizobium in different combinations. The treated seeds were shade dried, packed in gunny bags, and stored at room temperature to assess the impact of various treatments on seed quality metrics under ambient storage conditions. The results of bimonthly observations on seed quality parameters showed that there were substantial differences between the treatments for the characters under study. The T7 treatment recorded highest germination percentage (98 and 70.67), speed of emergence (12.1 and 10.1), electrical conductivity (0.169 and 0.292), seedling shoot length (14.9 and 8.65cm), seedling root length (14.5 and 8.52cm), seedling length (29.4 and 17.17cm), seedling fresh weight (5.55 and 2.5g), seedling dry weight (0.40 and 0.21g), seed vigour index-I (2881 and 1213), seed Vigour Index-II (53.9 and 14.84) over other treatments under study at initiation of studies (2MAS) and at 28 months of storage period respectively. The current study's findings showed that T7 treatment greatly outperformed all other treatments for all characters, maintaining an optimal germination percentage (70.67%) even up to 28 months of storage under ambient storage conditions.

Modelling the effect of pH and H2S on the germination of F. graminearum spores under different temperature conditions

Fusarium graminearum (F. graminearum) is a vital pathogen of Fusarium head blight (FHB). Hydrogen sulfide (H2S), which can be induced by stress in plants as a fungal inhibitor, affects the germination of spores through the detection of environmental factors such as temperature and pH. Based on mathematical models, F. graminearum was treated with different temperatures, pH, and H2S concentration to investigate spore germination events. This paper considered the synergistic effects of temperature and pH on spores in order to determine the optimal germination environment. Under these circumstances, the inhibition of spore germination with different concentrations of H2S was quantified. The results suggested that the germination time negatively correlates with the germinating rate. An increase in temperature altered the weak alkali preference of F. graminearum spores. At 28 °C, spores were more sensitive to the changes in pH. H2S gas could delay the germinating process significantly, however the required H2S concentration varied with environmental changes. This paper provides a perspective on the synergistic effect of temperature and pH on spore germination and contributes to determining the concentration of H2S as a management of FHB.

Changes in phenology can alter patterns of natural selection: the joint evolution of germination time and postgermination traits.

The timing of a developmental transition (phenology) can influence the environment experienced by subsequent life stages. When phenology causes an organism to occupy a particular habitat as a consequence of the developmental cues used, it can act as a form of habitat tracking. Evolutionary theory predicts that habitat tracking can alter the strength, direction, and mode of natural selection on subsequently expressed traits. To test whether germination phenology altered natural selection on postgermination traits, we manipulated germination time by planting seedlings in seven germination cohorts spanning 2 yr. We measured selection on postgermination traits relating to drought, freezing, and heat tolerance using a diverse combination of Arabidopsis thaliana mutants and naturally occurring ecotypes. Germination cohorts experienced variable selection: when dry, cold, and hot environments were experienced by seedlings, selection was intensified for drought, freezing, and heat tolerance, respectively. Reciprocally, postgermination traits modified the optimal germination time; genotypes had maximum fitness after germinating in environments that matched their physiological tolerances. Our results support the theoretical predictions of feedbacks between habitat tracking and traits expressed after habitat selection. In natural populations, whether phenological shifts alter selection on subsequently expressed traits will depend on the effectiveness of habitat tracking through phenology.

Application of zein-based germination inhibitors in potato postharvest storage

To address the problem of potato germination during postharvest storage, we prepared a series of zein-based germination inhibitors and tested their inhibitory effects on germination. The germination inhibitors were characterized by scanning electron microscopy (SEM), hydrophobicity, Fourier-transform infrared (FTIR) spectroscopy, and thermal gravimetric analysis (TGA). The results demonstrate that the germination inhibitors can form a hydrophobic film on the surface of potatoes, thereby reducing contact with, and absorption of, water. The application of an optimal germination inhibitor at a final zein concentration of 1.25 g/L was shown to reduce the germination rate of potatoes by 54% after 30 d of storage compared with the control group. In addition, the plant germination rate, height, and stem diameter of potatoes treated with the germination inhibitor were similar to those of the control group in the subsequent planting process, indicating that the germination inhibitor had no effect on potato cultivation. This study provides a safe and effective method for the post-harvest storage of potatoes, which has broad commercial applications.

Environmental factors affecting akinete germination and resting cell awakening of two cyanobacteria

Globally, cyanobacteria frequently cause blooms that outcompete other species in the waterbody, affecting the diversity, decreasing water exchange rates, and promoting eutrophication that leads to excessive algal growth. Here, Dolichospermum circinale (akinetes) and Microcystic aeruginosa (resting cells), were isolated from the sediment in the Uiam Dam in the North Han River and near Ugok Bridge in the Nakdong River, respectively. The morphology, germination process and rates, and growth was evaluated in different environmental conditions. D. cercinalis germination began on day two of culturing, with maximum cell growth observed on day ten. In contrast, M. aeruginosa exhibited daily increase in cell density and colony size, with notable density increase on day six. Next, different environmental conditions were assessed. Akinetes exhibited high germination rates at low light intensity (5—30 µmol/m2/s), whereas resting cells exhibited high growth rates at high light intensity (50—100 µmol/m2/s). Furthermore, both cell types exhibited optimum germination and growth in media containing N and P at 20—30° at a pH of 7—9. Our study reveals the optimum conditions for the germination and growth of cyanobacterial akinetes and resting cells isolated from river sediment, respectively, and will assist in predicting cyanobacterial blooms for appropriate management.

Modeling the influence of temperature, salt and osmotic stresses on seed germination and survival capacity of Stipa tenacissima L.

This work stands for a modelling approach to identify the cardinal temperature of germination of Stipa tenacissima L., its capacity to recover and its adaptation potential considering dormancy and viability after exposure to salinity and drought. Seed traits characterised before germination were tested. The seeds were incubated at temperatures of 10 to 30 °C and low osmotic potentials were induced using sodium chloride (NaCl) or polyethylene glycol (PEG 6000) solutions of 0 to −1.6 MPa. The capacity of seeds to recover and remain viable under stress conditions was quantified. Our results proved that the seed yields and sizes were uniform. The analysis of cardinal temperature by thermal time model exhibited an optimal germination temperature (T o) of about 19 °C, a base temperature (T b) of 0.6 °C and a ceiling temperature (T c) of 31 °C at 0 MPa. The base water potential Ψb (50) values ranged between −0.83 and −1.54 MPa and between −0.97 and −2.27 MPa for osmotic and salt stresses, at 30 °C and 20 °C, respectively. In conclusion, the species showed a lower seed recruitment related to a low drought tolerance (drought tolerance index = −0.5 MPa), To requirement and threshold sensitivity. Under salt stress, S. tenacissima used osmotic adjustment in order to germinate in a lower osmotic potential.

Seasonality, dispersal modes, and optimal germination times modulate the fruiting of tropical tree species

Abstract We investigated the associations of seasonality, dispersal modes and seed germination speeds with the fruiting of Clusia nemorosa, Pleroma fissinervium, and Vochysia pyramidalis in a gallery forest, Chapada Diamantina, Brazil. Observations of mature fruits with dispersing seeds were carried out from 2003 to 2006. Cross-correlation and circular statistics were performed to test the relationships among fruiting and abiotic factors, and phenological seasonality. Dispersion syndromes were defined and germination experiments were performed after seed collection (n =100/species), using four replicates. The species evidenced seasonal fruiting. Clusia nemorosa produced zoochoric seeds and V. pyramidalis anemochoric seeds, which were dispersed during the rainy season and positively correlated with precipitation; P. fissinervium produced autochoric seeds, released during the dry season to early rainy season, being positively correlated with insolation and negatively with humidity. The rotating wing seeds of V. pyramidalis were released in the rainy season and aided floating in watercourses, characterizing hydrochory. Clusia nemorosa and V. pyramidalis germinated (2-6 days) more rapidly than P. fissinervium (9 days). Seasonality, dispersal modes, and optimal germination conditions modulated the fruiting of the species examined, whose reproductive strategies responded to environmental drivers such as precipitation, favoring germination during the rainy season.

Dormancy and germination characteristics of Tarenaya hassleriana (Cleomaceae) seeds

Abstract: Elucidating the physiological and ecological mechanisms of seed dormancy and germination is of great significance for species conservation and the application of plant resources. Based on Baskin and Baskin’s classification system for seed dormancy, the cause of dormancy in Tarenaya hassleriana (Cleomaceae) seeds was studied using alternating temperature, cold moist stratification, dry storage, and GA3 soaking treatment. The results indicated that fresh mature T. hassleriana seeds had a combinational dormancy, including a physical dormancy and a type 2 non-deep physiological dormancy, and were photoblastic, with an optimal germination temperature of 35°C. In addition, fresh mature T. hassleriana seeds may be efficiently released from dormancy and promoted to germinate by an alternating temperature of 20 °C/30 °C, cold moist stratification, and cold moist stratification following dry storage. Furthermore, GA3 soaking treatment could also promote dormancy release and subsequent germination at 35 °C, and dry storage treatment could promote dormancy release and subsequent germination at 5-15 °C. These results also suggested that there were complex cross-talks among phytohormone, osmotic potential, and the temperature signaling regulatory pathways during dormancy release and germination of T. hassleriana seeds, which deserve further study.

Recruitment of Melaleuca quinquenervia (Myrtaceae) in the fringing forests of the Myall Lakes, NSW, Australia

Context Melaleuca quinquenervia is a widespread, keystone species of eastern Australian coastal forested wetlands. Populations of M. quinquenervia in the fringes of Myall Lakes, New South Wales, Australia exhibit low numbers of juveniles, infrequent recruitment and a dominance of mature individuals, raising concerns about stand replacement from conservation managers. In contrast, M. quinquenervia often recruits in large numbers and is highly invasive in wetlands around the world. Aims To explore factors that limit recruitment of M. quinquenervia within its native range. Methods Field deployed seed traps; soil-core sampling; a burial longevity trial and depth of emergence experiment; laboratory temperature, salinity and light germination experiments; a transplantation experiment; monitoring of field germination; and a litter/leachate experiment. Key results Low seed viability (5–26%) is offset by high canopy seed loads (250 000 to 120 million seeds per tree) released continuously throughout the year with a peak fall in summer (2000 to 5000 viable seeds per m2 per month), coinciding with optimal germination temperatures. Seedling emergence is reduced below 5 mm soil depth, there is a very low soil seedbank reserve, and germination is light-dependant. M. quinquenervia exhibited reduced germination percentage and rate as well as reduced survival of seedlings at salinities higher than 15 dS m−1 EC (electrical conductivity). The most favourable sites for seedling establishment are permanently moist with low salinity, protected from wave action via sedge vegetation, and sheltered from prevailing winds. There is an inhibitory effect of Casuarina leachate on germination. Conclusions Germination in the field is episodic, and tied to specific environmental conditions. Highest losses occur at the seedling establishment phase. Implications Future research avenues and management recommendations are provided.