Germination Temperature Research Articles

Establishment of procedure to evaluate soybean for various temperature regimes at seedling stage

Soybean is a legume crop and it has importance for both of its products, bean and oil. The bean of soybean contains many sorts of minerals and vitamins, while Soy oil contains various dietary minerals and used for various raw use and cooking purposes. But the major constraints of soybean production are linked with its germination and emergence which is mainly affected by soil moisture and temperature conditions. To identify the optimum temperature of soybean plant germination and adaptive variety for Pakistani regions, a seedling stage experiment was conducted in the chickpea laboratory of University of Agriculture Faisalabad, Pakistan. Basic purpose of this experiment was to establish the procedure for soybean cultivation to gain profitable yield and it was carried to focus on growth and development in both shoot and roots of the plant sown in specific temperature. Controlled uniform conditions of two different temperature treatments i.e., 25°C and 30°C were maintained and four local genotypes (NARC, Faisal, Ajmeri and Rawal-1) were used. These genotypes showed improved extensive shoot morphology of the plant, while the root morphology remained unaffected.

The New Is Old: Novel Germination Strategy Evolved From Standing Genetic Variation in Weedy Rice.

Feralization of crop plants has aroused an increasing interest in recent years, not only for the reduced yield and quality of crop production caused by feral plants but also for the rapid evolution of novel traits that facilitate the evolution and persistence of weedy forms. Weedy rice (Oryza sativa f. spontanea) is a conspecific weed of cultivated rice, with separate and independent origins. The weedy rice distributed in eastern and northeastern China did not diverge from their cultivated ancestors by reverting to the pre-domestication trait of seed dormancy during feralization. Instead, they developed a temperature-sensing mechanism to control the timing of seed germination. Subsequent divergence in the minimum critical temperature for germination has been detected between northeastern and eastern populations. An integrative analysis was conducted using combinations of phenotypic, genomic and transcriptomic data to investigate the genetic mechanism underlying local adaptation and feralization. A dozen genes were identified, which showed extreme allele frequency differences between eastern and northeastern populations, and high correlations between allele-specific gene expression and feral phenotypes. Trancing the origin of potential adaptive alleles based on genomic sequences revealed the presence of most selected alleles in wild and cultivated rice genomes, indicating that weedy rice drew upon pre-existing, “conditionally neutral” alleles to respond to the feral selection regimes. The cryptic phenotype was exposed by activating formerly silent alleles to facilitate the transition from cultivation to wild existence, promoting the evolution and persistence of weedy forms.

Dynamics of Germination Behaviour, Protein Secondary Structure, Technofunctional Properties, Antinutrients, Antioxidant Capacity and Mineral Elements in Germinated Dhaincha.

SUMMARYResearch backgroundDhaincha (Sesbania aculeata) is a forage legume primarily used for green manuring and animal feed. Good nutritional profile of dhaincha makes it a potential alternative legume in human nutrition. However, the presence of high amount of antinutrients poses a problem in its utilisation for food applications. The present investigation intends to germinate dhaincha seeds at different time-temperature regimes and to evaluate the process of germination to ascertain optimal conditions and improve its potential for utilisation.Experimental approachDhaincha seeds were germinated at 24, 28 and 32 °C for 24, 48 and 72 h. Germination characteristics and germination loss, spectral characteristics, technofunctionality, antinutrients, bioactive constituents, antioxidant capacity and mineral element content of germinated dhaincha were evaluated. Optimal balance of technobiofunctionality of germinated dhaincha seeds was validated by principal component analysis.Results and conclusionsSprout length and germination loss increased with the higher germination temperature and prolonged germination time. Seeds showed similar germination rate at 28 and 32 °C and it was markedly higher than at 24 °C. Germination for 24 h resulted in mild conformational changes in the secondary structure of proteins, whereas germination for 48 and 72 h exhibited major conformational changes in the β-sheets, resulting in the improvement in the hydration and foaming properties. Progression of germination (72 h) caused the decrease of tannin (24.47%), phytic acid (16.38%) and saponin (24.58%) mass fractions, and of trypsin inhibitor (40.33%) and lectin activity (62.50%). Slight decrease of DPPH˙ (3.7%) and ABTS˙+ (18.5%) values was also observed, whereas total flavonoid content (36.14%) and metal chelating activity (26.76%) increased. Total phenolics, FRAP, and reducing power decreased after 24 h, followed by a gradual increase. Zinc extractability increased drastically with germination. Germination at 28 °C for 72 h resulted in higher reduction of antinutrients with optimal retention of antioxidant activity and better functional characteristics, as validated by principal component analysis.Novelty and scientific contributionDhaincha is an unknown crop in Europe, and even in Asia it is predominantly used as green manure and animal feed. This research demonstrated that the intervention in germination can transform dhaincha into a promising crop for food industry. Germinated dhaincha exhibited enhanced technobiofunctionality for utilisation in various food formulations.

Thermal dependence in seed germination of Diospyros inconstans Jacq. (Ebenaceae)

Defining the cardinal temperatures for germination in the scenario of climate change with prediction of an increased terrestrial temperature plays an important role in conserving plant resources. This study aimed to define the cardinal temperatures, the time of conducting germination tests, and to apply the thermal time model for seeds of Diospyros inconstans. Thermal screening was carried out, based on germination tests performed in BOD chambers, at constant temperatures of 10, 20, 25, 30 and 40 °C, under a photoperiod of 12 hours/light. The cardinal temperatures for germination of D. inconstans seeds are 26.7 °C (optimal temperature), 13.8 °C (minimum temperature) and 37.7 °C (maximum temperature). Germination tests for the species can be conducted at optimum temperature, lasting 26 days for radicle emission and 63 days for formation of normal seedlings.

Temperature and incubation period affect Septoria pistaciarum conidium germination: disease forecasting and validation

Septoria leaf spot is an important disease of pistachio trees in Greece. This study aimed to determine effects of temperature and the incubation period on germination of conidia of Septoria pistaciarum, and to evaluate a generic model to forecast pistachio leaf spot under the field conditions of Aegina Island, Greece. The optimum temperature for conidium germination was 23°C, and germination was inhibited at 35 and 4°C. At constant temperature of 23°C, conidia commenced germination after 9 h. The predictive model indexed disease risk close to 100 at 10 May at two locations (Rachi Moschona and Vigla) in 2017, and first leaf spot symptoms were observed on 17 May. Moderate to high disease severity (>25% leaves infected) were observed in unsprayed trees at the end of May. In 2018, the model indexed risk close to 100 on 9 May at Rachi Moschona, and first symptoms were observed on 18 May. Moderate to high disease severity (>25% leaves infected) were observed in unsprayed trees on 25th of May. This study has shown that the forecasting model can be used in Aegina Island, Greece, to predict the severity of Septoria leaf spot of pistachio.

Effect of pretreatment, temperature, gibberellin (GA3), salt and water stress on germination of Lavandula mairei Humbert

Lavandula mairei Humbert is an endemic species of Morocco, it is considered as rare and threatened species. It grows spontaneously in arid and semi-arid bioclimates, and found its uses in traditional medicine for the treatment of various diseases such as gastrointestinal diseases, microbial infection, cough and asthma. With the optic of conservation, this study aims to evaluate the combined effect of temperature and pretreatment on L. mairei seeds germination. On the other hand, this study looks to assess the effect of different concentrations of gibberellin (GA3), polyethylene glycol (PEG 6000) and sodium chloride (NaCl) on seeds germination. The results revealed, an optimal germination temperature of 25 °C, and over 90 % of seeds are able to germinate without using any pretreatment. Nevertheless, pretreatment of the seeds with sulfuric acid and hydrogen peroxide increased the germination rate to over 96 %. It has also been demonstrated that treatment with gibberellin improves the germination rate of L. mairei seeds. In addition, the water deficit caused a drop in the germination rate (of about 11 %) starting from - 0.53 MPa. Thus, the salt stress estimated by the application of different concentrations of sodium chloride (NaCl) has shown that the germination percentage of L. mairei seeds decreased considerably when the concentration exceeds 150 mM. This study could be a basic guide for the possible cultivation and conservation programs of L. mairei Humbert, Moroccan endemic and threatened plant.

Effects of germinating temperature and time on metabolite profiles of sunflower (Helianthus annuus L.) seed.

Sprouts with higher levels of nutrients and lower content of antinutritional substances have been gained a growing interest in the influence on the human's health. The study of the influence of germination temperature and time on the metabolite profiles of sunflower seed was studied by a metabolomics approach based on gas chromatography–flame ionization detection (GC‐FID). Samples were extracted and fractionated covering a wide range of lipophilic and hydrophilic spectra. A total of 90 metabolites were identified by comparison with reference standards. Principal component analysis (PCA) revealed distinct dynamic changes in metabolites with the germinating time. Heatmap and agglomerative hierarchical clustering analysis revealed the differences and similarities among the samples. The germinating sunflower seeds clustered into three major groups. For instance, group I with a high content of sterols, monosaccharide, and amino acids, indicating the germination process, resulted in an increase in amino acids and monosaccharide. Group II had a high content of FAME and FFA. Relative targeted quantification of metabolites visually depicted by heatmap showed decreases in fatty acid methyl ester (FAME) and free fatty acid (FFA), and increases in amino acids, α‐tocopherol, sterols, and γ‐aminobutyric acid (GABA) during germination. Sunflower seeds germinated at 25°C were better for the accumulation of α‐tocopherol, stigmasterol, leucine, proline, methionine, glutamine, and GABA compared with those at 35°C. These results help to better understand how germination conditions change the nutritional quality of germinated sunflower seeds from a metabolite profile view, allowing for the rational screening and usage of germinated sunflower seeds in the food industry.

Accumulation of the Unknown Possible Saccharide’s Derivative Compound during Soybean Seed Germination

The effect of temperature on oligosaccharides profile during germination process of soybean seed was studied to enrich the basic knowledge on the producing method of soybean sprout with high functionality. In the experiment, the germination temperature conditions were set at 20 °C and 30 °C. Stachyose and raffinose as the main oligosaccharides were determined using the high-performance liquid chromatography with charged aerosol detector. Both stachyose and raffinose were changed depending on germination temperature; they decreased rapidly under both temperature conditions. Moreover, it also observed the accumulation of an unknown compound during germination process. Since the detection of this compound has present on oligosaccharides chromatographic system and there is no report has informed the accumulation of saccharides derivative compounds during soybean seed germination, this finding need to be further clarified.

Accelerated aging predicts the emergence of rice seedlings in the field

Selecting the most appropriate vigor test for rice to predict seedling emergence remains a challenge. This is mainly attributed to the diversity of available tests that evaluate vigor; however, there is a critical need for tests that can show a high correlation with field emergence. Thus, this study aimed to determine which vigor tests are the most efficient in predicting the emergence of rice seedlings, to facilitate correct selection for quality control analyses and pre-sowing for rice seed commercialization. Across two growing seasons, 2016/17 and 2017/18, different seed lots of ‘SCS122 Miura’ rice were subjected to vigor evaluations including germination test, electrical conductivity, cold test, low temperature germination, accelerated aging, root and shoot length, seedling dry weight, emergence speed, and emergence speed index, and greenhouse and field emergence tests. A completely randomized design with four replicates was used for the experiments. All statistical analyses were performed using R software. The germination rate for ‘SCS122 Miura’ seed lots in both growing seasons was greater than 80%. In both growing seasons, unlike the similar results obtained for field emergence, in the laboratory tests, differences were observed between these same seed lots. Electrical conductivity and emergence speed showed a negative correlation with greenhouse and field emergence. The vigor tests for accelerated aging, emergence speed, and dry weight are more efficient in predicting the emergence of rice seedlings. Among the tested methods, accelerated aging (41 °C for 120 h) is one of the most efficient for predicting the emergence of rice seedlings and the best option for laboratory analysis of quality control and pre-sowing owing to its practicality and time required for execution.

Effect of Low Temperature on Germination, Growth, and Seed Yield of Four Soybean (Glycine max L.) Cultivars

During germination at low temperatures, seeds rich in proteins may experience damage to their cytoplasmic membranes. The study aimed to investigate the influence of the germination temperature on growth, development, and yield of four cultivars of soybean, a typical thermophilic species. The seeds were germinated at 10, 15, and 25 °C in the dark. After 48 h, one part of the seeds was analyzed for their amylase and dehydrogenase activity, cell membrane permeability, and germination vigor. The other part was transferred into soil and cultivated up to yielding. Chlorophyll fluorescence, fresh (FW) and dry weight (DW) of shoots, pod and seed number, and seed DW were analyzed. The plants of cvs. ‘Abelina’, ‘Malaga’, and ‘Merlin’, germinating at low temperature, produced the highest number of seeds. Seed number negatively correlated with their DW and positively with the number of active reaction centers (RC/CSm) in all cultivars. In cvs. ‘Abelina’ and ‘Malaga’, the number of seeds also positively correlated with the index performance of photosystem II (PSII), which was the highest in all plants germinating at low temperature. We suggest cultivating cv. ‘Abelina’ in cooler regions, while cvs. ‘Petrina’ and ‘Malaga’ in warmer areas.

Abscisic, gibberellic, and salicylic acids effects on germination indices of corn under salinity and drought stresses

ABSTRACT The expression of genes that control germination-related processes in corn (Zea mays L.) is influenced by environmental factors. Germination of seeds may be facilitated by hormonal priming. The purpose of this investigation was to quantify the effects of different germination temperatures [(5, 10, 15, 20, 25, 30, 35, and 40°C), NaCl-induced stress (0, −0.4, −0.8, and −1.2 MPa), and priming solutions (control, hydropriming, abscisic acid (ABA), gibberellic acid (GA), and salicylic acid (SA)] (Experiment 1). Effects of germination temperatures, PEG 6000-induced stress (0, −0.4, −0.8, and −1.2 MPa), and priming solutions were also evaluated separately (Experiment 2). In both cases, a completely randomized design with four replications was used. Increasing temperatures from 5 to 25°C gradually improved germination percentage and rate, whereas temperatures > 25°C decreased these indices. After imposing drought (PEG 6000-induced stress) or salinity (NaCl-induced stress) treatments, hormonal priming caused germination to occur at a lower base temperature, compared with the non-priming treatment. However, the effect of hormonal priming was dependent on temperature. At sub-optimal temperatures (< 25°C), the highest germination percentage and rate were recorded after GA priming. At above-optimal temperatures (> 25°C), ABA priming resulted in the highest germination percentage and rate. Moreover, hydrothermal time constant decreased in hormone-treated seeds. Based on coefficient of determination (R2 ) and root mean square error (RMSE), a dent-like model predicted cardinal temperatures more accurately than a beta model did. Generally, GA-, SA-, and ABA-priming were recommended under sub-optimal, optimal, and above-optimal temperatures, respectively.

Variation in seed dormancy and germination among populations of Silybum marianum (Asteraceae)

AbstractMilk thistle (Silybum marianum) is a medicinal plant; however, lack of consistency in past dormancy studies has hindered propagation of this species from seeds. We tested the germination responses of freshly harvested and after‐ripened (stored for 2 and 7 months; 25°C at 50% relative humidity) seeds from three populations (P1, P2 and P3) in Iran at varying constant or alternating temperatures, with or without GA3 and in light and continuous darkness. No germination occurred in freshly harvested seeds incubated at any condition without GA3 application, indicating that all the seeds were dormant. Seeds from P1 and P2, which developed under relatively dry, warm conditions, germinated over a wider range of temperatures after 2 months of dry storage, indicating type 6 of non‐deep physiological dormancy (PD). Seeds from P3, which developed under relatively wet, cool conditions, incubated at constant temperatures (especially on GA3), exhibited an increase in maximum temperature for germination, indicating type 1 of non‐deep PD. Light improved germination of after‐ripened seeds, and GA3 application substituted for the light requirement for germination. This is the first report that environmental conditions during seed development may be correlated with differences in the type of non‐deep PD. We conclude that milk thistle seeds are positively photoblastic and photodormant and the germination responses of after‐ripened seeds from different populations are different under darkness. Therefore, the impacts of genetic differences and maternal effects on the induction of dormancy during seed development should be considered in attempts to domesticate this medicinal plant.

Germination at Extreme Temperatures: Implications for Alpine Shrub Encroachment.

Worldwide, shrub cover is increasing across alpine and tundra landscapes in response to warming ambient temperatures and declines in snowpack. With a changing climate, shrub encroachment may rely on recruitment from seed occurring outside of the optimum temperature range. We used a temperature gradient plate in order to determine the germination niche of 14 alpine shrub species. We then related the range in laboratory germination temperatures of each species to long-term average temperature conditions at: (1) the location of the seed accession site and (2) across each species geographic distribution. Seven of the species failed to germinate sufficiently to be included in the analyses. For the other species, the germination niche was broad, spanning a range in temperatures of up to 17 °C, despite very low germination rates in some species. Temperatures associated with the highest germination percentages were all above the range of temperatures present at each specific seed accession site. Optimum germination temperatures were consistently within or higher than the range of maximum temperatures modelled across the species’ geographic distribution. Our results indicate that while some shrub species germinate well at high temperatures, others are apparently constrained by an inherent seed dormancy. Shrub encroachment in alpine areas will likely depend on conditions that affect seed germination at the microsite-scale, despite overall conditions becoming more suitable for shrubs at high elevations.

The plasticity of the germinative response in the populations of two xeric species inhabiting two contrasting environments of central Mexico

AbstractThe species' germination response evolves based on its population environment; therefore, the responses of each local population evolve independently. We investigated two xeric species from central Mexico, Echeveria gibbiflora and Penstemon campanulatus, the populations of which inhabit two localities (Reserva Ecológica del Pedregal de San Ángel [REPSA] and Parque Ecológico de la Ciudad de México [PECM]) that differ in environmental conditions. For both species and populations, final germination, cardinal temperatures, thermal time and range of temperature for germination (RTG) were determined in seeds that were (a) collected recently, (b) stored in a laboratory for 2 months and (c) reciprocally buried in field conditions for 2 months. The results indicated that for both species, seed population, laboratory storage and temperature were significant for final germination. These responses indicated differences in germination based primarily on the site in P. campanulatus (PECM seeds germinated at higher percentages than REPSA seeds) and the burial site in the REPSA seeds of E. gibbiflora. Cluster and discriminant analyses were conducted for both species, identifying the following significant variables for group treatments: base temperature between the stored and buried seeds of E. gibbiflora and the ceiling temperature between the recently collected, stored and buried seeds of P. campanulatus. The results suggest that instead of seed population, burial (in both species) and laboratory storage (in P. campanulatus) narrowed the RTG. These responses could indicate plasticity in both germination and dormancy in response to environmental conditions experienced in the different habitats, which are crucial for understanding species' adaptive capacity.

Influence of temperature and germination time on diastatic power of blue and red maize (Zea mays L.) malts

Maize endosperm consists of about 70 % starch, which makes it an excellent substrate for fermentation. However, due to its low diastatic power, it is used in brewing as an adjunct, mainly. In order to include both red and blue maize as an enzyme source in the brewing process, the effect of temperature and time germination on the diastatic power of malts was studied. The research consisted in a completely randomized three-factor experimental design where the involved factors were colour of maize (blue and red), germination temperature (15, 20, and 25 °C), and germination time (3, 4, 5, 6, 7, 8, and 9 days). The response variables were germination percentage, acrospire length, malting yield, and diastatic power. Data was analysed through Analysis of variance and Comparison Multiple Tukey’s Test. Results showed that both temperature and germination time encouraged the acrospire length, which had a negative effect on malting yield. Regarding to diastatic power, it maintained an increase from third to seventh germination day, at the three tested temperatures. Additionally, as the germination temperature increased, the diastatic power also increased. The highest diastatic power for blue and red maize malts were 39 and 42 °L, respectively, and it was reached when these malts were germinated for 7 days at 25 °C. It was concluded that, by germinating both blue and red maize under the resulting optimum conditions, the obtained malts would be capable of converting their own starch.

Chickpea seed vigor evaluated by computerized seedling analysis

Computerized seedling analysis is a promising tool for assessing seed vigor, providing reliable and less subjective results. The aim of this study was to define a method for evaluating the vigor of chickpea seeds through computerized image analysis, using the Seedling Analysis System (Sistema de Análise de Plântula - SAPL®) as a basis. Two chickpea cultivars were evaluated, consisting of five seed lots of cv. BRS Aleppo and four seed lots of cv. Cícero. Test were performed on the seeds of each cultivar for initial characterization of the physiological potential of the lots, and the results were compared with the determinations made via SAPL®. The results showed high correlations between the variables obtained from computerized analysis and from traditional vigor tests, especially for the close relationship between the cold test and low temperature germination test with the corrected vigor index (r &gt; 0.9) evaluated on the fourth day after the beginning of the test. The total length of seedlings, length of the primary root, and growth and corrected vigor indices obtained through computerized analysis of seedlings on the 4th day after sowing allowed separation of the lots regarding vigor. Computerized analysis of seedlings using SAPL® is effective in determining the vigor of chickpea seed lots.

Determination of Optimum Germination Temperature and Dormancy Breaking Method for Seeds of Wild Herb

Determination of Optimum Germination Temperature and Dormancy Breaking Method for Seeds of Wild Herb

Effects of Light and Temperature on Germination of Eggert's Sunflower (Helianthus eggertii)

Helianthus eggertii is a rare perennial sunflower of barrens and open habitats in Kentucky, Tennessee, Alabama, and South Carolina in the United States (U.S.). Despite its delisting in the U.S. Endangered Species Act in 2005, little is known about the germination biology of H. eggertii other than seeds require cold stratification for optimal germination. Knowledge about the germination biology of rare species can aid in the management of natural populations and inform strategies for ex situ seed conservation and propagation. We examined how cold stratification, light, and temperature interact to affect seed germination in H. eggertii, and whether germination proportions varied among populations. At the time of maturity in October, seeds have primary physiological dormancy and require cold stratification or prolonged (> 8 wk) incubation in light at cool (15/6 C) temperatures to germinate. Seeds maintained a light requirement for germination when cold stratified in darkness, but not after cold stratification in light. However, seeds germinated to lower proportions after cold stratification in light relative to darkness, and when incubated at temperatures that mimic summer (35/20 C) compared to late spring (25/15 C). Germination varied widely among populations (23-58%), with plants from more open sites exhibiting lower germination proportions than those from partially shaded sites. Our results indicate seeds most likely germinate in early- to mid-spring, and light promotes germination of H. eggertii. Our results highlight the interactive role of light and temperature in determining seed dormancy break and germination in H. eggertii.

How to cope with the vulnerability of site specific fungicides on the control of Asian soybean rust

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi is the most important disease of the crop. The pathogen is highly aggressive under field conditions when the environmental conditions favor the disease development. The disease was first described in Japan, in 1902 and in 1914, it had already spread to several countries in Southeast Asia.). The first report in South America was made in Brazil in 1979 in wild soybeans and later in 2001 in the soythern area of the country in comercial plantations. P. pachyrhizi can naturally infect a wide range of plant species, including 41 species in 17 genera of the Fabaceae family. The symptoms of the disease can be seen on the abaxial and eventually on the adaxial surface of the lesions. In susceptible varieties the number of uredia per lesion varies from four to eight and the latent period around seven days. P. pachyrhizi requires more than 8 hours a day of continuous leaf wetness, and the optimal temperature for maximum germination around 22oC. There is no varieties with complete resistance to the disease available to planting. The main method of control of the disease is the application of fungicides. The main groups of fungicides to control the disease belongs to the demetilation inhibitores (DMI’s), quinone outside inhibitor (QoI’s) and carboxamides (SDHI). But with the continuous spraying with DMI’s and QoI’s alone to control ASR resistant mutants of P. pac HIhyrhizi multiplied in the population over the country. The use of mixture of DMI’S with QoI’s in the beginning proportioned resonable controle of the disease. But few years latter P. pachyrhizi acquired resistance to the mixture of triazol with stobolurins. Then it was introduced the carboxamide group (SDHI) to use in mixture with triazol with stobolurins. The triple mixture was then recommended for more a few years giving good results. Finally researchers decided to incorporate multisite fungicides in a mixture with triazol, strobilurin and or carboxamide to minimize the probability to build up resistant mutants in the population of P. pachyrhizi. The addition of multisite fungicides in a mixture with site specific is very important to reinforce the fight against fungal resistance. In conclusion to cope with the vulnerability of P. pachyrhizi to site specific fungicides the strategy has to involve integration of measures such as sanitary vacuum, rotation of a mixture of different biochemical mechanisms of action plus multisite, avoid sequential and curative applications, use of early cultivars and sowing at the beginning of the recommended season, eliminate voluntary soybean plants from the field, use of fungicides in the onset of preventively at least once before the planting lines closed, sowing at the beginning of the recommended season, and use of cultivars with resistance gene (s) to reduce the number of spraying. The present overview discuss how difficult is to cope with the resistance of P. pachyrhizi to site specific fungicides.

Effect of abiotic stresses on germination behaviour of Ruta chalepensis

This work aims to highlight the optimal temperature for the seed germination of Ruta chalepensis, an important threatened ethnomedicinal shrub, and assess its germination tolerance against salinity and water stresses as well. For this, the seeds were incubated firstly under different temperatures (5 to 30°C). After that, at 20°C, germination tests were performed under different sodium chloride (NaCl) concentrations (0 to 273.9 mM) and various polyethylene glycol solutions (PEG6000) (0 to -2.20 bar). Final germination percentage, velocity coefficient and latency time were subsequently the germination patterns determined and analysed. The optimum temperature for germination was 15°C, in which the maximum final germination percentage (85%) was noticed; germination fell steadily, however, above and below this temperature and completely ceased at 30°C. Germination behaviour of R. chalepensis seeds under osmotic stress conditions showed a significant effect of both NaCl and PEG6000. Germination decreased whether sodium chloride or polyethylene glycol was increased in the medium (p &lt; 0.05). Moreover, the salinity tolerance threshold was 205.4 mM, equivalent to 16 g L-1 NaCl, while water stress was -1.16 bar, corresponding to 80 g L-1 PEG6000. Beyond these thresholds, germination stopped. Dropping in velocity coefficient and postponing in latency time with increasing both stresses were recorded either. The sensitivity of R. chalepensis seeds to environmental stresses should be taken into account for successful conservation programmes, which should be implemented by sowing seeds and planting seedlings in fresh habitats with sufficient annual rainfall.