Final Germination Research Articles

Temperature Limits for Seed Germination in Industrial Hemp (Cannabis sativa L.)

Industrial hemp (Cannabis sativa L.) as a grain and fiber crop is experiencing a resurgence in North America. Due to governmental prohibition, there has been limited information on regional agronomic production systems including basic information on seed germination. This study was initiated to provide basic information on the relationship between temperature and germination in hemp seed. Germination was measured at constant temperatures ranging from 3 to 42 °C. Cardinal temperatures were determined for two industrial oil crop hemp cultivars (‘Georgina’ and ‘Victoria’). The optimal germination temperature indicated by a high mean germination percentage and rate was between 19 and 30 °C. Optimal (29.6 °C), base (3.4 °C) and ceiling (42.6 °C) temperatures were calculated from a linear regression of the germination rates to reach 50% germination for each temperature. The thermal time for ‘Georgina’ and ‘Victoria’ to reach 50% germination at suboptimal temperatures was 694 and 714 °C h, respectively. The osmotic and solid matrix-primed hemp seeds germinated faster than the untreated seeds, but the final germination percentages were not different. The primed seeds germinated faster at supraoptimal temperatures but did not impact final germination percentages in the thermally inhibited seeds.

Screening of Aggregatum Onion Varieties for Sodicity Tolerance

Sodicity is a major factor affects crop growth and productivity at global level. In the cultivablel and at global level, 23% is affected by salinity and 37% land by sodicity. Two seed propagating aggregatum onion varieties (CO 5, CO 6) and two bulb propagating aggregatum onion varieties (Permbalurlocal, thuraiyurlocal) were screened by employing germination test in an osmatic solution of NaHCO3 (Sodium bicorbanate). Three Replications of 20 seeds of each variety were counted and distributed over two layers of paper towel (21x21 cm) previously moistened with water equivalent to three times the dry weight of the paper and tied both ends with rubber band and kept in a plastic tray with different concentrations (0, 10 mM, 20 mM, 30 mM, 40 mM, 50 mM) of NaHCO3 (sodium bicorbanate). Also another bulb propagated varieties, perambalur and thuraiyur local varieties bulb directly sown in beaker have 1.5 kg sand. Control beaker irrigated with only water and other beakers irrigated with different concentrations (25 mM, 50 mM, 75 mM and 100 mM) of sodium bicarbonate solution. Germination percentage was recorded 7 days after. At the end of the 21th day,in four aggregatumonion varieties where final germination per cent, root length, shootlength, vigourindex, stresstolerant index, relative water content and membrane stability index, were recorded in NaHCO3 solution as against the distilled water was calculated. The experiment was designed as a completely randomized design with two factors. As a result a decline in all onion growth paramers, with increasing sodicity stress has been recorded. Significant differences were observed betweenthe varieties and different NaHCO3 concentrations. Irrespective of NaHCO3 concentrations two seed propagating aggregatum onion varieties, CO 6 recorded significantly maximum stress tolerant indexcompare with CO 5 and two bulb propagating aggregatum onion varieties, Thuraiyur local variety recorded significantly maximum stress tolerant index compare with Perambalur local in all sodicity concentation. Based on stress tolerant index, CO 6 and thuraiyur local variety tolerant to sodicity stress and CO5, perambalurlocal variety susceptible to sodicity stress.

Potassium Nitrate Priming Effect on the Germination of Tomato (Lycopersicum esculentum. Mill) cvs. “Mersa” and “Tekeze-1”

To compare the responses of two open-pollinated tomato varieties to germination parameters and shoot growth, seeds of open-pollinated tomato varieties, Mersa and Tekeze-1 were given osmopriming treatments with potassium nitrate (KNO3) in a lab setting. A completely randomized design with four replications was used. The analysis of variance revealed that both tomato varieties responded differently to priming with potassium nitrate concentrations significantly (P<0.05) for almost all measured traits. Potassium nitrate treatments also affected final germination percent (G%) and mean daily germination percent significantly (P<0.05) and germination index (GI) and shoot length (SL) (P<0.001). However, KNO3 did not have a significant effect on time for 50% germination (T50) and mean germination time (MGT). Variety Mersa showed better performance in germination percent (G%) and SL than Tekeze-1; while Tekeze-1 had shorter days for MGT and reached T50 faster than the Mersa variety. Potassium concentrations at 0.5% and 1.5% showed better germination results than the control and at 1% KNO3. The interaction of the Mersa variety with KNO3 at 1.5% and 1% resulted in the highest SL, but the Tekeze-1 variety had the highest shoot length at 0.5% KNO3 concentration, indicating that the varieties have different responses to the applied KNO3 rate. This study confirmed the possibility of enhancing seed germination through externally applied priming agents such as KNO3. Despite being a preliminary finding, this study demonstrated that tomato cultivars differ in how they react to KNO3 priming, and more research, using other tomato varieties and priming agents, is needed.

The Effect of Salinity (NaCl) Stress and Different Magnetic Applications on The Germination of Cucumber Seeds (Cucumis sativus L.)

Salinity stress is one of the main factors that limit seed germination and plant growth. Therefore, magnetic water was used because it had a positive effect on seed germination. This study was conducted to investigate the effect of magnetic (MT1, MT2, MT3, MT4, and MT5) treatment of water passing through magnets 1, 2, 3, 5, and 8 times respectively, and non-magnetic (NMT) treatment on the germination of cucumber seeds (Cucumis sativus L.) under salinity stress (NaCl) (S1 = 0.38 dSm-1, S2 = 4.0 dSm-1, S3 = 8.0 dSm-1). The experiment was conducted by the design of a one-way ANOVA with three replications. The results showed that water salinity stress a significantly decrease in the final germination percentage (FGP), germination index (GI), coefficient of the velocity of germination (CVG), germination percentage 4th day (GP), and germination rate index (GRI), while the mean germination time (MGT) increased significantly. In addition, the FGP, GP, GI, CVG, and GRI were significantly increased and the MGT was significantly decreased when using magnetic water compared to non-magnetic water. The highest values of FGP, GP, GI, CVG, and GRI were at S1 while they decreased by 7.8%, 10.0%, 15.8%, 2.4% and 16.2%, respectively in S3 (8.0 dSm-1), compared to S1 (0.38 dSm-1). The highest FGP values of 92.20% at MT4 were obtained with S1 salinity (0.38 dSm-1) and the lowest FGP value of 72.20% at NMT with water salinity S3 (8.0 dSm-1). The results of the research showed that magnetic water treatment has a positive effect on the germination of cucumber seeds and that salinity stress reduced the germination of seeds. Finally, it can be recommended to apply MT4 (water passed through the magnetic 5 times) to achieve the best germination of cucumber seeds.

Kinetics of Imbibition and Light Quality in Echinocactus Platyacanthus LK & O Germination

Given that germination is a crucial stage in the development of plants, it is essential to carry out studies on the factors that affect this phase. The optimal conditions for each species should also be defined, especially those that, by their nature, present such problems in their propagation and conservation that render them vulnerable. Many species of the cacti family belong to this group, so this research aims to contribute to the knowledge of some factors that impact the germination of Echinocactus platyacanthus. The first purpose of this work was to describe the kinetics of scarified seeds imbibition at 25, 30, and 35°C and their impact on the germination response. The evaluation of the effects of red light on the germinative response was established as a second purpose. The results showed that the imbibition process in scarified seeds fits a curve of the Weibull model, with 15.03, 15.62, and 18.84 hours α coefficients, and 0.08, 0.09, and 0.45 β coefficients for temperatures of 25, 30, and 35°C, respectively. In non-scarified seeds, the coefficients were 10.85, 13.11, and 13.06 hours α, and 0.12, 0.10, and 0.08 β for temperatures of 25, 30, and 35°C, respectively. Scarification and temperature favor rapid water uptake. The imbibition behavior is similar under both conditions, unlike the final germination percentage. Temperature influences the imbibition percentage and favors germination since the temperature of 35°C registered over 90%. The seeds irradiated with red light recorded 96% germination at 144 and 168 hours, confirming that light quality influences this response. A possible physical latency and mechanical dormancy are ruled out, demonstrating positive photodormancy. Key words: photodormancy, cactus, red light, scarification, germination

Response to Direct Selection against Drought Stress in Black Cumin (Nigella sativa L.)

Central Anatolia is prone to drought with low precipitation and high evapotranspiration which influence the growth of a several crops. The selection and cultivation of drought-tolerant crops that can survive and maintain under poor climatic conditions are very important. Black cumin (Nigella sativa L. Umbelliferae) is famous for aromatic, medicinal, and therapeutic uses in the Mediterranean region and elsewhere. Drought stress most often delays or reduces seed germination ending up in irregular and poor crop growth. The study aimed to compare the effects of −0.1, −0.2, and −0.4 MPa of PEG 6000 osmo-priming pretreatments for 12, 24, and 36 h and two PEG 6000 post-treatments of −0.05 and −0.15 MPa along with their respective controls for 14 days as post-treatment on seed germination and seedling establishment potential of Turkish cv. Cameli. The results showed significant differences among germination index, germination stresses tolerance index, germination speed, final germination percentage, seedling vigor index, mean germination time, shoot, root and seedling length, and seedling fresh and dry weight of pretreatments and post-treatments when compared to nonprimed and hydro-primed seeds used as control treatments. Osmo-priming pretreatments of black cumin using −0.2 or −0.4 MPa PEG 6000 for 24 or 36 hours in a medium containing −0.05 MPa PEG 6000 as post-treatment showed improved germination efficiency, with increased adaptation ability.

Two shades of grey: effect of temperature on seed germination of the escaping ornamental species Lychnis coronaria and Stachys byzantina

This paper describes germination and cytological variability in two popular ornamental and potentially invasive species, lamb’s ear Stachys byzantina and rose campion Lychnis coronaria. Both xerophytic species have the potential to invade natural habitats across Europe and create viable naturalised populations, with subsequent impacts on native vegetation. To assess the species’ invasiveness, seeds were collected from naturalised populations and germination was recorded under different temperature regimes. Flow cytometry, used to record cytological variability, indicated that all populations of both species were cytologically homogeneous. Germination success, an important means of distribution factor in both species, was significantly influenced by temperature, with final germination of L. coronaria being extremely high at temperatures > 15/10 °C (98.5%) and extremely low at temperatures < 10/5 °C (2.9%). The final germination in S. byzantina is the highest at 22/15 °C (55.6% germinated seeds), reduced to 40.3% at 15/10 °C and to 0.3% at temperatures lower than 10/5 °C. No significant differences in final germination were observed between escaping and non-escaping populations, although there were some differences between particular populations. Our results indicate germination temperature limits of two species whose non-native areas include Central Europe. The observed germination allows for successful generative reproduction of both species over their non-native ranges, suggesting that these species are likely to become invasive species of European grasslands soon.

Influence of various temperatures, seed priming treatments and durations on germination and growth of the medicinal plant Aspilia africana

For millennia, Aspilia africana has been used across Africa to treat various diseases including malaria, wounds, and diabetes. In this study, temperature influenced the in vitro germination of A. africana with highest final germination percentage (FGP) and germination index (GI) of 65.0 ± 7.64% and 2.26 ± 0.223, respectively, at 19.8 °C. Priming seeds with H2O, KNO3, and GA3 (gibberellic acid 3) improved both in vitro germination and ex vitro emergence of A. africana seeds. Seed priming with 1.44 times 10^{ - 3 } M GA3 produced overall highest in vitro FGP (from 90.0 ± 4.08% to 100 ± 0.00%) and GI (from 2.97 ± 0.385 to 3.80 ± 0.239) across all priming durations. Seeds primed with KNO3 had better germination parameters for 6 and 12 h compared to 18 and 24 h. Furthermore, the highest in vitro FGP (100 ± 0.00%) was observed in seeds primed for 12 h with 1.44 times 10^{ - 3 } M GA3. Ex vitro A. africana seed emergence was significantly enhanced by GA3 priming. Priming A. africana seeds with H2O, KNO3, and GA3 improved their growth after 3 months, with the overall best growth for seeds primed with 2.89 times 10^{ - 4 } M GA3. Seed priming of A. africana is a feasible approach for improving germination and seed emergence, and enhancing plant growth.

Can delaying germination reduce barriers to successful emergence for early‐germinating, fall‐sown native bunchgrass seeds in cold deserts?

Efforts to restore semiarid wildlands in the western United States predominantly use fall seeding. Fall conditions are more amenable to seeding, and successfully over‐wintered seeds or plants are poised to take full advantage of spring moisture. However, over‐winter mortality can be a barrier to seeding success. One solution to avoid winter mortality without sacrificing the benefits of fall seeding is to delay germination of fall‐sown seeds. At six northern Great Basin field sites over three planting years (18 trials), we tested whether a hydrophobic seed coating reliably delayed germination and increased seedling establishment of a native bunchgrass. Despite considerable variation among sites and years, seed treatment successfully reduced pre‐winter germination by 84% compared to untreated, but also consistently reduced final germination by 23%. Still, treatment resulted in an average of 2.1‐fold higher emerged seedling density in seven trials, six of which were among the eight trials where more than 50% of untreated seeds germinated pre‐winter. Emergence was greater for untreated seed in five trials, all of them in the same year, and all but one of them with below‐average total germination. Our treatment consistently reduced pre‐winter germination, but only improved emergence when pre‐winter germination of untreated seeds was high. Continued research is merited with germination‐delaying treatments and to experimentally define—and develop models that predict—winter‐related mortality barriers. We also suggest future exploration of bet‐hedging strategies that mix treated and untreated seeds where fall seeding is required and significant but variable risk of over‐winter seedling mortality exists.

Calcium chloride enhances growth and physio-biochemical performance of barley (Hordeum vulgareL.) under drought-induced stress regimes: a future perspective of climate change in the region

AbstractWater is the fundamental part of living systems and it plays a key role in supporting life on earth; however, fluctuations in climatic conditions lead to limitation of the ground water causing serious concerns. The present research study was aimed at assessing growth and physio-biochemical responses of barley to calcium chloride (CaCl2) solution (10 mM) applied through roots under induced drought stress for 5, 10, and 15 days. CaCl2, being an enhancer of osmolytes and antioxidant enzymes, counteracts the damaging effects caused by abiotic stresses. A pot experiment was conducted by sowing barley under induced drought stress for 5, 10, and 15 days, respectively. Plants exposed to different levels of the induced drought stress condition were treated with 10 mM of CaCl2 solution via roots during the seedling stage. Results indicated that water-limited conditions negatively affected plant growth parameters including final emergence percentage, final germination percentage, and mean emergence time. Moreover, absolute growth rate, relative growth rate, and net assimilation rate were significantly improved under 5, 10, and 15 days of drought stress supplemented with CaCl2 solution. Under drought conditions, an increase was observed in hydrogen peroxide (H2O2), glycine betaine (GB), and proline (PRO) content, and in ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and lipid peroxide (LPO) activities. H2O2 and LPO showed a significant decline with CaCl2 application under induced drought stress regimes. On the contrary, GB, PRO, APX, CAT, POD, and SOD contents of root and leaf were significantly improved with CaCl2 application under induced drought stress. In conclusion, CaCl2 solution effectively curbed the damages caused by oxidative stress via accumulating osmolytes and scavenging reactive oxygen species by activating the antioxidant enzymatic defence system of barley.

Mechanical Scarification Influence on Gleditsia assamica Bor Water Uptake and Germination

Physical dormancy is a typical kind of dormancy in Fabaceae species, including Gleditsia assamica. Physical dormancy is caused by the impermeability of the seed coat and can be alleviated, among others, by mechanical scarification. Previous studies on mechanical scarification effect on G. assamica seed focus only on its germination parameter without regard to its effect on seed water upatke. As germination is initiated with water uptake, current study aims to understand the treatment effect on both of seed water uptake and germination parameters. Tetrazolium dyeing and seed weight measurement trials were conducted to study the seed water uptake. Meanwhile, a germination test is conducted to investigate the treatment's influence on the seed germination parameters. This study shows that mechanical scarification can enhance G. assamica seed water uptake. The treatment was also significantly improve final germination percentage and germination speed index. This study result gives us a clearer understanding of the effect of mechanical scarification to alleviate G. assamica dormancy and germination, which will be advantageous to the species conservation and domestication efforts.

Mixing Hydrogel Granules into Peat Substrate Improves Germination and Enhances Growth and Physiological Performance of Tomato Seedlings

Abstract The effects of hydrogel granules mixed with peat substrate on germination, morphological and physiological parameters of plugged seedlings were tested in tomato seedlings, at two different irrigation regimes. Due to hydrogel presence, the germination speed was increased, whereas mean germination time was significantly reduced. Slight improvement was recorded regarding final germination, but no effect was found regarding the synchronisation index and seedling vigour index. Due to addition of hydrogel granules a significant increase occurred in dry matter of shoots and plants. No effect was found regarding dry matter of roots, but the presence of hydrogel granules significantly reduced the length of tap root. Interestingly, stomata conductance and chlorophyll index were higher than in control plants. No statistically significant interaction was found between hydrogel variants and irrigation frequency, i.e., the effect of different levels of hydrogel variants did not depend on irrigation frequency. Therefore, we recommend mixing hydrogel capsules into the substrate of plug seedlings to improve the morphological and physiological parameters of seedlings and reduce water and fertiliser leaching into the environment.

Effects of phosphate-containing additives and zeolite on maturity and heavy metal passivation during pig manure composting

This study investigated the effects of the combination of phosphogypsum with calcium oxide (PPG + CaO), superphosphate with calcium oxide (SSP + CaO) and zeolite (Zeolite) on composting maturity and heavy metal passivation in pig manure composting. The results showed that all treatments reached the maturity requirements and the phosphorus-containing additive treatments had higher final germination indices (GIs). Compared with CK, additive treatments enhanced the compost maturity by promoting volatile fatty acids (VFAs) decomposition (26.4%-30.5%) and formation of stable humus substances. All additive amendment treatments increased humic acid-like substances by over 20%, and the PPG + CaO treatment had the highest level of humus. Composting process reduced the bioavailability of Cu (49.2%), Cd (5.0%), Cr (54.3%), and Pb (26.6%). Correlation analysis found that the heavy mental passivation rate was significantly negatively correlated with the contents of VFAs and nitrogenous substances, and positively correlated with the pH, GI, humic acid content and the ratio of humic acid to fulvic acid (HA/FA). Therefore, the PPG + CaO treatment further increased the passivation rates of Cu (65.6%), Cd (21.7%), and Pb (48.7%) and decreased the mobilization of Zn by promoting maturity and humification during composting.

Profiling of foxtail millet (Setaria italica L.) germplasm using in vitro drought screening and SSR markers

AbstractFoxtail millet (Setaria spp.) is an ancient cereal crop, having a short cropping cycle. Drought tolerance was assessed in this crop at an early growth stage and the extent of genetic diversity was measured between the foxtail millet genotypes, applying DNA markers. Tolerance of 18 foxtail millet genotypes was studied in vitro under four levels of polyethylene glycol (0, 10, 20 and 30% PEG-6000). PEG-6000 decreased final germination percentage and led to a reduction in shoot and root length with different stress levels. The genotypes ISe 869, ISe 1851 and yellow spike show superiority in stress tolerance for germination and the growth of root and shoot traits. They also clustered together in the biplot diagram and dendrogram of the genotypes based on the morphological traits. Marker polymorphism index (PI) was 80.36% and a total of 132 polymorphic alleles (4.00 alleles/locus) were obtained from 33 polymorphic primers. Polymorphic information content (0.54–0.83) was highly informative with an average value of 0.67. A dendrogram distributed the genotypes into five distinct clusters based on simple-sequence repeat (SSR) data, independent of their geographical distribution. A relationship was established between the SSR markers and the genotypes ability to tolerate drought stress. The SSR markers used could contribute to conducting DNA profiling of foxtail millet, and facilitating their use in future breeding programmes for drought tolerance in this crop. Based on water-stress experiment, three most tolerant genotypes: ISe 869, ISe 1851 and yellow spike are recommended to be cultivated under drought conditions around the world.

Screening of Big Onion Varieties for Sodicity Tolerance at Cauvery Delta Zone in South India

Sodicity is a major factor affects crop growth and productivity at global level. Out of 1.5 billion ha of cultivable land at global level, 23% are affected due to salinity and 37% by sodicity. Fourteen Big onion varieties were screened by employing germination test in an osmatic solution of Na2CO3 (Sodium bicarbonate).Simultaneously, all the varieties were allowed to germinate in distilled water (control).Three Replications of 20 seeds of each variety were counted and distributed over two layers of paper towel (21x21 cm) previously moistened with water equivalent to three times the dry weight of the paper and tied both ends with rubber band and kept in a plastic tray with different concentrations ( 0, 25mM, 50mM, 75mM, 100 M ) of Na2CO3. At the end of the 21st day, final germination percent, root length, shoot length, root dry weight, shoot weight, Relative water content and membrane stability index, were recorded in Na2CO3 solution as against the distilled water was calculated. The experiment was designed as a completely randomized design with two factors. As a result a decline in all onion growth paramers, with increasing sodicity stress has been recorded. Significant differences were observed between the varieties and different Na2CO3 concentrations. Irrespective of Na2CO3 concentrations, Bhima Safed recorded significantly maximum stress tolerant index compared to other varieties and minimum stress tolerant index value recorded bhima red variety. Based on stress tolerant index, Bhima safed variety tolerant to sodicity stress and Bhima red variety sensitive to sodicity stress.

Bio-Priming of Soybean with Bradyrhizobium japonicum and Bacillus megaterium: Strategy to Improve Seed Germination and the Initial Seedling Growth.

Bio-priming is a new technique of seed treatment that improves seed germination, vigor, crop growth and yield. The objective of this study was to evaluate the effectiveness of Bradyrhizobium japonicum (commercial strains) and Bacillus megaterium (newly isolated strains) as a single inoculant and co-inoculant during seed bio-priming to improve seed germination and initial seedling growth of two soybean cultivars. The treated seeds were subjected to germination test (GT), cold test (CT) and accelerated aging test (AAT). B. megaterium significantly improved all parameters in GT and CT; final germination, shoot length, root length, root dry weight, and seedling vigor index in AAT, as compared to control. In addition, co-inoculation significantly increased all parameters except shoot dry weight in GT; all parameters in CT; germination energy, shoot length, root length, and seedling vigor index in AAT, in comparison to the control. Moreover, Br. japonicum significantly improved the germination energy, shoot length, shoot dry weight, root dry weight, and seedling vigor index in GT; all parameters in CT; shoot length, root length, and seedling vigor index in AAT, compared with non-primed seeds. Thus, B. megaterium strains could be used in soybean bio-priming as a potential single inoculant and co-inoculant, following proper field evaluation.

Seed germination traits and dormancy classification of 27 species from a degraded karst mountain in central Yunnan-Guizhou Plateau: seed mass and moisture content correlate with germination capacity.

In degraded karst ecosystem, vegetation restoration efforts almost exclusively rely on planted seedlings, but this is not effective to maintain community diversity and resilience. As seed functional traits, seed dormancy and germination are key to community assembly. Unfortunately, these elements are commonly overlooked in restoring degraded ecosystems. This work classifies seed dormancy of 27 species with different life forms that are common on a degraded karst mountain. We examined the effects of temperature regime and light conditions on percentage germination and assessed the relationships between seed traits and germination index using a partial least squares regression (PLSR). Approximately 48% of the investigated species had physiological dormancy, 37% were non-dormant, 7% had morphophysiological dormancy, 4% had morphological dormancy and 4% had physical dormancy. We found that 94% (15 out of 16) species had maximum germination in warm temperature regimes (20/13 and 25/18 °C), while the remaining species required cool temperatures (10/4 °C). PLSR analysis indicated a significant positive correlation between seed mass and T50m (time to 50% final germination), and a negative correlation between seed moisture content and percentage germination. Our findings indicate that seed traits are important factors in seed-based restoration practice. F. esculentum, O. opipara, P. fortuneana and S. salicifolia are recommended for direct seeding during the early rainy season to restore seriously degraded lands in subtropical karst regions.

Uncharted waters: Inbreeding negatively affects germination performance in Marathrum foeniculaceum (Podostemaceae)

In outcrossing species, inbreeding reduces fitness because homozygous deleterious alleles increase their frequency in what is called inbreeding depression. The theory well predicts this phenomenon; however, it is often unclear what proxies of fitness inbreeding might affect. Inbreeding depression in aquatic plants is not extensively studied. To fill this gap, we evaluated the effect of inbreeding trough experimental crosses (inbreeding vs. selfing) on parameters of seed germination performance (i.e., final germination percentage, germination speed and seed size) of the riverweed Marathrum foeniculaceum (Podostemaceae), using seeds collected in two locations of México. We found that the final percentage of germination is affected negatively by inbreeding, but its effect on the speed of germination and seed size were dependent on the river location. This indicates that, even when evaluating the seed germination of the same species, the population dynamics of each location can be different, which might be the result of their evolutionary history and local environmental conditions. These results are important for the design of effective in situ conservation strategies of Podostemaceae in their natural habitat.

Pre-germination treatments on Ochetophila trinervis, a native Andean tree with potential use for restoration

In a climate change scenario, global forest loss had a direct impact on the hydrological cycle, making the protection of soil and water resources a central issue. In the Central Andes of western Argentina, information on Chacay (Ochetophila trinervis) mountain forests is scarce. This tree thrives along river and stream banks, fixes atmospheric nitrogen, and grows in impoverished soils. The seeds of O. trinervis are characterized by physical or physiological dormancy, and germination requires technique application. The main goal was to evaluate the effect of mechanical and chemical scarification, cold stratification, and hot water immersion on the final germination percentage, germination speed index, and the mean germination time of O. trinervis seeds. Our results show that mechanical and chemical scarification are the treatments that best inhibit seed dormancy in this species. Mechanical scarification with sandpaper is the treatment that offers a balance between effective results and an easy-to-apply technique. Sulfuric acid (SA) treatment is also efficient in breaking dormancy, but we recommend applying it under extreme careful laboratory conditions. Highlitghs: Our findings support the hypothesis that the seeds of O. trinervis show physical dormancy because either mechanical (M) or chemical scarification (SA) techniques achieved the highest germination values. Our results indicate that mechanical scarification (M) might be a practical option for O. trinervis seedling germination in the Central Andes of Western Argentina. Sulfuric acid (SA) treatment is also efficient in breaking dormancy, but we recommend applying it under extreme careful laboratory conditions.

Allelopathic effect of Calotropis procera (L) leaves extract on seed germination and early growth of Arachis hypogeae (L) and Pennisetum glaucum (L)

The effect of aqueous leaves extract of Clotropis procera at 20%, 40% and 80% on seeds germination and early growth of Groundnut (Arachis hypogeae) and Millet (Pennisetum glaucum) was investigated. The results showed that the extract both at lower and higher concentration did not affect the seeds germination of the two plants species. Final germination percentage after ten days was increased by increasing the extract concentration especially on Millet where 100% and 95% germination was observed at 20% and 80% concentration of the extract respectively. Generally, the radicle and plumule growth was sensitive to different levels of the extract where the plumule length was decreased by increasing the extract concentration and some leaves began to die at higher concentration (80%) in Groundnut (Arachis hypogeae). However, plumule emergence and growth was stimulated in both lower (20%) and higher (80%) concentration in Millet (Pennisetum glaucum) seedlings more than control treatment. Therefore the seedlings of Groundnut were more affected by the aqueous extract of Clotropis procera than that of Millet. The implications of these findings are hereby discussed.