Pre-germination Treatments Research Articles

NEOTROPICAL TREE PRODUCTION: INSIGHTS INTO GERMINATION, GROWTH AND OUTPLANTING FOR Maytenus boaria

ABSTRACT Knowledge about tree production practices is essential to support forest restoration projects, but is still lacking for many tree species. Maytenus boaria is a neotropical tree distributed across the temperate and subtropical South American mountains. In central Argentina, it is mainly restricted to the most preserved forest remnants. Attempts to plant this species have had little success due to difficulties in seedling production and low seedling survival. We set up four trials aiming to identify the constraints of seedling production and outplanting. Under greenhouse conditions, we evaluated (i) pre-germination treatments and (ii) seedling response to inoculation with arbuscular mycorrhizal fungi (AMF). In the field, we planted M. boaria saplings as well as saplings of the most abundant tree in our study site and recorded (iii) survival and height for 10 years. Finally, (iv) we quantified natural recruitment in an attempt to determine M. boaria regeneration niche. Germination varied from 13.1 to 29.2% among treatments. Depulped seeds stratified at 5 ºC showed the highest germination (29.2%). Shoot phosphorus concentration in AMF-treated seedlings was significantly higher (45%) than in non-inoculated seedlings. Survival of M. boaria saplings was similar to that of the most abundant tree in our study site, but their lower height suggested limited growth. We recorded low abundance of M. boaria seedlings in the field; therefore, we were unable to identify the characteristics of its regeneration niche. Reforestation activities should include seed depulping and stratification at 5 ºC to improve germination. The capacity of AMF to enhance nutrition should be evaluated under field conditions.

Seed germination of five Prosopis shrub species (Fabaceae-Mimosoideae) from the Monte and Patagonia phytogeographic provinces of Argentina

The Patagonian species of the genus Prosopis exhibit distinctive features such as their shrub growth pattern. However, morphological or physiological differences among them have been poorly studied (e.g., germination). Considering this lack of information, we studied five Prosopis species from two different phytogeographic provinces: Monte and Patagonia. Particularly, we focused on the southern area of the Monte province and the Payunia District of the Patagonian province. We evaluated the effects of pre-germination treatments such as acid scarification using two different exposure times on these Prosopis species. The effectiveness of the treatments was related to the phytogeographic origin of the shrubs. The endemic species of Payunia District (Patagonia phytogeographic province) required longer times of acid scarification than those from the southern area of the Monte. In general, acid scarification resulted in high and homogeneous germination percentages. Our results provide useful information that contributes to improve the protocols necessary for the production of a high number of seedlings, which is required for successful restoration projects.

Germination success under different treatments and pod sowing depths in six legume species present in olive groves

This study analysed the germination success of pods of six annual native legumes species: Astragalus hamosus, Medicago minima, Medicago orbicularis, Medicago polymorpha, Medicago rigidula and Scorpiurus muricatus. The use of these species has been proposed as a means of generating and improving herbaceous cover in olive groves. Germination success was studied in terms of the variability in the number of seeds germinated per pod after 18 months at two different sowing depths, on the surface (S) and buried 10 mm (B). Pods were subject to five different pre-germination treatments: chemical scarification, consisting of immersion in sulphuric acid for 15 min (S_15) and 20 min (S_20), immersion in water for 48 h (W_48), pod precooled to -18ºC for one month (P_18º) and untreated pods (Con). The results showed that the effectiveness of the different treatments and sowing depths depended on the species, and that there were no problems of ‘sibling-competition’ in any of the treatments or at any of the sowing depths. Species with larger, non-spiralled pods, such as A. hamosus or S. muricatus, or with very loosely spiralled pods such as M. orbicularis, had greater germination rates when buried, mainly in the case of untreated pods and pods that were immersed in sulphuric acid for 20 minutes.

Effects of substrates, different pretreatment protocols and dehydration on the induction of seeds germination of <i>Xylopia aethiopica</i> (Dunal) A. Rich.

Despite its socio-economic importance, the cultivation of Xylopia aethiopica is not popular owing to the difficulty in seed germination. As a step in its domestication process, investigations were undertaken on germination requirements and desiccation tolerance of seeds. Three substrates (forest top soil, river sand and a mixture of forest top soil and river sand) and 18 pre-germination treatments including a control (untreated seeds), a mechanical scarification, six heat treatments which were done by soaking seeds in hot water (100 °C) for different lengths of time, and ten acid scarifications which were done by soaking seeds in either sulfuric acid or hydrochloric acid for different lengths of time were tested for their effect on seed germination. Results showed that mean percentage germination was higher on the mixture of forest top soil and river sand (29.4 ± 2.6%) than on other substrates tested. While untreated seeds and those soaked in hot water irrespective of the duration of treatment failed to germinate, seed dormancy was successfully broken by either mechanical or chemical scarification. Soaking seeds in either concentrated HCl or concentrated H 2 SO 2 for 5 min were the most effective treatments in breaking dormancy, with 80 ± 6.3% and 70 ± 6.3% mean germination recorded respectively. The desiccation tolerance test showed that X. aethiopica seeds are desiccation-tolerant and their storage behaviour is orthodox. This study shows that for propagating X. aethiopica from seeds, it is recommended that fresh or dried seeds be soaked in either concentrated HCl or concentrated H 2 SO 4 for 5 min, and that seeding be done in substrate composed of a mixture of forest top soil and river sand in a 1:1 (v/v) ratio. Keywords : Spice tree, domestication, seed dormancy, scarification, desiccation tolerance.

Seed germination in Ormosia macrocalyx , an endangered tropical forest tree

Background Ormosia macrocalyx is a tropical forest tree classified as endangered. Its seeds experience problems of dispersion and apparent physical dormancy due to their hard seed coating.
 Hypotheses 1) The stages of dehiscence of the fruits of Ormosia macrocalyx influence the germinative behavior of its seeds. 2) Pregerminative treatments will improve the germination process of the seeds stored under refrigeration.
 Study species Ormosia macrocalyx Ducker.
 Study site and period Villahermosa, Tabasco, Mexico from October 2012 to October 2014.
 Methods Two completely randomized experiments were conducted in order to analyze the germination process by 1) evaluating germination in seeds from fruit at three stages of dehiscence (closed, semi-open, and open fruit) and 2) applying four treatments, including three pregerminative treatments (water soaking for 24 h, mechanical scarification and scarification+1 % gibberellic acid) plus an untreated control, to seeds stored under refrigeration for 17 months.
 Results Differences were found in germination rate (GR), corrected germination rate (CGR) and time to attain 50 % germination (T50) among treatments in the first experiment, with the seeds from open fruits presenting the lowest response (3.31 % day-1 for GR and CGR, and 15.8 days for T50), although all treatments showed similar times for the initiation of germination (GI) and final germination percentage (GP). In the second experiment, the effect of scarification was greater than both the control and soaking treatments. Scarification treatment values were 68.0 % (GP), 12.0 days (GI), 4.53 % day-1 (GR), 6.65 (CGR) and 14.5 days (T50). Addition of gibberellic acid did not produce any further advantage over scarification alone.
 Conclusions Seeds from open fruits have lower germination rates, although the final GP is not affected. Stored seeds present physical dormancy but lose viability with storage and, when collected after remaining attached to the tree for undefined periods, scarification can greatly improve their germination rate.

Domestication of Xylopia parviflora (A. Rich.) Benth: testing different pre-treatment protocols and substrates for inducing seeds germination

Xylopia parviflora, one of the most highly valued indigenous fruit tree species in sub-Saharan Africa, is still exploited in the wild because it has not been domesticated yet. As a contribution to its domestication process, investigations were undertaken on germination requirements and desiccation tolerance of its seeds. Three substrates, three accessions, 13 pre-germination treatments and different levels of seed dehydration were tested for their effect on seed germination. Results showed that mean germination percentages were significantly higher both on river sand (37.95 ± 1.8%) and on mixture of forest top soil + river sand (40 ± 1.8%) than on forest top soil alone (31.03 ± 1.8%). Bangoua had the highest germination percentage (41.3 ± 1.8%), followed by Bayangam 2 (38.2 ± 1.8%) and Bayangam 1 (27.18 ± 1.8%). Untreated control seeds exhibited coat-imposed dormancy which was expressed by overall 5.5 ± 3.7% germination. The most effective treatment to overcome dormancy was hydrochloric acid treatment for 10 min, followed by sulfuric acid treatment for 5 min and mechanical scarification with respective germination percentages of 80.0 ± 3.7, 63.3 ± 3.7, and 56.6 ± 3.7%. The desiccation tolerance test showed that X. parviflora seeds are desiccation-tolerant and that their storage behaviour is orthodox.

Investigating the influence of selected texture-improved pretreatment techniques on storage stability of wholegrain brown rice: Involvement of processing-induced mineral changes with lipid degradation

This work aimed at investigating the effects of emerging texture-improved processing techniques including high hydrostatic pressure (HHP; 150–450MPa/10min), high-intensity ultrasonication (HIU; 17.83W·cm−2/30min) and germination (37°C/36h) pretreatments on lipid hydrolysis and oxidation development of wholegrain brown rice (WBR) during storage, in an attempt to ascertain a possible link between lipid degradation and the underlying mechanisms. The results showed that HHP and HIU treatments enhanced lipid hydrolysis and oxidation as indicated by the formation of free fatty acids (FFA) and thiobarbituric acid reactive substances (TBARS) respectively, whereas an opposite pattern was observed for germination. Storage process rather than after immediate treatments observed an increase in lipid oxidation of HHP and HIU-processed samples, which was related to processing-induced liberation of minerals. Quantitative and qualitative characterization via inductively coupled plasma-optical emission spectrometry (ICP-OES) and micro X-ray fluorescence (μ-XRF) analysis confirmed the shifts of mineral distribution in WBR grains in response to different pretreatments. The WBR-derived lipase was activated by Ca2+, and μ-XRF mapping indicated calcium enrichment in pericarp/aleurone layer and its mobilization to embryo during germination process where magnesium and manganese were significantly reduced. Multivariate analysis revealed a close relationship between increased lipid degradation and minerals including magnesium and manganese. This is the first time for reporting the effects of selected texture-improved techniques on lipid stability of WBR grains across storage process as well as validating the involvement of processing-induced mineral release in lipid degradation.

Germinação de sementes de Mimosa scabrella Benth. submetidas a diferentes condições de temperatura, armazenamento e tratamentos pré-germinativos

The objective of this study was to evaluate the effect of temperature, storage time and pre-germination treatments in the germination of Mimosa scabrella Benth seeds. The study was conducted at the University of the State of Santa Catarina, Lages. The experimental design was completely randomized, and analysis of variance was performed under the factorial 2×2×7 (two temperatures, two periods of storage, and seven pre-germination treatments). The average values were compared by Scott-Knott test at 5% probability. The temperatures employed were 25 and 30°C, the storage periods were eight months and no storage and pre-germination treatments were immersion in water at 80°C for periods of 3, 6, 9, 12, 15 and 18 hours. The results showed higher germination of seeds bracatinga in temperature 30°C, regardless of storage, and immersion for 3 hours in water at 80°C.

Germination responses in physic nut (Jatropha curcas L.) seeds to pregerminative treatments

Las semillas de pinon (Jatropha curcas L.) pueden presentar problemas de germinacion debido a su testa gruesa. Por lo anterior, el objetivo de esta investigacion fue evaluar el efecto de 13 metodos pregerminativos sobre la germinacion de semillas y uniformidad en la emergencia de plantulas de pinon. Los metodos consistieron en la combinacion de agua, cenizas de Manilkara bidentata y estiercol de cuy (Cavia porcellus), con dos sustratos (aserrin y arena). Se empleo un diseno completamente al azar con parcelas divididas. Se realizaron tres repeticiones de 50 semillas para cada tratamiento. Se evaluo inicio de germinacion, porcentaje de germinacion y emergencia. Los resultados indicaron que el remojo en agua a 62 °C fue letal para el embrion; mientras que la siembra directa en arena fue la mas tardia para iniciar la germinacion. El remojo en estiercol y la frotacion con cenizas mas remojo en estiercol, independientemente del sustrato, permitieron iniciar la germinacion en dos dias y alcanzar mas de 90 % de emergencia; por lo que se concluye que estos tratamientos pregerminativos fueron los mejores

New insights into the mechanism underlying Ricinus communis L. tolerance to drought stress during germination

Ricinus communis L. is an important oilseed crop species which is mostly cultivated in Brazil by family farmers in the northeastern semiarid region. This species is renowned by the quality and properties of the oil extracted from its seeds, which can be used for a diverse range of industrial applications. Furthermore, this species is considered to be tolerant to abiotic stresses such as drought stress. The use of post-harvest and pre-germination treatments on mature seeds can enhance their viability and vigor. In this context, the objective of this study was to investigate the effect of osmoconditioning on R. communis L. seed germinability parameters and events related to the reactivation of cell cycle, i.e. tubulin accumulation and microtubular cytoskeleton configurations. Osmoconditioning was applied to both fresh-harvested (FH) and dry seeds (DS), originating fresh-harvested osmoconditioned (FHO) and dry osmoconditioned (DO) seeds. In general, osmoconditioning promoted seed priming by enhancing seed germinability of FHO and DO seeds by means of better germination speed and uniformity, except for a decrease of uniformity in FHO seeds. Immunocytochemical and immunohistochemical analysis revealed an increasing accumulation of tubulin in FHO and DO seeds, followed by the accumulation of tubulin granules in DO seeds. Mitotic microtubules were only visible in FHO and DO seeds after radicle protrusion and, therefore, seed germination occurred solely by cell elongation, whereas FH and DS seeds required cell cycle reactivation and cell proliferation during imbibition, i.e. prior to radicle protrusion or germination per se. The prompt activation of microtubular cytoskeleton synthesis in seeds that were osmoconditioned might be a possible strategy of the species for faster and more uniform and vigorous seed germination and seedling establishment and, therefore, better survival during periods of drought in harsh environments. These findings provide important insights into the mechanism underlying plant adaptation to harsh environmental conditions, which would be very helpful to develop germination and seedling production protocols to obtain faster and more vigorous and uniform germination seedling stand for the sustainable exploitation of R. communis by small family farmers under the typical harsh conditions of the semiarid regions worldwide.

EFECTO DE TRATAMIENTOS PRE-GERMINATIVOS EN LA CALIDAD DE PLÁNTULAS GUAPINOL (HYMENAEA COURBARIL)

Esta investigación ha evaluado el efecto que tiene cinco tratamientos pre-germinativos en la calidad y estructura de las planta de guapinol (Hymenaea courbaril) debido a la elevada variabilidad en la germinación y emergencia con la siembra directa. Se evaluaron cinco tratamientos, midiendo el índice de germanización y velocidad de emergencia, parámetros de calidad (altura y diámetro) junto con la de biomasa (peso fresco y seco) de las plántulas, con lo que se estimó el índice de calidad de Dickson. Cada uno de los tratamientos consto de 50 repeticiones para un total de 250 plántulas dentro del experimento. Los datos se procesaron SPSS V.22.0 con los estadísticos: varianza, desviación estándar, análisis de varianza, obteniendo las pruebas estadísticas de correlaciones binarias, análisis de medidas repetidas y análisis de varianza (ANOVA), intra e inter grupos, a un 95% (P-valor 0.05) de confianza. Los resultados muestran diferencia entre los tratamientos tres (hidratación) y cuatro (escarificación mecánica) respecto al tratamiento uno (térmico) y dos (químico) donde no hay diferencia estadísticamente significativa. El tratamiento cinco (testigo) presenta diferencia estadística menor con todos los demás evaluados. Estos mismos datos permiten determinar un efecto positivo entre la aplicación de tratamientos pre-germinativos y el aumento de la calidad de la plántula de un 93.0%, esto se traduce a mayores posibilidades de sobrevivencia de la planta al ser trasplantada en campo. Debe probarse la combinación de los tratamientos uno y tres.

Methods of breaking seed dormancy for ornamental passion fruit species

The Passiflora L. genus covers a diversity of wild species with ornamental potential, especially due to the intrinsic beauty of its exotic flowers, flowering more than once a year and the lush foliage. However, Passiflora seeds present dormancy complicating seed germination and the establishment of commercial plant production with species with high ornamental potential. This study was conducted to determine the best pre-germination treatments to overcome seed dormancy for Passiflora quadrangularis, P. nitida, P. foetida, P. eichleriana, P. alata, P. cincinnata, P. mucronata, P. micropetala, P. suberosa, P. morifolia and P. tenuifila. The experimental design was completely randomized, with five treatments and four replicates, with 25 seeds per plot. Pre-germination treatments were: seeds soaked in 1,000 mg L- 1 GA3 (gibberellic acid) for 6 hours, seeds soaked in 0.2 % KNO3 (potassium nitrate) for 24 hours, seeds soaked in 1 % KNO3 for 24 hours, partial seedcoat scarification with sandpaper number 120 and control (seeds untreated). Percentage of germination, germination velocity index and radicle length were evaluated for all species. The results showed that GA3 was effective to overcome seed dormancy in P. suberosa (86%), P. morifolia (68 %) and P. tenuifila (54%). KNO3 1% had significant effect on overcoming dormancy in seeds of P. eichleriana (66%) and scarification with sandpaper increased seed germination of P. micropetala (38%).

Dormancy overcoming, temperatures and substrates on germination of Mimosa tenuiflora Willd seeds

Mimosa tenuiflora Willd., popularly known as jurema-preta, is an arboreal species of great importance for the brazilian Northeast due to its uses as a medicinal plant and in the restoration of degraded soils. No information is available in the Rules for Seed Analysis and the Instructions for Seed Analysis of Forest Species regarding ideal conditions for of this species. Thus, this study aimed at evaluating the influence of pre-germination treatments, in addition to verifying the germination performance at different temperatures and in different substrates. In both experiments, four replicates of 25 seeds were used for each treatment. In experiment I, seeds were submitted to the following methods for overcoming dormancy: witness - Intact seeds (T1) immersion in water at 100 °C for 1 (T2), 2 (T3), 3 (T4), 4 (T5), 5 (T6) and 6 min (T7), immersion in concentrated sulfuric acid for 1 (T8), 4 (T9), 7 (T10), 10 (T11) and 13 min (T12), scarification on sandpaper n° 80 (T13) and lopping in the region opposite the micropyle (T14). In experiment II, seed germination was evaluated in four types of substrates: between sand, paper on, paper roll and between vermiculite and at six different temperatures: 20, 25, 30, 35, 40 °C and alternating between 20 and 30 °C. Immersion in hot water for 1, 2, 3, 4, 5 and 6 min, sulfuric acid treatment for 10 and 13 min, sand paper and lopping were the most appropriate treatments to overcome seed dormancy. The seed germination of M. Tenuiflora should be carried out at 25 °C on paper roll substrate.

Effect of Pre-Germination Treatments on Germination and Watering Regimes on the Early Growth of Pycnanthus Angolensis (Welw) Warb

Effect of Pre-Germination Treatments on Germination and Watering Regimes on the Early Growth of Pycnanthus Angolensis (Welw) Warb

Effects of Nonthermal Plasma Treatment on Decontamination and Sprouting of Radish (Raphanus sativus L.) Seeds

Sprout-related foodborne disease outbreaks are increasingly becoming a concern for food safety. The primary sources of microbial contamination in ready-to-eat sprouts are contaminated seeds, which are improperly disinfected prior to sprouting. In recent years, the application of nonthermal plasmas for seed decontamination is increasingly being investigated as a substitute to regular pre-germination treatments. The present study was intended to evaluate the potentiality of corona discharge plasma jet (CDPJ) for decontaminating microorganisms on radish seeds and to determine the plasma exposure effects on the seed germination as well as physicochemical properties of sprouts grown from the CDPJ-treated seeds. Microbial contaminants, namely, aerobic bacteria, Bacillus cereus, Escherichia coli, Salmonella spp., and molds and yeast were detected in the seeds. All the microorganisms found in the seed samples were reduced in the range of 1.2–2.1 log CFU/g upon treatment using the CDPJ for 3 min. Pseudo-first-order kinetics provides the best fit to the microbial inactivation patterns. The plasma seed treatment for up to 2 min showed beneficial effects on seed germination rate and growth of seedlings. Compared to untreated controls, sprouts grown from the CDPJ-treated seeds exhibited no significant changes in the levels of moisture (mean range 85.45–87.51%), reducing sugars (0.547–0.550%), total phenolic content (6.14–6.29 μg GAL/g), and DPPH radical scavenging activity (78.03–78.60%). Sensory characteristics of radish sprouts grown from the plasma-treated (up to 2 min) seeds were not significantly different from controls. In conclusion, the CDPJ treatment of radish seeds for 2 min not only decreased the seed microbial counts but also led to the improvement of their germination rate and seedling growth, without negatively affecting the physicochemical and sensory properties of their corresponding sprouts.

Germination and Clonal Propagation of the Endemic Shrub Corema album, a Vulnerable Species with Conservation Needs and Commercial Interest

In this study, we aimed to explore regeneration possibilities of Corema album (L.) D. Don by determining germination mechanisms and testing vegetative propagation methods. We analyzed seed viability under natural conditions, carried out germination treatments and a greenhouse experiment to study clonal propagation. We confirmed that C. album seeds present physiological dormancy, broken by ingestion by natural dispersers (rabbits and foxes), and that seed viability under natural conditions is lost after one year. In vitro germination was better achieved with a 200 ppm gibberellic acid treatment. Clonal propagation proved to be a successful technique for the production of C. album. Treating cuttings with IBA 0.2, w/v, at 20% resulted in the highest rooting percentage, while planting rooted cuttings in a substrate of perlite with vermiculite 1:1 was essential for plant survival. Our results show that both germination pretreatments and cutting propagation are powerful tools for the production of this valuable species. Both methods could be incorporated for population regeneration in natural habitats, and for the potential establishment of the species as a new crop for consumption and pharmacological purposes.

Germination and Vigour Responses of Seeds of Three Cassava Varieties to Pre-germination Treatments and Storage Durations

Germination and Vigour Responses of Seeds of Three Cassava Varieties to Pre-germination Treatments and Storage Durations

Germination rate of endangered cloud forest trees in Mexico: potential for ex situ propagation

ABSTRACTDeforestation and elimination of reproductive adult trees in Mexican tropical montane cloud forest (TMCF), due to traditional selective logging, threaten the maintenance of more than half of the tree species in this ecosystem. The objective of this study was to evaluate germination in threatened TMCF tree species in order to assess their propagation potential for conservation efforts. Given that seed size is an important trait influencing germination, the relationship between seed size and mean time to germination (MTG) was evaluated. Seeds of 10 valuable TMCF tree species were sown in a controlled environment and germination rates were recorded until reaching their maximum value. All species displayed potential for propagation from seed without pre-germination treatments. Final germination percentages were as follows: Fraxinus uhdeii = 36.3 ± 7.4% (mean ± 1 SE), Juglans pyriformis = 50.6 ± 6.5%, Magnolia vovidesii = 90.8 ± 1.1%, Meliosma alba = 68.4 ± 6.8%, Ocotea disjuncta = 64.1 ± 12.9%, Oreomunnea mexicana = 17.8 ± 4.4%, Quercus germana = 18.1 ± 1.9%, Sideroxylon contrerasii = 27.1 ± 12.6%, Ulmus mexicana = 33.6 ± 3.7%, and Zanthoxylum melanostictum = 12.7 ± 2.2%. Time required to reach maximum germination varied widely among species; from 49 days in F. uhdei to 434 days in S. contrerasii. No significant correlation was found between seed mass and MTG. While ex situ germination is an important aspect of propagation to reinforce populations of these species, further assessment of germination and transplanted seedling survival under varied TMCF conditions is required.

Tratamentos pré-germinativos para sementes de Hymenaea stigonocarpa Mart. ex Hayne

http://dx.doi.org/10.5007/2175-7925.2016v29n4p1Hymenaea stigonocarpa, conhecida como jatobá-do-cerrado, pertence à família Fabaceae (Leguminosae) e está incluída na categoria de espécie “quase ameaçada de extinção”. Seus indivíduos ocorrem em áreas de cerrado e cerradão e suas sementes apresentam dormência física. Em razão dessa característica, este estudo teve por objetivo avaliar diferentes tratamentos pré-germinativos em sementes de H. stigonocarpa, sendo eles: imersão em fogo, ácido sulfúrico, ácido clorídrico, acetona, éter e água quente (100°C), além de escarificação mecânica com lixa e corte do tegumento com alicate de unha, lavagem em água corrente por 2 h. Os resultados obtidos pelos tratamentos foram comparados aos da testemunha, que não foi submetida a nenhum deles. Os parâmetros analisados foram: a porcentagem de germinação, o Índice de Velocidade de Germinação (IVG) e os percentuais de sementes duras e firmes e de sementes mortas. Os resultados obtidos foram: a) germinação: a água fervente e o ácido sulfúrico foram superiores aos da testemunha; b) IVG: a água fervente, o ácido sulfúrico, o fogo e a lixa foram superiores aos da testemunha; e c) não foram observadas diferenças estatísticas entre a testemunha e os demais tratamentos para o percentual de sementes mortas. Em vista disso, os tratamentos com a água fervente e o ácido sulfúrico se mostraram os melhores, considerando-se os parâmetros analisados.

Cold-Moist Stratification Improves Germination in a Temperate Terrestrial Orchid

ABSTRACT Seed dormancy is a common evolutionary adaptation in temperate plant taxa. Dormancy mechanisms can prevent seeds from germinating at inopportune times, such as a cold period. We report the influence of pregermination stratification treatments on in vitro seed germination and seedling development in Platanthera chapmanii, a rare temperate terrestrial orchid native to the southeastern USA. Seeds were subjected to 0, 8, or 12 wk of cold-moist stratification at 5°C; mean seed viability was 89%. At 9 mo after plating, seeds exposed to 8 and 12 wk of stratification resulted in higher germination (Stage 1; 32% and 35%, respectively) in comparison to 25% germination in nonstratified seeds. Once a protocorm developed a leaf primordium (i.e., reached Stage 2), development to Stage 3 (root development) was independent of the pregermination treatments. Exposure to artificial lights for 3, 4, and 5 mo resulted in 32%, 44%, and 63% of the Stage 2 seedlings, respectively, developing into Stage 3 photosynthetic...