Dormancy Breaking Research Articles

Epicotyl morphophysiological dormancy in seeds of Paeonia ostii (Paeoniaceae): Seasonal temperature regulation of germination phenology

Paeonia is one of the most popular ornamental plants in temperate regions, and its seeds have epicotyl dormancy. Our primary aim was to determine the sequence of temperatures required for radicle and shoot emergence in seeds of P. ostii and how these two distinct stages of dormancy-break are correlated with natural seasonal temperature changes. We tested the effects of various temperature regimes and sequences of regimes on growth of the underdeveloped embryo inside the seed, radicle emergence and shoot growth in the laboratory and germination responses to temperature under natural temperatures in an experimental garden and analyzed ABA and GA concentrations during the dormancy-breaking process. Prior to radical emergence, embryo length increased c. 330%. Embryo elongation and radicle emergence occurred in early October following seed dispersal in summer. The epicotyl-plumule did not differentiate until after embryo growth was completed and the radicle had emerged. Cold stratification was required to break epicotyl dormancy; consequently, shoot emergence did not occur until February when the temperature began to increase. Thus, seed dormancy break in P. ostii is phenologically well adapted to the seasonal cycle of the temperate zone. ABA and GA analyses suggest that root dormancy might be due to high ABA content and shoot dormancy to low GA content. • Seeds of Paeonia ostii have deep simple epicotyl morphophysiological dormancy. • The plumule does not differentiate until embryo growth is competed. • Radicle emergence occurs only at warm temperatures in autumn. • Shoots emerge only in spring in root-emerged seeds that have been cold stratified. • The timing of dormancy-break is regulated by changes in seasonal temperatures.

Regulation of the Bud Dormancy Development and Release in Micropropagated Rhubarb 'Malinowy'.

Culinary rhubarb is a vegetable crop, valued for its stalks, very rich in different natural bioactive ingredients. In commercial rhubarb stalk production, the bud dormancy development and release are crucial processes that determine the yields and quality of stalks. To date, reports on rhubarb bud dormancy regulation, however, are lacking. It is known that dormancy status depends on cultivars. The study aimed to determine the dormancy regulation in a valuable selection of rhubarb ‘Malinowy’. Changes in carbohydrate, total phenolic, endogenous hormone levels, and gene expression levels during dormancy development and release were studied in micropropagated rhubarb plantlets. Dormancy developed at high temperature (25.5 °C), and long day. Leaf senescence and dying were consistent with a significant increase in starch, total phenolics, ABA, IAA and SA levels. Five weeks of cooling at 4 °C were sufficient to break dormancy, but rhizomes stored for a longer duration showed faster and more uniformity leaf growing, and higher stalk length. No growth response was observed for non-cooled rhizomes. The low temperature activated carbohydrate and hormone metabolism and signalling in the buds. The increased expression of AMY3, BMY3, SUS3, BGLU17, GAMYB genes were consistent with a decrease in starch and increase in soluble sugars levels during dormancy release. Moreover, some genes (ZEP, ABF2, GASA4, GA2OX8) related to ABA and GA metabolism and signal transduction were activated. The relationship between auxin (IAA, IBA, 5-Cl-IAA), and phenolic, including SA levels and dormancy status was also observed.

Reciprocal Field Transplant Experiment and Comparative Transcriptome Analysis Provide Insights Into Differences in Seed Germination Time of Two Populations From Different Geographic Regions of Zostera marina L.

Seagrasses are the only submerged marine higher plants, which can colonize the sea through sexual (via seeds) reproduction. The transition between seed dormancy and germination is an important ecological trait and a key stage in the life cycle of higher plants. According to our observations, the seeds of Zostera marina L. (eelgrass) in Swan Lake (SL) and Qingdao Bay (QB) in northern China have the same maturation time (summer) but different germination time. To investigate this phenomenon, we further carried out reciprocal transplantation experiment and transcriptome analysis. Results revealed that differences in the seed germination time between the two sites do exist and are determined by internal molecular mechanisms as opposed to environmental factors. Furthermore, we conducted comparative transcriptome analysis of seeds at the mature and early germination stages in both locations. The results that the number of genes related to energy, hormone and cell changes was higher in SL than in QB, could account for that the dormancy depth of seeds in SL was deeper than that in QB; consequently, the seeds in SL needed to mobilize more related genes to break dormancy and start germination. The results could have important practical implications for seagrass meadow restoration via seeds and provide in-depth and comprehensive data for understanding the molecular mechanisms related to seagrass seed germination.

Seed germination responses to salinity for three rare wetland plants of spring-fed arid systems

Spring-fed wetlands within arid systems host unique species of plants, many of which are threatened due to the vulnerability of these ecosystems. Increased salinity and drier hydrologic regimes due to anthropogenic activities threaten these systems. Furthermore, limited knowledge regarding key life history traits of species jeopardize the restoration and management of their rare plants. Here, we evaluated key aspects of the seed ecophysiology of three rare plants of the Southwestern United States: Helianthus paradoxus (Pecos sunflower), Cirsium wrightii (Wright's marsh thistle), and Agalinis calycina (Leoncita false-foxglove). We examined seed dormancy break under controlled conditions and evaluated the effects of field-derived salinity gradients on seed dormancy break and germination. Seeds of C. wrightii were nondormant at dispersal, germination was high (>70%) under all treatments and was not affected by the tested salinities. Germination in H. paradoxus was high (>70%) following cold stratification, but increasing salinities reduced germination. A. calycina seeds required cold stratification, but germination was low (<50%) under all tested treatments and increasing salinities during incubation had the greatest negative effects in this species. Our findings contribute to the restoration of rare wetland plants within spring-fed arid marshes susceptible to groundwater declines and human-induced salinization.

Seed Dormancy Class and Ecophysiological Features of Veronicastrum sibiricum (L.) Pennell (Scrophulariaceae) Native to the Korea Peninsula.

Veronicastrum sibiricum is a perennial species distributed in Korea, Japan, Manchuria, China, and Siberia. This study aimed to determine the requirements for germination and dormancy break of V. sibiricum seeds and to classify the kind of seed dormancy. Additionally, its class of dormancy was compared with other Veronicastrum and Veronica species. V. sibiricum seeds were permeable to water and had a mature embryo during seed dispersal. In field conditions, germination was prevented by physiological dormancy, which was, however, relieved by March of the next year, allowing the start of germination when suitable environmental conditions occurred. In laboratory experiments, the seeds treated with 0, 2, 4, 8, and 12 weeks of cold stratification (4 °C) germinated to 0, 79, 75, 72, and 66%, respectively. After the GA3 treatment (2.887 mM), ≥90% of the seeds germinated during the four incubation weeks at 20/10 °C. Thus, 2.887 mM GA3 and at least two weeks at 4 °C were effective in breaking physiological dormancy and initiating germination. Therefore, the V. sibiricum seeds showed non-deep physiological dormancy (PD). Previous research, which determined seed dormancy classes, revealed that Veronica taxa have PD, morphological (MD), or morphophysiological seed dormancy (MPD). The differences in the seed dormancy classes in the Veronicastrum-Veronica clade suggested that seed dormancy traits had diverged. The results provide important data for the evolutionary ecological studies of seed dormancy and seed-based mass propagation of V. sibiricum.

The sweet and musky scent of home: biogenic ethylene fine-tunes seed germination in wetlands.

Wetlands are known for comparatively high production of biogenic ethylene from decomposed sediment. Because the gas has various well-documented effects on seed physiology, we asked whether it can be a vital seed germination cue for wetland plants. Specifically, we explored whether ethylene plays an ecological role in (i) breaking/weakening seed dormancy, (ii) broadening the germination niche width, (iii) promoting germination speed or (iv) altering the germination requirements of six plant species with different occurrence along a hydroperiod gradient. In a factorial experiment, both ethylene-treated and untreated seeds were incubated in combinations of temperature (constant versus fluctuating), illumination (light versus darkness) and oxygen (aerobic versus hypoxia) with and without cold stratification. Our results revealed seed exposure to ethylene did not weaken or break dormancy without cold stratification treatment. However, ethylene helped to broaden the germination niche width, increased overall germination percentage and speed of cold-stratified (non-dormant) seeds. This indicates that ethylene helps those seeds that lost dormancy (non-dormant) to sense favourable water-saturated versus flooded substrate depending on their requirement for aerobic versus hypoxic conditions to trigger germination. We conclude that ethylene does not interfere directly with the dormancy-breaking process in autumn-dispersed seeds that are naturally cold-stratified in winter and germinate in spring/summer. However, ethylene plays a crucial ecological role as a 'flood detector' for different wetland plant communities (reed, mudflat, swamp, shallow water) to synchronize germination of non-dormant seeds in the most suitable habitat at the right time.

Germinability and Seedling Growth Performance of Chilli (Capsicum annuum) Seeds in Response to Different Gibberellic Acid Concentrations Pre-Treatment

Chilli seeds are always associated with physiological dormancy characteristics or endogenous dormancy that has affected their germination potential. Problems noticed on the low seed germination rate, vigour growth, further may lead to the poor seedling growth pattern of chilli crop production. Gibberellic Acid (GA3) which is usually used as a treatment solution is not a new advent of seed dormancy breaking methods for chilli. But, looking forwards to a better GA3 concentration is still needed for the discovery of this treatment potential effect on chilli seed germinability and seedling growth. Thus, this study aimed to evaluate the effect of different GA3 concentrations on seed emergence and seedling growth performance in chilli. In this experiment, chilli seeds were imbibed with 25 mg/L, 75 mg/L and 125 mg/L concentration of GA3 with three replications each; for 24 hours at room temperature (32±4°C) and the untreated seeds as a control. The data collection on final germination percentage was taken daily for 21 days after sowing. While the 15 germinated seeds were directly planted on the 5 polybags arranged in the net house of Junaidy Jonik Farm, Sabah, Malaysia. The experiment was arranged in a completely randomized design with three replications. Data were subjected to analysis of variance with SAS version 9.4 and the significant means were separated by the least significant difference test at P&lt;0.05. Significant differences were observed in the seed germinability measured; germination rate index (GRI), mean germination time (MGT) and final germination percentage (FGP), as well as on seedling vigour index (SVI) between treated and control seeds. Conversely, plant height, number of internodes, number of leaves and fresh weight of seedlings showed no significant differences among treatments. It was concluded that the use of GA3 was able to enhance chilli seeds germinability and could display a better SVI than the control. It is recommended to use GA3 treatment at 25 mg/L of concentration, as it may give an advantage to both economic and biological importance in producing higher germinability and seedling growth performance in chilli.

Overcoming dormancy in seeds of Dietes bicolor (Steud.) Sweet ex Klatt

Abstract Seminiferous propagation of Dietes bicolor is hindered by the probable physical and/or morphophysiological dormancy. The objective was to analyze the efficacy of different methods of overcoming dormancy in D. bicolor seeds to determine a possible pre-germination treatment for the species. Two experiments were conducted: (I) Evaluation of the breaking of physical dormancy, in which the treatments of mechanical scarification were carried using sandpaper #100; chemical scarification with sulfuric acid (H2SO4) for 5 and 10 minutes and immersion in hot water (70 ºC), also, for 5 and 10 minutes, were evaluated. The intact seed was considered a control. (II) Evaluation of morphophysiological dormancy, in which the seeds were submitted to combined treatments of stratification of hot temperature (20-35 °C) and/or cold temperature (9 ºC), distributed in periods of 0, 1, and 2 weeks, totalizing 9 treatments. In both experiments, germination percentage (G), germination speed index (GSI), and first count (FC) were determined, using a randomized block design, and evaluated by the Scott-Knott test at 1% and Dunnett’s test at 5%. The use of H2SO4 10 minutes induced 42% germination, 0.52 GSI, and 18% FC, but only FC was significantly different from the control. In the second trial, the treatment that spent only two weeks in hot temperatures (20-35 ºC) showed the highest germination (30%), compared to the control (G = 22%). These results provide relevant information for understanding the physiology of D. bicolor germination, in addition to contributing to the optimization of pre-germination practices for this important ornamental species.

Effects of various dormancy breaking treatment on seed germination in Sclerorhachis leptoclada boiss: an endangered medicinal plant in arid area

The aim of this study was to investigate the effect of pre-sowing treatments and temperature on Sclerorhachis leptoclada Boiss. seed germination. The following treatments were used), hot water (soaking in water at 70?C and 90?C for 5 second), Moist Chilling (Soaking in water at 2?C for 7,14 and 21day with the temperature gradually falling to room temperature), scarification by 0.2% potassium nitrate (soaking for 24 h and 48 h) and Gibberellic acid (GA: at concentrations of 250, 500 and 750 ppm soaking for 24 h and 48 h) and Distilled Water (control). The percentage of germination, germination rate, germination start (GS), mean germination time (MGT), and germination vigor index were determined as germination indices. Root and shoot length, root fresh weight, root dry weight, shoot fresh weight, shoot dry weight and seedling dry weight were evaluated as growth factors at the end of the incubation period. Second experiment was carried out to study the effect of temperature on seed germination. It was observed that both the physical and chemical scarification methods were effective in enhancing S. leptoclada seed germination and growth. The highest germination rate, percentage of germination and germination vigor index was observed with Moist Chilling (Soaking in water at 2?C for 14 day), 0.2% potassium nitrate (soaking for 48h) and GA (at concentration of 250 ppm soaking for 48h) in compare with control. Also the highest growth factors were found in Moist Chilling (Soaking in water at 2?C for 7day) treated seeds and the lowest occurred in hot water treatments. The other results showed that higher temperature was more effective lower temperature for seed germination.

Proteomic Analysis of Chrysanthemum Lateral Buds after Removing Apical Dominance Based on Label-Free Technology

Studying the genetic basis and regulatory mechanism of chrysanthemum lateral bud outgrowth is of great significance for reduction the production cost of cut chrysanthemum. To clarify the molecular basis of lateral bud elongation after removal of apical dominance in chrysanthemum, label-free quantification analysis was used to analyze the proteome changes after apical bud removal. Quantitative real-time PCR (qPCR) was used to analyze the changes in the expression of three plant hormone-related genes. A total of 440 differentially expressed proteins were successfully identified at three time points during the lateral bud elongation. The number of differentially expressed proteins in the three stages (24 h/0 h, 48 h/0 h, 48 h/24 h) were 219, 332, and 97, respectively. The difference in expressed proteins in the three comparison stages mainly involves RNA processing and modification; translation, ribosomal structure and biogenesis; Posttranslational modification, protein turnover, and chaperones. Path analysis showed that there was various physiological activities in the process of lateral bud dormancy breaking and elongation, which involved energy metabolism, biosynthesis, signal transduction and stress response in the growth process of lateral buds. qPCR indicated that the expression of cytokinin synthesis related gene was significantly increased after the removal of apical dominance, while the expression of strigolactones synthesis related gene experiences a dramatic fall to promote the development of the lateral buds. However, there was a drop before a slight increase in the expression of the auxin synthesis related gene, which was mainly due to the removal of apical dominance that led to the loss of indoleacetic acid in the main stem. However, with formation of the new apical source, indoleacetic acid can be released again.

Early Germination of Pequi Seeds and Post-Planting Seedling Performance in the Northwestern of Rio de Janeiro

With the aim of using rustic species such as pequi (Caryocar brasiliense Camb) for the rational management of degraded areas of Northwestern state of Rio de Janeiro, two experiments were sequentially conducted. In the first, seed dormancy breaking was evaluated in an experiment conducted in a completely randomized design, with six treatments, three replicates and 10 seeds per plot. Treatments were combinations of seeds with or without scarification + gibberellic acid (GA) or water. Forty-five days after sowing, 73% germination was observed in treatment mechanical scarification + GA (MS+GA). In the second experiment seedlings obtained from treatment MS + GA were evaluated in the field, concurrently with a control. At 20 and 44 months, both treatments presented the same biometric characteristics and sixty-one months after planting, flowering began. Scarification following by treatment with GA anticipates seedlings production and did not compromise the performance of these seedlings in the post-planting period.

Dormancy and evaluation of the physical-physiological quality in sweet potato [Ipomoea batatas (L.) Lam.] seeds by image analysis

Abstract: For the germination of sweet potato (Ipomoea batatas) seeds to occur, it is necessary to overcome dormancy, which makes it difficult to assess their physiological potential. The aim of this research was to define a methodology to overcome the dormancy of sweet potato seeds and use image analysis to determine their physical and physiological quality. Four genotypes of sweet potato seeds were used, namely UFVJM-5, UFVJM-22, UFVJM-38 and UFVJM-65. To overcome dormancy, chemical scarification with 98% H2SO4 for 10 and 20 minutes, hot water at 95 °C for 10 and 20 minutes, and mechanical scarification with electric grinder were tested. To evaluate the physical quality, the seeds were analyzed with X-rays and classified as intact, empty and malformed seeds. Using the GroundEye® system, the characteristics of color dominance, seed geometry and seedling length were quantified. Treatments with mechanical scarification with grinder and 98% sulfuric acid, for an immersion period of 20 minutes, are efficient to break dormancy in sweet potato seeds. There are genetic divergences between sweet potato genotypes, promoting the formation of different groups. The characteristics of color and geometry of the seeds are the ones that most contribute to genetic diversity of genotypes.

Ten years from propagule to mature plant of Butia purpurascens Glassman (Arecaceae): an endemic and endangered palm of the Brazilian Cerrado.

With occurrence mainly in the southwest Goiás, Butia purpurascens has fruits and leaves widely extracted by the regional population. Coexists with exotic grasses, frequent burnings and cattle's grazing and trampling. Young individuals are rarely seen. We aim to provide information about propagules, seedling formation and the monitoring of saplings of B. purpurascens until adults in reproductive phase. Fruits were selected, measured and benefited after harvest. Of 6,000 fruits collected 3,112 were discarded for being perforated by Conotrachelus weevils. The experiment divided 2,600 fruits into 13 treatments, distributed in ripe and immature fruits, with and without pulp. In addition, we adopt mechanical and chemical break dormancy mechanisms, different storage periods and seeding depths. After sixteen months of monitoring, the formation of eleven seedlings was obtained without distinction of any treatment. Seedlings and saplings developed slowly, taking two years to emit the first metaphyll. Over time, ten individuals died, most from fungal attack. After ten years, the only surviving palm generated two inflorescences, which produced fruit. The inefficient seedling production and the slow development of saplings, combined with the impact of the extractivism and the high rate of predation of the pyrenes, suggest the low recruitment rate of the species observed, in natural conditions. This type of data is one of the important tools for creating guidelines for the species conservation. Therefore, we suggest considering the reclassification of B. purpurascens as a Critically Endangered species in the Official List of Threatened Brazilian Species of Extinction.

Interruption of Seed Dormancy and In Vitro Germination of the Halophile Emerging Crop Suaeda edulis (Chenopodiaceae)

Suaeda edulis (Flores Olvera &amp; Noguez) is a halophile species that grows in saline environments, with concomitant difficulties to germinate and reproduce. Once a null germination under a salinity gradient or fresh water was observed, a plant-growth bioregulator (BioR) was applied to interrupt dormancy and improve germination in vitro. This BioR is composed of gibberellins and adjuvant regulators; and 12.5, 25.0, and 37.5 mg L−1 of gibberellins with immersion at 24, 48, and 72 h were assayed. Most of the normality and homoscedasticity tests were favorable, except in three of 24 cases. On the germination percentage (transformed values), the dose 25.0 mg L−1 reflected the highest values of 5.5 and 6.0 units at 48 and 72 h. For the mean germination time, the highest level of 37.5 mg L−1 at 24 h reflected the best response. For the germination rate, the best one was 25 mg L−1 at 48 h, reaching 12% per day, but for the germination speed coefficient, the best value was observed with 25.0 mg L−1 at 24 h. It was concluded that to improve germination of S. edulis seeds, it is necessary to assess a dose-gradient of gibberellins, starting at 25.0 mg L−1, with higher values to break dormancy.

TEKNOLOGI ULTRAFINE BUBBLES UNTUK PEMATAHAN DORMANSI BENIH CENDANA (Santalum album L.)

Sandalwood seed has two types of dormancy, namely physical dormancy and physiological dormancy which is a combination of the Two-part is called morphophysiological dormancy. There is for breaks dormancy in sandalwood for earlier embryo maturation and elongation also it has hard and impermeable skin. Its structure consists of layers of thick-walled palisade-like cells especially on the outermost surface and the inside has a waxy coating and curse material. The objective of this study was to break of seed dormancy with technology Ultrafine Bubbles (UFB) on the morphophysiological dormancy on sandalwood seeds. The experiments used a randomized complete block designed (RCBD) with 3 replications. The data were analyzed using ANOVA and will be continued using the DMRT test at the 5% level. The research was conducted from February - March 0f 2020. The results showed that immersion using UFB water with oxygen 20 ppm or either UFB free oxygen for 24 and 48 hours combined with physical scarification and chemical scarification could accelerate germination in 13 days after germination (appeared radicle), percentage of growth speed (GS) is 4.67%, maximum growth (MG) in 21 days after sowing is 66.67% with normal sprouts 2-4 leaves have grown.

Germinability and Seedling Growth Performance of Chilli (Capsicum annuum) Seeds in Response to Different Gibberellic Acid Concentrations Pre-Treatment

Chilli seeds are always associated with physiological dormancy characteristics or endogenous dormancy that has affected their germination potential. Problems noticed on the low seed germination rate, vigour growth, further may lead to the poor seedling growth pattern of chilli crop production. Gibberellic Acid (GA3) which is usually used as a treatment solution is not a new advent of seed dormancy breaking methods for chilli. But, looking forwards to a better GA3 concentration is still needed for the discovery of this treatment potential effect on chilli seed germinability and seedling growth. Thus, this study aimed to evaluate the effect of different GA3 concentrations on seed emergence and seedling growth performance in chilli. In this experiment, chilli seeds were imbibed with 25 mg/L, 75 mg/L and 125 mg/L concentration of GA3 with three replications each; for 24 hours at room temperature (32±4°C) and the untreated seeds as a control. The data collection on final germination percentage was taken daily for 21 days after sowing. While the 15 germinated seeds were directly planted on the 5 polybags arranged in the net house of Junaidy Jonik Farm, Sabah, Malaysia. The experiment was arranged in a completely randomized design with three replications. Data were subjected to analysis of variance with SAS version 9.4 and the significant means were separated by the least significant difference test at P&lt;0.05. Significant differences were observed in the seed germinability measured; germination rate index (GRI), mean germination time (MGT) and final germination percentage (FGP), as well as on seedling vigour index (SVI) between treated and control seeds. Conversely, plant height, number of internodes, number of leaves and fresh weight of seedlings showed no significant differences among treatments. It was concluded that the use of GA3 was able to enhance chilli seeds germinability and could display a better SVI than the control. It is recommended to use GA3 treatment at 25 mg/L of concentration, as it may give an advantage to both economic and biological importance in producing higher germinability and seedling growth performance in chilli.

Experimental Warming Hastens Physical Dormancy Break and Germination in Tropical Fabaceae.

Climate warming may threaten the germination strategies of many plants that are uniquely adapted to today’s climate. For instance, species that employ physical dormancy (PY) – the production of seeds that are impermeable to water until high temperatures break them, consequently synchronizing germination with favorable growing conditions – may find that their seeds germinate during unfavorable or potentially fatal periods if threshold temperatures are reached earlier in the year. To explore this, we subjected the seeds of five species with physical dormancy (from the genera Abrus, Bauhinia, Cassia, Albizia, and Acacia) to “mild” (+2°C) and “extreme” (+4°C) future warming scenarios and documented their germination over 2 years relative to a control treatment. Under current climatic conditions, a proportion of seeds from all five species remained dormant in the soil for 2 years. A mild warming of 2°C had little to no effect on the germination of four of the five study species. Contrastingly, an extreme warming of 4°C dramatically increased germination in all five species within the first year, indicating a reduction in their ability to persist in the soil long-term. Cassia fistula was particularly susceptible to warming, exhibiting a similar increase in germination under both mild and extreme warming relative to control. Our findings suggest that climate warming in the tropics may cause the seeds of species that rely on physical dormancy to stagger the risk of unsuccessful germination across years to leave soil seed banks prematurely – the long-term implications of which remain unknown.

Potassium Nitrate Treatment Is Associated with Modulation of Seed Water Uptake, Antioxidative Metabolism and Phytohormone Levels of Pea Seedlings

(1) Background: Seed treatment with potassium nitrate (KNO3) has been associated with dormancy breaking, improved germination and enhanced seedling growth and uniformity in a variety of plant species. However, the KNO3 effect seems to be dependent on plant species and treatment conditions. (2) Methods: We describe the effect of incubation of dry pea seeds with different KNO3 concentration on water uptake kinetic, early seedling growth, antioxidant metabolism and hormone profile in pea seedlings. (3) Results: Low (0.25 mM) KNO3 levels increased seedling water uptake and growth, whereas high (40 mM) levels decreased seedling growth. KNO3 treatment differentially affected the antioxidant defences. Low KNO3 levels maintained the activity of antioxidant enzymes, while high levels reduced the activity of H2O2-scavenging enzymes. KNO3 induced a progressive decline in ascorbate levels and reduced (GSH) and oxidised (GSSG) glutathione. Low KNO3 levels strongly increased GA1 and decreased ABA in both seedlings and cotyledons, resulting in a decline in the ABA/GAs ratio. (4) Conclusions: Pea seed treatment with a low KNO3 level promoted early seedling growth. In this process, an interaction among KNO3, antioxidant defences and ABA/GAs ratio is proposed.

First report of Ophiosphaerella narmari causing spring dead spot of hybrid bermudagrass in China.

Hybrid bermudagrass (Cynodon dactylon×C. transvaalensis) is widely used as turf in transition zone of China. Spring dead spot (SDS) is one of the most damaging diseases of hybrid bermudagrass. Symptoms of SDS appear when hybrid bermudagrass starts to break dormancy with warm temperature in early spring. The symptoms show sunken, circular or irregularly shaped, straw-colored patches, with 20 to 100 cm in diameter. The patches maintain dormant as the surrounding uninfected turfgrass resumes growth and turns green. SDS pathogens are soilborne fungi that colonize roots, stolons and rhizomes, infected roots or rhizomes become black and eventually collapse. Three species of fungi are reported to cause SDS: Ophiosphaerella herpotricha (Fr) J. Walker; O. korrae (J. Walker & A.M. Smith) Shoemaker & C.E. Babcock; or O. narmari (J. Walker & A.M. Smith) Wetzel, Hubert & Tisserat (Walker and Smith 1972; Walker 1980; Shoemaker and Babcock 1989; Wetzel et al. 1999). However, distribution of the three species may vary by geographical region (Cottrill et al. 2016). In October 2020, symptoms of SDS were observed on hybrid bermudagrass fairways of Taihu golf course in Wuxi, Jiangsu province. Root samples of SDS were collected, symptomatic roots with 3-4 cm length were cut, washed 2-3 times, surface sterilized in 0.6% NaOCl for 5 min, rinsed and blotted dry for 2 min and placed on potato dextrose agar (PDA) amended with 50 mg L-1 each of ampicillin, streptomycin sulfate and tetracycline. Plates were incubated in the dark at 25℃ for 5-7 days, Hyphae growing from the roots were transferred to new PDA plates. A total of 7 fungal isolates with morphology similar to SDS pathogens were obtained (Tredway et al. 2009). The genomic DNA was extracted from 2 of them (7-41, 8-6) and amplified with universal primers ITS5 and ITS4 (White et al. 1990). PCR products were sequenced (deposited as MW536995 and MW536994 in GenBank, not available yet) and showed 99.79% similarity to O. narmari (KP690979). Pathogenicity tests were performed on 'Tifdwarf' hybrid bermudagrass (9-week-old in 5 × 20 cm Cone-Tainers containing a sand and nutrition substrate mixture). Eight oat seeds infested with O. narmari were inserted 5 cm below the soil surface in the root zone of hybrid bermudagrass. The inoculated turfgrass grew for five weeks in the growth chamber with a 12-h day/night cycle of 25/20°C and 90% relative humidity. A control treatment was inoculated with 8 noninfested sterile oat seeds, and each treatment was replicated 3 times. The root tissues of hybrid burmudagrass inoculated with O. narmari became black and necrotic, no symptoms were observed on the roots of noninfested plants. O. narmari was consistently reisolated from symptomatic roots, and confirmed by PCR as mentioned above. To the best of our knowledge, this is the first report of O. narmari caused spring dead spot in the transition zone of China. The identification of SDS caused by O. narmari will have important implications for the management of this root-rot species on hybrid bermudagrass.

Accounting for variability when resurrecting dormant propagules substantiates their use in eco-evolutionary studies.

There has been a steady rise in the use of dormant propagules to study biotic responses to environmental change over time. This is particularly important for organisms that strongly mediate ecosystem processes, as changes in their traits over time can provide a unique snapshot into the structure and function of ecosystems from decades to millennia in the past. Understanding sources of bias and variation is a challenge in the field of resurrection ecology, including those that arise because often‐used measurements like seed germination success are imperfect indicators of propagule viability. Using a Bayesian statistical framework, we evaluated sources of variability and tested for zero‐inflation and overdispersion in data from 13 germination trials of soil‐stored seeds of Schoenoplectus americanus, an ecosystem engineer in coastal salt marshes in the Chesapeake Bay. We hypothesized that these two model structures align with an ecological understanding of dormancy and revival: zero‐inflation could arise due to failed germinations resulting from inviability or failed attempts to break dormancy, and overdispersion could arise by failing to measure important seed traits. A model that accounted for overdispersion, but not zero‐inflation, was the best fit to our data. Tetrazolium viability tests corroborated this result: most seeds that failed to germinate did so because they were inviable, not because experimental methods failed to break their dormancy. Seed viability declined exponentially with seed age and was mediated by seed provenance and experimental conditions. Our results provide a framework for accounting for and explaining variability when estimating propagule viability from soil‐stored natural archives which is a key aspect of using dormant propagules in eco‐evolutionary studies.