Termination Of Dormancy Research Articles

THE ROLE OF CYTOKININ AND GIBBERELLIN IN POTATO TUBER SPROUTING

Potato (Solanum tuberosum L.) is a highly sensitive crop to tuber dormancy. This can be initiated by various factors, including moisture stress, high or low temperature, day length, hormonal imbalance, and heredity. Breaking of tuber dormancy is therefore important for seed potato multiplication, rapid post-harvest disease testing, and early production in the field or green house. Cytokinin (CK) and gibberellin (GA) in combination will terminate dormancy and increase sprout growth earlier than using GAs alone. And also using only CK will terminate dormancy earlier than using GAs alone, but subsequent sprout growth will be hampered. In this review, the current knowledge and possible utilization of CK and GA, which can be used for termination of dormancy and sprout growth of potato tubers, have been reviewed and discussed. The role of CK and GA to mitigate the harmful effects of endogenous and environmental stresses in potato sprouting is also examined. In addition, numerous biochemical and physiological processes principal to improved potato sprouting under the consequence of these hormones are discoursed in detail.

Physiological and molecular mechanisms associated with potato tuber dormancy.

Tuber dormancy is an important physiological trait that impacts post-harvest storage and end-use qualities of potatoes. Overall, dormancy regulation of potato tubers is a complex process driven by genetic as well as environmental factors. Elucidation of the molecular and physiological mechanisms that influence different dormancy stages of tubers has wider potato breeding and industry-relevant implications. Therefore, the primary objective of this review is to present current knowledge of the diversity in tuber dormancy traits among wild relatives of potatoes and discuss how genetic and epigenetic factors contribute to tuber dormancy. Advancements in understanding of key physiological mechanisms involved in tuber dormancy regulation, such as apical dominance, phytohormone metabolism, and oxidative stress responses, are also discussed. This review highlights the impacts of common sprout suppressors on the molecular and physiological mechanisms associated with tuber dormancy and other storage qualities. Collectively, the literature suggests that significant changes in expression of genes associated with the cell cycle, phytohormone metabolism, and oxidative stress response influence initiation, maintenance, and termination of dormancy in potato tubers. Commercial sprout suppressors mainly alter the expression of genes associated with the cell cycle and stress responses and suppress sprout growth rather than prolonging tuber dormancy.

Maternally derived variation in the early termination of dormancy in Daphnia pulex

Maternally derived variation in the early termination of dormancy in Daphnia pulex

New Insights into the Role of Alternating Temperatures and Cyanide in the ROS-Mediated Cardoon Seed Dormancy Termination

Physiological dormancy in wild cardoon (Cynara cardunculus var. sylvestris) can be terminated by achenes exposure to alternating temperatures, likely with the participation of reactive oxygen species (ROS). Cyanide is a natural compound that mediates seed dormancy removal in some plant species in association with oxidative signalling exerted by ROS. To date, no study has been conducted on the cyanide effect on ROS homeostasis during the germination of cardoon. Here, we showed that the addition of cyanide at low concentrations in dormant cardoon achenes promotes dormancy breakage at a constant temperature, speeds up germination to alternating temperatures and promotes ROS accumulation in embryonic axes of dormant achenes. The in-silico transcriptome analysis showed that the expression levels of transcripts of genes associated with ROS signalling and production, calcium signalling, gibberellins biosynthesis and cell wall loosening were significantly up-regulated at the alternating temperatures imbibition condition. In contrast, the expression of gene transcripts associated with the inhibition of germination, ABA biosynthesis and signalling were up-regulated at the constant temperature imbibition. However, no significant difference in lipid peroxidation or protein carbonylation levels was observed when achenes were imbibed at constant or alternating temperature conditions. These results suggest that dormancy termination triggered by alternating temperatures or cyanide could be mediated by ROS production and signalling in the cardoon embryonic axis, but this does not determine extensive protein carbonylation.

Yam Tuber Dormancy and Sprouting: The Role of Concentration Dynamics of Endogenous Gibberellic Acid

The role of endogenous gibberellic acid (GA ) in the regulation of yam (Dioscorea spp.) tuber 3 dormancy was investigated by determining the changes in the endogenous GA levels during 3 natural dormancy progression. Two Dioscorea rotundata cultivars ('Pona' and 'Labreko') and one Dioscorea alata cultivar ('CRI-Ahoɔdenfoɔ') used in these studies have varying dormancy duration. Endogenous GA levels determined for the yam tubers ranged from 1.53 – 3.05 mg/g dw 3 and 1.23 – 1.58 mg/g dw for 'Pona'; 1.53 – 3.40 mg/g dw and 1.25–1.57 mg/g dw for 'Labreko'; 1.48 – 3.62 mg/g dw and 1.28 – 1.60 mg/g dw for 'CRI-Ahoɔdenfoɔ', respectively, for the outer and inner portions. 'Pona' and 'Labreko' had dormancy break at 60 days after harvest (DAH), but at 90 DAH for 'CRI-Ahoɔdenfoɔ'. Generally, GA levels increased from harvest to the maximum 3 at 30 DAH, then declined to the minimum at 60 DAH before finally increasing again at 90 DAH for the outer portions of the yam tuber. For the inner portions of the tuber, GA levels rather 3 declined significantly to the minimum at 30 DAH, increased at 60 DAH and then decreased again at 90 DAH. GA levels in the outer portions of the tubers increased by 84-122%, 65-77% and 61- 3 65%, respectively, in 'CRI-Ahoɔdenfoɔ', 'Labreko' and 'Pona', but decreased in the inner portions by 19-23%, 24-26% and 26-28%. Essentially, higher amounts of endogenous gibberellins in yam tubers induced longer dormancy duration whereas lower amounts were indicative of dormancy termination and subsequent initiation of sprouting.

Modelling changing sensitivity to alternating temperatures during induction of secondary dormancy in buried Polygonum aviculare L. seeds to aid in managing seedbank behaviour

AbstractSeed dormancy is a common attribute of many weed species in temperate habitats that controls the seasonality of weed emergence from soil seedbanks. For some weed species, it is not enough to reduce seed dormancy, as germination can only proceed after exposure to dormancy termination factors (i.e. light and alternating temperatures). Sensitivity to alternating temperatures in Polygonum aviculare seeds increases during dormancy release. However, it is not known whether this sensitivity is lost during dormancy induction. The aim of this study was to investigate and quantify the changes in dormancy level of P. aviculare seeds during secondary dormancy induction, as measured by changes in sensitivity to alternating temperatures driven by the soil temperature. To achieve these objectives, seeds were stratified at 5°C until obtaining a minimum dormancy level. The seeds were then buried in pots and induced into secondary dormancy by storing them at 10, 15, 20 and 25°C for different time periods. During storage, seeds were exhumed periodically and exposed to different cycle‐doses of 10/24°C (12 h/12 h) (0, 1, 3, 5 and 15 cycles) to test germination. Our results showed that the high sensitivity to alternating temperatures achieved during primary dormancy release, decreased during secondary dormancy induction with a rate that is temperature dependent. These changes in sensitivity to alternating temperatures were quantified as a function of the accumulation of thermal time, which was calculated over a base temperature of 7.9°C. Coupling the present model with a previous one to assess changes in sensitivity to alternating temperatures during dormancy release, allowed us to develop a model for the prediction of cyclic changes in sensitivity to alternating temperature in relation to the thermal environment experienced by the seeds during burial. We present this model as a valuable tool for managing the weed seedbank through different agronomic practices.

Oxygen Consumption as a Measurement of Diapause Termination in the Korean Native Bumblebee, Bombus ignitus

Bumblebees are a commercially important pollinator of both agricultural crops and natural plants, particularly tomato, which require huge, buzzing pollinators. The artificial rearing of these bees is increasing to meet the growing demand, and breaking diapause is a critical element in this process. As the pre-diapause Bombus ignitus queen has a higher metabolic rate than that of the post-diapause B. ignitus queen, we hypothesized that there would be a difference in the oxygen consumption of the queen before and after wintering. Therefore, we measured the rate of oxygen consumption of B. ignitus queens to create a barometer for evaluating diapause termination. The O2 uptake of B. ignitus queens was 39.0 μL/㎎ wt./min just after emergence and increased rapidly from 186.3 μL/㎎ wt./min at 6 h after emergence to 354.2 μL/㎎ wt./min one day after emergence. The rates of oxygen uptake of the queens during the first 6 days after emergence raised from 354.8 μL/㎎ wt./min at one day to a maximum level of 494.7 μL/㎎ wt./min in the 5-day-old queens, which corresponds to 3.4-fold increase from that just after emergence. When evaluating the oxygen consumption of queens that are presumed to have completed hibernation in the nature, we found that the oxygen consumption was 265.1~306.2 μL/㎎ wt./min, similar to that of the queen bees in this study the first day after hibernation. Therefore, we defined the standard for termination of dormancy of B. ignitus queen bees in the range of 250~300 μL/㎎ wt./min. Furthermore, our results indicate that oxygen consumption can provide important information for the indoor rearing of B. ignitus. During the wintering period, the oxygen consumption of the B. ignitus queen bees clearly increased as time passed, and the oxygen consumption value of the queen bees sampled at the 4th month of hibernation was 195.7 μL/㎎ wt./min, which was close to the oxygen consumption value at the end of hibernation. The queen bees, which were stored at 2.5℃ for artificial wintering, showed the highest oxygen consumption value after the end of hibernation. Based on these findings, we concluded that oxygen consumption of the bumblebee can provide rare insight for artificially raising B. ignitus as a barometer for measuring diapause termination in this species.

A stratification thermal time-based model as a tool for designing efficient methodologies to overcome seed dormancy constraints to kiwifruit seedling production

Kiwifruit (Actinidia deliciosa A. Chev. C.F. Liang and A.R. Ferguson) seedling production in the nursery is usually impaired because of low seed germination resulting from primary dormancy. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification), but further incubation under fluctuating temperatures (20/30 °C) is a requirement for dormancy termination. The aim of this study was to establish functional relationships between changes in the sensitivity of the seed population to different cycle-doses of fluctuating temperature and dormancy alleviation under different times and stratification temperatures. We propose a model based on the concept of stratification thermal time to predict changes in the fraction of the seed population that would germinate as a function of the number of fluctuating temperature cycle-doses. Results showed that stratification at cool temperatures produced higher rates of change than stratification at warmer temperatures. Construction of response curves with a thermal time scale was possible because seeds that had accumulated similar stratification thermal time achieved similar germination percentages in response to cycle-doses of fluctuating temperatures. The model was tested against independent experimental data yielding good agreement between predicted and observed data. Overall, this constitutes an important tool to overcome dormancy in a way that should result in a more efficient and faster production of kiwifruit seedlings or rootstocks.

Lower Levels of Adiponectin and Its Receptor Adipor1 in the Uveal Melanomas With Monosomy-3.

PurposeAdiponectin is an insulin-sensitizing and anticarcinogenic hormone that is encoded by a gene on chromosome 3. Here, we analyzed the expression of adiponectin and its receptor Adipor1 in primary uveal melanoma (UM) with regard to the monosomy-3 status and clinical factors, as well as the physiological response of UM cells to adiponectin.MethodsImmunohistochemistry was performed on the primary UM of 34 patients. Circulating melanoma cells (CMC) were isolated by immunomagnetic enrichment. Monosomy-3 was evaluated by Immuno-FISH. Gene expression was analyzed using the RNAseq data of The Cancer Genome Atlas study. Cultures of choroidal melanocytes and UM were established from the samples of two patients. The proliferative potential of the UM cell lines Mel-270 and OMM-2.5 was determined by immunocytochemistry, immunoblotting, cell cycle analysis, nucleolar staining, and adenosine triphosphate (ATP) levels.ResultsUM with monosomy-3 exhibited a lower immunoreactivity for adiponectin and Adipor1, which was associated with monosomy-3-positive CMC and the development of extraocular growth or metastases. Both proteins were more abundant in the irradiated tumors and present in the cultured cells. Gene expression profile indicated the impairment of adiponectin-mediated signaling in the monosomy-3 tumors. Adiponectin induced a significant decline in the ATP levels, Ki-67 expression, cells in the G2/M phase, and nucleolar integrity in UM cultures.ConclusionsAdiponectin deficiency appears to enhance the metastatic potential of the UM cells with monosomy-3 and the termination of tumor dormancy. Counteracting insulin resistance and improving the serum adiponectin levels might therefore be a valuable approach to prevent or delay the UM metastases.

Plasticity in dormancy behaviour of Calanoides acutus in Antarctic coastal waters

Abstract Copepods that enter dormancy, such as Calanoides acutus, are key primary consumers in Southern Ocean food webs where they convert a portion of the seasonal phytoplankton biomass into a longer-term energetic and physiological resource as wax ester (WE) reserves. We studied the seasonal abundance and lipid profiles of pre-adult and adult C. acutus in relation to phytoplankton dynamics on the Western Antarctic Peninsula. Initiation of dormancy occurred when WE unsaturation was relatively high, and chlorophyll a (Chl a) concentrations, predominantly attributable to diatoms, were reducing. Declines in WE unsaturation during the winter may act as a dormancy timing mechanism with increased Chl a concentrations likely to promote sedimentation that results in a teleconnection between the surface and deep water inducing ascent. A late summer diatom bloom was linked to early dormancy termination of females and a second spawning event. The frequency and duration of high biomass phytoplankton blooms may have consequences for the lifespan of the iteroparous C. acutus females (either 1 or 2 years) if limited by a total of two main spawning events. Late summer recruits, generated by a second spawning event, likely benefitted from lower predation and high phytoplankton food availability. The flexibility of copepods to modulate their life-cycle strategy in response to bottom-up and top-down conditions enables individuals to optimize their probability of reproductive success in the very variable environment prevalent in the Southern Ocean.

English

Potato, an important food and nutrition security can be produced two or more times in a year in Ethiopia. It plays an important role in human diet and a source of income for smallholder farmers. However, its productivity is low owing to limited availability of planting materials and poor tuber sprouting of improved varieties. Lack of quality seed is a major problem affecting expansion of potato production.  The objective of the study is to determine effects of different methods and rates of Gibberellic acid (GA3) application on dormancy of potato variety, Gera cultivar. The experiment was conducted at Holetta Agricultural Research Center during 2008 to 2009. It consisted of five levels of GA3 as haulm application, a week prior to destruction and five levels of GA3 as a dipping treatment immediately after harvest for 24 h. Randomized Complete Block Design with three replications was used. Result revealed GA3 application affects dormancy and sprouting. Haulm application of GA3 at 750 and 1000 ppm reduced dormancy period by 24 to 27 days, respectively. Dipping treatments of 40 and 50 ppm reduced dormancy period by 18 to 20 days, respectively. The study indicated that haulm application of GA3 at 750 or 1000 ppm and dipping treatments of 40 or 50 ppm resulted in early dormancy termination, shoot emergence and increased sprout.   Key words:  Gibberellic acid, dormancy breaking, haulm application, dipping, sprout induction.

Ecology and Physiology of Dormancy in a Changing World: Introduction to a Virtual Symposium in The Biological Bulletin.

Ecology and Physiology of Dormancy in a Changing World: Introduction to a Virtual Symposium in The Biological Bulletin.

Copepod Embryonic Dormancy: "An Egg Is Not Just an Egg".

Long-lasting embryonic dormancy in invertebrates defies our understanding of what constitutes life because, for example, eggs of some copepods can delay hatching for decades or even centuries. Copepods, often millimeter-sized crustaceans, are some of the most numerous multicellular organisms on earth and are key organisms in most aquatic food webs. Some important free-living marine and estuarine species overwinter or oversummer by arrested embryogenesis in dormancy. The present contribution discusses the complex mechanisms behind embryonic dormancy by compiling knowledge from the 42 calanoid copepods from the superfamily Centropagoidea with well-described embryonic dormancy, which has been of scientific interest for decades. However, the determination of categories of copepod resting eggs-that is, diapause and quiescence, transitions between categories, the mechanisms controlling arrested development by the embryos, and how they interact with their surroundings-is not fully understood. Moreover, a clear link between the presence of the free-swimming population and their resting eggs in sediments is still not convincingly demonstrated. Here I evaluate the relative significance of potential cues driving the production of and the phase shift between egg categories. Understanding the initiation and termination of embryonic dormancy is of great importance for fundamental science-that is, population and food web ecology as well as climate science, aquaculture live feed, and ballast water research. Molecular techniques are developing rapidly, especially within health sciences, thus providing relevant tools applicable for plankton research. Here I suggest that applying molecular methods in addition to traditional physiological approaches in future research will lead to greater understanding of copepod embryonic dormancy, one of nature's wonders.

Examining population-specific hatching cues of salinity and light for Artemia franciscana

Dormancy, the physiological start of rest, occurs in numerous animal species. Many crustaceans release various types of encased embryos in a state of dormancy (e.g., cysts, ephippia, etc.). These dormant propagules require specific combinations of abiotic environmental cues to terminate dormancy. Our goal was to determine if population-specific responses to varying levels of salinity and light (photoperiod) would be present in dormancy termination of the brine shrimp, Artemia franciscana, from distinct environments. Therefore, we cross-factored different salinity concentrations and photoperiods with three A. franciscana populations collected from geographically distinct environments. To measure population-specific response, hatching success (i.e., hatching percentage) was calculated for each treatment. Our results supported the hypothesis that diverse populations of A. franciscana do have population-specific responses to photoperiod and salinity ranges, which affect hatching success (e.g., a population from Portugal showed the greatest hatching success at a salinity of 50 g/l, while populations from Spain and the U.S.A. exhibited the greatest hatching success at 25 g/l). These population-level differences should be taken into consideration during experimentation, especially when examining hatching success in this model organism.

Effect of Growth Regulators and Ethanol on Termination of Dormancy in Potato Tubers

ResumenEl principal objetivo de este estudio fue encontrar la mejor práctica para inducir la brotación en tubérculos de papa en dormancia. Comparamos dos protocolos para romper la dormancia, basados en inmersión de yemas (ojos) aislados del tubérculo, en una solución acuosa de ácido giberélico (GA3) y cinetina (estándar 1), o en una solución acuosa de GA3, tiourea, y daminozida (estándar 2), con un nuevo enfoque reportado basado en etanol. Probamos el efecto del etanol solo o en combinación con GA3 y/o cinetina en la liberación de la dormancia y en la brotación de los tubérculos de papa. Como modelo usamos dos genotipos de papa (variedades Pasat y Dorota), con dormancia larga de 5 y 10 semanas, respectivamente. Mostramos que el estándar 2 fue el tratamiento más efectivo tanto para romper la dormancia como para promover el crecimiento del brote, especialmente para la variedad Dorota, para la cual el tratamiento indujo un 82.3% de los ojos del tubérculo a brotar 28 días después del tratamiento, y a producir 93.2% de plantas emergidas después de 28 días subsecuentes de cultivo en invernadero. Para esta variedad se observó eficacia similar con la combinación de 4% de etanol con GA3 y cinetina. La misma concentración de etanol en combinación con GA3, pero sin cinetina, fue el tratamiento más eficiente para romper la dormancia de la variedad Pasat. No obstante, la diferencia entre las diversas combinaciones de tratamientos fue insignificante estadísticamente. El etanol solo o en combinación con cinetina indujo pobremente el rompimiento de la dormancia, confirmando el principal papel de GA3 en el rompimiento artificial de la dormancia. De aquí que nuestro estudio mostró que el estándar 2 es el enfoque más efectivo para el rompimiento de la dormancia por lo menos con variedades de dormancia larga.

Seed dormancy cycling and the regulation of dormancy mechanisms to time germination in variable field environments.

Many molecular mechanisms that regulate dormancy have been identified individually in controlled laboratory studies. However, little is known about how the seed employs this complex suite of mechanisms during dormancy cycling in the variable environment of the soil seed bank. Nevertheless, this behaviour is essential to ensure germination takes place in a favourable habitat and climate space, and in the correct season for the resulting plant to complete its life cycle. During their time in the soil seed bank, seeds continually adjust their dormancy status by sensing a range of environmental signals. Those related to slow seasonal change (e.g. temperature) are used for temporal sensing to determine the time of year and depth of dormancy. This alters their sensitivity to signals related to their spatial environment (e.g. light, nitrate, and water potential) that indicate that conditions are suitable for germination, and so trigger the termination of dormancy. We review work on the physiological, molecular, and ecological aspects of seed dormancy in Arabidopsis and interpret it in the context of dormancy cycling in the soil seed bank. This approach has provided new insight into the co-ordination of mechanisms and signalling networks, and the multidimensional sensing that regulates dormancy cycling in a variable environment.

Dormancy and germination responses of kiwifruit (Actinidia deliciosa) seeds to environmental cues

AbstractSeed germination of the kiwifruit (Actinidia deliciosaA. Chev. C.F. Liang and A.R. Ferguson), a deciduous, perennial vine, is low because of seed dormancy. The main purpose of this study was to characterize kiwifruit seed dormancy and germination in response to environmental factors such as temperature and light. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification) of at least 3 weeks at 2 or 5°C. Alleviation of dormancy is accomplished by incubation at fluctuating temperatures (20/30°C). A red light pulse did not affect germination, whereas a far-red light pulse strongly inhibited germination. This inhibition was readily reverted by a second pulse of red light, indicating that phytochromes are also involved in dormancy alleviation. Although seed germination was inhibited by the fruit pulp, the latter prevented neither perception of low temperature nor changes in the light sensitivity of the seeds. Therefore, it can be advanced that kiwifruit seeds will only germinate after dispersal if the time–temperature requirement for dormancy alleviation and fluctuating temperatures for dormancy termination are fulfilled. Perception of a closed canopy might interfere with dormancy termination.

Pericarp‐Imposed Dormancy in Sunflower: Physiological Basis, Impact on Crop Emergence, and Removal at an Industrial Scale

Sunflower (Helianthus annuus L.) achenes often display pericarp‐imposed dormancy, which is long‐lasting and causes serious problems to crop production and the seed industry. For this study we assessed an extensively used sunflower inbred line that has this type of dormancy. Our goals were (i) to determine the effect of pericarp on germination and to evaluate its impact on crop field emergence, (ii) to provide insight into the physiological basis of pericarp‐imposed dormancy by determining the effects of abscisic acid (ABA) accumulation in the embryo and the embryo sensitivity to ABA during incubation at different temperatures, (iii) to assess the effect of oxidant agents and other compounds on dormancy termination, and (iv) to evaluate the feasibility of using oxidants to remove dormancy at an industrial scale. Incubation at high temperatures (i.e., 25 to 30°C) allowed the expression of dormancy, which was imposed by the pericarp and was accompanied by an increase in embryo sensitivity to ABA, but not in ABA concentration. Treated achenes with sodium hypochlorite, or their incubation in presence of an ethylene precursor or gibberellins overcame dormancy. ABA concentration decreased during incubation when treated with sodium hypochlorite. Application of sodium hypochlorite on a commercial seed lot (i.e., washing with 3 and 7%, after additional chemicals used by the industry were applied) resulted in higher germination compared with dormant non‐treated controls. Field trials showed that pericarp‐imposed dormancy reduced crop emergence in the inbred line tested herein. However, treating achenes with sodium hypochlorite using described industrial procedures improved field emergence.

Terminating dormancy: hatching phenology of sympatric large branchiopods in Siangtian Pond, a temporary wetland in Taiwan

Large branchiopods adapt to stochastic temporary wetlands by means of rapid development and production of dormant eggs. Unhatched eggs build the egg bank that bridges the frequent unfavorable periods. Dormancy termination is complex not only in appropriate hatching times, but also in hatching fractions. We investigated the parameters of hatching phenology including the initial hatching time, hatching duration, hatching rate, and cumulative hatching rate of two sympatric large branchiopods, Branchinella kugenumaensis (Ishikawa, 1895) and Eulimnadia braueriana Ishikawa, 1895, in Siangtian Pond in northern Taiwan, to explore the hatching strategies. In the laboratory studies, substrate samples with quantified egg numbers were inundated and dehydrated periodically and repetitively until no further hatching occurred, and the according parameters were recorded and calculated. We found that for both species, the hatching time was focused early in the hydroperiod. Most larvae hatched in the early hydroperiods. Overall, E. braueriana had a higher hatching rate through hydroperiods, and a higher cumulative hatching rate (82.9%) than B. kugenuaensis (47.5%). Early and concentrated hatching in a given hydroperiod could be adaptive, leading individuals to mature before the end of hydroperiod and reducing the frequency of abortive hatching. Since the hydroperiods of Siangtian Pond were synchronous with torrential rains, to incline the hatchings toward early hydroperiods is more preferable than to spread over several hydroperiods under the predictable hydroregime. Generally, the hatching phenology of E. braueriana, i.e., the longer the hatching duration and higher hatching rate, the better the adaptation to the hydroregime of Siangtian Pond.

A framework for the interpretation of temperature effects on dormancy and germination in seed populations showing dormancy

AbstractTemperature is a key factor affecting both dormancy and germination. In non-dormant seeds, when temperature is within the thermal range permissive for germination, it just regulates germination velocity, while in seeds presenting dormancy it can also be affecting dormancy level, dormancy termination and the expression of dormancy itself. This dual effect of temperature on dormancy and germination often leads to misinterpretation of obtained germination results and confounds the analysis of temperature effects in seed populations presenting some degree of dormancy. In the present paper we discuss the effect of temperature in the regulation of dormancy level and its implications in dormancy expression, as an attempt to construct a conceptual framework that allows distinguishing between the effects of temperature on dormancy and germination. Finally, we present examples of how a better understanding of these effects could help us to interpret the mixed effects of temperature on both processes during incubation of seeds presenting dormancy.