Development of integrated weed management strategies requires knowledge of weed emergence timing and patterns, which are regulated primarily by water and thermal requirements for seed germination. ...Laboratory experiments were conducted in fall 2017 to fall 2018 to quantify the effect of osmotic potential and temperature on germination of 44 kochia Bassia scoparia (L.) A.J. Scott populations under controlled conditions. Bassia scoparia populations were collected in fall 2016 from northern (near Huntley, MT, and Powell, WY) and southern (near Lingle, WY, and Scottsbluff, NE) regions of the U.S. Great Plains. Ten osmotic potentials from 0 to −2.1 MPa and eight constant temperatures from 4 to 26 C were evaluated. Response of B. scoparia populations to osmotic potential did not differ between the northern and southern regions. At an osmotic potential of 0 MPa, all B. scoparia populations had greater than 98% germination, and the time to achieve 50% germination (t
50) was less than 1 d. At −1.6 MPa, 25% of seeds of all B. scoparia populations germinated. Osmotic potentials of −0.85 and −1.9 MPa reduced B. scoparia germination by 10% and 90%, respectively. Regardless of temperature regime, all populations exhibited greater than 88% germination. The germination rate was highest at temperatures between 15 to 26 C and did not differ between populations from northern versus southern regions. At this temperature range, all populations had a t
50 of less than 1 d. However, at 4 C, B. scoparia populations from the northern region had a higher germination rate (5 h) and cumulative germination (7%) than populations from the southern region. Overall, these results indicate a wide range of optimum temperatures and osmotic potential requirements for B. scoparia germination.
The kiwano (Cucumis metuliferus E. Mey) is a cop of wide geographical distribution, with a significant increase in relation to marketing worldwide due not only to his life being too long at room ...temperature, as well as to the constant search market consumer for exotic products. Thus, demand and marketing of its seeds are increasing, creating the need for the establishment of state and federal standards and the development of appropriate methodologies for evaluating the quality of them. Thus, the objective of this study was to determine the methodology for the substrate, temperature and time count for the germination test on Kiwano seeds. The evaluations consisted of four substrates: paper roll, on paper, in sand and on sand at four temperatures: 20, 25 e 30°C constant and 20-30°C alternating. The effect of substrate and temperature on seed performance was evaluated using germination, speed index and mean germination time. The experiment was conducted in a completely randomized design with treatments arranged in a factorial 4 x 4 (substrates x temperatures) with four replications. The test germination in seeds of kiwano should be done on the paper roll at constant temperature of 25°C or alternating 20-30°C, with counting starting and ending in the fifth and tenth day, respectively.
Due to the expansion of the wild crop to regions with higher temperatures is important to develop cultivars adapted to high heat. The aim was to select tests for evaluating seed physiological quality ...of wild radish to estimating genetic characters in order to select cultivars adapted to high temperature conditions. Hundred of half-brothers of wild radish were subjected to germination test and vigor (first count of germination, classification of seedling vigor, accelerated aging test, germination and testing of the first count at high temperature as well as seedling emergence in field. The germination test, first count test, accelerated aging and high germination test (20-35degreesC) can be used for the selection of wild radish crop populations adapted to germination and field emergence under high temperatures.
Due to the expansion of the wild crop to regions with higher temperatures is important to develop cultivars adapted to high heat. The aim was to select tests for evaluating seed physiological quality ...of wild radish to estimating genetic characters in order to select cultivars adapted to high temperature conditions. Hundred of half-brothers of wild radish were subjected to germination test and vigor (first count of germination, classification of seedling vigor, accelerated aging test, germination and testing of the first count at high temperature as well as seedling emergence in field. The germination test, first count test, accelerated aging and high germination test (20-35degreesC) can be used for the selection of wild radish crop populations adapted to germination and field emergence under high temperatures. Key words: genetic gain, heritability, Raphanus sativus, seeds, vigor. Devido a expansao da cultura do nabo-forrageiro para regioes com temperaturas mais elevadas, torna-se de importancia o desenvolvimento de cultivares adaptadas a altas temperaturas. Neste trabalho, o objetivo foi selecionar testes de avaliacao da qualidade fisiologica de sementes nabo-forrageiro que estimam caracteres geneticos, visando a selecionar genotipos adaptados a condicoes de alta temperatura. Para isso, sementes de 100 progenies de meio-irmaos de nabo-forrageiro foram submetidas a teste de germinacao e vigor (primeira contagem de germinacao, classificacao do vigor de plantulas, teste de envelhecimento acelerado, germinacao e teste da primeira contagem a altas temperaturas), bem como emergencia de plantulas em campo. O teste de primeira contagem, germinacao, envelhecimento acelerado, primeira contagem e germinacao em alta temperatura (20-35degreesC) sao recomendados para delinear estrategias de selecao de populacoes de nabo-forrageiro adaptados a germinacao e emergencia de plantulas em campo, em condicoes de altas temperaturas. Palavras-chave: ganho genetico, herdabilidade, Raphanus sativus, sementes, vigor.
The kiwano (Cucumis metuliferus E. Mey) is a cop of wide geographical distribution, with a significant increase in relation to marketing worldwide due not only to his life being too long at room ...temperature, as well as to the constant search market consumer for exotic products. Thus, demand and marketing of its seeds are increasing, creating the need for the establishment of state and federal standards and the development of appropriate methodologies for evaluating the quality of them. Thus, the objective of this study was to determine the methodology for the substrate, temperature and time count for the germination test on Kiwano seeds. The evaluations consisted of four substrates: paper roll, on paper, in sand and on sand at four temperatures: 20, 25 e 30°C constant and 20-30°C alternating. The effect of substrate and temperature on seed performance was evaluated using germination, speed index and mean germination time. The experiment was conducted in a completely randomized design with treatments arranged in a factorial 4 x 4 (substrates x temperatures) with four replications. The test germination in seeds of kiwano should be done on the paper roll at constant temperature of 25°C or alternating 20-30°C, with counting starting and ending in the fifth and tenth day, respectively. Key words: kiwano, substrate, temperature. O kino (Cucumis metuliferusE. Mey) e uma olericola de ampla distribuicao geografica, com aumento significativo em relacao a comercializacao no mundo inteiro, devido nao so a sua vida util ser muito longa em temperatura ambiente, como tambem pela constante busca do mercado consumidor por produtos exoticos. Assim, a demanda e a comercializacao de suas sementes estao aumentando, gerando a necessidade do estabelecimento de padroes estaduais e federais e do desenvolvimento de metodologias adequadas para a avaliacao da qualidade delas. Dessa maneira, o objetivo deste trabalho foi determinar a metodologia quanto ao substrato, temperatura e tempo de contagem para o teste de germinacao em sementes de kino. As avaliacoes constaram de quatro substratos: rolo de papel, sobre papel, entre areia e sobre areia e quatro temperaturas: 20, 25 e 30°C constantes e 20-30°C alternada. O efeito dos substratos e temperaturas sobre o desempenho das sementes foi avaliado pelo teste de germinacao, indice de velocidade e tempo medio de germinacao. O experimento foi instalado em delineamento inteiramente ao acaso, com os tratamentos distribuidos em esquema fatorial 4 x 4 (substratos x temperaturas), com quatro repeticoes. O teste de germinacao em sementes de kino deve ser realizado no rolo de papel, a temperatura constante de 25°C ou alternada de 20-30°C, com a contagem inicial efinal, no quinto e decimo dia, respectivamente. Palavras-chave: kino, substrato, temperatura.
First off the mark: early seed germination Weitbrecht, Karin; Müller, Kerstin; Leubner-Metzger, Gerhard
Journal of experimental botany,
06/2011, Volume:
62, Issue:
10
Journal Article
Peer reviewed
Most plant seeds are dispersed in a dry, mature state. If these seeds are non-dormant and the environmental conditions are favourable, they will pass through the complex process of germination. In ...this review, recent progress made with state-of-the-art techniques including genome-wide gene expression analyses that provided deeper insight into the early phase of seed germination, which includes imbibition and the subsequent plateau phase of water uptake in which metabolism is reactivated, is summarized. The physiological state of a seed is determined, at least in part, by the stored mRNAs that are translated upon imbibition. Very early upon imbibition massive transcriptome changes occur, which are regulated by ambient temperature, light conditions, and plant hormones. The hormones abscisic acid and gibberellins play a major role in regulating early seed germination. The early germination phase of Arabidopsis thaliana culminates in testa rupture, which is followed by the late germination phase and endosperm rupture. An integrated view on the early phase of seed germination is provided and it is shown that it is characterized by dynamic biomechanical changes together with very early alterations in transcript, protein, and hormone levels that set the stage for the later events. Early seed germination thereby contributes to seed and seedling performance important for plant establishment in the natural and agricultural ecosystem.
Seeds often exhibit great plasticity of germination in response to environmental variability and uncertainty. The causes of this plasticity, however, remain poorly understood, and comparative ...phylogenic analyses of such plasticity are rare. Here, we analyzed a field germination dataset including 474 species exposed to three different levels of light availability, using comparative phylogenetic methods. We calculated the plasticity of germination in response to light availability (PGGP) based on the maximum germination proportion (GPmax), PGT50 based on the time required to reach 50% of GPmax, PGRGV based on the relative germination velocity (RGV), and PGTotal based on all three of these germination traits. We found that closely related species shared similar light plasticity of germination behavior. Different aspects of germination plasticity in response to light availability were related to specific traits or local environment. PGGP was associated with adult longevity and local water habitat, while PGT50 was related to seed mass and local water habitat, and PGRGV was marginally significantly related to plant height. PGTotal was significantly associated with adult longevity and water habitat. These results suggested that different aspects of germination plasticity were located at specific niche dimension, and local habitats with sufficient soil moisture induced great plasticity germination in response to light environment. As such, they can simplify our understanding of germination, promote the exploration of the general law of germination, and further increase our understanding of species diversity maintenance, adaptation, and evolution from the perspective of germination.
Summary
Seed is vital to the conservation of germplasm and plant biodiversity. Seed dormancy is an adaptive trait in numerous seed‐plant species, enabling plants to survive under stressful ...conditions. Seed dormancy is mainly controlled by abscisic acid (ABA) and gibberellin (GA) and can be classified as primary and secondary seed dormancy. The primary seed dormancy is induced by maternal ABA. Here we found that AtPER1, a seed‐specific peroxiredoxin, is involved in enhancing primary seed dormancy. Two loss‐of‐function atper1 mutants, atper1‐1 and atper1‐2, displayed suppressed primary seed dormancy accompanied with reduced ABA and increased GA contents in seeds. Furthermore, atper1 mutant seeds were insensitive to abiotic stresses during seed germination. The expression of several ABA catabolism genes (CYP707A1, CYP707A2, and CYP707A3) and GA biosynthesis genes (GA20ox1, GA20ox3, and KAO3) in atper1 mutant seeds was increased compared to wild‐type seeds. The suppressed primary seed dormancy of atper1‐1 was completely reduced by deletion of CYP707A genes. Furthermore, loss‐of‐function of AtPER1 cannot enhance the seed germination ratio of aba2‐1 or ga1‐t, suggesting that AtPER1‐enhanced primary seed dormancy is dependent on ABA and GA. Additionally, the level of reactive oxygen species (ROS) in atper1 mutant seeds was significantly higher than that in wild‐type seeds. Taken together, our results demonstrate that AtPER1 eliminates ROS to suppress ABA catabolism and GA biosynthesis, and thus improves the primary seed dormancy and make the seeds less sensitive to adverse environmental conditions.
Significance Statement
Loss‐of‐function of AtPER1 (a 1‐cysteine peroxiredoxin) enhances seed germination and reduces primary seed dormancy and seed sensitivity to adverse environment. AtPER1 suppresses the transcription of ABA catabolism genes and promotes the transcription of GA biosynthesis genes by detoxifying ROS in Arabidopsis seeds.
To investigate the role of stored and neosynthesized mRNAs in seed germination, we examined the effect of α-amanitin, a transcriptional inhibitor targeting RNA polymerase II, on the germination of ...nondormant Arabidopsis seeds. We used transparent testa mutants, of which seed coat is highly permeable, to better ascertain that the drug can reach the embryo during seed imbibition. Even with the most permeable mutant (tt2-1), germination (radicle protrusion) occurred in the absence of transcription, while subsequent seedling growth was blocked. In contrast, germination was abolished in the presence of the translational inhibitor cycloheximide. Taken together, the results highlight the role of stored proteins and mRNAs for germination in Arabidopsis and show that in this species the potential for germination is largely programmed during the seed maturation process. The α-amanitin-resistant germination exhibited characteristic features. First, this germination was strongly slowed down, indicating that de novo transcription normally allows the synthesis of factor(s) activating the germination rate. Second, the sensitivity of germination to gibberellic acid was reduced 15-fold, confirming the role of this phytohormone in germination. Third, de novo synthesis of enzymes involved in reserve mobilization and resumption of metabolic activity was repressed, thus accounting for the failure in seedling establishment. Fourth, germinating seeds can recapitulate at least part of the seed maturation program, being capable of using mRNAs stored during development. Thus, commitment to germination and plant growth requires transcription of genes allowing the imbibed seed to discriminate between mRNAs to be utilized in germination and those to be destroyed.
Plant germination ecology involves continuous interactions between changing environmental conditions and the sensitivity of seed populations to respond to those conditions at a given time. ...Ecologically meaningful parameters characterizing germination capacity (or dormancy) are needed to advance our understanding of the evolution of germination strategies within plant communities. The germination traits commonly examined (e.g., maximum germination percentage under optimal conditions) may not adequately reflect the critical ecological differences in germination behavior across species, communities, and seasons. In particular, most seeds exhibit primary dormancy at dispersal that is alleviated by exposure to dry after-ripening or to hydrated chilling to enable germination in a subsequent favorable season. Population-based threshold (PBT) models of seed germination enable quantification of patterns of germination timing using parameters based on mechanistic assumptions about the underlying germination physiology. We applied the hydrothermal time (HTT) model, a type of PBT model that integrates environmental temperature and water availability, to study germination physiology in a guild of coexisting desert annual species whose seeds were after-ripened by dry storage under different conditions. We show that HTTassumptions are valid for describing germination physiology in these species, including loss of dormancy during after-ripening. Key HTT parameters, the hydrothermal time constant (θHT) and base water potential distribution among seeds (Ψb(g)), were effective in describing changes in dormancy states and in clustering species exhibiting similar germination syndromes. θHT is an inherent species-specific trait relating to timing of germination that correlates well with long-term field germination fraction, while Ψb(g) shifts with depth of dormancy in response to after-ripening and seasonal environmental variation. Predictions based on variation among coexisting species in θHT and Ψb(g) in laboratory germination tests matched well with 25-yr observations of germination dates and fractions for the same species in natural field conditions. Seed dormancy and germination strategies, which are significant contributors to long-term species demographics under natural conditions, can be represented by readily measurable functional traits underlying variation in germination phenologies.
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