Mobilization of seed storage proteins is crucial to high vigor in common bean seeds

ABSTRACT: Seed germination is a complex process controlled by many factors, in which physical and biochemical mechanisms are involved and the mobilization of reserves is crucial for this process to occur. Although, seed reserve mobilization is usually thought to be a post-germination process, seed reserve proteins mobilization occurs during germination. This study quantified seed proteins of bean genotypes during different hydration times, in order to understand the process of protein mobilization and whether there is relationship of this biochemical component with seed vigor. This study was conducted using seeds with different levels of vigor, genotypes with highest (13, 42, 55 and 81) and lowest (07, 23, 44, 50, IPR-88-Uirapurú and Iapar 81) physiological quality. High vigor genotypes showed greater efficiency in hydrolysis and mobilization of protein component, because they presented low globulins content in cotyledons at radicle protrusion in relation to low vigor genotypes (07, 23 and 50). The protein alpha-amylase inhibitor, observed in all genotypes, is involved with the longer time needed for radicle protrusion, according to the band intensity difference in genotypes 07, 44 and Iapar 81.

Physiology of Seed Dormancy and Germination-A Review

Seed dormancy is considered as an inherent property which outlines the environmental conditions in which the seed is accomplished to evolve. To better understand seed dormancy mechanisms, a series of rigorous studies examining seed metabolism in relation to gibberellin and abscisic acid have been organised. Abscisic acid is a hormone involved in the formation of primary dormancy, whereas gibberellins are a hormone involved in the induction of germination. During changes in dormancy certain variations in sensitivity can be observed. In the higher plants as the dormancy is present across all climatic regions differing responses in the environment has resulted due to adaptation. As a result of this variance, incubation is timed to avoid adverse weather conditions in order to promote reproductive growth and plant establishment. All molecular mechanisms emphasizing kernel latency initiation, conservation and improvement play a large part in the evolution and adaptation of these seeds and plants and their importance is indescribable. Together genetic and environmental factors are liable for triggering seed dormancy. For the induction of seed dormancy and besides its release the balance between the intensity of ABA plus GA remain in charge. There is a triphasic pattern of germination including imbibition i.e rapid uptake of water, enzyme activation and initiation of embryo growth resulting in the radicle protrusion. The dormancy state is regulated not only by the seed maturation environment, but it also changes over time after shedding in a way that is determined by the ambient environment.

Osmopriming with Polyethylene Glycol (PEG) for Abiotic Stress Tolerance in Germinating Crop Seeds: A Review

Abiotic stresses such as drought, extreme temperature, and salinity can negatively impact seed germination and plant growth and have become major limitations to crop production. Most crops are vulnerable to abiotic stress factors during their early growth phase, especially during seed germination and seedling emergence. Rapid crop seed germination and seedling establishment is known to provide competitive advantages over weeds and improve yields. Seed osmopriming is defined as a pre-sowing treatment in which seeds are soaked in osmotic solutions to undergo the first stage of germination, but radicle protrusion has not occurred. The process of osmopriming involves prior exposure of seeds in low-water-potential solutions. Osmopriming can generate a series of pre-germination metabolic activities, increase the antioxidant system activities, and prepare the seed for radicle protrusion. Polyethylene glycol (PEG) is a popular osmopriming agent that can alleviate the negative impacts of abiotic stresses. This review summarizes research findings on crop responses to seed priming with PEG under abiotic stresses. The challenges, limitations, and opportunities of using PEG for crop seed priming are discussed with the goal of providing insights into future research towards effective application of seed priming in crop production.

Alleviating Salinity Stress During Seed Germinating by Priming Techniques : A Review

Seed germination and seedling growth are the two critical stages for crop establishment. These stages are the most sensitive to abiotic stresses, which decreases the germination percentage and increases germination time. Due to such abiotic stress, the germination of crop fails in adverse conditions. Salinity is one of the major abiotic stress, which adversely affects almost every aspect of the plant’s physiology, biochemistry and decreases yield. Salinity is the most severe threat to agriculture and major environmental factors that limit crop growth and productivity. Various techniques have been shown to improve emergence and stand establishment under salt stress. One of the most frequently utilized technique is seed priming. The seed priming process deals with the prior exposure of abiotic stress, making a seed more resistant to future exposure. Seed priming stimulates pre-germination metabolic activities and enhances radicle protrusion. It enhances the antioxidant defense system and the repair of membranes. The process of seed priming and the mechanism of the effect of salinity on seed germination have been discussed. The physiological, biochemical, and molecular changes induced by priming leading to seed enhancement have also been covered.

Key metabolic pathways involved in seed primary physiological dormancy maintenance of Korean pine seed

ABSTRACTThe metabolic changes that occurred during either cold stratification or after-ripen treatment, and in both dormant seeds and after-ripened seeds either under the dry state or during imbibition have been extensively explored. Much less is known about those present in both dormant seeds and cold stratified seeds during the same period of incubation under favorable germination conditions. Metabolite composition was investigated in both embryo and megagametophyte of primary physiological dormant seeds (PPDS) of Pinus Koreansis collected at 0 week, 1 week, 2 weeks, 4 weeks and 6 weeks of incubation, and of cold stratified seeds with released primary physiological dormancy (RPPDS) sampled at 0 week and 1 week of incubation, seed coat rupture stage and radicle protrusion stage. Embryo contained higher levels of most metabolites compared to megagametophyte. Strong metabolic changes occurred at 1 week and 4 weeks of incubation in PPDS, with most metabolites were significantly accumulated in 4-weeks-incubated PPDS. A larger metabolic switch was found in RPPDS between 1-week-incubation and seed coat rupture stage. Especially, there was a significant major decrease in the relative levels of most phosphorylated sugars and amino acids. The carbohydrate metabolism, especially pentose phosphate pathway and tricarboxylic acid cycle were more active pathways in the embryos of 4-weeks-incubated PPDS, but the operation rate of most amino acid metabolism was lower compared to 1-week-incubated RPPDS. We suggest that a larger metabolic switch in the embryo of PPDS after 4 weeks of incubation may assist in maintaining primary dormancy.One-sentence summaryA larger metabolic switch in dormant seeds after 4 weeks of incubation under favorable conditions for germination may maintain primary physiological dormancy of Korean pine seeds.

ScreenSeed as a novel high throughput seed germination phenotyping method

A high throughput phenotyping tool for seed germination, the ScreenSeed technology, was developed with the aim of screening genotype responsiveness and chemical drugs. This technology was presently used with Arabidopsis thaliana seeds to allow characterizing seed samples germination behavior by incubating seeds in 96-well microplates under defined conditions and detecting radicle protrusion through the seed coat by automated image analysis. This study shows that this technology provides a fast procedure allowing to handle thousands of seeds without compromising repeatability or accuracy of the germination measurements. Potential biases of the experimental protocol were assessed through statistical analyses of germination kinetics. Comparison of the ScreenSeed procedure with commonly used germination tests based upon visual scoring displayed very similar germination kinetics.

Is it possible to estimate longevity through the analyses used to measure the initial physiological potential in soybean seeds?

The analysis of longevity can support decisions about the length of seed lot storage until commercialization, since this characteristic implies the maintenance of viability over time. Seed longevity is analyzed by the p50 test, which expresses the time to lose 50% of the initial viability. Seeds with high vigor and germination have greater physiological potential and, thus, a greater capacity to maintain quality throughout the storage period. However, there has been little research on the correlations between the analysis of p50 (longevity) and the tests used to measure physiological potential (germination and vigor) of lots, which can be used as a tool to make inferences about longevity using the most traditional tests. Thus, the objective of this study was to investigate which tests used to measure the potential of lots can estimate p50. To this end, germination and vigor were evaluated using traditional tests while longevity was assessed in eight soybean seed lots. Correlations and linear regression were tested for the traditional variables versus p50. It was found that the use of accelerated aging, electrical conductivity, and time to 50% radicle protrusion has high potential to estimate longevity as measured by p50.

Exogenous antioxidants on quality of cabbage seeds

During seed germination there is production of reactive oxygen species, which, in a controlled way, are important to cell signaling and protection against pathogens, but, in excess, impair germination. Therefore, the objective of this study was to assess the action of different compounds on antioxidant mechanisms and enzymatic activation in cabbage seeds. Compounds like kojic acid, thymol and tyrosol were used to imbibe the cabbage seeds together with distilled water, and a control treatment without imbibition was used as well, with subsequent assessment by means of germination test, endosperm rupture, vigor, radicle protrusion, and assessment of seedling biochemical analyses by the activity of enzymes ascorbate peroxidase, catalase, superoxide dismutase and α-amylase. Data were subjected to analysis of variance and to the LSD means comparison test. Seeds treated with tyrosol presented higher results on the rupture of the endosperm, germination and vigor, and root development increased with use antioxidants. For the activity of antioxidant enzymes in seedlings, only kojic acid showed increase in the superoxide dismutase activity. There was also a reduction in the catalase activity with the use of thymol and tyrosol compounds compared to dry-seed assessments. After tyrosol treatment, ascorbate peroxidase enzyme was not detected, and water-imbibed seeds showed higher α-amylase activity. The use of antioxidant compounds has beneficial effects on cabbage seeds, and soaking with tyrosol led to better physiological quality, with activation of antioxidant defense mechanisms during germination.

Storage of short-lived seeds of Inga vera subsp. affinis in osmotic medium

Inga vera subsp. affinis (Fabaceae) is a tree species native to riparian forests in Southeast Brazil and is key for the restoration of deforested areas. The species produce seeds that are highly recalcitrant. Extreme sensitivity to desiccation as well as vivipary are commonly observed in mature seeds, which also tend towards polyembryony. Past research has shown that typical strategies to store seeds are inapplicable to Inga vera as viability is completely lost when seeds are either dried to around 28% water content (wet basis) or stored at 5°C for a few weeks. Here, we examine the feasibility of storing the seeds under hydrated conditions but at reduced water potential. Freshly collected seeds were kept under conventional storage conditions (plastic bags in cold chamber, 5°C) and in polyethylene glycol (PEG) solutions (−1.6 and −2.4 MPa) at 10°C. Seed germination was assessed after various intervals of time, until all seeds had lost viability. Before storage, seeds attained 100% germination and produced an average of 1.8 normal seedlings per seed (due to polyembryony). Storage in PEG at −1.6 MPa maintained 90% germination (radicle protrusion) and one normal seedling per seed on average for more than 200 d. Osmotic storage likely slowed down metabolism within the seed and hence consumption of food reserves. The storage time achieved has practical applications for in situ restoration, but cannot address ex situ germplasm conservation. Extending shelf life for an additional 6 months allows tree nurseries to optimize the production of seedlings so that they can be planted during the wet season.