Full Germination Research Articles

Effect of Different Priming Treatments on Quality of Long-Term Stored Seeds of Apium graveolens var. rapaceum DC

In order to improve germplasm preservation of local cultivar “Friulano”, belonging to Apium graveolens var. rapaceum (Miller) Gaudin) seed germination of a seed lot, stored for prolonged time at -20°C, was assessed in comparison to that of a commercial cultivar. In order to increase the seed performance during germination, three different priming pre-treatments (hydropriming for 24 h, osmopriming for 24 h, and osmopriming for 7 days) were performed. Additionally, seed sowing was undertaken on both potting soil and Petri dish plate condition. Analysis of seed quality was estimated by measurement of germination percentage, germination energy and the time to reach the 50% of full germination (T50). The results evidenced that conservation of celeriac dried seeds of “Friulano” cultivar at -20°C for one year maintained a good level of seed germination (ranging from 38% to 53%), not statistically diverse from the that of commercial cultivar, for both short hydro- and osmopriming treatments. The germination percentage increased when primed seeds have been treated in Petri dishes (up to 70%-80%). Furthermore, osmopriming for 24 h positively affected the germination energy, similarly to that observed in commercial cultivar, being statistically higher compared to hydropriming- and prolonged osmopriming-treated samples. Accordingly, T50 in short osmopriming treated seeds was low, indicating that this treatment induced a rapid and uniform germination, being most of the seeds germinated within one week. In conclusion, these findings represent an important informative step in amelioration of ex situ conservation of a rare autochthonous horticultural cultivar in North-eastern of Italy.

In Vitro Propagation and Cryopreservation by V-Cryoplate Technique of Foeniculum Vulgare Mill = الإكثار الدقيق والحفظ باستخدام تقنية صفائح الألمنيوم لنبات الشومر البري

In this study, mass production of Foeniculum vulgare Mill was successfully achieved from seeds using in vitro propagation technique. Seeds were surface-sterilized and inoculated on the surface of hormone-free Murashige and Skoog (MS) medium until full germination. For shoot proliferation, different concentrations (0.0, 0.1, 0.6, 1.0, 1.6, 2.0) of (BA, kinetin, 2ip, and TDZ ) were used. The best results were obtained on MS medium supplemented with BA (1.6 mg/L) which gave (7.4 shoot with 3.9 cm height). Rooting was also experimented at different levels of (IBA, IAA or NAA). The highest root number (8.0) and length (3.6 cm) revealed on MS medium supplemented with 1.0 mg/L NAA. For cryopreservation of Foeniculum vulgare Mill shoot tips; a regrowth percentage up to (90 %) was obtained when shoot tips were precultured on 0.3 M sucrose for 7 days. These results pave the way to conserve and propagate this valuable medicinal plant.

Peculiarities of the Woody Plants Re-Bloom

The data of literary sources concerning the bloom of angiosperm plants and deviation in the development of a flower and inflorescence, in particular untimely flowering, was generalized; our observation results of some peculiarities of re-bloom of woody plants in the National Dendrological Park Sofiyivka of NAS of Ukraine (NDP Sofiyivka) were discussed. The flowering process was formed during a long-term evolution of a propagation system of angiosperm plants as a basis of fertilization and further fruit and seed development. As a result of vernalization and photoperiodism reactions, flowering (under regular conditions) occurs in the most favorable period for pollination and fertilization of every plant. However, various deviations, in particular, the untimely (most frequently double, sometimes threeand four-fold) flowering occurs in this perfect process of generative organ formation of angiosperm plants. An increased number of reports about re-bloom (at the end of summer at the beginning of fall) of the representatives of various woody plant species whose flowers usually blossom in May-June prompts the analysis of the available information concerning the mechanisms of flowering and the causes which lead to deviation of flowering processes. Flowering of the woody plant representatives of the collection fund of the NDP Sofiyivka was studied; statistics about re-bloom in different cities of Ukraine were monitored. The classification of re-bloom facts was carried out according to V.L. Vitkovskiy (1984). Although this classification has mostly a stated nature, it was good enough when being formulated and, with certain conditions, it can be applied nowadays. Accordingly, using this classification, abnormal cases can include facts of early summer-fall flowering and early winter flowering. A late spring flowering can be adaptive response of damaged plants to exogenous stresses, due to which the probability of sexual propagation remains. Early spring-early summer flowering is a dual-natured category which, under certain conditions, may have adaptive meaning and facilitate seminal propagation. Most cases of untimely flowering registered in NDP Sofiyivka represent a group of early summer-fall flowering, in some cases late spring flowering occurred though. Secondary flowering is usually connected with meteorological peculiarities of the year. Most frequently it is seen in very dry years, first of all, after hot and dry spring. The rebloom can have an adaptive nature in case of development seeds with full germination, moreover the immature germs of underdeveloped seeds formed from the flowers of early summer-fall flowering can be used in breeding programs.

A role for seed storage proteins in Arabidopsis seed longevity.

Proteomics approaches have been a useful tool for determining the biological roles and functions of individual proteins and identifying the molecular mechanisms that govern seed germination, vigour and viability in response to ageing. In this work the dry seed proteome of four Arabidopsis thaliana genotypes, that carry introgression fragments at the position of seed longevity quantitative trait loci and as a result display different levels of seed longevity, was investigated. Seeds at two physiological states, after-ripened seeds that had the full germination ability and aged (stored) seeds of which the germination ability was severely reduced, were compared. Aged dry seed proteomes were markedly different from the after-ripened and reflected the seed longevity level of the four genotypes, despite the fact that dry seeds are metabolically quiescent. Results confirmed the role of antioxidant systems, notably vitamin E, and indicated that protection and maintenance of the translation machinery and energy pathways are essential for seed longevity. Moreover, a new role for seed storage proteins (SSPs) was identified in dry seeds during ageing. Cruciferins (CRUs) are the most abundant SSPs in Arabidopsis and seeds of a triple mutant for three CRU isoforms (crua crub cruc) were more sensitive to artificial ageing and their seed proteins were highly oxidized compared with wild-type seeds. These results confirm that oxidation is involved in seed deterioration and that SSPs buffer the seed from oxidative stress, thus protecting important proteins required for seed germination and seedling formation.

Pericarp structure of Glebionis coronaria (L.) Cass. ex Spach (Asteraceae) cypselae controls water uptake during germination

AbstractGlebionis coronaria (L.) Cass. ex Spach is a common Mediterranean weed producing distinctive central and peripheral dormant cypselae with a hard fruit coat, which was previously hypothesized to impose physical dormancy. Analysis of water uptake in cypselae and in naked seeds showed that it preferentially takes place at the basal end of the fruit; however, seeds within an intact pericarp do not fully imbibe when compared with naked seeds. Germination was not significantly different between the two heteromorphs, and afterripening or cold stratification did not increase germination, while warm stratification at 35/20°C, as revealed by logistic regression, resulted in a significant improvement. However, loss of viability was also rapid at these high temperatures. Central and peripheral cypselae generally showed very low germination. In both heteromorphs, faster and higher germination (60–70%) was reached only after extensive scarification of pericarp tissue, and full germination was observed only after complete removal of pericarp tissue. Although the pericarp significantly reduced water uptake, no palisade layer(s) of macrosclereids could be observed. Xylem-vessel elements were found running through the basal end of the pericarp and forming the main point of water entry. We reject the hypothesis that G. coronaria cypselae have physical dormancy. Instead, water uptake and germination are impeded by: (1) directed water uptake, mainly through a pericarp-spanning channel-like structure; and (2) mechanical constraint on embryo growth exerted by the hard pericarp. The channel-like structure forms the principal system for controlling seed germination.

MICROPHENOLOGICAL PHASES OF BARLEY SEED GERMINATION: DESCRIPTION, TIME OF START AND DURATION

Purpose. The purpose of present study was to propose improved full scale of morphologically distinct phases of germinating barley seeds and on the bases of that scale to determine each phase time of start and its duration. Methods. Seeds of five spring and five winter varieties have been germinated under optimal condition от paper in plastic bags. Morphology of each seed was registered during seven 24-hour-periods (until seed full germination) with 2 hours interval. On the bases of obtained data we made the description of each phase and calculated the time of its commencement and duration. Results. New improved scale of germinating barley seeds phases, which we named “microphenological phases of seed germination” (MPPSG), is created and each phase is described. The scale consists of eight phases, both well-known (dry seed, start of seed imbibition, radicle emergence, coleoptile emergence and seedling coming-to-be) and three new phases of roots growth (Roots1 of “fork”, Roots2 of “short roots” and Roots3 or “long roots”). The time of each phase commencement and its duration were calculated. It was shown that full time of germinating seed roots growth (R1 + R2 + R3) occupies about 50 % of germination time. Practical implications. Improved scale of MPPSG of barley may be used to study processes of physiology, biochemistry, genetics and others in germinating seeds phase by phase, and then to discuss obtained data as it was process in individual barley seed. Also this MPPSG scale may be used in practical seed farming to evaluate seed lots and in plant breeding to compere barley varieties.

Reduced seed germination in Arabidopsis over-expressing SWI/SNF2 ATPase genes.

In the life of flowering plants, seed germination is a critical step to ensure survival into the next generation. Generally the seed prior to germination has been in a dormant state with a low rate of metabolism. In the transition from a dormant seed to a germinating seed, various epigenetic mechanisms play a regulatory role. Here, we demonstrate that the over-expression of chromatin remodeling ATPase genes (AtCHR12 or AtCHR23) reduced the frequency of seed germination in Arabidopsis thaliana up to 30% relative to the wild-type seeds. On the other hand, single loss-of-function mutations of the two genes did not affect seed germination. The reduction of germination in over-expressing mutants was more pronounced in stress conditions (salt or high temperature), showing the impact of the environment. Reduced germinations upon over-expression coincided with increased transcript levels of seed maturation genes and with reduced degradation of their mRNAs stored in dry seeds. Our results indicate that repression of AtCHR12/23 gene expression in germinating wild-type Arabidopsis seeds is required for full germination. This establishes a functional link between chromatin modifiers and regulatory networks towards seed maturation and germination.

EFFECT OF CALCIUM AND TWO EXTRACTS LICORICE AND SOLUAMINE TO DECREASE DAMAGE OF DROUGHT AND IMPROVING YIELD PARAMETERS OF POTATO CV. LATONA

This study was carried out at vegetables field of Horticulture and landscape department. College of Agriculture and Forestry. Mosul University. Iraq, during spring season 2010 , to investigate the effect of water stress: two levels of watering were applied, normal irrigation and exposing plants to water stress by no water supply during period of tubers formation and development (46 and 76 days after planting), calcium ion at 200 mg.L-1 concentration and two natural extracts Licorice at 3 g.L-1 and Soluamine at 2 m.L-1 in additional to control, each treatment applied three times ( first applied at full germination stage, while the second and third application were at 20 days and40 days after the first application. All treatments added by three methods of application (foliar application, adding to soil and foliar application + adding to soil). The experiment included 24 treatments which conducted in a Split – plot system within R.C.B.D Design. Each treatment was replicated three times, analysis of variance and Duncan's multiple range test at 0.05 were applied for all research data. Results obtained could be summarized as follows: Exposing potato plants to water stress caused a significant decrease in marketable yield . Application of calcium, Licorice and soluamine increased tuber 's number , plant yield, and marketable yield and reduced the drought damage on yield parameters. Application of calcium and two natural extracts (Licorice and soluamine) to the soil caused a significant increase in tubers weight, plant yield and total yield as compared to foliar application method. Generally, application of Licorice by third method under normal irrigation was the best interaction treatment

Compartment-specific pH monitoring in Bacillus subtilis using fluorescent sensor proteins: a tool to analyze the antibacterial effect of weak organic acids

The internal pH (pHi) of a living cell is one of its most important physiological parameters. To monitor the pH inside Bacillus subtilis during various stages of its life cycle, we constructed an improved version (IpHluorin) of the ratiometric, pH-sensitive fluorescent protein pHluorin by extending it at the 5′ end with the first 24 bp of comGA. The new version, which showed an approximate 40% increase in fluorescence intensity, was expressed from developmental phase-specific, native promoters of B. subtilis that are specifically active during vegetative growth on glucose (PptsG) or during sporulation (PspoIIA, PspoIIID, and PsspE). Our results show strong, compartment-specific expression of IpHluorin that allowed accurate pHi measurements of live cultures during exponential growth, early and late sporulation, spore germination, and during subsequent spore outgrowth. Dormant spores were characterized by an pHi of 6.0 ± 0.3. Upon full germination the pHi rose dependent on the medium to 7.0–7.4. The presence of sorbic acid in the germination medium inhibited a rise in the intracellular pH of germinating spores and inhibited germination. Such effects were absent when acetic was added at identical concentrations.

Comparative study of seed germination and growth of Kochia prostrata and Kochia scoparia (Chenopodiaceae) under salinity

Soils of arid regions of Central Asia contain salts of different types that may differentially affect seed germination and plant development. We studied effect of NaCl, Na 2SO 4, 2NaCl + KCl + CaCl 2 and 2Na 2SO 4+K 2SO 4+MgSO 4 on germination of Kochia prostrata and Kochia scoparia seeds under a range of concentrations from 0.5 to 5% and at two constant temperature regimes +22 °C and +6 °C. The observed salt tolerance limit of germination at constant temperature +22 °C for both species was 5–6%, while at low temperature (+6 °C) this limit was 2%. The salt tolerance of young plants (before flowering) was 3% for NaCl. Low concentrations of sulfuric and mixed salts had a stimulating effect on seed germination in K. prostrata. Despite similarity of salt-tolerance limits the studied species showed a significant difference in seed recovery ability, i.e. the ability of ungerminated, salt-soaked seeds to germinate after transfer to fresh water. K. scoparia demonstrated a full germination recovery after seed transfer to distilled water while K. prostrata showed only a partial recovery.

Infecção de sementes de trigo com Bipolaris sorokiniana pela técnica de restrição hídrica

A inoculacao de fungos fitopatogenicos em sementes pela tecnica da restricao hidrica e relativamente recente. Este trabalho objetivou avaliar o efeito de potenciais osmoticos (-0.4, -0,6 e -0.8) do substrato BDA, modificado por adicao de sacarose, em interacao com o tempo de exposicao (46, 72 e 96 h), na infecao de sementes de trigo por Bipolaris sorokiniana. Foram analisadas a eficiencia da infeccao e a inibicao da germinacao durante e apos a aplicacao dos tratamentos. De acordo com os resultados, periodos de tempo superiores a 48 horas de exposicao a colonia fungica nao foram inibitorios a germinacao completa das sementes, a qual incrementou linearmente com o aumento do tempo de contato com o inoculo fungico. A eficiencia de infeccao nao diferiu para os potenciais osmoticos e tempo de exposicao, variando de 0,53 a 0,92. No entanto, a capacidade germinativa das sementes apos os tratamentos foi significativamente reduzida apos o periodo de 48 horas de exposicao das sementes ao substrato modificado contendo a cultura fungica.

GR24, a synthetic analog of strigolactones, stimulates the mitosis and growth of the arbuscular mycorrhizal fungus Gigaspora rosea by boosting its energy metabolism.

Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that participate in a highly beneficial root symbiosis with 80% of land plants. Strigolactones are trace molecules in plant root exudates that are perceived by AM fungi at subnanomolar concentrations. Within just a few hours, they were shown to stimulate fungal mitochondria, spore germination, and branching of germinating hyphae. In this study we show that treatment of Gigaspora rosea with a strigolactone analog (GR24) causes a rapid increase in the NADH concentration, the NADH dehydrogenase activity, and the ATP content of the fungal cell. This fully and rapidly (within minutes) activated oxidative metabolism does not require new gene expression. Up-regulation of the genes involved in mitochondrial metabolism and hyphal growth, and stimulation of the fungal mitotic activity, take place several days after this initial boost to the cellular energy of the fungus. Such a rapid and powerful action of GR24 on G. rosea cells suggests that strigolactones are important plant signals involved in switching AM fungi toward full germination and a presymbiotic state.

New Roles of Phytochromes during Seed Germination

Among the most important environmental sensors in plants are the phytochromes, members of a duplicated‐gene family of photoreceptors. We characterized the functional diversification of this gene family with respect to a single ecologically important and highly environmentally sensitive process—germination—and thereby addressed the consequence of gene duplication in the evolution of environmental sensitivity. We exposed single and multiple mutants of different phytochromes of Arabidopsis thaliana to dormancy‐breaking or dormancy‐inducing treatments that resemble different seasonal environmental conditions, and we recorded their germination responses. Much redundancy of function occurred, but an impressive degree of functional diversification was also apparent. Specifically, PHYB was an important contributor to germination when seeds did not receive low‐temperature imbibition. It interacted nonadditively with PHYA, whose contribution to germination was redundant to that of PHYB and most apparent when seeds experienced high followed by low temperatures. We also determined that PHYD was necessary for full germination when seeds were exposed to a high temperature during imbibition. PHYE appears to contribute redundantly to germination, except when seeds experienced high followed by low temperatures. Finally, we found new evidence that PHYA and possibly PHYD redundantly contribute to the suppression of germination. The diversification of activities of all these phytochromes during this one process of germination suggests that they all have a combined function in the regulation of germination responses to complex seasonal conditions and that gene duplication can contribute to the evolution of precise responses to variable environments.

AN IMPROVED METHOD FOR BREAKING DORMANCY IN SEEDS OF SESBANIA SESBAN

SUMMARYDormancy in seeds of Sesbania sesban is caused by a water-impermeable seed coat (hard seeds or hardseededness). A two-phase pretreatment technique was developed for breaking seed dormancy and was validated using different accessions and seed lots. Seeds were first soaked in water at 80 °C for 8 min and prepared for the germination test. Ungerminated hard seeds at the first count (after four days incubation) during the germination test were then subjected to a second treatment by mechanically scarifying the seed coat. The effects of water temperature and variation in initial hardseededness and viability among and within accessions were also investigated. The optimum water temperature, allowing maximum seed germination without increasing the percentage of abnormal seedling/dead seeds was 80 °C. The mean percentage of hard seeds across 30 seed lots of six accessions was reduced to 26% after phase 1 and to 0% after phase 2. In addition, full germination occurred within only 10 days for treated seeds while germination in untreated seeds had reached only 48% after 14 days. Significant differences existed among the seed lots within the accessions (p > 0.05) for the percentage of initial hard seed and for the effects of treatments on breaking seed dormancy. The two-phase technique developed was validated using over 1000 seed lots of S. sesban, and it was found to be a rapid and cost-effective method for breaking hard seed dormancy with potential for wider use for hard-seeded legumes.

Cytokinins and urea derivatives stimulate seed germination in Lotus corniculatus L.

We studied the effects of various cytokinins and urea derivatives on germination of aged seeds of in Lotus corniculatus L. The following substances were applied: N6-isoprenoid cytokinins (isopentenyl adenine and zeatin), adenine sulfate, N6-aromatic cytokinins (kinetin, benzyladenine) and their N9-ribosides, N-benzyl-9-(2- tetrahydropyranyl)adenine, and urea derivatives (diphenylurea, thidiazuron, and chloro-pyridyl phenylurea). With the exception of adenine sulfate, all cytokinins increased the percentage of seed germination up to twofold, depending on their kind and concentration. It is concluded that cytokinins may be among the missing factors in aged seeds of L. corniculatus contributing to the implementation of their full germination potential. They could be used to improve germination of both freshly harvested and aged seed samples, if necessary. .

Seed dormancy and germination in the summer annual Galeopsis speciosa

SummaryThis study examined germination and dormancy in Galeopsis speciosa (Lamiaceae), a common summer annual weed in cold‐temperate areas. Seeds collected in southern Sweden were subjected to several experiments. The seeds were dormant at maturity. Seeds sown outdoors after collection produced a small number of seedlings that emerged early in the spring. After long cold stratification or stratification outdoors over two winters, the maximum germination was 40–50%; germination occurring over a wide range of temperatures. Warm stratification preceding cold stratification had no effect on germination, but repeated warm and cold periods seemed to promote germination. Gibberellic acid (GA) stimulated germination, but full germination was only achieved after more than 2 months of incubation at the most suitable temperature regime tested. Excised embryos grew and developed into normal seedlings. With these results, the species does not fit into the currently used system for seed dormancy classifications. The response to GA and the growth of excised embryos indicate non‐deep or intermediate physiological dormancy, but dormancy alleviation by stratification was not in line with the guiding principles for these classifications. Galeopsis speciosa has a strong dormancy that is sufficiently alleviated during the winter to allow germination of only part of a seed batch each year; hence a stepwise germination pattern occurs over a period of several years.

Phytic acid mobilization is an early response to chilling of the embryonic axes from dormant oilseed of hazel (Corylus avellana)

Dormancy of hazel (Corylus avellana L.) seeds is alleviated by a chilling treatment during which cytological, hormonal, and biochemical changes occur. Phytic acid and phosphate mobilization have been examined during this treatment. Phytic acid accounted for 0.7% and up to 3.2% of dry weight in axiferous and cotyledonary tissue, respectively. Phytic acid levels in embryonic axes were reduced by 60% within the first 3 weeks of chilling, with little subsequent change, in contrast to warm-imbibed tissue where levels did not change significantly. In cotyledons, phytic acid was mobilized to a lesser extent. Phosphate levels expressed on a fresh weight basis remained almost unaltered suggesting either the operation of a homeostatic mechanism for intracellular concentration or rapid utilization due to active metabolism. Phytase activity increased during stratification in both axiferous and cotyledonary tissue. The initial rise observed was associated with dormancy alleviation, since it occurred before the realization of full germination potential by the seeds and not in warm-imbibed tissue. Protein bodies were isolated from hazel seeds by non-aqueous density gradients. Phytase activity was closely associated with the purified organelles, where phytic acid was located by light microscopy. Overall, these findings suggest that phytic acid mobilization by phytase and previously described processes associated with protein bodies, such as considerable proteolysis, are early participants in the plethora of events leading to seed dormancy relief and germination in hazel.

Quantitative and qualitative changes in seed quality during seed developmemnt and maturation in pea (Pisum sativum L.)

Full germination capacity and vigour cannot be attained until seeds rench physiological maturity. This study was designed to assess the quantitative changes in seed quality of pea (Pisum sativum L.) during development and maturation and to fix the physiological maturity stage. A field trial was conducted with pea ev. 'Bonneville' and seeds were harvested in 7 days interval from the starting of flowering and assessed for quality parameters in laboratory. Seed dry weight attains maximum at 49 DAA which is being concluded as the physiological maturity stage. Seed moisture content at this stage was 30%. The onset of ability to germinate occured at 21 DAA. Maximum seedling dry weight and vigour index occurred at 49 DAA. Electrical conductivity and free amino acid reduced as maturation of seed advanced but the seed protein content found to be increased.

Onset of germinability, desiccation tolerance and hardseededness in developing seeds of Peltophorum pterocarpum (DC) K. Heyne (Caesalpinioideae)

In the hot and dry conditions in which seeds of the tree legume Peltophorum pterocarpum develop and mature in Vietnam, seed moisture content declined rapidly on the mother plant from 87% at 42 d after flowering (DAF) to 15% at 70 DAF. Dry weight of the pods attained a maximum value at about 42 DAF, but seed mass maturity (i.e. the end of the seed-filling phase) occurred at about 62 DAF, at which time seed moisture content was about 45–48%. The onset of the ability of freshly collected seeds to germinate (in 63-d tests at 28–34°C) occurred at 42 DAF, i.e. about 20 d before mass maturity. Full germination (98%) was attained at 70 DAF, i.e. at about 8 d after mass maturity. Thereafter, germination of fresh seeds declined, due to the imposition of a hard seed coat. Tolerance of desiccation to 10% moisture content was first detected at 56 DAF and was complete within the seed population by 84 DAF, i.e. about 22 d after mass maturity. Hardseededness began to be induced when seeds were dried to about 15% moisture content and below, with a negative logarithmic relation between hardseededness and moisture content below this value.

Release of reactive oxygen intermediates (superoxide radicals, hydrogen peroxide, and hydroxyl radicals) and peroxidase in germinating radish seeds controlled by light, gibberellin, and abscisic acid.

Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA3) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during germination, utilizing the apoplastic oxidation of 2',7'-dichlorofluorescin to fluorescent 2',7'-dichlorofluorescein as an in vivo assay. Germination in darkness is accompanied by a steep rise in ROI release originating from the seed coat (living aleurone layer) as well as the embryo. At the same time as the inhibition of germination, far-red light and ABA inhibit ROI release in both seed parts and GA3 reverses this inhibition when initiating germination under far-red light. During the later stage of germination the seed coat also releases peroxidase with a time course affected by far-red light, ABA, and GA3. The participation of superoxide radicals, hydrogen peroxide, and hydroxyl radicals in ROI metabolism was demonstrated with specific in vivo assays. ROI production by germinating seeds represents an active, developmentally controlled physiological function, presumably for protecting the emerging seedling against attack by pathogens.