Ethylene In Germination Research Articles

Role of ethylene in germination and seedling growth of littleseed canarygrass (Phalaris minor Retz.)

Littleseed canarygrass is a major weed of wheat in rice–wheat cropping system of North-West India. The present study was conducted to study the role of ethylene in germination ecology and seedling growth of littleseed canarygrass and wheat using cobalt chloride (inhibitor of ethylene synthesis) and ethephon (ethylene source). Cobalt chloride at concentrations ≥0.1 mM caused significant reduction in germination (%), germination index and increased the mean germination time of littleseed canarygrass, whereas wheat seeds exhibited significant decrease in germination (%) at cobalt chloride concentrations ≥0.5 mM. Cobalt chloride at higher concentrations significantly reduced the seedling growth of littleseed canarygrass and wheat with more pronounced effect on root length as compared to shoot length. It also significantly increased the membrane leakage and soluble sugar content of seedlings of both species with concomitant decrease in chlorophyll and protein content. Ethephon at 0.1 and 1 mM concentrations significantly increased the germination (%), speed of germination with concomitant decrease in mean germination time as compared to control. Ethephon concentrations 0.1 and 1 mM had no effect on membrane leakage, total soluble sugars and protein content but increased the chlorophyll content in seedlings of both species. Seed dormancy of littleseed canarygrass induced by higher concentrations of cobalt chloride, i.e., 2.5 and 5 mM could also be overcome by treatment with 1 mM ethephon, confirming the role of ethylene in germination of this weed.

Carrot seed germination and ethylene production at high temperature in response to seed osmopriming

ABSTRACT Carrot ( Daucus carota ) seed germination can be erratic or reduced under high temperatures above 35oC.Priming circumvents seed thermoinhibition in several crops, including carrot. The involvement of ethylene in germination at supra-optimal temperatures has been reported in other species, but its role in carrot seed germination has not been examined. The main objective of this study was to determine whether priming-mediated improvement in carrot seed germination at high temperature was associated with increased ethylene production. Seeds of two tropical carrot genotypes (‘Alvorada’ and ’Brasilia’) were incubated over a range of temperatures. ‘Brasilia’ seeds were primed for 72 hours in aerated PEG solutions at 15oC under light conditions and germination tested at 20 and 35oC. Seeds of a thermosensitive genotype ‘Arrowhead’ were primed for 0, 4, 8 and 12 days in aerated PEG solutions at 15oC under light conditions. Seeds were incubated at 20 and 35oC, and ethylene production was measured immediately before visible radicle protrusion. Temperatures above 30⁰C decreased seed germination percentage of ‘Alvorada’ and ‘Brasilia’. Priming increased ‘Brasilia’ seed germination at 35oC. ‘Arrowhead’ germinated 96% at 20oC, and 13% at 35oC. Seed germination and ethylene production in a ‘Arrowhead’, a thermosensitive genotype increased in response to increased duration of primimng. The results suggest that seed priming circumvents thermoinhibition of carrot seed germination by increasing ethylene production at high temperatures. Keywords: Daucus carota L., thermotolerance, stand establishment, vigor, cultivars.

Carrot seed germination and ethylene production at high temperature in response to seed osmopriming

Carrot (Daucus carota) seed germination can be erratic or reduced under temperatures above 35ºC. Priming circumvents seed thermoinhibition in several crops, including carrot. The involvement of ethylene in germination at supra-optimal temperatures has been reported in other species, but its role in carrot seed germination has not been examined. The objective of this study was to determine whether priming-mediated improvement in carrot seed germination at high temperature was associated with increased ethylene production. Seeds of two tropical carrot genotypes (Alvorada and Brasília) were incubated over a range of temperatures. 'Brasilia' seeds were primed for 72 hours in aerated PEG solution at 15ºC under light conditions and germination tested at 20 and 35ºC. Seeds of a thermosensitive genotype 'Arrowhead' were primed for 0, 4, 8 and 12 days in aerated PEG 6000 solutions at 15ºC under light conditions. Seeds were incubated at 20 and 35ºC, and ethylene production was measured immediately before visible primary root protrusion. Temperatures above 30ºC decreased seed germination percentage of 'Alvorada' and 'Brasilia'. Priming increased 'Brasilia' seed germination at 35ºC. 'Arrowhead' germinated 96% at 20ºC, and 13% at 35ºC. Seed germination and ethylene production of 'Arrowhead', a thermosensitive genotype, increased in response to increased duration of priming. The results suggest that seed priming circumvents thermoinhibition of carrot seed germination by increasing ethylene production at high temperatures.

Ethylene and lettuce seed germination

Ethylene can stimulate seed germination and overcome dormancy in many species. For instance, the inhibitory effect of high temperature on lettuce seed germination can be overcome by exogenous ethylene. Involvement of ethylene in seed germination is a widely accepted fact, but the mechanistic details are poorly understood. A critical factor in ethylene studies is the response of seed germination properties to various ethylene inhibitors. Lettuce seed has been used as a model to study the role of ethylene in seed germination at high temperature. The role of ethylene in germination is not known but either ethylene evolution or addition of 1-aminocyclopropane-1-carboxilic acid (ACC) have been associated with increased activity of endo-beta-mannanase, a cell-wall enzyme that weakens the endosperm and allows lettuce seed to germinate at high temperature. This review describes some results on seed germination studies in response to ethylene and its possible role in promoting germination at high temperature.

Ethylene in seed formation and germination

AbstractAbstract In seed formation the role of ethylene has received little attention. The data available on zygotic embryogenesis suggest an association of the ethylene biosynthetic pathway and seed maturation. Over the course of dicot embryogenesis, ACC-oxidase mRNA can be expressed in the cotyledons and embryonic axis. However, as maturation proceeds, cotyledonary ACC-oxidase expression disappears. In some seeds that develop primary dormancy, ethylene synthesis can be among the prerequisites for breaking dormancy. Moreover, the persistence of dormancy may be related to the difficulty of the embryonic axis to produce the necessary ethylene levels or to low tissue sensitivity. The use of inhibitors of ethylene biosynthesis or its action has provided data implicating an ethylene requirement for seed dormancy or germination in some species. However, the role of ethylene in germination remains controversial. Some authors hold that gas production is a consequence of the germination process, while others contend that ethylene production is a requirement for germination. Furthermore, among seeds that require ethylene, some are extremely sensitive to the gas, while others require relatively high levels to trigger germination. Recent studies withXanthium pennsylvanicumseeds suggest that β-cyanoalanine-synthase is involved in ethylene-dependent germination. In addition, regulation of the partitioning ofS-adenosyl-L-methionine (AdoMet) between the ethylene vs polyamine biosynthetic pathways may be a way of controlling germination in some seeds. Such regulation may also apply to the reversal of seed thermoinhibition, which can occur when polyamine synthesis is inhibited, thereby strongly channelling AdoMet towards ethylene. The biological models and approaches that may shed additional light on the role of ethylene during seed germination are presented.

Role of Ethylene and Short-Chain Saturated Fatty Acids in the Smoke-Stimulated Germination of Cyclopia Seed

Summary The seeds of both Cyclopia intermedia and Cyclopia subternata exhibited a seed coat imposed dormancy. However, seeds of the former species also exhibited an embryo dormancy which could be broken by exposure to smoke or ethylene. This stimulating effect of smoke and ethylene was inhibited by exposure to NBD, indicating that ethylene in the smoke was responsible for the stimulation of germination. The involvement of ethylene in germination in both species was clearly demonstrated by the inhibition of germination after treatment with AOA. Differences in germination between the two species can not be ascribed to differences in ethylene production. Seeds of C. subternata , however, showed a much higher capacity to bind ethylene than seeds of C. intermedia . Pulse treatments with octanoic acid or smoke-saturated water stimulated germination in C. intermedia due to an increase in ethylene sensitivity, while longer treatments inhibited germination in both species. It appears that octanoic acid present in smokesaturated water was responsible for the reaction of the seeds to the water.

On the Role of Ethylene in Seed Germination and Early RootGrowth of Pisum sativum

Summary Requirement for endogenous ethylene in germination of pea seeds was investigated by using inhibitorsof ethylene synthesis, 2-aminoethoxylvinyl glycine and cobalt ions, and ethylene action, 2,5-norbornadiene. In particular, continuous application of high concentrations of aminoethoxyvinyl glycine alone or combined with cobalt ions did not affect germination, although inhibiting almost completely ethylene production. On the other hand, these inhibitors increased the length and decreased the diameter of elongating pea roots. Anatomical analysis showed that changes in root morphology were related to changes in the dimensional shape of cortical cells. Application of 2,5-norbornadiene from the start of imbibition strongly inhibited pea germination and the inhibition was mostly counteracted by ethephon. However, seeds fully escaped the sensitivity to NBD after 15 h of imbibition.

Ethylene biosynthesis and strigol‐induced germination of Striga asiatica

Germination of witchweed [Striga asiatica (L.) Kuntze], an important parasite on cereal crops, is stimulated by several natural and synthetic compounds. In the present study the role of ethylene in germination of Striga asiatica in response to strigol was examined. Unconditioned seeds and those conditioned for 3 days produced negligible amounts of ethylene in response to strigol. However, extending the conditioning period to 5 and 8 days increased ethylene evolution by more than 10‐fold. Ethylene production preceded radicle protrusion and was detectable within 3h after treatment. No germination was observed in the first 6 h of exposure to strigol. Germination and ethylene production increased with strigol concentration. Strigol‐induced germination was considerably reduced by the ethylene action inhibitors. 2. 5‐norbornadiene, silver thiosulphate and CO2. The ethylene precursor 1‐aminocyclopropane‐1‐carboxyac acid (ACC) at 5 to 200 μM elicited neither germination nor ethylene production. However, a combination of strigol and ACC resulted in a high germination rate and copious ethylene production. Both germination and ethylene production were reduced by CoCl2 and cyclobeximide, inhibitors of the ethylene‐forming enzyme and of protein synthesis, respectively. The results are consistent with a model in which conditioning and strigol are required to remove a restriction on the ethylene biosynthetic pathway and in which the ethylene‐forming enzyme is rate limiting.

Changes in sensitivity of Amaranthus retroflexus L seeds to ethylene during preincubation. II. Effects of alternating temperature and burial in soil

Abstract. The effects of diurnally alternating temperatures and of prolonged burial in the soil on germination response of redroot pigweed (Amaranthus retroflexus L.) seeds to ethylene were investigated. Percentage germination in a 12 h/12 h, 23° C/35° C temperature regime roughly equalled that observed at constant 35° C, and greatly exceeded that observed at 30°C. Preincubation for 61 d in alternating temperatures, which were gradually increased to simulate soil warming in spring, caused little germination in the absence of ethylene, but considerably enhanced sensitivity to ethylene. Seeds kept in soil in the same temperature regime failed to show the response to ethylene, and the soil itself removed ethylene from the soil atmosphere.After burial in a field plot either over winter or during the summer, seeds had a very low ethylene response threshold (0.01−0.05 cm3 m−3) and strong response to ethylene (70–95% germination at 51 cm3 m−3 compared to 1–20% without ethylene). Germinability of seeds buried overwinter declined between 10 May (85%) and 24 May (7%), and 90% of those recovered on or after 24 May had a visible rupture in the seed coat. Apparently, germination had begun during burial, but was arrested by unknown causes in an early phase and was followed by seed deterioration.Although the role of ethylene in germination of buried seeds remains uncertain, the greatly enhanced sensitivity to ethylene observed in pigweed seeds after burial deserves further investigation.

Ethylene Requirement for Germination of Partly After‐ripened Apple Embryo

AbstractThe effect and involvement of ethylene in germination of partially after‐ripened apple (Malus domestica Borkh. cv. Antonovka) embryos were studied. The requirement of ethylene for germination was shown by the use of a rhizobitoxine analog and 8‐hydroxy‐quinoline sulphate which are inhibitors of ethylene biosynthesis, and by mercuric perchlorate, a trap for endogenously produced ethylene. Excised apple embryos were found to produce progressively greater amounts of ethylene with increasing periods of after‐ripening. Inhibition of germination by rhizobitoxine analog or abscisic acid was accompanied by inhibition of ethylene formation in embryos. Thus ethylene appears to be required for the release of dormancy and germination of apple embryos.

Dormancy Regulation in Subterranean Clover Seeds by Ethylene

In the past there have been scattered reports of breaking of dormancy in seeds by ethylene (4, 11) or by ethylene chlorohydrin (5) which apparently acts on plants through a release of ethylene (12). The advent of gas chromatographic techniques has made it possible to show that many seeds produce ethylene naturally during the germination process (8,9, 10); these reports raise the interesting possibility that the production of ethylene by the imbibed seed may contribute to the breaking of dormancy. This possibility has been examined for peanuts by Toole et al. (10) and Ketring and Morgan (6), who concluded that the ethylene production may actually contribute to the breaking of dormancy. From studies with lettuce, Abeles and Lonski (1) reached the opposite conclusion since ethylene was produced mainly by those seeds which were going to germinate, and there were only small increases in percentage germination in the presence of added ethylene. We have been studying the role of ethylene in germination of seeds of several species, and our evidence indicates that in some seeds there is a substantial response to ethylene in breaking of dormancy, and further that the ethylene produced by the seed can have a regulatory role in determining whether or not germination will be achieved.