The effect of lettuce seed extracts on lettuce seed germination

Speer, Henry L.; Tupper, Dorothy

doi:10.1139/b75-074

Cited by 19 publications

(16 citation statements)

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“…Metabolism did not become a substantial cause of reduction until after 12 hr of imbibition. Leaching of an endogenous inhibitor, presumably ABA, into water medium has recently been reported (19). Decline of ABA content in Fraxinus americana seeds previously permeated with 14C-ABA in dichloromethane was found to result largely from metabolism and only to a small extent from leaching (16).…”

Section: Resultsmentioning

confidence: 94%

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Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

Braun¹,

Khan²

1975

Plant Physiol.

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The concentrations of abscisic acid in Grand Rapids lettuce (Lactuca sativa L.) seeds imbibed under conditions which promote or inhibit germination were determined by electron capture-gas chromatography. The concentration of abscisic acid in dry seeds was 12 to 14 nanograms per 100 milligrams. During 24-hour imbibition, the abscisic acid content diminished more rapidly during conditions which allow germination (25 C in (3,11,12,18). Similarities in the effects of high temperature (35 C) and ABA and their interactions with kinetin and GA3 have been shown recently (7).Probably the absence of germination in darkness or at high temperatures is controlled at some stage by a high level of inhibitor(s) and/or a low level of promoter(s) (6). Gas chromatographic evidence for the presence of ABA in dry Grand Rapids lettuce seed has recently been reported (19). The present investigation was undertaken to determine the contents of ABA in Grand Rapids lettuce seeds during imbibition under conditions which prevent and allow germination. MATERIALS AND METHODSIn the light versus dark experiment, Grands Rapids lettuce (Lactuca sativa L.) seeds were imbibed at 25 C in diffuse white light or in total darkness. In the 25 versus 35 C temperature experiments, seeds were imbibed in diffuse white light at these two tem- Seeds (400 mg dry weight) were collected in test tubes and cold 80% ethyl alcohol was added. Seeds from the dark treatment were collected under a dim green safelight. Tubes with samples were then stored at -30 C until homogenized. Seed samples were homogenized in cold ethyl alcohol (80%/) in a TenBroeck homogenizer and transferred to flasks, the final volume being 40 ml. The homogenates were left overnight at 5 C on a shaker.The preparations were then filtered in vacuo through a Buchner funnel, the filtrates were collected in round bottomed flasks, and the extract was evaporated to near dryness using a rotary film evaporator under vacuum.Extract purifications were based on the method described by Seeley (14). After evaporating the ethyl alcohol, the residue was taken up in water, and the pH was adjusted to 8.3 with 10% ammonium hydroxide. The aqueous extract was partitioned three times with equal volumes (30 ml) of dichloromethane which was discarded. The aqueous fraction was adjusted to pH 2.6 with 10% HC1 and again partitioned three times with dichloromethane. The dichloromethane phases were pooled and evaporated to dryness. The residue was quantitatively transferred with ethyl acetate and divided equally between two test tubes and the ethyl acetate evaporated with a stream of dry nitrogen gas.Quantitative determination of ABA in the seed extracts was achieved by adaptation of the electron capture-gas chromatography techniques described by Seeley and Powell (15), Seeley (14), and Braun (2). The present determinations were performed using a Perkin-Elmer 900 gas chromatograph equipped with a 3% OV-1 column and a Nickel-63 electron capture detector operated in the pulsed voltage mode (10,000 pulses/sec).At th...

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Section: Resultsmentioning

confidence: 94%

“…Gas chromatographic evidence for the presence of ABA in dry Grand Rapids lettuce seed has recently been reported (19 Seeds (400 mg dry weight) were collected in test tubes and cold 80% ethyl alcohol was added. Seeds from the dark treatment were collected under a dim green safelight.…”

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confidence: 99%

Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

Braun¹,

Khan²

1975

Plant Physiol.

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“…Grand Rapids, prolonged dark, or high temperature incubations may also decrease photosensitivity until the seeds become unresponsive to R, i.e. secondarily dormant (3,4,9,27,31, 34,35).…”

Section: Introductionmentioning

confidence: 99%

“…Grand Rapids, prolonged dark, or high temperature incubations may also decrease photosensitivity until the seeds become unresponsive to R, i.e. secondarily dormant (3,4,9,27,31, 34,35).In most previous studies of secondary dormancy, its onset has been monitored at only one temperature, thus, little is known about the changes in GT50 Light during the induction of secondary dormancy. In the present study, changes in germination have been monitored over a wide range of temperatures in the examination of the effects of interactions among light, temperature and growth regulators on the induction of secondary dormancy in three lettuce cultivars.…”

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Factors Affecting the Induction of Secondary Dormancy in Lettuce

Kristie¹,

Bassi²,

Spencer³

1981

Plant Physiol.

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The relationship between the temperature at which germination of 50% of the seeds is inhibited in the light (GTso Light) and secondary dormancy was investigated in three cultivars of Lactuca sativa L. Seeds were incubated for varying periods under non-germinating conditions and subsequent germination in response to red light (R) was determined over a wide range of temperatures. Dark incubation at 32 C reduced the GT5o Light of cv. New York but did not affect germination at temperatures below 24 C. Dark, 32 C incubation had no effect on the GTso Light of cv. Great Lakes. In cv. Grand Rapids, dark incubation at 15, 24, 32, or 35 C initially reduced the GTso Light. However, longer incubations induced a secondary dormancy, i.e., the seeds became unable to germinate at all temperatures in response to R given after the high temperature incubation. A single exposure to R at the binning of a 32 C incubation slowed the induction of secondary dormancy. Repeated exposures to R prevented the induction of secondary dormancy, but did not prevent a decline in the GT50 Light. GA8 mimicked the effect of repeated R.The differences in the germination behavior of the three cultivars suggest that there may be qualitative differences in the germination mechanism of these cultivars. This research demonstrates the significance of monitoring germination at a range of temperatures to avoid misinterpretation of the data.osmotic pressure have been shown to be related to changes in one or both of these GT50 (21, 24).Incubation of fully imbibed seeds under conditions not suitable for germination is known to reduce their germination potential. High temperature incubations can induce a light requirement in dark germinating lettuce seeds (1, 2), i.e., the seeds become photodormant. This effect has been attributed to a decline in the GT50 Dark (1 1, 12). In the light sensitive cv. Grand Rapids, prolonged dark, or high temperature incubations may also decrease photosensitivity until the seeds become unresponsive to R, i.e. secondarily dormant (3,4,9,27,31, 34,35).In most previous studies of secondary dormancy, its onset has been monitored at only one temperature, thus, little is known about the changes in GT50 Light during the induction of secondary dormancy. In the present study, changes in germination have been monitored over a wide range of temperatures in the examination of the effects of interactions among light, temperature and growth regulators on the induction of secondary dormancy in three lettuce cultivars.In this paper, high-temperature incubation refers to the lowest temperature capable of suppressing germination to zero in both light and dark treatments; and secondary dormancy refers to the seeds that become incapable of germination in response to R at any temperature.Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent. As the temperature rises above the optimum (18), germination declines sharply, often falling from 100%o to near 0% with an increase of only 2 or 3 degrees C (23). The temperature at ...

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A comparison of thermo- and skotodormancy in seeds of Lactuca serriola in terms of induction, alleviation, respiration, ethylene and protein synthesis

Small

Gutterman

1992

Plant Growth Regul

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Lactuca serriola L., which was found to enter skotodormancy at a relatively low temperature, was used to try and ascertain differences in thermo-and skotodormancy.Abbreviations: SE, standard error; V,, total respiratory rate; V,, , respiratory rate inhibited by cyanide; Valt , total respiratory capacity inhibited by SHAM and denoted alternate respiration; V,,, residual respiration; PMSF, phenylmethylsulfonyl fluoride; panacide, 5,5'-2,2'-dihydroxydiphenylmethane; SHAM, salicylhydroxamic acid.Germination of L. serriola was found to be red/far red reversible and was inhibited more severely in the dark than in the light as the temperature was increased. Dark germination at an intermediate temperature (25 "C) was effected by GA, but not by kinetin or ethylene. Imbibition at 25 "C in the dark for 12 d induced skotodormancy and imbibition at 37 "C for 8 d induced thermodormancy. Light plus a hormone was required to break both types of dormancy. Kinetin and ethylene were less effective than GA, in alleviating thermodormancy but all three hormones effectively broke skotodormancy. Induction of thermodormancy was prevented by GA, but not by kinetin, ethylene or red light. All three hormones prevented the induction of skotodormancy. Anaerobiosis prevented the induction of skotodormancy and prevented the loss of dark GA, -mediated germination following high temperature. However, anaerobiosis during high temperature was largely ineffective in preventing the high temperature induced lack of subsequent light-mediated germination. Thermodormantseeds had a lower respiratory rate, ethylene and protein synthesis capacity than skotodormant seeds. In both the dormancy types these parameters were lower than in non-dormant seeds. Thermodormant seeds had a lower Vcyt rate and higher Va,, rate than skotodormant seeds.Although the two dormancy types synthesized some similar polypeptides, they differed qualitatively from one another and from the protein synthesis pattern of non-dormant seeds.It is concluded that the two dormancy types are controlled partly by the same mechanism (blockage of a dark GA,-mediated germination pathway), but that in thermodormancy the light-mediated germination pathway is also blocked.

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The effect of lettuce seed extracts on lettuce seed germination

Cited by 19 publications

References 3 publications

Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

Factors Affecting the Induction of Secondary Dormancy in Lettuce

A comparison of thermo- and skotodormancy in seeds of Lactuca serriola in terms of induction, alleviation, respiration, ethylene and protein synthesis

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