Reversal of (±) ‐Abscisin II Induced Inhibition of Lettuce Seed Germination and Seedling Growth by Kinetin

Sankhlá, N.; Sankhla, Daksha

doi:10.1111/j.1399-3054.1968.tb07243.x

Cited by 72 publications

(36 citation statements)

References 17 publications

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“…The role of the phytohormones GA and abscisic acid (ABA) on regulation of germination of the lettuce seeds is important. Application of bioactive GA mimics the effect of R (Kahn and Goss, 1957;Ikuma and Thimann, 1960), whereas application of ABA inhibits germination induced by R or application of bioactive GA (Kahn, 1968;Sankhla and Sankhla, 1968). Endogenous levels of the bioactive GA GA 1 are up-regulated by phytochrome (Toyomasu et al, 1993), and those of ABA are down-regulated by phytochrome or application of GA 1 in lettuce seeds (Toyomasu et al, 1994).…”

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confidence: 99%

Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Sawada

Aoki²,

Nakaminami³

et al. 2008

Plant Physiol.

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Germination of lettuce (Lactuca sativa) 'Grand Rapids' seeds is regulated by phytochrome. The action of phytochrome includes alterations in the levels of gibberellin (GA) and abscisic acid (ABA). To determine the molecular mechanism of phytochrome regulation of ABA metabolism, we isolated four lettuce cDNAs encoding 9-cis-epoxycarotenoid dioxygenase (biosynthesis; LsNCED1-LsNCED4) and four cDNAs for ABA 8#-hydroxylase (catabolism; LsABA8ox1-LsABA8ox4). Measurements of ABA and its catabolites showed that a decrease in ABA level coincided with a slight increase in the level of the ABA catabolite phaseic acid after red light treatment. Quantitative reverse transcription-polymerase chain reaction analysis indicated that ABA levels are controlled by phytochrome through down-regulation of LsNCED2 and LsNCED4 expression and up-regulation of LsABA8ox4 expression in lettuce seeds. Furthermore, the expression levels of LsNCED4 decreased after GA 1 treatment, whereas the levels of expression of the other two genes were unaffected. The LsNCED4 expression was also down-regulated by red light in lettuce seeds in which GA biosynthesis was suppressed by AMO-1618, a specific GA biosynthesis inhibitor. These results indicate that phytochrome regulation of ABA metabolism is mediated by both GA-dependent and -independent mechanisms. Spatial analysis showed that after red light treatment, the ABA decrease on the hypocotyl side was greater than that on the cotyledon side of lettuce seeds. Moreover, phytochrome-regulated expression of ABA and GA biosynthesis genes was observed on the hypocotyl side, rather than the cotyledon side, suggesting that this regulation occurs near the photoperceptive site.Plants undergo correct morphogenesis by responding to light and adapt to various forms of light. In addition to imbibition, some seeds require light to germinate and are called photoblastic seeds. Photoblastic seeds germinate after irradiation with red light (R; wavelength approximately 600-700 nm), and this effect of R is cancelled by successive irradiation with far-red light (FR; wavelength approximately 700-750 nm). The effects of R and FR are reversible. This type of germination, called photogermination, was discovered by experiments using lettuce (Lactuca sativa) 'Grand Rapids' seeds (Borthwick et al., 1952). The energy from wavelengths of R is mainly required for photosynthesis. This strategy allows survival of small seeds in which storage substances are low, such as the seeds of lettuce, tomato (Solanum lycopersicum), tobacco (Nicotiana tabacum), and Arabidopsis (Arabidopsis thaliana). The typical reversible photoreaction of lettuce seeds allowed Butler et al. (1959) to detect the pigment that acts as the R/FR receptor in extracts from etiolated cotyledons of Brassica rapa and etiolated shoots of Zea mays using differential spectrophotometry, and this photoreceptor was named phytochrome.Many studies to elucidate the mechanisms of photoblastic lettuce seed germination have been carried out for over a half century, including biochemica...

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Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Sawada

Aoki²,

Nakaminami³

et al. 2008

Plant Physiol.

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“…WXe have shown that cytokinins overcome the inhibitoryaction of several natural inhibitors in the germination of the photosensitive Grand Rapids lettuce seed (4,5). There are other reports of cytokinin-inhibitor antagonism in germinationl and dormancy (6,7,10,12,14). Chrispeels and Varner have shown that gibberellic acid (GA3) induced a-amylase synthesis in the excised barley aleurone is inhibited by abscisic acid and revrersed only partially by excess GA) (2).…”

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Inhibition of Gibberellic Acid-induced Germination by Abscisic Acid and Reversal by Cytokinins

Khan

1968

Plant Physiol.

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“…Dark germination of Grand Rapids lettuce seeds is promoted by GA3 (4) and ABA inhibits germination induced by GA3 or light (5,13). Increasing the concentration of GA3 in the presence of ABA does not overcome ABA inhibition unless a cytokinin is also present (5).…”

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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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Reversal of (±) ‐Abscisin II Induced Inhibition of Lettuce Seed Germination and Seedling Growth by Kinetin

Cited by 72 publications

References 17 publications

Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Phytochrome- and Gibberellin-Mediated Regulation of Abscisic Acid Metabolism during Germination of Photoblastic Lettuce Seeds

Inhibition of Gibberellic Acid-induced Germination by Abscisic Acid and Reversal by Cytokinins

Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

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