Primary, preventive and permissive roles of hormones in plant systems

Khan, Anwar A.

doi:10.1007/bf02860831

Cited by 100 publications

(48 citation statements)

References 138 publications

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“…Afterward, the levels of all stimulatory hormones gradually decrease. This observation agrees with the Khan's (1975) concept of designated, selective functions of hormones in the control of seed germination and dormancy. According to that concept, the completely, deeply dormant embryos are unable to germinate because of a too high level of ABA (inhibitor) and, simultaneously, too low concentrations of GA, CK, and/or JA.…”

Section: Regulatory Complex Involved In Dormancy Removalsupporting

confidence: 91%

Metabolic control of embryonic dormancy in apple seed: seven decades of research

Lewak

2010

Acta Physiol Plant

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Embryonic dormancy is defined as a set of blocks imposed upon a process(es) cardinal for growth. In apple seeds, all these blocks are removed as a result of cold treatment (stratification), but some of them are also affected by light and/or hormonal treatments. This review summarizes published data related to the modes of action of above factors on the changes in the levels of endogenous hormones and some other plant growth regulators (e.g., hydrogen cyanide), and on certain enzymes involved in mobilization of seed reserves and catabolism of their hydrolysis products. Phytochrome and activities of acid lipase and a protease have been indicated as receptors of light and low temperature, respectively. Several chains of events initiated by these two environmental factors and leading to dormancy removal are proposed, and the sites of their control by hormones and HCN are indicated. These chains are postulated to contribute to the elimination of particular blocks that hinder germination and therefore to be involved in the mechanisms of dormancy breakage.

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Section: Regulatory Complex Involved In Dormancy Removalsupporting

confidence: 91%

Metabolic control of embryonic dormancy in apple seed: seven decades of research

Lewak

2010

Acta Physiol Plant

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“…Kinetin has also been shown to largely overcome thermodormancy in lettuce seeds imposed by high temperature during imbibition whereas GA3 has little effect (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).…”

supporting

confidence: 66%

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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“…Cytokinins are involved in many physiological processes. They withdraw seeds from dormancy and promote germination, especially when combined with other promoting agents, including gibberellins (Reeve and Crozier, 1974;Khan, 1975;Socolowski and Cicero, 2011).…”

Section: Discussionmentioning

confidence: 99%

Desiccation tolerance in seeds of Annona emarginata (Schldtl.) H. Rainer and action of plant growth regulators on germination

Corsato

Ferreira

Barbedo

2012

Braz. J. Plant Physiol.

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Annona emarginata (Schldtl.) H. Rainer ("araticum-de-terra-fria") is used as a rootstock for several species of Annonaceae. It is suggested that these seeds should be sown immediately after extraction and, therefore, they could be intolerant to desiccation. There are several mechanisms involved with desiccation tolerance. Soluble sugars, for example, can accumulate and act as osmoprotectants for the membrane system during desiccation. The aim of this study is to assess desiccation tolerance in A. emarginata seeds. In addition, we examined the soluble sugars involved in desiccation tolerance. Finally, we determined the effect of gibberellic acid (GA 4+7 ) and N-(phenylmethyl)-aminopurine in promoting the germination of seeds with different water contents. The experiment consisted of a randomized 4x5 factorial design (desiccation levels x concentration of growth regulators). After drying, seeds containing 31 (control), 19, 12 and 5% water were incubated in different concentrations of GA 4+7 N-(phenylmethyl)-aminopurine (0, 250, 500, 750 and 1000 mg L -1 ) for 60 hours. The experiment was conducted in a germination chamber with alternating temperature and photoperiod of 20ºC for 18 hours of darkness and 30ºC for 6 hours of light. We analyzed electrical conductivity, germination rate, mean germination time, germination speed, frequency and uniformity of germination, percentage of dormant seeds and soluble sugar profile in intact seeds through high-performance liquid chromatography (HPLC). The data were subjected to analysis of variance, and the means were compared using Tukey's test at a threshold of p<0.05. The results showed that seeds of A. emarginata appears to be desiccation tolerant and, also, that sucrose increases when seed water content is reduced to values as low as 12%, exogenous GA 4+7 +N-(phenylmethyl)-aminopurine improves its germinability.

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Primary, preventive and permissive roles of hormones in plant systems

Cited by 100 publications

References 138 publications

Metabolic control of embryonic dormancy in apple seed: seven decades of research

Metabolic control of embryonic dormancy in apple seed: seven decades of research

Endogenous Abscisic Acid Levels in Germinating and Nongerminating Lettuce Seed

Desiccation tolerance in seeds of Annona emarginata (Schldtl.) H. Rainer and action of plant growth regulators on germination

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