scholarly journals (207) Sensitivity of Two Lettuce Genotypes to Abscisic Acid during Germination

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1070A-1070
Author(s):  
Jiyoung Hong ◽  
Daniel Cantliffe
Keyword(s):  
Abscisic Acid ◽  
High Temperature ◽  
Seed Maturation ◽  
Lettuce Seed ◽  
Dark Condition ◽  
Optimal Range ◽  
Lettuce Seeds ◽  
Lettuce Seed Germination ◽  
Dark Green ◽  
Better Than

In many lettuce (Lactuca sativa L.) cultivars, temperatures above 30 °C can inhibit germination completely. Lettuce seeds imbibed at supraoptimal temperature for 72 hours or more will not germinate even when the temperature is returned to the optimal range. Sung et al. (1998) reported that thermosensitive `Dark Green Boston' and thermotolerant `Everglades' responded to temperature at seed maturation by being able to show greatly enhanced germination at 36 °C when seeds were matured at 30/20 °C. Abscisic acid (ABA) plays an important role relative to both dormancy and germination of many seeds and may contribute to lettuce seed thermodormancy. Therefore, sensitivity of `Everglades' and `Dark Green Boston' to ABA of seeds maturated at 30/20 °C and 20/10 °C in light and dark was determined. Seeds were germinated at 20 °C and 36 °C in light and dark. All seeds of `Dark Green Boston'and `Everglades' matured at 30/20 °C and 20/10 °C germinated similarly regardless of maturation temperature and light/dark condition at 20 °C. At 36 °C in dark, both genotypes matured at 30/20 °C germinated more than those matured at 20/10 °C. `Dark Green Boston' genotypes were more sensitive to ABA (0.5, 1, 10, 50, 100 μM) during germination at 36°C in dark. When ABA was added, seeds matured at 30/20 °C germinated better than those matured at 20/10 °C, regardless of genotype. At 36 °C in light, 40% of both genotypes were inhibited at 0.5 μM ABA. At 36 °C in dark, germination of all seeds but `Everglades' matured at 30/20 °C were completely inhibited at all ABA concentrations. Thus, seed maturation temperature has an influence on lettuce seed germination at high temperature and sensitivity to ABA.

scholarly journals Preventing thermoinhibition in a thermosensitive lettuce genotype by seed imbibition at low temperature

2003 ◽  
Vol 60 (3) ◽  
pp. 477-480 ◽  
Author(s):  
Warley Marcos Nascimento
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
High Temperatures ◽  
Lactuca Sativa ◽  
Lettuce Seed ◽  
Temperature Dependent ◽  
Lettuce Seeds ◽  
Lactuca Sativa L ◽  
Lettuce Seed Germination ◽  
Dark Green

Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent and under high temperatures, germination of most of genotypes can be erratic or completely inhibited. Lettuce seeds of 'Dark Green Boston' (DGB) were incubated at temperatures ranging from 15° to 35°C at light and dark conditions. Other seeds were imbibed in dark at 20°; 25°; 30°; and 35°C for 8 and 16 hours and then transferred to 20 or 35°C, in dark. Seeds were also incubated at constant temperature of 20° and 35 °C, in the dark, as control. In another treatment, seeds were primed for 3 days at 15°C with constant light. DGB lettuce seeds required light to germinate adequately at temperatures above 25°C. Seeds incubated at 20°C had 97% germination, whereas seeds incubated at 35°C did not germinate. Seeds imbibed at 20°C for 8 and 16 hours had germination. At 35°C, seeds imbibed initially at 20°C for 8 and 16 hours, had 89 and 97% germination, respectively. Seeds imbibed at 25°C for 16 hours, germinated satisfactory at 35°C. High temperatures of imbibition led to no germination. Primed and non-primed seeds had 100% germination at 20°C. Primed seeds had 100% germination at 35°C, whereas non-primed seeds germinate only 4%. The first hours of imbibition are very critical for lettuce seed germination at high temperatures.

scholarly journals Structural Changes in Lettuce Seed During Germination at High Temperature Altered by Genotype, Seed Maturation Temperature, and Seed Priming

2008 ◽  
Vol 133 (2) ◽  
pp. 300-311 ◽  
Author(s):  
Yu Sung ◽  
Daniel J. Cantliffe ◽  
Russell T. Nagata ◽  
Warley M. Nascimento
Keyword(s):  
Cell Wall ◽  
High Temperature ◽  
Structural Changes ◽  
Anatomical Study ◽  
Seed Priming ◽  
Seed Maturation ◽  
Mechanical Resistance ◽  
Lettuce Seed ◽  
Endosperm Cell ◽  
Dark Green

To investigate thermotolerance in seeds of lettuce (Lactuca sativa L.), primed, nonprimed, or seeds matured at 20/10 and 30/20 °C (day/night on a 12-h photoperiod) were imbibed at 36 °C for various periods and then dissected. Structural changes in seed coverings in front of the radicle tip were observed during germination at high temperature. Thermotolerant genotypes, ‘Everglades’ and PI 251245, were compared with a thermosensitive cultivar, ‘Dark Green Boston’. In all seeds that germinated, regardless of seed maturation temperature or priming, a crack appeared on one side of the cap tissue (constriction of the endosperm membrane near the basal end of the seed) at the micropylar region and the endosperm separated from the integument in front of the radicle tip. Additional changes took place during imbibition in these seeds; the protein bodies in the vacuoles enlarged and gradually depleted, large empty vacuoles formed, the cytoplasm condensed, the endosperm shrank, the endosperm cell wall dissolved and ruptured, and then the radicle elongated toward this ruptured area. The findings suggested that the endosperm layer presented mechanical resistance to germination in seeds that could not germinate at 36 °C. Weakening of this layer was a prerequisite to radicle protrusion at high temperature. Seeds of ‘Dark Green Boston’, ‘Everglades’, and PI 251245 matured at 30/20 °C had greater thermotolerance than those matured at 20/10 °C. Results of the anatomical study indicated that the endosperm cell walls in front of the radicle of seeds matured at 30/20 °C were more readily disrupted and ruptured during imbibition than seeds matured at 20/10 °C, suggesting a reason why these seeds could germinate quickly at supraoptimal temperatures. Similar endosperm structural alterations also were observed in primed seeds. Priming led to rapid and uniform germination, circumventing the inhibitory effects of high temperatures. From anatomical studies conducted to identify and characterize thermotolerance in lettuce seed germination, we observed that genotype, seed maturation temperature, or seed priming had the ability to reduce physical resistance of the endosperm by weakening the cell wall and by depleting stored reserves leading to cell collapse.

The effect of lettuce seed extracts on lettuce seed germination

1975 ◽  
Vol 53 (7) ◽  
pp. 593-599 ◽  
Author(s):  
Henry L. Speer ◽  
Dorothy Tupper
Keyword(s):  
Abscisic Acid ◽  
Liquid Chromatography ◽  
Seed Germination ◽  
Seed Coat ◽  
Gas Liquid Chromatography ◽  
Lettuce Seed ◽  
Lettuce Seeds ◽  
Grand Rapids ◽  
Lettuce Seed Germination ◽  
Seed Extracts

Lettuce seeds (Lactuca sativa var. Grand Rapids) were found to contain inhibitory substances, one of which is probably abscisic acid. Extracts from seeds were characterized by gas–liquid chromatography, and peaks coincident with abscisic acid were found.The germination water surrounding seeds made secondarily dormant was subjected to gas–liquid chromatography and was also found to contain peaks coincident with abscisic acid. It was also determined that the inhibitory substances are localized in the embryo but not in the endosperm or seed coat.

scholarly journals 402 Lettuce Seed Germination and Endo-mannanase Activity are Stimulated by Ethylene at High Temperature

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 513B-513 ◽  
Author(s):  
Warley M. Nascimento ◽  
Daniel J. Cantliffe ◽  
Donald J. Huber
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
Enzyme Regulation ◽  
Seed Priming ◽  
Lettuce Seed ◽  
Endosperm Cell ◽  
Lettuce Seeds ◽  
Mannanase Activity ◽  
Lettuce Seed Germination

Temperatures above 30 °C may delay or inhibit germination of most of commercial lettuce cultivars. Ethylene enhances lettuce seed germination at high temperatures. Enzyme-mediated degradation of endosperm cell walls appears to be a crucial factor for lettuce germination at high temperature. The galactomannan polysaccharides in lettuce endosperm cell wall are mobilized by endomannanase. The role of endo-mannanase during germination of lettuce seeds at high temperature (35 °C) and the possible role of etlene in enzyme regulation were investigated. Seeds of thermotolerant (`Everglades'-EVE) and thermosensitive (`Dark Green Boston'-DGB) lettuce genotypes were incubated at 20 and 35 °C in water, 10 mM of 1-aminocyclopropane-1-carboxylic acid (ACC), or 20 mM of silver thiosulphate (STS). Also, seeds were primed in an aerated solution of polyethylene glycol (PEG), or PEG+ACC, or PEG+STS. Untreated seeds germinated 100% at 20 °C. At 35 °C, EVE germinated 100%, whereas DGB germinated only 33%. Seed priming or adding ACC during imbibition increased germination of DGB to 100% at 35 °C. Adding STS during imbibition led to a decrease in germination at 35%C in EVE and completely inhibited germination of DGB. Priming with STS led to reduced germination at 35%C of both genotypes. EVE produced more ethylene than DGB during germination at high temperature. Providing ACC either during priming or during germination led to an increase in endo-mannanase activity, whereas STS inhibited mannanase activity. Higher endo-mannana activity was observed in EVE than DGB seeds. The results suggest that ethylene might overcome the inhibitory effect of high temperature in thermosensitive lettuce seeds via weakening of endosperm due to increased endo-mannanase activity.

scholarly journals Ethylene evolution and endo-beta-mannanase activity during lettuce seed germination at high temperature

2004 ◽  
Vol 61 (2) ◽  
pp. 156-163 ◽  
Author(s):  
Warley Marcos Nascimento ◽  
Daniel James Cantliffe ◽  
Donald John Huber
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
Seed Priming ◽  
Inhibitory Effect ◽  
Lettuce Seed ◽  
Ethylene Evolution ◽  
Radicle Protrusion ◽  
Mannanase Activity ◽  
Lettuce Seed Germination ◽  
Dark Green

High temperatures during lettuce seed imbibition can delay or completely inhibit germination and the endosperm layer appears to restrict the radicle protrusion. The role of endo-beta-mannanase during lettuce seed germination at 35°C and the influence of ethylene in endo-beta-mannanase regulation were investigated. Seeds of 'Dark Green Boston' (DGB) and 'Everglades' (EVE) were germinated in water, or 10 mmol L-1 of 1-aminocyclopropane-1-carboxylic acid (ACC), or 10 mmol L-1 of aminoethoxyvinylglycine (AVG), or 20 mmol L-1 of silver thiosulphate (STS). Seeds were also primed in polyethylene glycol (PEG), or PEG + ACC, PEG + AVG, or PEG + STS. Untreated seeds germinated 100% at 20°C. At 35°C, EVE seeds germinated 100%, whereas DGB seeds germinated only 33%. Seed priming or adding ACC during incubation increased germination at 35°C. Higher ethylene evolution was detected in EVE than in DGB during germination at 35°C. AVG did not inhibit seed germination of DGB at 35°C, but STS did. Higher endo-beta-mannanase activity was observed in EVE compared with DGB seeds. Providing ACC either during priming or during germination increased endo-beta-mannanase activity, whereas AVG and STS led to decreased or no activity. Ethylene may overcome the inhibitory effect of high temperature in thermosensitive lettuce seeds due to increased endo-beta-mannanase, possibly leading to weakening of the endosperm.

scholarly journals Structural Changes in Lettuce Seed during Germination Altered by Genotype, Seed Maturation Temperature, and Priming

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 526E-527
Author(s):  
Yu Sung ◽  
Daniel J. Cantliffe ◽  
Russell T. Nagata
Keyword(s):  
Cell Wall ◽  
High Temperature ◽  
Seed Germination ◽  
Structural Changes ◽  
Anatomical Study ◽  
Seed Maturation ◽  
Mechanical Resistance ◽  
Lettuce Seed ◽  
Endosperm Cell ◽  
Lettuce Seed Germination

Thermotolerance in lettuce seed at high temperature was investigated using primed and nonprimed seed or seeds matured at 20/10°C and 30/20°C. During seed germination at 36°C, the structural changes of the seed coverings in front of the radicle tip were observed in an anatomical study. In all seeds during imbibition, regardless of seed maturation temperature or priming, a crack appeared on one side of the cap tissue and the endosperm separated from the integument in front of the radicle tip. Additional changes took place during imbibition: the protein bodies in the vacuoles enlarged and were gradually depleted, large empty vacuoles formed, the cytoplasm condensed, the endosperm shrank, the endosperm cell wall dissolved and ruptured, then the radicle elongated toward this ruptured area. The findings suggested that the papery endosperm layer presented mechanical resistance to lettuce seed germination and the weakening of this layer was a prerequisite to radicle protrusion at high temperature. Seeds of `Dark Green Boston', `Everglades', and PI 251245 matured at 30/20°C had greater thermotolerance than those matured at 20/10°C. Results of the anatomical study indicated that the endosperm cell walls in front of the radicle of seeds matured at 30/20°C were more easily disrupted and ruptured during early imbibition than seeds matured at 20/10°C, suggesting that these seeds could germinate quickly at supra-optimal temperatures. From anatomical studies conducted to identify and characterize thermotolerance in lettuce seed germination, it was observed that genotype thermotolerance had the ability to reduce physical resistance of the endosperm by weakening the cell wall and by depleting stored reserves.

ACTION AND INTERACTION OF MONOCHROMATIC LIGHT ON PHOSPHATE METABOLISM OF GERMINATING LETTUCE SEEDS

1962 ◽  
Vol 40 (7) ◽  
pp. 965-974 ◽  
Author(s):  
Kenneth Surrey
Keyword(s):  
Energy Flow ◽  
Spectral Band ◽  
Red Light ◽  
Monochromatic Light ◽  
Lettuce Seed ◽  
Phosphate Metabolism ◽  
Lettuce Seeds ◽  
Phytochrome System ◽  
Lettuce Seed Germination ◽  
Partial Suppression

A previously described photoresponse of lettuce seed germination to red and far-red light is shown to be paralleled by a response of phosphate metabolic activity: (1) When seeds were continuously irradiated, red light accelerated and far-red suppressed their phosphate uptake and esterification. (2) The influence of monochromatic light on phosphate metabolism of seeds, determined after 36 and 64 hours of germination, respectively, indicated maximum potentiation between 550 and 650 mμ, maximum suppression beyond 700 mμ, and partial suppression at 475 mμ. Stimulation was encountered at 400 mμ, but with shorter wavelengths of the ultraviolet spectrum, suppression appeared again. (3) Photoactivation of phosphate metabolism in response to each of the three loci (550, 600, and 650 mμ, i.e., green, orange, and red light, respectively) of the potentiating spectral band was reversed by far-red (750 mμ) light. These activations and inhibitions could be reversed several times in an alternating sequence. Complete reversibility depended entirely upon the magnitudes of the radiant flux for the two counteracting wavelengths, and this was characteristic for each pair of antagonistic wavelengths. In view of the association of phytochrome with the isolated mitochondria and of the specific manner in which their phosphorylation activity is influenced by light, it is suggested that a part of the energy flow required for cellular development may be channeled through the mitochondrial–phytochrome system.

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