scholarly journals Thermotolerance in Lettuce Seeds: Association with Ethylene and Endo-β-mannanase

2000 ◽  
Vol 125 (4) ◽  
pp. 518-524 ◽  
Author(s):  
Warley M. Nascimento ◽  
Daniel J. Cantliffe ◽  
Donald J. Huber
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
Ethylene Production ◽  
Potential Role ◽  
Endosperm Tissue ◽  
Lettuce Seeds ◽  
Radicle Protrusion ◽  
Mannanase Activity ◽  
Dark Green

Weakening of the endosperm tissue around the radicle tip before radicle protrusion and a potential role of endo-β-mannanase during germination of lettuce seeds (Lactuca sativa L.) at high temperature (35 °C) were investigated. Seeds from the thermotolerant genotypes `Everglades' and PI 251245 had greater endo-β-mannanase activity before radicle protrusion at 35 °C than the thermosensitive genotypes `Dark Green Boston', `Valmaine' and `Floricos 83'. Thermotolerant genotypes also generated more ethylene at high temperature. At 35 °C, germination of `Dark Green Boston' and `Everglades' seeds produced at days/nights of 20/10 °C was 10% and 32%, respectively, whereas germination of seeds produced at days/nights of 30/20 °C was 67% and 83%, respectively. Higher endo-β-mannanase activity was observed before radicle protrusion in `Dark Green Boston' seeds produced at 30/20 °C compared with those produced at 20/10 °C. A relationship between seed germination at high temperature, ethylene production, and an increase in endo-β-mannanase activity before radicle protrusion was confirmed.

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.

Endo-β-mannanase Activity and Seed Germination of Thermosensitive Lettuce Genotype in Response to Temperature and Seed Priming

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 543a-543 ◽  
Author(s):  
Warley M. Nascimento ◽  
Daniel J. Cantliffe ◽  
Donald J. Huber
Keyword(s):  
Seed Germination ◽  
High Temperatures ◽  
Seed Priming ◽  
Inhibitory Effect ◽  
Lettuce Seed ◽  
Lettuce Seeds ◽  
Radicle Protrusion ◽  
Mannanase Activity ◽  
Dark Green ◽  
Response To Temperature

Under high temperatures (above 30 °C) in the greenhouse (transplant industry) or field, lettuce germination can be erratic or completely inhibited. Seed priming circumvents thermodormancy of lettuce seeds and allows germination at higher temperatures. Weakening of the endosperm layer of lettuce seeds is a prerequisite to radicle protrusion at high temperatures. Enzyme-mediated degradation of endosperm cell walls may be a crucial factor for lettuce seed germination at high temperatures. Softening of the endosperm could occur during seed priming and result in improved germination. A single-seed assay for endo-β-mannanase was used to follow the activity of this enzyme during priming in lettuce seeds. We also investigated the effects of seed priming on seed germination and mannanase activity at both inhibitory and non-inhibitory temperatures for seed germination in a thermosensitive lettuce cultivar Dark Green Boston. Seeds were primed for 3 days at 15 °C with constant light in aerated solutions of polyethylene glycol (PEG) at an osmotic potential of –1.2 MPa. Afterward, seeds were rinsed and redried at 10 °C and 45% RH for 3 days. Primed and nonprimed seeds germinated 100% at 20 °C. At 35 °C, primed seeds germinated 100%, whereas nonprimed seeds did not germinate. During priming, endo-β-mannanase activity increased between 24 and 72 h after the beginning of osmotic imbibition. Mannanase activity persisted in primed seeds, even following seed drying. Radicle protrusion did not occur under the priming conditions used in this study. Higher enzyme activity was observed in primed seeds compared with nonprimed seeds. The results suggest that priming overcomes the inhibitory effect of high temperature in thermosensitive lettuce seeds by weakening of endosperm due to increased endo-β-mannanase activity.

scholarly journals Using a Puncture Test to Identify the Role of Seed Coverings on Thermotolerant Lettuce Seed Germination

1998 ◽  
Vol 123 (6) ◽  
pp. 1102-1106 ◽  
Author(s):  
Yu Sung ◽  
Daniel J. Cantliffe ◽  
Russell Nagata
Keyword(s):  
Seed Germination ◽  
Turgor Pressure ◽  
Seed Priming ◽  
Lettuce Seed ◽  
Tissue Resistance ◽  
Radicle Protrusion ◽  
Puncture Force ◽  
Lettuce Seed Germination ◽  
Dark Green

Temperature is an important environmental factor that affects lettuce (Lactuca sativa L.) germination. The present research was conducted to determine the role of seed coverings on lettuce seed germination at high temperature. Five lettuce genotypes were primed in order to bypass thermoinhibitional effects on germination. During germination of primed and nonprimed seeds, imbibition followed a normal triphasic pattern. Primed seeds had higher final water content, a decreased imbibitional phase II, and germinated at 36 °C compared to nonprimed seeds of thermosensitive genotypes, which did not germinate at 36 °C. Puncture tests were conducted to determine the force required to penetrate the whole seed or endosperm of the five genotypes at 24 and 33 °C. `Dark Green Boston', a thermosensitive genotype, had the highest mean resistance (0.207 N) and PI 251245, a thermotolerant genotype, had the lowest (0.139 N). Resistance to penetration of the endopserm of the five genotypes was different at both temperatures. However, three thermotolerant genotypes had lower endosperm resistance than two thermosensitive types. At 36 °C, the penetration force for primed and nonprimed seeds was compared after the first hour of imbibition and 1 hour before radicle protrusion. The force required to penetrate the seed was affected by genotype, seed priming, and duration of imbibition. Puncture force decreased as imbibition time at 36 °C increased in primed and nonprimed seed of each thermotolerant genotype but not in the thermosensitive genotypes. Priming reduced the initial force necessary to penetrate the seed and endosperm in all genotypes. Thus, for radicle protrusion to occur, there must first be a decrease in the resistance of the endosperm layer as evidenced by priming or thermotolerant genotype. Then, the pericarp and integument are sufficiently weakened so that tissue resistance is lower than the turgor pressure of the expanding embryo, allowing germination to be completed.

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 Role of Cassava CC-type Glutaredoxin MeGRXC3 in Regulating Sensitivity to Mannitol-Induced Osmotic Stress Dependent on its Nuclear Activity

2021 ◽  
Author(s):  
Meng-Bin Ruan ◽  
Xiao-Ling Yu ◽  
Xin Guo ◽  
Ping-Juan Zhao ◽  
Ming Peng
Keyword(s):  
Seed Germination ◽  
Seedling Growth ◽  
Nuclear Localization ◽  
Potential Role ◽  
Nuclear Activity ◽  
Transactivation Activity ◽  
Transcription Factor Genes ◽  
Related Transcription Factor ◽  
Stress Dependent

Abstract BackgroundWe previously identified six drought-inducible CC-type glutaredoxins in cassava cultivars, however, less is known about their potential role in the molecular mechanism by which cassava adapted to abiotic stress. ResultsHerein, we investigate one of cassava drought-responsive CC-type glutaredoxins, namely MeGRXC3, that involved in regulation of mannitol-induced inhibition on seed germination and seedling growth in transgenic Arabidopsis. MeGRXC3 overexpression up-regulates several stress-related transcription factor genes, such as PDF1.2, ERF6, WRKY40, and WRKY53 in Arabidopsis. Protein interaction assays show that MeGRXC3 interacts with Arabidopsis TGA2 and TGA5 in the nucleus. Eliminated nuclear localization of MeGRXC3 failed to result mannitol-induced inhibition of seed germination and seedling growth in transgenic Arabidopsis. Mutation analysis of MeGRXC3 indicates the importance of conserved motifs for its transactivation activity in yeast. Additionally, these motifs are also indispensable for its functionality in regulating mannitol-induced inhibition of seed germination and enhancement of the stress-related transcription factors in transgenic Arabidopsis.ConclusionsMeGRXC3 overexpression confers mannitol sensitivity in transgenic Arabidopsis possibly through interaction with TGA2/5 in the nucleus, and nuclear activity of MeGRXC3 is required for its function.

The Role of Callistemon Fruits and Infructescences in Protecting Seeds from Heat in Fires

1998 ◽  
Vol 46 (2) ◽  
pp. 235 ◽  
Author(s):  
Claire L. Brown ◽  
Robert J. Whelan
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
High Intensity ◽  
Room Temperature ◽  
Seed Viability ◽  
Protective Role ◽  
Percentage Germination ◽  
Low Intensity ◽  
Australian Plant

A number of Australian plant species tolerate fires because seeds are protected in woody fruits and are released after fire, but there is little information about the role of the fruit, or a collection of fruits, in protecting seed from the heat of a fire. This study examined the effects of various temperatures applied to infructescences of Callistemon citrinus (Curtis) Skeels on seed germination. The protective role of the dense collection of fruits in maintaining seed viability was tested by experimentally ‘thinning’ infructescences before heating. Heating of infructescences significantly increased the percentage of seeds germinating from less than 20% at room temperature to over 35% at 200˚C, but caused a decline, with further temperature increase to 800˚C. There was a slight but statistically significant increase in the percentage germination of seeds from thinned infructescences. Increased germination following exposure to high temperature may be a way for a plant to synchronise germination after high-intensity fire, while spreading it out if seeds are released in the absence of fire or after a low-intensity fire.

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