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  1. #1
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    Germination Temperature

    Hey yall. Hope all is well. I have a question. Ive got my seeds in some potting mix in a seed starting tray. All ive got is a regular heating pad like you put on your back. Ive got it under several towels and then some pot holders and then another couple towels on top of that and then some wooden dowels on top for some air flow because it was too hot with the tray sitting on those. The temp on top of the soil is still 82°. Thats a little over the 80° max that ive read everywhere. Is 2° going to make a difference or am i overthinking it? Thanks in advance for any information or feedback. Happy smokes yall!
    ​Keep it smokey!

  2. #2
    Senior Member Smokin Harley's Avatar
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    Re: Germination Temprature

    Tobacco seed requires light . I keep a heat mat on under the flat (no towels) and a fluorescent light fixture (on 24/7) over it to attain 80* ( I lay a small thermometer across the flat cells ),adjust the distance of the light to soil surface . I don't think 2* will make much difference . I usually have germination in under a week and as soon as 3 days
    "We make our own Whiskey and our own smoke too, aint too many things these ol' boys cain't do..." -A Country Boy Can Survive ,Hank Williams Jr.

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  3. #3
    Administrator deluxestogie's Avatar
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    Re: Germination Temprature

    Only a few tobacco varieties require light to germinate. Most will germinate well in total darkness. Those few that require light need only a brief exposure to bright light, on the order of a minute or two.

    On the other hand, exposure to light won't hurt any tobacco seed.

    Bob

  4. #4
    Administrator deluxestogie's Avatar
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    Re: Germination Temprature

    [Heaven knows where I first posted this in 2011 (maybe HTGT), but it fits this discussion. I found it among my saved files.]


    Temperature, Light and "Priming" of Tobacco Seed

    SUMMARY: Temperature and light both have an effect on seed germination. The effects seem to vary with the age of the seed, the variety of cultivar, the source and crop year of the seed--even for the same cultivar, as well as the growing condition of the parent plant during seed maturation. So, every opinion on the subject of light (needs light vs. don't need no stinkin' light) voiced by the members of this forum are correct, under various circumstance. The germination temperature ranges discussed in the following papers are of interest. (Since they are expressed in ºC, I've included a conversion chart after the first article.) In the current context, "priming" refers to a period of brief hydration of the seed, followed by drying before germinations begins.

    M. D. Hartley, J. F. Spears, W. D. Smith, L. R. Fisher and J. R. Schultheis (2001) RESPONSE OF FLUE-CURED TOBACCO CULTIVARS NC 71 AND NC 72 TO SEED PRIMING: I. LABORATORY EVALUATIONS OF LIGHT AND TEMPERATURE EFFECTS ON GERMINATION RATE AND SYNCHRONY. Tobacco Science: January 2001, Vol. , No. , pp. 6-10.

    http://www.tobaccoscienceonline.org/...82-4623-45.1.6 (accessed 4/4/2011)

    Quote Originally Posted by Hartley, et al.
    Abstract:
    Seed priming is frequently used in the tobacco seed industry to increase seed germination rate and uniformity and to overcome temperature imposed dormancy. However, it is not known if all seedlots respond equally to priming. This research was conducted to evaluate the influence of temperature, light, and priming on two widely-planted flue-cured cultivars. Experiments were conducted in 1999 and 2000 using the flue-cured tobacco cultivars NC 71 and NC 72. For each cultivar and year, primed and non-primed pelleted seeds from the same seed lot were used. Seeds were germinated at constant 20°C, and alternating 30/20°C, 30/15°C, and 23/20°C in both light and dark environments. The days required to reach 90% germination (D90) and a modified index of synchrony (ISM) were determined. In 1999, priming decreased the rate of germination (higher D90) and reduced ISM for NC 71, but had no effect on speed or uniformity of germination of NC 72 compared with non- primed seeds. Germination of primed seeds of both cultivars at 30/20°C was significantly faster than germination at 30/15°C, 23/20°C and constant 20°C, compared with non-primed seeds. All seeds, whether primed or non-primed, germinated better in the dark at 30/20°C and 30/15°C than at 23/20°C or constant 20°C. However, priming improved the germination of NC 71 and NC 72 at 23/20°C and constant 20°C in the dark. In 2000, differences between cultivars were not observed; however, the D90 was influenced by temperature and priming. When averaged across cultivars and germination temperatures, priming reduced D90 by one day (10 vs 9). D90 was lowest at 30/20°C (8 days) followed by 23/20°C (9 days), constant 20°C (10 days), and 30/15°C (11 days). Priming and temperature did not effect ISM or total percentage germination at 14 days after planting in the light. However, in the dark, constant 20°C resulted in the lowest percentage germination of all treatments. In the dark, priming increased the germination of both cultivars. In these experiments, the benefits of priming were not consistent between years. Priming may be of some benefit with some varieties, in some production years; however, a positive, consistent response over a range of light conditions, cultivars, and temperatures was not seen in this study.


    Excerpts:
    The objectives of this study were to determine the effects of priming on the germination of two widely-grown flue-cured cultivars and to evaluate the influences of temperature and light on percent germination as well as the rate and synchrony of germination.

    Seed priming is a germination enhancement technique used to modify physiological events during germination or early seedling growth. It allows the uptake of water to initiate the early events of germination, but the seed is allowed to dry before the radicle begins to grow. The goals of priming are to increase the germination rate, increase germination percentages, allow germination over a broader range of environments, and improve seedling vigor, which would ultimately promote more uniform seedling emergence. Priming is an enhancement that can eliminate some levels of dormancy, such as the photodormancy found in several tobacco (Nicotiana tabacum) cultivars.

    Kasperbauer found that light-sensitivity of tobacco seed may be temperature related. Seeds of the cultivars Havana 142 and Connecticut Broadleaf germinated in the dark at 15°C (60 and 36%, respectively), but neither cultivar had greater than 1% germination at 30°C. Photodormancy of tobacco seed occurs mainly in freshly harvested seed. Seed stored under proper conditions for several months, however, usually lose this dormancy. Toole demonstrated that the germination of some photodormant species could be promoted by exposure to light at constant temperature or to darkness at alternating day/night temperatures that mimic typical diurnal fluctuations.

    These data, and data from Brockelhurst and Dearman, suggest that seed lots can vary greatly in their response to priming, even within a cultivar. Because of this variability, the optimum priming conditions must be determined for each seed lot in order to obtain the greatest seed-priming response. Preliminary research by Smith et al. demonstrated differences in cultivar response to priming. For example, priming increased the rate of emergence of NC 71, NC 72, and K 394, but decreased the emergence rate for K 326 and K 346.

    **********************

    Temperature treatments included constant 20°C and alternating day/night regimes (8 hour day/16 hour night) of 30/20°C, the standard Association of Official Seed Analysts procedure, and 30/15°C, and 23/20°C. Each germinator contained cool-white 110-watt GE fluorescent bulbs...that remained lit during the eight-hour day period. Fifty seeds were placed in a 100 × 15 mm sterile plastic Petri dish containing one 15 mm blue blotter paper soaked with 7 ml of distilled water. Petri dishes containing seeds that received the light treatment were placed inside small clear plastic bags to prevent moisture loss. Dark treatment dishes were wrapped in heavy-duty aluminum foil to prevent light penetration and reduce moisture loss.

    [1999 seedlot]There was no difference between germination of seed in light or dark treatments exposed to 30/20°C or 30/15°C. However, seed, especially the non-primed seeds, placed in dark conditions at 23/20°C and constant 20°C germinated more slowly than at other temperatures. Upon completion of the dark germination experiment (14 DAP), non-germinated seeds readily germinated when exposed to light (data not shown). Therefore, the non-germinated seeds were still viable. NC 71 primed seed exposed to the 23/20°C and 20/20°C dark treatments averaged 78% germination, while NC 71 non-primed averaged 24%. Under identical conditions, primed and non-primed seeds of NC 72 averaged 86% and 63% germination in the dark.

    [2000 seedlot]Regardless of cultivar or the use of or lack of priming, seed germination was reduced in the absence of light compared to those treatments with light. When evaluated 14 DAP, ungerminated seed from dark treatments were viable and germinated rapidly following exposure to light (data not shown).

    Temperature played a major role in germination in light and dark treatments. More ideal temperature regimes, such as 30/20°C, resulted in more rapid germination and emergence than priming alone. Also, alternating temperatures, as seen in the 30/20°C and 30/15°C treatments, was more important to germination in the dark than priming. Temperature considerations seem to be most important for enhancing the speed of seed germination.
    Temperature Conversion
    • 15ºC = 59ºF
    • 18ºC = 64.4ºF
    • 20ºC = 68ºF
    • 23ºC = 73.4ºF
    • 26ºC = 78.8ºF
    • 30ºC = 86ºF
    • 32ºC = 89.6ºF


    Jodie J. Clarke, Development of a Greenhouse Tobacco Seedling Performance Index, Thesis submitted to the Faculty of Virginia Polytechnic Institute and State University, 2001.

    http://scholar.lib.vt.edu/theses/ava...1SPIthesis.PDF (accessed 4/4/2011)

    Excerpts from her thesis:
    Quote Originally Posted by Clarke
    Germination of seed and seedling vigor can be affected by temperature and light conditions in the greenhouse (Bunn and Splinter, 1961). As the optimum temperature changes, germination is reduced rapidly, and the most rapid germination rate occurred when temperatures were 26 to 32ºC (Bunn and Splinter, 1961).

    The importance of quantity of light, as well as the effects of seed treatments in overcoming light quantity requirements, is not known. The quality, quantity, and intensity of light may affect the light treatments.

    Maximizing germination depends heavily on the ability to optimize and control soil temperature and moisture at the seed level for a specific crop (Styer and Koranski, 2000). Tobacco seed germinates at an optimum temperature range of 18 to 23ºC. Within this optimum range, most germination will usually occur between 7 to 12-d after seeding. Lower temperatures may delay emergence thereby increasing nonuniformity, while higher temperatures may actually decrease germination (Hutchens, 1999). Crops differ in the optimum soil moisture for germination. Commercial tobacco and a popular bedding plant are in the genus Nicotiana. Species of this genus have shown to favor soil with a medium moisture level for the first two phases of germination. Producers describe moderate moisture as moisture, although not visible on the surface, is apparent to the touch, and the media is not light colored (Styer, 2000). A germinating tobacco seed can perish in less than 4 h under droughty conditions. In contrast, an over-abundance of moisture is one of the leading causes of poor germination and seedling failure in float-system greenhouse production (Hutchens, 1999).
    Bob

  5. #5
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    Re: Germination Temprature

    Will cool winter indoor temps seriously effect germination.

  6. #6
    Senior Member Alpine's Avatar
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    Re: Germination Temprature

    Of course they do. Expect a few days to a couple of weeks delay in germination if temps are around 16C. This is true if the seeds are viable or “fresh”. With older seeds (or seeds not kept in nearly ideal conditions) germination time will be more or less the same, but with far less success (i.e. lots of seeds for a few plants). But be patient, you’ll be surprised!

    pier

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    Re: Germination Temprature

    well on the positive note your not far from Don so you get some tobacco leaf there. Any time I have germinated seeds for planting outside has been warm water and tissue paper that is kept damp. Once it sprouts put it in some soil and not sure why it would be not different than a tobacco seed.

  8. #8
    Administrator deluxestogie's Avatar
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    Re: Germination Temprature

    Quote Originally Posted by burge View Post
    ...not sure why...
    Because you have not done it. Read the FAQ.

    Bob

  9. #9
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    Re: Germination Temprature

    I had them covered with foil from wednesday to sunday. the cat laid on top of em saturday night. i pulled the foil off sunday and there were very few sprouts (like maybe 5 out of maybe 100 seeds) so i covered them back up, blocked them with a box to keep the cat off, and theyve been there for 2 more days now. id read to cover them but it seems from yalls responses that i really shouldnt have to. ill open them tonight and if theres no more improvment i think ill start over. i think maybe the cat messed up most of em. ill try it without the foil this time. thanks for the feedback yall. i really appreciate it
    ​Keep it smokey!

  10. #10
    Administrator deluxestogie's Avatar
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    Re: Germination Temprature

    Once the seed germinates, it needs light.

    Bob

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