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Re: CULT:Germination and Nitrogen:(germination & heat mats)


The information about nitrogen was <not> specific to germination of iris
seeds.  It was in a book reviewing all kinds of literature related to
seed germination.  Some of the generalizations may or may not apply to
irises.

From a section on Chemical Environment, Liquid Phase, Chapter 1, Dov
Koller, Environmental Control of Seed Germination, In: Seed Biology, vol
II, T.T. Kozlowski (editor), 1972:
<Most ions which can be expected to be in the soil solution do not seem
to have any specific regulatory activity on seed germination.  There are
two notable exceptions.  One is the nitrate ion, several salts of which
have a widespread stimulatory effect on germination, particularly on
species with light-requiring seeds .....The other ion which has been
reported to have a regulatory effect on germination is calcium.....>

Since iris seeds don't seem to require light to germinate, nitrate may
not have any effect. ?? But like the ripening apples, it can't hurt.

In Chapter 3, T.A. Villiers, Seed Dormancy,
Another tidbit was in a general discussion about gas exchange in imbibed
[i.e., soaked and plumped] dormant seeds:

<As emphasized by Nikolaeva (1969) in her classification of dormancy
types, the restricting effect of the seed coats on gas exchange is
usually accompanied by one or more factors imposing dormancy on the
seed, and this observation is supported by the range of
dormancy-releasing stimuli which are effective in these cases, including
exposure to light and certain photoperiodic regimes, chilling
temperatures, and the application of gibberellic acid and dormancy
breaking chemicals such as thiourea, nitrites, and nitrates.  .......>

Keep in mind that this section of the book is discussing metabolic
activity in seeds as they break dormancy - a complicated story for
sure!  Production and breakdown of proteins, nucleic acids (both contain
nitrogen), sugars, energy transfers etc etc.   I can't tell from the
context whether or not the phrase 'dormancy breaking chemicals' refers
to levels of those chemicals that would normally occur in nature or at
elevated, experimental levels.

There is another section on phosphate metabolism, but no mention of
external application of phosphate.  Ditto for calcium & boron, more in
reference to amounts available to the parent plant and subsequent
effects on germinability/disease susceptibility (damping off etc) in the
seeds they produce.

Another mention of nitrate is in a chapter on Metabolism of Germinating
Seeds by Ching in reference to lipase activity in fatty seeds.  Are iris
seeds fatty??  I barely know enough about plant physiology to be able to
read this stuff....

Elsewhere in Ching's chapter:
<In embryonic tissue, ....[sugars & some other things] might be ample in
seeds, [but nitrogen containing compounds & some other stuff] are needed
for biogenesis of new cellular constituents, particularly in
meristematic tissues [cells where growth takes place].

Finally, more from Koller's chapter:
<Recent studies have shown that imbibed seeds of [clovers] produce
ethylene as well as carbon dioxide, and that their germination is
promoted by both of these substances.....[Production of these gases] may
[provide] an ecological advantage, by favoring germination within the
soil, where their concentration can increase as a result of the high
diffusive resistance.>

I dont' remember reading anything specific about nitrogen in the book
John loaned me, but will check.

So, you guys, is all that any help at all in deciding what to do?  It
made me decide to water my germinating seeds with house plant strength
Miracle Grow.  I figure it won't hurt anything and it might boost along
some seeds that are still trying to decide what to do.

--
Linda Mann east Tennessee USA zone 7/8

American Iris Society web site <http://www.irises.org>
iris-talk/Mallorn archives: <http://www.hort.net/lists/iris-talk/>
iris-photos/Mallorn archives: <http://www.hort.net/lists/iris-photos/>

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