Re: Re: REB: blades/fan/stalk formation

Thanks for the response Chuck.? Doubt anyone will have both the money & time to conduct such studys any time soon.? Until then, guess the best we'll get is speculations.? 

A modern study would use growth chambers were the growing conditions could be controlled and the specific triggers identified.
Betty Wilkerons
Bridge In Time Iris Gardens/KY/zone 6 . . . where the stalks are setting fast!? Lots of seedlings to view and evaluate.? Stalks on the re-selects.? 


-----Original Message-----
From: irischapman@aim.com
To: iris@hort.net
Sent: Fri, 18 Apr 2008 8:30 am
Subject: [iris] Re: REB: blades/fan/stalk formation


Flower bud set has shown up in three studies, as far as I know. Germany 1932, Japan, 1952 and 1966. The German study found bud set mid June. The 1952 Japan study found early Sep, the Japan 1966 study showed mid to late August. These were all field studies, so the conditions triggering bud set were not controlled, but left to mother nature. A modern study would use growth chambers were the growing conditions could be controlled and the specific triggers identified. Based on the differences, I would suspect that maturity of rhizome by itself is not enough. The rhizomes would reach maturity sooner in Japan, as the studies would indicate that they had warmer growing condition then the German study. The trigger would need to involve maturity of rhizomes to some extent. This is shown by the fact that we don't have regular summer bloom. If mature rhizomes had flower bud set, then the plant would not be mature enough in spring but be mature later in season, and hence summer bloom. Maturity is not enough by itself as the flower bud set would occur much earlier in Japan. It in not likely to be a photoperiod trigger as again, it would thus not show such as disparity between Germany and Japan. This leaves temperature as a likely candidate. As in the Japan 1966 study, the ambient day time temperature was 26C, it thus would not likely be day time temperature. This leaves night temperature as likely trigger, or at least one of the triggers. If I had the chance to do a controlled study, I would look as a study with mature plants exposed to the same day temperature and various night temperatures and look at flower bud set based on days of night temperature. I would use photoperiods as in Japan 1966 study. After getting some parameters on this, I would then use the optimal night temperature as found and try different night lengths. From there I would check plant maturity levels and then day temperatures. All in different studies.?
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Until this is done, we can only speculate.?
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Indeed, many fall blooming seedlings do show up to be rebloomers, but not all. Indeed it can be genetic, but this does not necessarily mean rebloom genetics. I have on seferal occasions grown seedlings over winter, inside, from December on. These are seedings that had summer estivation in fridge, after not germintin in the spring. After having been grown under lights all winter, they wer faily mature come spring. From these plants, I can get over half the plants to bloom in the fall, seeming triggered by photoperiod. None of the plants had an estivation. Of note is that these are SDB seedlings, and the ones thet were the fastest, more vigorous growers, were the ones most likely to have maiden bloom in the fall. I can't recall if any of these plants had rebloom gentics, but it is a distinct possibility., as I do have a lot of rebloom crosses floating around. In any case , of these only a couple proved to rebloom. Of couse this does suggest that it was a rebloom cross. So genetically, these fall maiden bloomers may be good plants to use for rebloom crosses.?
A second observation involves the cross of Forever Blue and Summoned Spirit. These two plants are extremely fast increasers. Both produce three generation of plants in our short growing season. Summoned Spirit does not have any rebloom genetics that I know of. But then rebloom genetics were very far back in FB genetics. I have gotten one rebloomer from this cross (more evaluation yet to come as it was an 06 cross) and I don't know yet if it is a cyclic or everblooming plant. But the common genetic is plant vigour. This was a cross designed to test out plant growth as a possible rebloom factor, and so far it does seem to be a factor.?
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Lateral growth suppression is the means by which trees grow more up then sideways. The dominant growth tip (top) sends a represent down the plant stem, to the side shoots, so side shoots don't grow as fast. If you cut off the top of a tree, the branches just below that, start growing at a faster rate. I suspect that the same thing happens with Iris plants. That is the mother rhizome sends bloom suppressants to the daughter rhizomes. This is one way of keeping daughter plants from blooming out of season (ie summer bloom). Remember, vernalization is a permanent change. That is all plant tissues grown from a vernalized plant act as if they had been vernalized). The suppressing plant hormones take some time to pass on their message. If the plant increases are growing very fast, (as in Forever Blue) then perhaps they are growing so fast, that the repressing hormones don't have time to act. Remember, this is pure unadulterated speculation at this point in time.?
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So, maiden fall bloomers would seem to have some of the genetics needed for rebloom, but perhaps not all of the factors needed.?
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Perhaps this answers some of your speculation, or al least some fuel for further speculation.?
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Chuck Chapman?
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Date: Thu, 17 Apr 2008 07:56:34 -0400?
From: autmirislvr@aol.com?
Subject: Re: [iris] Re: REB: blades/fan/stalk formation?
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Chuck,?
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Can rebloom happen, even once, if a rebloom gene is not a part of the irise's DNA???
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Some of the irises that bloom the first fall don't prove to be regular rebloomers, but many do.? A rather high percent here.? It's enough to?make me really excited about them when they occur.? Two (tried)?last fall (despite the drought) and were marked so I could watch their progress.? One is Star Gate X Matrix and the other is Tara's Choice X Again & Again.? Both crosses should make for strong rebloomers.??
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As a rule, strong rebloomers show the trait almost immediately.??
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If rebloom genes were not responsible in some way, then all irises, including the diehard oncers, could bloom the first fall???
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Another characteristic that seems to be connected to rebloom--the ability to miss the first spring but bloom that summer.? Around here, it's not uncommon for a rhizome to still be immature at bloom time (first spring,) but then bloom a month or two later.? My understanding of genes would say that a gene must be in place for this to happen???Otherwise all irises could and would do this???
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Se?
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I have also found that first year bloom in fall doesn't mean it is a rebloomer. It means something, but I don't know what.??
Betty/zone6/KY?
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