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Peach, pear, apple, cherry, and many other fruit trees seem to have flowers comprised of five petals. Assuming there is no evolutionary advantage to confusing students of trees, is there a plausible reason (evolutionary or otherwise) the morphology is so regimented? Are the trees related? Do they like the same pollinators?

Thanks for any insight.

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2 Answers

up vote 10 down vote accepted

Peach, apricot, plum, pear, apple, cherry trees are plants of the same family, Rosaceae, so they are closely related. They share many more aspects than the five petals. In fact, other plants in this family, and even many other dicots have five petal, simply because their share a common ancestry.

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Thanks, I didn't realize this. –  daniel Apr 30 '13 at 0:41
    
But common ancestry still does not solve the problem: Why 5 ? and not 2 or 3 or even 4 ? Why optimized for Rosales Order at 5, and Brassicaceae for 4 and Numerous for many others ? A number game for sure- but any thoughts on the Advantages these numbers confer? Better reproductive adaptations ?-if then how n why ? –  user3654 May 25 '13 at 19:13
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@BBM: The answer might also be that "it just happens to be like this". Not every trait of an organism confers an advantage, and much less is "optimized". You could be interested in reading: evolution.berkeley.edu/evolibrary/misconceptions_faq.php#b8 –  biozic May 25 '13 at 22:49
    
@BBM: early flowering plants had indeterminate petal numbers. The general trend has been towards fewer petals, with fixed numbers. The specific number probably isn't important. However, having a consistent number within a species might confer an advantage in terms of developing a stable relationship with pollinators. Having a consistent number of petals, along with consistent colouring, would enable more controlled & targeted advertising. –  Tyler May 28 '13 at 12:45
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It is hard finding answers to this question, which also interests me a lot. The most satisfying answer I have found is detailed in this paper http://www.ijpam.eu/contents/2012-78-3/6/6.pdf.

From the abstract : "This article examines why many flowers are five-petaled through the use of a five-petal model that draws insight from the location of cell clusters at a shoot apex, rather than from concepts such as the Fibonacci sequence or the Golden ratio which have been referred to in the past. The conclusions drawn are that flowers are most likely to be five-petaled, followed by six-petaled flowers, and that four petals are unstable and almost no flower can be seven-petaled."

As for the alternative theory alluded to at the end of this abstract, you may want to check out the work of mathematician Michael S. Schneider (Master's Degree in Mathematics Education from University of Florida). His answer revolves around this idea where, much like what Plato proposed, geometry is seen as the fundamental building block of the universe and where geometric patterns (therefore numbers) are given different meanings based on observational data. In this theory the number five is seen as the "flag of life" if you will. Look-up an image of a DNA strand viewed along axis, I find it interesting that it's mostly in series of five.

That being said, the article I linked certaintly contains a more satisfying answer to your question.

Hope this helped.

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If possible add in the main conclusions of the paper you referenced, helps just in case the link doesn't work in the future –  AndroidPenguin Jul 9 '13 at 23:14
    
This was a in interesting and entertaining article, thank you. It is true that many more flowers than those mentioned in the first answer or my question have 5 petals. –  daniel Jul 10 '13 at 3:22
    
I just edited my answer to include the main conclusions. Also, I would like to put an emphasis here on the following quote from the paper : 'I do not deny the Fibonacci sequence theory in every aspect, but it does not sufficiently explain why a flower is five-petaled.' I think it could very well be that both the fibonacci sequence theory (in nearly all flowers, the number of petals is a Fibonacci number) AND this new theory can co-exist in a way. Anyways, glad this helped. –  VincentB Jul 10 '13 at 7:09
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