Question regarding order of maturation

cinemike(8)August 23, 2013

I have been fascinated and by the chance realisation that the inflorescence of plants can start low down, near the crown or start from the top. I gather these two 'orders of maturation' are called 'basipetal' and 'acropetal'.

My question is: what determines whether a plant is acropetal or basipetal, are there any other possibilities and does it occur always in families or are there both basipetal and acropetal plants in the same family or genus?

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cinemike, I don't think I have ever seen an inflorescence open from the flower at the tip and work its way toward the base of the inflorescence. I may be wrong so please give me an example is you have one in mind. I'm not using basipetal and acropetal terminology because an inflorescence may stand upright or droop, depending on the plant.

I recently took a course in plant physiology and we did cover flowering, florigens, and flower signaling, but I don't remember having covered the way inflorescence opened. What I'm about to explain is my hypothesis for inflorescence maturation.

I think that florigens, flower-inducing hormones produced in the leaves, reach the base of the inflorescence and trigger those flowers to bloom. In the meantime, those blooming flowers produce antiflorigens. There are grafting experiments that support the existence of hormones that block flowering. I think that those antiflorigens delay the opening of the proceeding flowers. When the initial flowers reach a certain age, they may stop producing antiflorigens to allow the florigens to take effect on the next set of flowers. This is the most rational explanation I can think of.

What is harder to explain is how cucurbits open one male flower at a time from a set of 6 or 7 male flowers that form at one node. These flowers don't seem to be arranged into an inflorescence, yet the plant still manages to open just one male flower a day.

I used Plant Physiology 3rd ed. by Taiz and Zeiger as my reference.

    Bookmark   August 24, 2013 at 9:15PM
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All of the plants from the family Asteraceae, as far as I can see open 'top down' (basipetal) - Inula, Cosmos, Erigeron etc.
Many plants in the Solanaceae family - notably Datura also evidence this.
As regards the curcurbits, surely it is the same effect as you mention. At a micro level there are the microbuds and each flower produces the antiflorigens until they die, then the next one in acropelal succession does its bit.

What I am looking for is some sort of explanation as to what determines whether an inflorescence is acropetal of basipetal, and if, for example it is some sort of evolutionary development that has divided plants into these two distinct groups.

From further reading, I have discovered that leaf development can be acropetal or basipetal.... so there is another question - must leaf development and flower development both be acropeatal or basipetal, or can there be basipetal leaves and acropetal flowers (or vice versa).... and, most importantly, what determines it?

    Bookmark   August 25, 2013 at 3:55AM
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