I've often wondered why blooms of specific plant species are visited some years, but not every year.  Dutch clover was a major honey plant in northern NY when I was young, but not now.  For the last several years, I've watched it....no bees.  However, this year I see bees working the Dutch clover.  What is different?

There is a paper I found from the Journal of Plant Physiology, vol. 27, no. 1, Jan 1952, pp 95-110, called "Some factors affecting nectar secretion in red clover" by R. W. Shuel.  Here is a quote:


"Little is known about the basic mechanism of nectar secretion.  Two general theories are extant:  1.  That sugar secretion and water secretion are distinct phases, water secretion being analogous to guttation and dependent on root pressure (cited)  2.That secretion occurs as one phase, nectar being secreted in its final form as the result of a specific cellular activity (cited).  Bonnier (cite) has presented evidence for a positive relationship between secretion and root pressure.  (NOTE:  This is basic plant physiology; I was trained in this, and can confirm it to be true...it is similar to guttation)  Radtke (cited) on the other hand, has shown that secretion can occur in the absence of root pressure in isolated flowers floated on sucrose solutions (cited, but NOTE:  from a physiologist's point of view...big deal. Ask me why if interested.)


Recently Arens (cite) has advanced an hypothesis in which secretion, absorption, and transport of solutes are treated as closely related phenomena dependent on electro-osmotic currents at the surface of the tonoplast.  The energy necessary for the maintenance of the oxidation-reduction potentials across the membrane is assumed to be supplied by respiration."


From this I gather that the quality of nectar is a product of two processes:  one that is essentially the same as guttation, but the second is more nebulous...sugar production is driven by respiration, and may or may not occur depending on the level of plant stress.  If the point of nectar production is to attract pollinators, then it seems to me that the process which supplies sugar is essential, else why bother with nectar production at all?  Yet we have years where certain plants flower but do not make a nectar that is attractive to honeybees.  Is that nectar attractive to other pollinators?  If not...well, Occam's razor would suggest that there is no reason to produce flowers, at all, if they cannot be pollinated.  This year my peach trees did not bloom.  I assume that the reason is it was too cold during the winter.  That makes sense to me...the plant was too severely stressed, so it didn't make an effort to reproduce in favor of simply replenishing itself and surviving.  However, if the peaches had bloomed and produced a nectar that was low in sugar and unattractive to pollinators...that just does not make sense.  Yet that seems to happen among some plants, such as the Dutch clover.

Do any of you know more about this?  Why do some plants bother to produce flowers that haven't got enough sugar to attract pollinators like honey bees?  Or, are they attracting DIFFERENT pollinators...and if so, what ones?


Christina


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