Thursday, May 2, 2013

Hello! I'm Veronica. I'll Be Your Nectar Guide Today

The plant below is called Veronica.  That's its scientific name and its common name.  In our outdoor classroom, it's located on the rocks behind the pond, and it's blooming like crazy right now.  Veronica flowers have something really neat called nectar guides. 

Nectar Guides on Veronica Flowers

Nectar guides help bees find flowers.  They point to the part of the flower that contains the nectar, which is what bees are looking for.  Nectar is sugary plant sap found in the base of many flowers, and it is perfect bee food.  I like to think of nectar guides working a lot like the stripes and lights on airport runways telling airplane pilots where to land their planes.

Why would flowers advertise where their nectar is?  It turns out flowers are offering the nectar in a bargain.  Do you see those tiny white structures poking out of the flowers in the picture above?  Those are anthers, and they contain a dust called pollen.  Flowers must have pollen moved from one flower to another in order to be able to grow seeds to grow a new generation.  While a bee sips the nectar in a flower, those anthers are in the perfect place to dab some powdery pollen onto the bee.  Then the bee rubs off the pollen at the next flower it goes to.  The flowers are giving the bees a meal in return for moving their pollen from one place to another.  (Do you remember the name for a close relationship between two organisms where both organisms benefit?  The answer is at the bottom of this page.)

Bee-pollinated flowers usually have nectar guides.  Flowers that are small, fragrant and with a shallow cup for nectar are usually bee-pollinated, and we have lots of bee-pollinated plants at our outdoor classroom to discover.  You may not always notice nectar guides on bee flowers because sometimes the guides are invisible to human eyes.  Strangely enough, there are more colors of light than humans can see.  Rainbows actually have more stripes than humans see, in colors we haven't imagined.  Bees can probably see one more stripe on the rainbow than we can.  We call this color ultraviolet, and know it exists because we can detect ultraviolet with machines.  But how do we know bees can see ultraviolet?  Because scientists have given bees eye tests!  Scientists tested bees' eyesight by making fake flowers.  On some flowers, they painted nectar guides with an ultraviolet dye.  When you offer fake flowers to bees, the bees are way more curious about the ones with the ultraviolet nectar guides than the ones without nectar guides.  Scientists have detected ultraviolet nectar guides on real flowers (sunflowers have ultraviolet nectar guides).

Go back to the picture above and see if you can find the nectar thief.  A nectar thief is something that steals nectar without moving pollen - a parasite!  The nectar thief on our Veronica flowers is an ant toward the left of the picture.  As we learned last week, ants eat sugar, so it's no surprise that they would like flower nectar.  The ants are too small for the anthers to dust them with pollen, so they slip in, drink the nectar and slip out again without helping the plant.  Ants mostly use smell and taste to find their way in the world, so they probably don't even notice the nectar guides.  If you are jealous of bees for seeing one more color than we do, then you're really going to be mad at ants.  Scientists think ants can smell and taste an enormous number of things humans can't, with much more precision.  If you don't believe me, try closing your eyes and finding your way around using just your nose and tongue, and you will appreciate just how much better ants' senses are.

Answer: Mutualism

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