By Wendy Langhans

[view:node_ad=5]Last
week we talked about how plants respond to leaf-eating predators through a
biochemical "fight or flight" response.

 

When a insect takes a bite out of a plant, the plant
responds by producing jasmonic acid. 
This triggers a variety of defensive responses:

 

 protective chemicals
that make the plant taste bad

 protective chemicals
that hinder the attacker's digestion 

 protective chemicals
that attracts predators of the attacking insect

 protective
bio-mechanical structures (with sharp points)

 

But just because a plant can fight doesn't mean it always should. 

A plant has a limited supply of energy; a defensive response
will divert metabolic resources away from other tasks.  And in the spring, no task is more important
that growing.

 

Especially in the spring, plants need to grow.  If they don't – and neighboring plants do,
they won't be able to get the sunlight they need to survive.  Sometimes plants need to make tough choices –
growth versus defense.

 

So how do they make this tough
choice?   As it turns out, the are "blinded
by the light".  Plants become more
resistant to the effects of jasmonic acid in response to the amount of
infra-red light bouncing off neighboring plant leaves.  The more light – the more resistance.  However, this same infra-red light increases
a plant's production of growth hormone. 
The more light – the more growth. 

 

So as the potential competition for light increases, fewer
plant resources are diverted to defense and more resources are committed to
growth. 

 

As an analogy, picture a hot-rodder in a 32 Ford.  How do you think he will respond when he sees
a souped up Chevy approaching in his rear-view mirror?  It reminds me of a phrase from Bruce
Springsteen's, "Blinded by
the Light":

 

 
And she was
blinded by the light

 
Cut loose
like a deuce another runner in the night

 

Perhaps we're more similar to plants than we thought.

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Upcoming Outdoor Events: 

 

Saturday, March 21, 8:00-10:00
AM.  Morning Bird Hike in Towsley
Canyon.  Towsley
Canyon is a year-round home for
birds.  They like our Mediterranean
climate, the local bounty and the California
sunshine.  Bring your binoculars and meet
at the entrance.  Heavy rain cancels.  For map and directions go here.

Sponsored by the Mountains Recreation and Conservation
Authority.

 

Saturday, March 21, 10-12 AM.  Wildflower hike at Elsmere
Canyon.

Heavy rain cancels.  For map and directions go here.  Park at the entrance to Whitney
Canyon.

Sponsored by the Mountains Recreation and Conservation
Authority.

 

Saturdays, March 14 & 28, and every Wednesday, 8:00 AM.  Trail Maintenance Volunteers at Towsley Canyon.

Come join our trail maintenance volunteers for camaraderie
and a heart-thumping workout.  For more information contact Steve Ioerger at 661-291-1565.

 

 

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You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report",
brought to you by your hometown radio station KHTS (AM1220) and by the
Mountains Recreation and Conservation Authority.

 

For the complete MRCA hike and activity schedule and for
trail maps, click here or go to www.LAMountains.com.