All that Colour

Q: Dear I-Know-You'll-Always-Be-Smarter-Than-Me-100-Hour-Board,

I've read that trees use energy to change the pigment of their leaves in the fall. So, why bother? If this is truly a Darwinian world what possible evolution breakthrough could possible make trees benefit from this? And was there a time when the trees didn't change the pigment of their leaves?

Regards,

A 100-Hr-Board-Wannabe-Critchlow

PS. Why don't you ever comment on Critchlow's Counter?

A: Dear 'Kritchlow'

What the heck is a critchlow anyway? I mean I do think it is hugely more scary than any monster in myth - this 'small, aged, hairy man'. And he tells stories at a counter? Don't you sell anything? Counters are for counting things or selling goods. A hearth, table, den I can understand, but unless your selling me BS, I don't get the counter thing.

As to fall colors. Your first statement is true and false. Some leaves require energy to change color, others don't. Here's the 50,000ft overview first.

• Chlorophyll is used to turn photons into energy used in the CAM cycle of plants to undertake carbon fixation - turning CO2 and water into sugar.


• Chlorophyll is green and makes leaves green.


• Chlorophyll is constantly destroyed by the sunlight and must be replaced.


• The tree slowly shuts down chlorophyll production (clogs the arteries with cork) to slow down energy production as the winter months come. This is a function of weather, drought, age, time cycle from the first leaves, etc. Basically that the energy required to keep the leave healthy and move food around is not justified by the decreased food production in low light months.


• Food is moved from the leaves into the tree slowly in the transition. This takes energy (remember this). You need to keep part of the factory functioning as you tear it down.


• Remaining energy is in the leaves as they fall and used as fertilizer as it rots.


• When chlorophyll dies carotenoids in the leave (that have always been there) emerge from the 'masking' green color - these are yellow, brown and orange (they color carrots, corn, etc.) THIS color change requires NO energy b/c it is a side affect of chlorophyll balance changing.


• BUT...here's where your question comes in...some trees PRODUCE anthcyanins (reds, purples) as the summer winds down and fall comes. This does take energy. And in cooler night temps it happens more (more vibrant colors in bright days - cool nights).
  

So why? Doesn't make sense that trees would still use more energy to create a colour change as the leaves. There are two theories to date (many have come and gone over time).

• Photoprotection: The new colors absorb light and dissipate it as heat. This protects the leaf from damaging rays as the leaf slowly dies. This goes well into the preserve energy production as the leaf shuts down.


• Coevolution: Red leaves may serve as a signal to aphids that they shouldn't eat here. Or that 'specialized' ones should. This is a coevolved function. Although isn't as wide spread to be the whole truth. Some birds and animals are attracted to the leaves perhaps helping with seed distribution.

The truth is probably a combination of the two, that has evolved over time. Sort of like the evolutionary reason young, poorer portions of the population rely on bling (I swear this is a valid evolutionary study...we can talk about that sometime).

So for now - enjoy the leaves changing. I did last week on a drive to Pittsburgh. Oh wow - incredible.

Happy Fall,

100 Hour Board

PS - As to the question of posting on Critchlow's blog...I offer the following reasons:

• Perfection needs no comment


• If art demands critique than is it really art?


• Lack of interesting topics - I mean fart jokes? Really?


• Still confused on why I should talk to a little, hairy old man with the inability to eat ruffage


• I don't need to add any pithy, sarcastic remarks to make you look bad


• I'll wait until you stop making fun of the 100 Hour Board with a link titled "Stupid ?s Dumber Answers"