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2013 Winter Issue 5 (February 15, 2013)

ArbNotes

February 15, 2013
By Marie Schaedel

Spring flowers are just around the corner - according to the groundhog! Come March, a blast of white will once again ‘spring’ up from the ground all over the Arb. A white that is delicate, fragrant, and seductive (if you happen to be a pollinator).

The majority of spring flowers tend to be white, which differentiates them from summer flowers. White does not blend into the landscape, which may increase the odds of pollinator attention when there are still relatively few flowers in bloom.

The differences between spring and summer flowers don’t stop there, however. Nearly every obvious physical difference between these two classes of flowers come from a long and gory evolutionary battle of survival, underscoring the fact that plants are much more strategic than we often give them credit for.

You can think of spring flowers as gluttonous, and summer flowers as abstemious. For starters, spring flowers photosynthesize more rapidly than summer flowers.

Photosynthesis is a process that converts light and carbon dioxide into sugars that plants can use for growth. For every plant, there is a point at which an increase in light does not increase the rate of photosynthesis; photosynthesis plateaus because the plant cannot operate any more efficiently than it already is.

For spring flowers, this point is reached at a much higher light level than it is for summer flowers. This means that summer flowers reach their maximum rate of photosynthesis under lower light conditions.

Spring flowers face relatively little competition for light, owing to the fact that they are the first ones out of the ground – this explains why they seem so imprudent when it comes to the efficiency with which they use light.

Summer flowers, on the other hand, tend to confront significantly shadier conditions: more shade from trees means more competition for light.

Unsurprisingly, summer flowers also use carbon dioxide more efficiently for the same reason. The physical outcome is that spring flowers have thicker leaves, thicker support structures, grow more rapidly, and stay closer to the ground.

Summer flowers are forced to be larger so that they don’t get shaded out by taller competitors. If summer flowers face more competition for light, they also face more competition for pollination. As a result, they tend to stay in bloom longer than spring flowers, which increase their odds of being noticed.

When spring finally arrives, take a walk in the Arb, look at the flowers, and see if you can reason out why they look the way they do. Pay particular attention to leaf structure and leaf color. However, don’t eat any of them! Enticing as they seem, spring flowers are usually poisonous.

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