Do you know the plant clock of Carl Von Linné ?
This 18th-century Swedish physician and botanist had the idea of building a clock composed exclusively of certain varieties of flowers. These varieties, he noticed, only opened and closed at specific times of the day.
So you could tell the time by looking at which flowers were open.
Flowers aren't the only things that find their way by light.
At night, the body needs rest to regenerate some of its functions.
Seasonal monitoring is based not only on temperature, but also on the duration of daylight. A constantly lit tree will react as if daylight were permanent:
The early appearance of leaves (which risk freezing) won't benefit caterpillars, which feed on young, tender leaves that won't be eaten by birds.
Light alters the perception of day/night alternation, and inhibits plant dormancy, which enables them to survive the onset of winter.
In New York, leaf fall is delayed by 1 month.
A recent Chinese study has highlighted an unexpected effect of continuous tree lighting in cities.
Artificial light at night influences the nutritive and defensive properties of plants, which in turn influences the living conditions of herbivorous insects and the predators that depend on them.
According to the researchers, city light at night lengthens photosynthesis and alters the structure and composition of tree leaves.
They measured their size, stiffness, water, nutrient and tannin content. Leaves that grow in conditions of near-constant light develop more fibers and tannins, increasing their resistance and making them more difficult for insects to nibble.
This will have a domino effect on urban ecosystems: by modifying these characteristics, the artificial light halos of street lamps can deprive herbivorous insects of their food.
