Excerpts from Jim Conrad's
Naturalist Newsletter

from the January 22, 2012 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins; limestone bedrock; elevation ~39m (~128ft), N20.675°, W88.569°; central Yucatán state, MÉXICO
A TOMATO FLOWER'S CIRCADIAN RHYTHM
Circadian rhythms are daily cycles of activity displayed by many kinds of organisms. If you experience jetlag when traveling across time zones you're feeling the effect of your own waking/sleeping circadian rhythm. I've grown tomatoes ever since I was a kid but it wasn't until this week when I was paying special attention to a certain flower (more below) that I realized that tomato flowers have their own circadian rhythm governing their openings and closings.

To be sure I was seeing it, in the very dim light of the evening of the day when I first noticed what was happening I took a picture of my flower, along with some neighbors, that I knew had been open all day. The next morning I photographed the same flowers fully reopened. The late-dusk/early morning shots are shown below:

tomato flowers, closed at dusk, open next morning

Until now I'd assumed that closed flowers seen in the evening were just young blossoms not yet open, and if there were no open flowers, then it was because all the pollinated ones had fallen off. It's amazing just how unobservant a person can be, especially with regard to ordinary, everyday events.

What a lesson the tomato flower teaches.