Push-pull pollination

Beekeepers are well aware that plants exert some control over their pollination by attracting them by producing nectar at different seasons and even at different times of day. But here's a very smart plant dating back 300 million years that tells insects when it's time to move on:

Cyads have distinct male and female plants, and both produce large, club-like “flowers”. There is, however, a key difference between them: male flowers provide nourishment to insects, which can eat the pollen, but female plants do not.

So ...

Females produce low and constant levels of a number of chemicals that can attract the pollinating insects. Male flowers produce similar levels of those chemicals for much of the day. But, at midday, when the temperature at the flowers heats up, male flowers start producing much more of these chemicals. They make such high levels, in fact, that insects are repelled from the male flowers—tests in the lab show that high levels can even be lethal to the insects.

Given that female chemical output doesn't change, the authors assume that the insects will move on to their flowers, bringing the pollen to its needed destination. As things cool down in the evening, male plants drop back to normal levels of the chemicals, and the cycle can repeat. The authors term this "push-pull" pollination.