Plant Activity on Kiawah— Morning and Night
Story and photographs by Jane Ellis
Yes, plants can tell time! They have circadian rhythms( 24-hour cycles of activity) just like the rest of us. Of course, these activities often depend on environmental clues such as light, dark, and temperature. Flowering in certain plants is a response to the length of daylight— it’ s actually a response to the length of the dark period not light! Some plants only bloom when the amount of light per day exceeds a species specific length of time such as 12 or 14 hours. These we call long-day( short-night) plants.
Here on Kiawah some of these might be the early summer bloomers. Others, such as some of our goldenrods, camphorweed, grasses, and morning glories are short-day plants and bloom when the days begin to shorten in the late summer and early fall. Still other plants are day neutral and can bloom all summer long like the beach plants, sea rocket, and silver-leaf croton. What about the ones whose blooms open and close at different times of the day and night? Below are a few interesting examples found on our beautiful Island.
Flowers of the Morning Magnolias: Thought to be some of the most ancient flowering plants, magnolias have a unique flowering sequence. The flowers open early in the morning on the first day with the female stigmas receptive to the male pollen, but the flower’ s own pollen is not mature. These flowers give off a lovely fragrance, and the stigma produces an exudate loaded with sugars ready for any insect to dine upon.
Most researchers believe that beetles are the main pollinators of magnolias although some conclude that different species of bees have taken over this spot. The flowers close that first night, forming floral chambers where beetles may mate, find food( sometimes eating flower parts), enjoy protection and warmth, and in the process pollinate the flowers. The next morning the flower reopens, and the male stamens are ready to shed an abundance of mature pollen, but the flower’ s own female stigmas are no longer receptive.
A researcher determined that one magnolia flower could produce approximately 58 million pollen grains, and this pollen falls into the cup-shaped petals. Flowers remain open for several days, so the beetles and other insects gather pollen then head to other flowers that may be just opening on their first day. This process increases chances of cross-pollination with other magnolias. Amazing timing!
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