The daily dance of flowers following the sun is more fascinating than most of us realize.

When I was a child, I was fascinated by Queensland field (Lophostemon confertus) growing in our yard. I noticed that its leaves would hang vertically after lunch in the summer, and the next morning they would be more or less horizontal.

This is an example of heliotropism, which literally means moving in relation to the sun. This is most evident when spring comes and different species of flowers burst into bloom—you might even get the impression that some of the flowers are watching you as they move.

Many of us probably first encountered heliotropism at home, in kindergarten or elementary school, watching the huge, yellow-and-black inflorescences of aptly named sunflowers move as they grow.

These flowers follow the sun spectacularly on balmy and shining spring or summer days. Sometimes they move in an arc of almost 180⁰ from morning to evening.

Now that the shining days are back and the flowers are in full bloom, let’s take a closer look at why this phenomenon is so compelling.

Sun Tracking Mechanics

Several flowering species exhibit heliotropism, including alpine buttercups, Arctic poppies, alfalfa, soybeans, and many daisy-type species. So why do they do it?

Flowers are truly in the advertising game and will do everything in their power to attract the right pollinator as effectively and efficiently as possible. There are several possible reasons why tracking the sun could have led to more productive pollination.

Flowers, following the sun, absorb more solar radiation, which causes stay warmerWarmer temperatures respond to and even reward pollinating insects, which are more busy when they have a higher body temperature.

Optimal flower warmth can also stimulate pollen development and germination, resulting in higher fertilization rates and more seeds.

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So the flowers are clearly moving. But how?

Many species of flowering heliotropes have a special layer of cells called a cushion. just below the flower heads. These cells pump water across the cell membranes in a controlled manner, allowing the cells to become completely inflated like a balloon or become empty and flaccid. The changes in these cells allow the flower head to move.

When potassium is transferred from neighboring plant cells to the cushion cells, water follows and the cells swell. When they transfer potassium from the cells, they become flaccid.

Potassium pumps are also involved in many other aspects of plant movement. This includes the opening and closing of stomata (petite adjustable leaf openings), the rapid movement of mimosa leaves, or the closing of a fly trap.

But sunflowers dance differently

In 2016 scientists have discovered that the example of heliotropism – the sunflower – moved differently.

They found that the sunflower’s movement results from significantly different growth rates on opposite sides of the flowering stem.

On the east side, the cells grow and lengthen rapidly during the day, which slowly moves the flower westward as the daylight hours pass—following the sun. At night, the cells on the west side grow and lengthen more rapidly, which moves the flower back eastward during the night.

Then everything is prepared so that the whole process starts again the next day at dawn. It is repeated every day until the flower stops growing and movement ceases.

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While many people are aware of heliotropism in flowers, the heliotropic leaf movement is less frequently noticed or known. Plants with heliotropic flowers do not necessarily have heliotropic leaves and vice versa.

Heliotropism develops in response to very specific environmental conditions and factors. affecting flowers may differ from those affecting the list.

For example, flowers are all about pollination and seed production. For leaves, it’s about maximizing photosynthesis, avoiding overheating on a warm day, and even reducing water loss in harsh, arid conditions.

Some species, such as Queensland box, orient their leaves so that they are somewhat horizontal in the morning, taking full advantage of available sunlight. But there are also cases where the leaves orient themselves vertically to the sun in midday to minimise the risk of heat damage.

Plants are vigorous

It’s uncomplicated to think of plants as inert organisms. But of course they are constantly changing, responding to their environment and growing. They are vigorous in their own way and we tend to assume that when they change it will be at a very ponderous and steady pace.

Heliotropism shows us that this is not necessarily the case. Plants that change daily can be a bit unsettling because we sense the change but may not be aware of what is causing our uneasiness.

I’m still keeping a close eye on those Queensland boxes!

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