How Plants Tell Time

TL;DR

Plants can move without brains by using chemical reactions, such as phytochrome switching between Pr and Pfr forms, to control turgor pressure and move their leaves and flowers in response to day and night cycles.

Transcript

[INTRO ♪] Plants don’t have brains. This is probably not news to anyone. Plants also don’t have muscles, or anything resembling a nervous system, and yet… they can move. In some plants, this is actually pretty dramatic—think Venus flytraps. But there are tons of plants that move more slowly, and they do it in time with the coming of day and night. ... Read More

Key Insights

• 💪 Plants can move without brains or muscles by using chemical reactions and turgor pressure control.
• 😛 Nyctinasty is the process through which plants tuck their leaves in at night, but its specifics are still not fully understood.
• 🎮 Phytochrome, a molecule that switches between different forms depending on light conditions, plays a crucial role in controlling turgor pressure and plant movement.
• 🍃 Leaf-closing and leaf-opening substances are involved in the nighttime movement of leaves and flowers.
• 🥳 Heliotropism allows plants to actively follow the sun during the day, contributing to optimal sunlight exposure.
• 😎 The hormone auxin plays a role in sunflowers' ability to face the sun, influencing stem growth and direction.
• 😀 Sunflowers exhibit solar tracking in young plants but face east once fully mature.

Questions & Answers

Q: How do plants tuck their leaves in at night without a brain or muscles?

Plants tuck their leaves in at night through a process called nyctinasty, which involves chemical reactions and the control of turgor pressure in pulvini, acting like flexible joints, rather than relying on muscles or a brain.

Q: What is the role of phytochrome in plant movement?

Phytochrome is a molecule that absorbs light and participates in a reversible chemical reaction. It switches between the Pr form, absorbing red light during the day, and the Pfr form, absorbing far red light during the night. The presence of Pfr in the pulvini controls turgor pressure, causing the plant to move its leaves.

Q: How do flowers open and close at night?

The opening and closing of flowers at night is not fully understood, but it involves oscillating chemical reactions similar to leaf movements. Leaf-closing and leaf-opening substances, as well as unidentified factors, likely play a role in this process.

Q: How do plants follow the sun during the day?

Plants exhibit a type of plant movement called heliotropism to maximize sunlight exposure. This movement is controlled by turgor pressure in pulvini, where the leaves continuously move to track the sun throughout the day, rather than just opening and closing.

Summary & Key Takeaways

• Many plants, such as legumes and wood sorrels, tuck their leaves in at night in a process called nyctinasty, which is still not fully understood by scientists.

• Chemical reactions, specifically the conversion between the Pr and Pfr forms of the phytochrome molecule, play a key role in the movement of plants by controlling turgor pressure in pulvini, acting like plant joints.

• Heliotropism is another type of plant movement where plants actively follow the sun during the day, maximizing sunlight exposure, and flowers may also track the sun to benefit pollinators and seed development.