Curious Facts / Nature
Where does a cactus photosynthesize without broad leaves?
Look at a saguaro’s green column and spines as parts with different roles.
The green column is a stem
A saguaro, with its arm-like branches, does not display broad leaves like a tree. Its thick green column stands out instead. That part is the stem.
The stem contains chlorophyll, a pigment that absorbs light energy for photosynthesis. To find where photosynthesis happens, look beyond familiar leaf shapes to the green stem.
Spines have a different role
A saguaro’s spines are modified leaves. That does not mean they serve as its main photosynthetic surface. They help deter animals from eating the plant and cast shade on the stem.
This is one example, the saguaro. Letting go of the idea that photosynthesis requires broad leaves makes it easier to see how an unfamiliar plant’s parts share different tasks.
Different roles on the same plant
A comparison of the saguaro’s stem and spines.
- Green stem
- Contains chlorophyll and carries out photosynthesis.
- Spines
- Modified leaves that help with protection and shade.
Visual evidence: Arizona State University, Ask A Biologist — Secrets of Desert Plants · National Park Service — Cacti and Desert Succulents
What did you discover?
2 questions · Read the explanation and evidence, then continue to the next question.
Sources and scope
- Arizona State University, Ask A Biologist — Secrets of Desert Plants
Transcript: saguaro spines as modified leaves; green column as stem; chlorophyll and stem photosynthesis
- National Park Service — Cacti and Desert Succulents
Adaptations / Spines: modified leaves, protection, shade and reduced water loss
Scope of this fact
- The saguaro is the example. This does not imply that every cactus has the same leaf form.
Original writing and English translation by Rantap