Let there be light

It is dark. A world of soil.

Something is moving.

A tiny seed!

Perhaps round and wrinkly1.

Root protrudes down, out of thirst,

eager to explore.

The young stem2 grows upward, longer and longer,

with a vigour resembling a rattlesnake rising to its defence.

At the top, a hook3 emerges,

a protection against the big harsh terrestrial nature.

Inside the hook are two (or one) young leaflets4,

small, pale5 and tender,

like folded palms holding what is to come6.



Searching for light!

A gap breaks in the earth.

Let there be light7!

Molecules innumerable8 suddenly see-

they shift their shapes,

they touch other molecules,

the other molecules touch others.

A melody, or a song,

hidden in the cacophony of many random encounters9.

Some genetic codes are turned on10,

some proteins are made11,

some reactions begin.

Suddenly, the plant glows green12.

Tiny solar panels build up inside the cells-

full of tubing and storage tanks13.

The lanky stature replaced by a sturdy silhouette14.

The hook unwinds, and leaflets expand-

as birdwings stretching and flapping in the sun.

Here we are, a tiny seedling!

Ready for a full life ahead.


1. Specific features of a plant are called “traits”, and traits have genetic basis that follows inheritance laws (see Gregor Mendel’s experiments).

2. Hypocotyl

3. Apical hook

4. Cotyledons

5. Cotyledons accumulate Pchlide (chlorophyll precursor with a yellowish colour) in the dark.

6. Shoot apical meristem

7. How plants change their development in response to light is termed “photomorphogenesis”. A movie by Roger P. Hangarter is  an excellent illustration of this.

8. Photoreceptor proteins

9. A cell is a crowded environment in terms of how many molecules it has. Proteins often bump into each other by chance (see figure below by David S. Goodsell). But many proteins have interactions with specific partners, producing certain biological effects.

10. A process termed transcription

11. A process termed translation

12. In angiosperms the conversion from Pchlide to chlorophyll (with a green colour) is strictly dependent on light. One of the proteins controlling greening in the upstream is Golden2-like (GLK) transcription factor.

13. Chloroplasts are cellular organelles that need light to fully develop. They contain structures such as thylakoid (a structured membrane system) and starch granule (as storage).

14. A type of protein controlling hypocotyl elongation is expansin.

Planter’s Punch

Under the heading Planter’s Punch we present each month one special aspect of the CEPLAS research programme. All contributions are prepared by our early career researchers.

About the author

Pengxin Yu is a doctoral researcher in the group of Ute  Höcker at the Institute for Plant Sciences (UoC).  His research focuses on studying the transcription factor proteins  involved in the production of chlorophyll in plants. Before joining CEPLAS, he completed his Bachelor's degree in the group  of Luke Mackinder at the University of York in the UK where he  contributed to the assembly of a carboxysome-based carbon  concentrating mechanism in plants.

Further Reading

Kreiss, M., Haas, F.B., Hansen, M., Rensing, S.A., Hoecker, U., Co‐action of COP1, SPA and cryptochrome in light signal transduction and photomorphogenesis of the moss Physcomitrium patens. The Plant  Journal, 114 (1), 159-175 (2023) doi.org/10.1111/tpj.16128

Hernández-Verdeja, T., Lundgren, M.R. GOLDEN2-LIKE transcription factors: A golden ticket to improve crops? Plants, People, Planet, 6  (1), 79-93 (2024) doi.org/10.1002/ppp3.10412