Animation 25.2 Went's Experiment

INTRODUCTION

Experiments by Charles and Francis Darwin demonstrated that the tip of a plant's shoot senses light, and that some kind of chemical signal travels from the tip to the growing region. The shoot responds to this signal by bending the toward the light.

In the 1920s, Dutch botanist Frits Went attempted to isolate the chemical signal from the tips of oat coleoptiles. This animation follows a recreation of his experiment and provides an opportunity for you to predict some of his experimental results.

Video titled: Animation 25.2 Went's Experiment

Transcript Area

Textbook Reference: Key Concept 27.4 Plants Have Constitutive and Induced Responses to Pathogens and Herbivores, p.671

CONCLUSION

Experiments on growing seedlings showed that the plants grow toward light in response to a signal generated in the tip of the coleoptile. This signal, a hormone now known as auxin, moves down the dark side of the plant to stimulate faster growth on that side, causing the plant to curve toward the light.

Frits Went first isolated the hormone by placing severed coleoptile tips on blocks of agar. Auxin molecules diffused into the agar, and Went was able to stimulate growth in decapitated shoots by placing the auxin-containing agar onto the cut ends of the shoots. Went's experiment represented the first time anyone had isolated a hormone from a plant.

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