BIOL 1030 Chapter Notes - Chapter 39: Axillary Bud, Seed Dormancy, Auxin

• School: University of Manitoba
• Department: Biological Sciences
• Course: BIOL 1030
• Professor: Scott Kevin

Document Summary

Chapter 39 plant responses to internal and external signals. In most cases, these responses to stimulation involve the increased activity of certain enzymes: this occurs through two mechanisms: by stimulating transcription of mrna for the enzyme or by activating existing enzyme molecules (post-translational modification). In transcriptional regulation, transcription factors bind directly to specific regions of dna and control the transcription of specific genes. In 1926, frits went extracted the chemical messenger for phototropism, naming it auxin: modifying the boysen-jensen experiment, he placed excised tips on agar blocks, collecting the hormone. If an agar block with this substance was centered on a coleoptile without a tip, the plant grew straight upward. Plant hormones help coordinate growth, development, and responses to environmental stimuli. In the absence of cytokinins, a piece of parenchyma tissue grows large, but the cells do not divide. In the presence of cytokinins and auxins, the cells divide, while cytokinins alone have no effect.