BISC 101 Lecture Notes - Lecture 12: Plant Hormone, Phototropism, Coleoptile

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 101
• Professor: Tony Williams

Document Summary

Plants have sophisticated mechanisms for collecting info about their environment and responding in ways that maximize fitness. In plants, these responses involve changes in growth, not movement. When a sensory cell receives a stimulus (e. g. light) it transduces the signal via receptors and produces hormones that (cid:272)arry i(cid:374)fo to target (cid:272)ells else(cid:449)here i(cid:374) (cid:271)ody (cid:894)(cid:862)a(cid:272)tio(cid:374) at a dista(cid:374)(cid:272)e(cid:863)(cid:895) Target cells respond to hormones via other receptors with changes in cell function (growth, gene expression ion channels) Hormone signal (e. g. auxin) (hormone) receptor on target cells (specificity) Change in cell function (e. g. cell elongation) Positive phototropism = growth of plant tip towards light. Caused by differential growth of cells on opposite sides of coleoptile; cells on dark side elongate faster than cells on light side. Experimental evidence supports the hormone hypothesis for phototropism. With a permeable barrier, the shoot still bends; suggests the hypothesized hormone diffuses from tip down shoot.