Lab and Plant Hormones Overview

Lab Experiment Overview

Plant Hormones

  • Discussion on plant hormones, focusing on oxins and their functions.

  • Definition of a hormone:

    • A signaling molecule that can regulate gene expression and target specific areas in the organism.

Traditional Classes of Plant Hormones

  • Introduction of five traditional plant hormones as a focus, though acknowledging more exist today:

    • Auxins

    • Cytokinins

    • Ethylene

    • Abscisic acid

    • Gibberellins

  • Discussion on three newer plant hormones:

    • Brassinosteroids

    • Jasmonic acid

    • Salicylic acid

Auxins

  • Discovered by Peter Witt in 1926; the name derived from Greek meaning "to increase."

  • Produced from the tip of leaves and moves from the tip to the base of the plant.

  • Key Example: Indoleacetic Acid (IAA)

  • Merits an understanding of herbicides like 2,4-D (synthetic auxin) and its historical context (Agent Orange).

Phototropism

  • Description:

    • Phototropism is the tendency of a plant to bend towards light.

    • First published findings by Charles Darwin in 1881.

    • Darwin's experiments involved oat stems (coleoptiles).

  • Darwin's findings:

    • Bending occurs due to auxin distribution from the light to the shaded side of the plant.

Auxin Transport

  • Unique aspect of auxin's movement characterized as "polar transport".

  • Transport Directions: Basipetal (downward) and Acropetal (upward only through vascular tissue).

  • Involvement of carrier proteins:

    • OX1: Influx protein that brings auxin into cells.

    • PIN proteins: Efflux proteins facilitating the movement of auxin out of cells in a unidirectional manner, primarily at the base of cells.

Functions of Auxins

  • Regulation of:

    • Phototropism (growth towards light)

    • Apical dominance (inhibition of lateral bud growth by apical bud).

    • Wound healing and regeneration of vascular tissue.

  • Apical Dominance: Explanation and role of auxins in controlling lateral growth in trim and cut shrubs.

Additional Functions & Applications of Auxin

  • Involvement in fruit development and delays in leaf drop.

  • Parthenocarpy: Development of seedless fruits facilitated by auxin applications.

  • Role in horticulture: Usage of Indole butyric acid (IBA) in increasing root production and assisting vegetative propagation.

Cytokinins

  • Definition and discovery through experiments with coconut milk and its connection to cell division (cytokinesis).

  • Synthetic variant: Kinetin and the relationship to adenine.

  • Natural occurrence discovered in corn (zeatin).

Cytokinins' Functions

  • Primarily responsible for cell division and growth in plants.

  • Lack of cytokinins results in irregular root growth and inhibits normal plant development.

  • Regulate root growth and can override apical dominance by promoting lateral bud growth (though not naturally).

Genetic Transformation in Plants

  • Explanation of transformation, with an example of luciferase from fireflies used in tobacco plants.

  • Insights into delaying plant senescence, correlated to potential applications in human cosmetics.

Closing Notes

  • Overview of auxins and cytokinins covering their definitions, functions, applications, and importance in plant biology and horticulture.

  • Encouragement for further study and understanding of plant hormones.