The Role of Light and Growth Regulators in Seed Germination
• A temporary suspension of visible growth of any plant structure containing a meristem (Lang 1987).• After embryo and endosperm development• To initiate germination, three conditions must be met;
1. Must be viable2. Must be subjected to appropriateenvironmental conditions3. Any primary dormancy must be removed
• Light has been recognized around the mid- nineteenth century as a critical factor controlling germination (Crocker, 1930).• The photochemically reactive pigment Phytochrome has been shown to be involved in the mechanism of light sensitivity in seeds (Bewley and Black, 1985).
• When an imbibed seed is exposed to red light (600-760 nm) phytochrome (P) changes to Pfr which promotes germination.• When exposed to far-red light (760-800 nm), inhibits germination
• Specific endogenous plant growth substances have important roles in the control of dormancy.• Most of these are; – Abscisic Acid (ABA) – Gibberellinc Acid (GA) – Cytokinins – Others (Indoleacetic Acid, Kinetin, Auxin)
In this experiment the effect of light and certaingrowth regulators on seed germination will beinvestigated.
TREATMENTS REPLICATE 1 REPLICATE 2 Germinated Percent Germinated Percent seeds germination seeds germination1.Dark (Control) 10% 4 8% 52. White Light 4 8% 4 8%3. W/ GA3 + Dark 10 20% 10 20%4. w/ IAA + Dark 4 8% 1 2%5. w/ ABA + White 4 8% 1 2%6. Blue Light 0 0 0 07. Green Light 0 0 0 08. Red Light 8 16% 6 12%9. Infrared 1 2% 0 0
Red light promotes germinationPhytochrome 660 Phytochrome 730(red absorbing) (far-red absorbing) Far-red light inhibits germinationFigure 1. Effects of red and far-red light on the photochemically reactivepigment phytochrome and lettuce seed germinatio
• The membranes of the seed coats and/or the endosperm act as light sensors; once removed light control disappears.