FRST 200 Lecture Notes - Lecture 13: Serotiny, Pinus Contorta, Taproot
Document Summary
**seeds remain dormant until correct signals are received: embryo dormancy df has. Caused by levels of plant growth regulators (hormones) Some inhibit germination, some promote, balance important. Synthetic hormones can be used to break dormancy. Otherwise embryo dormancy often broken by low temperature. And then when conditions get warmer again, they can grow. 4-5 degrees is usually best: other types of seed dormancy. Embryo immaturity - seed must grow "after ripen" Seed coat impermeability - prevents entry of water or oxygen. Need to be abraded - scarification (naturally, fungal attack, artificially, sand paper or sulphuric acid) Seed coat dormancy - desert or tropical species. Light requiring seed: some need only a little dim light e. g. some spruce and pine, some affected by day length. Many require the right kind of light, weedy species, lettuce, birch, scots pine: green light doesn"t work, red light works, far-red light reverses the effect of red light, prevented germination in the shade.
