Transcript Germination
Germination Biology 104 Authors: What conditions are required to make a seed “germinate”? • Germination begins with imbibition, as the seed absorbs water to make the seed coat permeable. • Imbibition breaks dormancy, which allows germination to begin. • Seeds need moisture, proper temperature, darkness and light. What does germinate mean? Germinate- To begin to grow or develop, to develop into a plant or individual as a seed spore or bulb. To put forth shoots; sprout; pullulate. Why do germinated seeds produce roots first? Why not leaves first? The part of the plant that emerges from the seed first is the embryonic or primary root. This allows the seedling to become anchored in the ground, and start absorbing water. After the roots absorb water, the embryonic shoot emerges from the seed. Where does the energy and material come from to create the growing root? The seed has energy and raw material stored in the cotyledons or the endosperm, which supports the growth of the plant until it is able to photosynthesize. Why don’t all seeds germinate at the same time? Why do some germinate faster and others a little slower? Germination Time varies with temperature so expect considerable variation. Growing days are a certain number of days when growing conditions are favorable. If the plant does not get enough growing days it will die before flowering. What would be the consequences of germinating too soon or too late? Would this make any difference if these plants were growing “in the wild”? Why might some not have germinated at all? If a seed germinates too early it might exhaust its food reserves before it ever touches the ground, environmental conditions that are suitable for seedling growth might not coincide with seed maturity. Example: if a seed germinates in late summer then it will have to face the cold of winter. Common causes of failure are soil: being too heavy, wet or cold, or allowed to dry out, not given slow seeds long enough to come up, pest eating the seeds, not giving dormant seeds the proper pretreatment, poor air circulation, and over-watering. Reasons of burning out are due to placing seeds in full sun, or outdoor conditions too quickly. Often, seeds require a preceding period of dormancy. Dormant- inactive, latent, but capable of being activated, suspension of metabolic process. Seeds of many temperature-climate angiosperms will germinate only after a prolonged period of cold. An inhibitor within the seed usually abscisic acid, or ABA, is gradually broken down at a low temperature until finally there is not enough to prevent germination when other conditions become favorable. This is an obvious mechanism of survival, preventing seeds from germinating during an unseasonably warm spell in the autumn. ABA- plant hormone that maintains a water balance of plants, prevents seed embryos from germinating, induces the dormancy of seeds. Sources: Dictionary.com Wikipedia Biology: Life on Earth Lovetoknowgardner.com