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Plant Reproduction. Terms. Propagation/Reproduction –The process of increasing numbers of a species, or perpetuating a species Sexual Reproduction – The union of an egg (ovule) and sperm (pollen), resulting in a seed. 2 parents creating a 3 rd individual is referred to as sexual propagation
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Terms • Propagation/Reproduction –The process of increasing numbers of a species, or perpetuating a species • Sexual Reproduction – The union of an egg (ovule) and sperm (pollen), resulting in a seed. 2 parents creating a 3rd individual is referred to as sexual propagation • Asexual Reproduction/Vegetative – Utilizing a part or parts of 1 parent plant. The new plant is a clone (exact duplication) of its parent • Hybrid Vigor – Refers to the tendency of hybrid plants to be stronger and survive better than plants of a pure variety
Sexual/Asexual Comparison • Sexual Propagation Advantages • Less Expensive • Many parts can be produced quickly • Crosses result in hybrid vigor • Avoids passing on some diseases • Asexual Propagation Advantages • Less time is required to produce a salable (fit for sale) plant • Plants are genetically identical • The only way to produce some plant varieties
Parts of a Seed • Embryo- The young multi-cellular organism before it emerges from the seed • Endosperm- A source of stored food, consisting primarily of starches • Seed Coat- Consists of 1 or more protective layers that encase the seed • Cotyledon- A seed leaf that stores food in the form of starch and protein for use by the embryo • Epicotyl- The portion of the embryonic stem above the point at which the stem is attached to the cotyledon(s)
Germination • Germination – A seed sprouting or starting to grow • Dormant – Resting stage, no active growth • To germinate the seed must be placed in certain favorable conditions • The 4 environmental factors that must be right for effective germination are water, air, light, and temperature
Germination-Water • Imbibition (the absorption of water) is the 1st step in the germination process • It allows the seed to fill all of its cells with water • A good germination medium is important – (Too dry – death of the embryo) (Too wet – Rotting) • In some species the seed coat is very hard and water cannot penetrate the endosperm. The seed can be scarified (nicking the seed coat with a knife or file) to remedy this. • Also can soak the seed in concentrated sulfuric acid or soaking the seeds in hot water for 12 to 24 hours
Germination - Air • Viable seed is alive and capable of germinating, respiration takes place in all viable seed • Oxygen is required • As germination starts, the respiration rate increases • Germination will be reduced or inhibited if oxygen supply is limited or reduced
Germination - Light • Some seeds are stimulated to grow by light and some are inhibited by the presence of light • Many agronomic crops do not require light • Many ornamental bedding plants are more likely to require light for germination. Ex – Impatiens, Petunia
Germination-Temperature • Heat is important for germination and effects the germination rate • The only way to control field crops is to plant when the ground is warm • A knowledge of the heat requirement is required in plants grown in greenhouses
Asexual PropagationStem Cuttings • Stem Tip Cuttings • Stem Section Cuttings • Cane Cuttings • Heel Cuttings • Single-Eye Cuttings • Double-Eye Cuttings
Asexual PropagationLeaf-Type Cuttings • Leaf Cuttings • Leaf Petiole Cuttings • Leaf Section Cuttings • Split-Vein Cuttings
