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 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

Monocot Germination

Dicot Germination

Asexual Propagation Stem Cuttings Stem Tip Cuttings Stem Section Cuttings Cane Cuttings Heel Cuttings Single-Eye Cuttings Double-Eye Cuttings

Asexual Propagation Leaf-Type Cuttings Leaf Cuttings Leaf Petiole Cuttings Leaf Section Cuttings Split-Vein Cuttings

Asexual Propagation Root Cuttings

Asexual Propagation Simple Layering

Asexual Propagation Tip Layering

Asexual Propagation Air Layering

Asexual Propagation Division

Asexual Propagation Grafting= T-Budding

Asexual Propagation Tissue Culture