HORT 100 Week 5 Notes
HORT 100 Week 5 Notes HORT 100-001
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This 4 page Class Notes was uploaded by Erin Wade on Friday September 23, 2016. The Class Notes belongs to HORT 100-001 at Colorado State University taught by Hughes, Harrison G in Fall 2016. Since its upload, it has received 4 views. For similar materials see Horticultural Science in Agriculture / Horticulture at Colorado State University.
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Date Created: 09/23/16
9/21/16 Plant Propagation Sexual propagation (seed propagation is not exactly the same as sexual propagation, because of apomixis) Asexual propagation (vegetative) Seed Formation ● Life cycle of a typical plant ● Megasporogenesis formation of megaspores inside the ovules, diploid cell in ovule or mother cell undergoes meiosis, and produces four haploid megaspores ● Microsporogenesis formation of microspores in microsporangia (pollen sacs). Diploid cell in microsporangium or mother cell undergoes meiosis, and produces four haploid microspores ● Double fertilization joining of female gametophyte with two male gametes ● Zygote used product of the fusion of two haploid gametes a fertilized ovum ● Embryo formation sperm (1N) unites with egg (1N) to produce diploid (2N) embryo ● Food storage material endosperm ● Seed coverings protects rest of seed ● Apomixis not true sexual propagation Seed storage and viability ● Storage ○ Recalcitrant highly hydrated when they shed from the plant and ready to germinate, die if stored for long periods of time ○ Orthodox everything else, relatively dry at time of maturity, stay alive in dry environment ■ Different ranges of time that different seeds can survive ● Viability ○ Float test determine whether a seed has an embryo and nutrients in it still, if it sinks it is still good ○ Standard germination tests to determine germination time and seed quality/viability ○ Tetrazolium stain soak seeds and living seeds will take in the stain ○ Excised embryo test use for woody plants, excised and incubated and they either grow or decay Seed dormancy ● Seed coat dormancy limits gas and water exchange ○ Scarification tmt damage seed coat using acid, then plant and it wil germinate ● Embryo dormancy something on the interior is not allowing it to germinate ○ Stratification tmt hold seed for 68 weeks in cool moist condition, breaks down natural chemicals and releases dormancy ● Double dormancy both seed coat and embryo are dormant ● Rudimentary dormancy secondary dormancy, where it goes back to being dormant after starting to germinate and not getting enough water ● Chemical inhibitors slows down reaction ● Why does dormancy occur? ○ In nature these seeds might fall into moist conditions (stratification), it might get washed out and scrape against rocks or break (scarification) ○ Only germinates in wet conditions to make sure the plant will get enough water Environmental factors ● Quiescent seeds are resting and waiting for right conditions, but not dormant ● Water have sufficient water for seed to absorb (60% water in seed) ● Temperature not too extreme ● Aeration not just in air, need to respire ● Light some plant are inhibited by light, others require light ● Freedom from disease and salts salts reduce moisture, not enough for plant Seed Certification ● Breeders seed most pure seed, held by seed company or originator of cultivar, strictly handled ● Foundation seed offspring of breeder seed ● Registered seed offspring of breeder or foundation seed and used to produce certified seed ● Certified seed relative quality is ensured to be able to sell to growers Planting Seeds ● Mechanization seeding using machines to do labor intensive planting ○ Seed coating coating seeds to make them round so that they can be handled more easily, pass through mechanical apparatus and be separated and planted one at a time ● Seeding for plugs clumps of dirt with seeds in it that can be sold and distributed ○ Seed priming prepare seed to germinate correctly using enzyme treatment ○ First paper on priming published by someone at CSU Seed Plugs Coated seeds 9/23/16 Basis for Aesexual Propagation Maintain specific genotype, because it has the exact genes we want May be the only means of propagation for some plants if the seeds have been bred out May be faster than using seeds, because they can skip the juvenile stage Create usual forms, they are all uniform Juvenile plants vs. Adult plants Juvenile plant is incapable of reproducing doesn’t produce seeds or flowers Juvenile plant might need support to stay upright Concepts of maturation ● Ontogenetic origination and development of an organism ● Homoblastic leaves are all very similar ● Heteroblastic leaves start to differentiate Chimera organism that contains more than one genotype, mixture of genetically different materials (each layer is genetically different) ● L1 layer epidermis, outermost ● L2 layer more complex cortex, part of vascular system, gametes ○ Divides horizontally and vertically ● L3 layer bulk of vascular system and pith tissue(cross section of stem) ○ Divides horizontally and vertically Ex of chimeras Cutting propagation Stem cuttings ● Herbaceous ● Softwood ● Ripe wood/Semihardwood ● Hardwood winter