Vegetative and Cutting Propagation

Transcription

1 15 Vegetative and Cutting Propagation Text Pages: ; Objectives: 1. Be able to describe and explain the origins of clones. 2. Be able to describe, explain, and summarize managing sources for vegetative propagation. 3. Be able to describe and explain important terms involved in cutting propagation. I. ORIGIN OF CLONAL CULTIVARS A. Clones are selected for Some Specific Traits 1. Clones are extremely important to 2. High value of specific horticultural species B. Seedling Selection 1. Most cultivars grown as clones came from a. Improved plants could arise by chance or b. Important point: Superior or distinct qualities of 2. A clone can be multiplied in two ways: a. Multiple propagations from the same plant

2 16 b. Consecutive generations from a single plant leads 3. Seedling clones must be tested for a. Did environment cause a trait to change and b. Did some other manipulation cause c. Example: 4. Summary: Discovered seedling cloned as a cultivar should be tested for: a. Phenotype changes due to b. How adaptable the new clone/ cultivar is C. Mutations 1. A "different" seedling is caused by 2. A clone can 3. Mutations can be caused by 4. The ability of a genetic change to show in the phenotype depends on: a. The trait must be

3 17 b. The mutant cell must survive, multiply, and c. The trait must be 5. Bud-sport or bud-mutation is a branch a. The appearance seems sudden b. The branch appears to have originated c. Fruit trees, particularly the apple cultivar D. Biotechnology 1. Recombinant DNA technology 2. If a gene that produces a protein that a. Examples: b. The new cultivars are reproduced and sold II. MANAGING PLANT SOURCES FOR VEGETATIVE PROPAGATION A. Introduction B. True-to-Name 1. Making sure the plants are 2. Mistakes in labeling

4 18 3. Use "fingerprint" methods, protein or C. True-to-Type 1. The phenotype of the progeny plants must conform 2. Deviations my be the result of 3. Visual inspection is used D. Freedom from Pathogens 1. Infected plant material can be a reservoir 2. Plants are tested for pathogens, such as a. Visual inspection b. Culture indexing c. Serology-ELISA d. Biochemical methods 3. Plant sources should be free from pathogens before III. BIOLOGY OF CUTTING PROPAGATION A. Introduction B. Definitions 1. Cutting - a plant part removed a. Using cuttings is an asexual process b. The piece or part may have to regenerate

5 19 2. Totipotency - all the genetic information needed to regenerate a. A property of all vegetative b. For cuttings, the genetic information is present to reproduce 3. Parenchyma cell wound tissue made of parenchyma cells a. Cells are non-differentiated or unorganized tissue b. Consider scar tissue 5. - the capability of mature or previously developed cells to initiate cell a. Parenchyma cells b. Examples: mung bean 6. Adventitious - a. Examples: root from b. Shoot or bud arising from a c. Adventitious organs can form from 7. Preformed adventitious roots - adventitious roots that form naturally

6 20 a. Examples: b. Most plants, however, must have roots induced 8. - form in response to wounding IV. EVENTS LEADING TO ROOT FORMATION Text pages: Objectives: 1. Be able to describe and summarize cutting response to wounding (three steps) and the four stages of de novo root formation. 2. Be able to describe and explain the two types of root formation with regard to callus. 3. Be able to explain the processes involved in regenerating plants from leaf and root cuttings. 4. Be able to describe and explain polarity in cuttings and its effects on cutting propagation. 5. Be able to describe the practical aspects of polarity on cutting propagation. 6. Be able to describe and summarize the effects of buds and leaves on root formation by stem cuttings. A. Introduction B. Response to Wounding is the first step and has 1. Injured tissues die, form a plate/layer of dead tissue a. The protective material at the cut surface prevents b. Example:

7 21 2. Living cells near wound divide and 3. Certain cells in the area of the vascular cambium and phloem begin C. De novo Root Regeneration involves four stages 1. Dedifferentiation of specific differentiated cells a. This step is the first and foremost b, Without cells capable of dedifferentiation, the remaining steps for root formation 2. Formation of root initials near a. Certain cells had to dedifferentiate to 3. Root primordia develop is the third stage a. Meristems develop 4. Adventitious root emerge from D. Type of Root Formation two types 1. Direct root formation new roots a. Lacks intervening callus stages b. Easy-to-root plants often 2. Indirect Root Formation -

8 22 a. Diagram b. More difficult-to-root species may have V. INFLUENCES ON ROOTING CUTTINGS A. Introduction Many factors can affect cuttings and root formation B. Polarity 1. Polarity is defined as any situation in which 2. Cuttings show polarity since 3. Polarity is very difficult or a. Examples: i. willow stems ii. experiments with dandelion root b. Physiological nature of polarity i. polarity is inherent within ii. polarity is unrelated to metabolites

9 23 iii. auxin gradients in the stem 4. Practical Aspects of Polarity a. Keep cuttings in proper orientation b. Keep cutting alive since C. Buds and Leaves Affect Rooting of Stem Cuttings 1. Buds and developing buds have been shown to a. The presence of buds is important for b. Removal of buds can inhibit c. Buds that are just about to grow d. Buds produce auxins, and e. Buds may also produce additional substance(s) 2. Leaves appear to strongly stimulate rooting a. New leaves are thought to promote root b. Leaves also help cuttings root by c. Too much leaf area can be detrimental to rooting since i. leaf area can be reduced by

10 24 ii. cuttings that form roots early have a better chance D. Summary c:\plsc300\12notes-2.doc