28 Questions on Propagation of Horticultural Plants - Study Guide | HORT 227, Exams of Gardening and Horticulture

Download 28 Questions on Propagation of Horticultural Plants - Study Guide | HORT 227 and more Exams Gardening and Horticulture in PDF only on Docsity! STUDY EXAM QUESTIONS FOR SECOND MIDTEM EXAM Here is a set of questions from which the next exam wi11 be produced. Please: TRUE/FALSE. Use T or F. There are no "tricky" statements. __ T__ Budding would be a good way to clone a thornless blackberry that is a LI chimera. __ T__ Fall budding is preferred in climates like Wisconsin. __ F__ An L-1 chimeral mutant, can be readily propagated by seed. - Shoot cuttings or budding. Must have intact Meristem. F Shoot culture is used to rid a plant of a systemic virus. -_Meristem culture. They might be the same thing? _ F Somaclonal variation refers to a form of aberrant plant created by incompatibility in grafting. -_Plants that come out of microculture differ from original sourse F Seed can propagate the thornless character in an LI chimera raspberry. F A sport is a `good old propagator'. -_A cloning error where the mutant takes over the whole bud F Multiplication in commercial shoot cultures is best done through adventitious bud formation. -_Don’t want to risk propagating a mutant or virus. Use Axillary Bud Stimulation. F Embryo culture is a type of microculture that is used to rid a plant of a systemic virus. -_Meristem culture F Callus cultures generally use both gibberellin and cytokinin. -__Auxin and Cytokinin __T___ Organ cultures require multiplication by adventitious shoot formation. __T__ Seed quality includes genetic purity, freedom from weed and non-crop seeds, low inert matter, and high germinability. __ T__ Soil can be a good storage medium for weed seeds because of a lack of oxygen, an abundance of C02, and a lack of red light. ___T___ Cultivars can be either clones or seed propagated __T___A seed orchard is a natural area where the undesirable trees have been rogued-out. - Controlled area of geographic isolation __F___ Gibberellins can be used to both stimulate germination and promote adventitious rooting. - Gibberellins stimulate cell elongation, breaking and budding, seedless fruits, and seed germination. __T___ Cool and moist is the best condition for lowering ABA and increasing GA levels during stratification. ___F___A hybrid cultivar can be perpetuated by collecting seed from the hybrid plants each year - Can’t collect seed from hybrid. No specific parents. ___T__. A thornless chimeric blackberry is most reliably propagated (maintains its thornlessness) by shoot culture, not callus culture. ___T__. A mutant genotype located in the LII layer of a chimeric plant can be perpetuated by seed from the chimeric plant. - Can propagate the gene of an LII by seed, but not the whole plant T Reversed polarity can be used in a procedure called nurse grafting. F An interstock will overcome incompatibility evidenced by phloem degeneration (death of phloem tissues near the graft union). SHORT ANSWER 1. A poplar is clonally propagated by micropropagation using callus culture but the resultant plants show variation among each other in form and growth. Explain the cause of the problem. - High propagation rate resulted in a change in chromosome structure, numbers, DNA sequence or mutation affecting the whole meristem. Thus causing Somaclonal variation. How can it be solved and still use micropropagtion? - Don’t propagate off-types. Avoid adventitous shoot regeneration. 3. Referring to callus culture and shoot culture, compare the following. -  Basis of multiplication of the resultant propagules  Callus multiplies much faster. 90bil/yr vs 9mil/yr  Genetic-fidelity of the resultant propagules  Shoot culture more effective.  Ease of using the procedure for a plant never previously microcultured  Shoot cultures are easier, use ex-vitro. a) For each of these three categories, cite two specific causes (problems) that could lead to the observed poor seedling stand. (in other words, what are two causes of low seed viability, etc., etc.). Now detail as much of the physiological (or morphological) bases for each problem as you can. (30 pts.) - Low seed viability o Embryo may not be alive or may not have one.  Embryo can’t germinate if it’s not there or dead o Seed may be old.  Over time embryonic cells die and cannot be replaced - Poor germination environment o Lack of water, sunlight, air as well as having an awkward temp.  Imhibition to break seed coat, may not break physiological dormancy if temp or sunlight isn’t correct o Flooding or heat may have killed seed pre-germination.  Burn up embryo. Drown embryo. - Lack of pregermination treatments o If the seedlings weren’t stratified before planting, the embryonic dormancy phase would not have been broken.  If embryonic dormancy isn’t broken the seed will not sprout o If seedlings weren’t scarified, water and gases may not have penetrated seeds  Wouldn’t be able to help induce root growth b) How might you have differentiated between these possible specific problems (that you cited above) before you planted all the seed? (8 pts.) - Make sure you have new, young, healthy seeds. - Monitor environment closely - Remember to pretreat 23. Offer one plausible explanation for each of the following observations. For each explanation, (1) give as much detail as you an as to the physiological/morphological basis of the response, and (2) describe one practical method of overcoming the problem. Do not give trite solutions; concentrate on important and meaningful concepts. Be specific as to the treatments, chemicals used, etc. (8 pts. each) ***a) Seedlings germinated in a flat show severe transplant shock (stress) when moved to the field. The plant can only be economically propagated by seeds. b) A plant loses its variegation when propagated by seed. Micropropagation is the only other successful clonal propagation method. - Lost the specific gene when propagated by seed. - Propagate by meristem culture to keep the chimeric trait c) Seed does not germinate when planted too deep. - Doesn’t obtain enough sunlight or water to break physiological dormancy. - Plant it less deep. d) Highly viable seed that normally germinates well does not germinate after exposure to high temperature in the field after planting. The seed is still viable. - Temperature of field is preventing vernalization that is required to break dormancy. May also prevent imhibition. - Shade field e) Seed of a particular species stores better in a cool, moist, environment instead of a cold, dry environment. - For seeds that cannot dry f) Seed does not germinate in shade. - Not enough light to break physiological dormancy. Need light for growth of seedling. - Put it in light g) Viable seed of a woody perennial does not germinate even though properly cleaned and stratified. - Need suitable growing conditions. Large seeds survive under extreme conditions for many years. - Make sure it’s scarified enough. Make sure weather is suitable. 24. You are a famous propagator and give a public lecture about your work to a large group of socially and environmentally active citizens. To your surprise, you get a number of questions challenging your use of cloning techniques for propagation. Offer a discussion theme that would support such an opinion. - minimizes genetic diversity, doesn’t maintain genetic purity, genetic vulnerability, diseases can be propagated with clone Offer a discussion theme that would support your dependence on cloning. - Can produce high yielding crops, can produce drought and pest resistance crops, can produce crops with more nutrition in it, DNA combination in order to select specific features of different plants, consistency across generations 25. If a scion on a good graft dies, what part of the graft union process will be most disrupted? Why? - The vascular system. The scion controls the union in the cambium by cells and the stock produces the callus. The death of the scion causes the vascular regions to not be aligned. This prevents water and photosynthate transportation and weakens the plant. 26. Offer two different lines of evidence that hormones coming from the stock are a major part of the effects on the scion in a graft. - Low amount of nitrogen moving to shoot dwarfs growth. - The increase in ABA and decrease in Gibberellins less elongation of shoots, dwarfing plants 27. Why might all the scions that are normally compatible (successfully grafted for many seasons) to a certain rootstock die after grafting to the same rootstock genotype and during the last three growing seasons (using the same grafting technique)? - Probably a virus -Would an interstock help overcome this problem? Explain. o It can help, but it’s usually not a solution. It can try to help replace the vascular system that was destroyed in phloem degeneration, but it won’t overcome it. 28. Cite four reasons why one would use grafting to clone a unique plant even though the scion roots readily using cuttings. - Disease resistance. Cold hardiness. Established roots. Maintain a select genotype. Repair. Avoid rejuvenation, influence growth phase.