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Questions and Answers
What is a significant limitation of using Arabidopsis as a model tree species?
How does the domestication process of tree species contribute to bioeconomy?
Which of the following is NOT a main step in the domestication process of agroforestry trees?
Why is tree cloning beneficial for conservation projects?
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Which stage is the first in the micropropagation protocol by axillary budding?
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In the micropropagation protocol for axillary budding, what ratio is essential during the shoot multiplication phase?
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What distinguishes adventitious budding from other budding types?
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What does not contribute to the primary goal of tree cloning?
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What is the primary purpose of applying higher concentrations of auxins and cytokinins during the induction of buds?
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Why is it important to sterilize the explants before initiation of the culture?
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What is a key characteristic of a vitrified plant?
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During the acclimatization process of in vitro plants, what is gradually reduced?
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What factor along with genotype can impact the success of an in vitro culture?
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What condition primarily causes vitrification in plants?
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What is a common consequence of phenolic exudation on in vitro material?
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Which of the following is NOT a step in the adventitious budding process?
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What does regeneration from a callus primarily lead to in tissue culture?
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What is the definition of somaclonal variation?
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Why is cell culture preferred for the production of secondary metabolites over extraction from fresh plant tissues?
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What is a primary advantage of using cell culture for producing secondary metabolites like taxol?
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What characterizes the tissue mass referred to as a callus in tissue culture?
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What role do phenolic compounds play during the stress of explants?
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Which of the following is NOT a recommended tip for managing phenolic exudates in explants?
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During which phase of somatic embryogenesis do you obtain cotyledonary somatic embryos?
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What is a key difference between somatic and zygotic embryos?
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What does the term 'embling' refer to in plant propagation?
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Which statement accurately defines direct micropropagation?
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What is an expected advantage of indirect micropropagation?
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Why can some rhizobacteria have a beneficial effect on in vitro plants?
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Which microorganism is NOT classified as a Plant Growth Promoting Microorganism?
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What beneficial effect do PGPR have on in vitro plants?
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What is a synthetic seed?
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Which tree species was first replicated using somatic embryogenesis?
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What characterizes haploid plants?
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What is the main advantage of doubled haploid plants in trees?
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Which of the following helps enhance acclimatization in plants?
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Study Notes
Arabidopsis as a Model Tree
- Arabidopsis is not a suitable model for trees, as it lacks secondary wood production, a long life cycle, dormancy, and complex crown structure.
Domestication of Trees
- Domestication of tree species is important for bioeconomy, which utilizes renewable bioresources for food, materials, and energy.
- Domestication increases wood and derivative production, mitigates climate change, promotes ecosystem recovery, relieves pressure on natural forests, and provides opportunities for genetic and ecological study.
Stages of Domestication
- The domestication process in agroforestry involves human-guided evolution of species for cultivation, driven by market demands.
- Key steps include exploration and collection, evaluation, tree breeding, propagation techniques, germoplasm modification, germoplasm distribution, and utilization/marketing.
Tree Cloning for Conservation
- Tree cloning is valuable in conservation as it allows for multiplication without altering DNA, preserving genetic diversity in both in situ and ex situ collections.
Micropropagation by Axillary Budding
- Axillary budding micropropagation involves stages of explant selection, culture initiation and establishment, shoot multiplication, rooting, and acclimatization.
- Explants are sterilized and placed in a medium, promoting callus formation.
- Shoot multiplication requires a high concentration of cytokinins relative to auxins, with potential auxin supplementation for specific species.
Micropropagation by Adventitious Budding
- Adventitious budding micropropagation involves the formation of new buds from non-meristematic tissues (e.g., leaves, internodes) using higher concentrations of auxins and cytokinins.
- Adventitious budding involves explant selection, sterilization, bud induction through meristematic activity initiation in non-meristematic cells, shoot development, rooting, and acclimatization.
- Axillary budding is more stable and predictable, while adventitious budding offers higher multiplication rates but with a higher risk of genetic variability.
Acclimatization of In Vitro Plants
- Acclimatization is crucial for in vitro plants as they obtain sugar from the medium, not photosynthesis, necessitating adaptation from heterotrophy to autotrophy.
- Plants require adaptation from in vitro medium to soil conditions, typically taking 2-4 weeks with gradual humidity reduction and light intensity increase in a greenhouse setting.
Factors Affecting In Vitro Culture Success
- Factors influencing in vitro culture success, besides genotype, include explant sterilization, medium components (phytohormones, sugar source), illumination, humidity, and tissue source.
Vitrified Plants
- Vitrified plants exhibit glassiness and translucency due to hyperhydricity, a detrimental condition leading to significant losses in in vitro cultivation.
- Prevention is crucial, as recovery of vitrified plants is challenging.
Phenolic Exudation
- Phenolic exudation, occurring upon explant excision and placement in new environments, releases toxic compounds that hinder micropropagation and may induce necrosis.
- Mitigation strategies include using antioxidants like ascorbic and citric acid in the culture medium, frequent subculturing, and maintaining low light intensity and optimal temperature to minimize phenolic exudation.
Somatic Embryogenesis Protocol
- Somatic embryogenesis in micropropagation involves stages of in vitro initiation (explant selection and sterilization for embryogenic culture), multiplication (proliferation of the culture, excluding cryopreservation), maturation (development of cotyledonary somatic embryos), desiccation, germination, greenhouse acclimatization, and tree culture.
Distinction Between Somatic and Zygotic Embryos
- Zygotic embryos arise from gametic reproduction, resulting from the fusion of paternal and maternal genetic material (n+n).
- Somatic embryos originate from somatic cells and possess the same DNA as the explant organism.
Embling Definition
- An embling is a plant derived from somatic embryogenesis.
Direct vs. Indirect Micropropagation
- Indirect micropropagation involves an intermediate step of callus formation before the development of new organs, used when direct shoot or root formation from the explant is not feasible.
- Direct micropropagation skips the callus formation step, leading to faster results, reduced somaclonal variation (genetic instability arising from tissue culture), and improved production efficiency.
Benefits of PGPR on In Vitro Plants
- Plant Growth Promoting Rhizobacteria (PGPR) can enhance in vitro plant development, leading to greater vigor in the field, improved rooting in challenging species, reduced reliance on chemical fertilizers, enhanced acclimatization, and disease prevention through antimicrobial compound production.
Other Plant Growth Promoting Microorganisms
- Beyond rhizobacteria, other microorganisms act as Plant Growth Promoting Microorganisms (PGPM):
- Endophytic fungi: residing within plant tissue, enhancing nutrient uptake, promoting growth hormone production, and increasing environmental stress tolerance.
- Nitrogen-fixing bacteria: augment nitrogen availability, particularly important for plants in nitrogen-limited environments.
- Plant-growth promoting yeast: promoting growth and providing biocontrol against detrimental fungi.
- Mycorrhizal fungi: forming symbiotic relationships with plant roots, facilitating nutrient uptake, enhancing water absorption, and promoting disease resistance.
Somatic Embryogenesis Application in Tree Species
- Somatic embryogenesis was first demonstrated in Santalum album in the 1960s and has since been applied to various woody angiosperms, including pine, poplar, eucalyptus, citrus species, and certain tropical trees.
Synthetic Seeds
- Synthetic seeds are encapsulated propagation materials (e.g., somatic embryos, shoot buds, callus aggregates) containing supplementary nutrients and protection beyond basic encapsulation.
Haploid Technology
- Haploid technology produces plants with a single set of chromosomes (haploids), achieved by manipulating pre-gametic cells to arrest their development into mature gametes using antimitotic agents during metaphase or anaphase.
- Androgenesis involves isolating microspores before they become pollen and cultivating them into haploid plants.
- Haploids are more susceptible to disease and infertile; therefore, chromosome doubling is necessary to produce fertile plants, resulting in double haploids or homozygous diploids.
- Double haploid production eliminates the need for backcrosses in conventional breeding, particularly beneficial for trees with lengthy ontogenic cycles.
Double Haploid Advantages in Trees
- Double haploid plants offer several advantages in tree breeding, such as:
- Reduced breeding time due to the absence of backcrosses.
- Uniformity in progeny, as they are genetically identical.
- Enhanced selection efficiency due to the homozygous nature of double haploids.
Regeneration from Callus
- Regeneration from callus, which is an unorganized meristematic tissue mass, involves inducing either organogenesis (direct formation of organs like shoots or roots) or somatic embryogenesis following callus formation.
Somaclonal Variation
- Somaclonal variation refers to the genetic variability generated during tissue culture cycles, driven by factors like repeated subculturing, altered hormone application, and prolonged in vitro maintenance.
Cell Culture for Secondary Metabolite Production
- Producing secondary metabolites using cell culture systems is more advantageous than extraction from fresh plant tissues due to:
- Higher production rates to meet industrial demands.
- Avoidance of depletion of natural resources, including endangered species and soil.
- Targeted selection for enhanced gene expression of desired metabolites.
- Feasibility of mass production, as illustrated by taxol, a chemotherapeutic substance.
- Reduced time required, especially for tree species.
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Description
Explore the significance of tree domestication in bioeconomy and its impacts on wood production and climate change. This quiz will also cover key stages of domestication and the role of tree cloning in conservation efforts. Understand how these processes are vital for sustainable forestry and ecosystem recovery.
