Tree Domestication and Conservation

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Questions and Answers

What is a significant limitation of using Arabidopsis as a model tree species?

It exhibits high crown complexity.

It has a dormancy period.

It is a long-living organism.

It lacks secondary wood production. (correct)

How does the domestication process of tree species contribute to bioeconomy?

It increases reliance on natural forests.

It decreases the production of renewable resources.

It mitigates climate change and enhances ecosystem services. (correct)

It focuses solely on timber production.

Which of the following is NOT a main step in the domestication process of agroforestry trees?

Tree breeding.

Soil degradation assessment. (correct)

Germoplasm modification.

Propagation technique.

Why is tree cloning beneficial for conservation projects?

It allows for genetic preservation. Signup and view all the answers

Which stage is the first in the micropropagation protocol by axillary budding?

Culture initiation and establishment. Signup and view all the answers

In the micropropagation protocol for axillary budding, what ratio is essential during the shoot multiplication phase?

AUXs/CKs ratio should favor Citokinins. Signup and view all the answers

What distinguishes adventitious budding from other budding types?

Buds can arise from non-meristematic tissue. Signup and view all the answers

What does not contribute to the primary goal of tree cloning?

Enhancing genetic variability. Signup and view all the answers

What is the primary purpose of applying higher concentrations of auxins and cytokinins during the induction of buds?

To initiate meristematic activity in non-meristematic cells Signup and view all the answers

Why is it important to sterilize the explants before initiation of the culture?

To prevent contamination from microorganisms Signup and view all the answers

What is a key characteristic of a vitrified plant?

Visible glassiness and translucency Signup and view all the answers

During the acclimatization process of in vitro plants, what is gradually reduced?

Humidity Signup and view all the answers

What factor along with genotype can impact the success of an in vitro culture?

Medium components used Signup and view all the answers

What condition primarily causes vitrification in plants?

Hyperhydricity Signup and view all the answers

What is a common consequence of phenolic exudation on in vitro material?

Enhanced tissue necrosis Signup and view all the answers

Which of the following is NOT a step in the adventitious budding process?

Seed germination Signup and view all the answers

What does regeneration from a callus primarily lead to in tissue culture?

Organogenesis or somatic embryogenesis Signup and view all the answers

What is the definition of somaclonal variation?

Genetic variability generated through tissue culture cycles Signup and view all the answers

Why is cell culture preferred for the production of secondary metabolites over extraction from fresh plant tissues?

It allows for larger and more controlled production Signup and view all the answers

What is a primary advantage of using cell culture for producing secondary metabolites like taxol?

Allows for large-scale production in a shorter time Signup and view all the answers

What characterizes the tissue mass referred to as a callus in tissue culture?

It is an unorganized meristematic tissue mass Signup and view all the answers

What role do phenolic compounds play during the stress of explants?

They can cause necrosis and hinder micropropagation. Signup and view all the answers

Which of the following is NOT a recommended tip for managing phenolic exudates in explants?

Increasing temperature of the culture medium. Signup and view all the answers

During which phase of somatic embryogenesis do you obtain cotyledonary somatic embryos?

Maturation phase. Signup and view all the answers

What is a key difference between somatic and zygotic embryos?

Zygotic embryos result from the fusion of gametes. Signup and view all the answers

What does the term 'embling' refer to in plant propagation?

A plant derived from somatic embryogenesis. Signup and view all the answers

Which statement accurately defines direct micropropagation?

It yields results faster without preparing callus. Signup and view all the answers

What is an expected advantage of indirect micropropagation?

It allows for the regeneration of shoots from unprepared explants. Signup and view all the answers

Why can some rhizobacteria have a beneficial effect on in vitro plants?

They enhance nutrient absorption and growth. Signup and view all the answers

Which microorganism is NOT classified as a Plant Growth Promoting Microorganism?

Lactic acid bacteria Signup and view all the answers

What beneficial effect do PGPR have on in vitro plants?

They reduce the need for chemical fertilization Signup and view all the answers

What is a synthetic seed?

An encapsulated propagation material with nutrition Signup and view all the answers

Which tree species was first replicated using somatic embryogenesis?

Santalum album Signup and view all the answers

What characterizes haploid plants?

They have only one set of chromosomes Signup and view all the answers

What is the main advantage of doubled haploid plants in trees?

They bypass several backcrosses in breeding Signup and view all the answers

Which of the following helps enhance acclimatization in plants?

PGPR Signup and view all the answers

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.