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faktor pertumbuhan dan perkembangan tumbuhan - gen dan hormon tumbuhan biologi bab sama materi
Biologi Tv
Overview
This video explains the internal factors that influence plant growth and development, focusing on genes and plant hormones. It details how genes control traits like color and differentiation, though this topic will be explored further in Mendelian genetics. The main focus is on seven plant hormones: auxin, cytokinin, gibberellin, abscisic acid, ethylene, traumalin, and kalin. Each hormone's production site, primary functions, and specific roles in processes like cell elongation, cell division, apical dominance, phototropism, fruit ripening, and stress response are discussed with examples.
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Chapters
- Plant growth and development are influenced by both internal and external factors.
- Internal factors originate from within the plant itself.
- This video will focus on internal factors: genes and hormones.
Understanding these internal factors is crucial for comprehending how plants grow, respond to their environment, and develop specific characteristics.
A mung bean seed needs water (an external factor) to become a sprout, highlighting that growth requires multiple influences.
- Genes are the genetic material that code for traits in living organisms.
- In plants, genes influence characteristics such as form, size, color, and cell differentiation.
- Detailed discussion on genes controlling plant traits will be covered in future lessons on Mendelian genetics.
Genes provide the fundamental blueprint for a plant's potential growth and development, dictating its inherent characteristics.
Different genes result in rose bushes having flowers of varying colors, such as red or white.
- Auxin, also known as indole acetic acid, is produced mainly in the shoot tips and transported downwards.
- It stimulates growth by promoting cell elongation.
- Auxin is responsible for apical dominance, inhibiting the growth of lateral buds, and causes stems to bend towards light (positive phototropism).
Auxin's role in cell elongation and directional growth is fundamental to how plants achieve their characteristic shapes and reach for light.
When light comes from one side, auxin concentrates on the shaded side of the stem, causing cells there to elongate faster and the stem to bend towards the light source.
- Cytokinin is primarily produced in the roots but can be synthesized elsewhere.
- It stimulates growth by promoting cell division.
- Cytokinin encourages lateral (side) bud growth and can delay the aging of plant organs by directing nutrients.
Cytokinin balances auxin's effects by promoting cell division and branching, influencing the overall architecture and longevity of the plant.
Cytokinin is more effective in promoting side shoot growth when the top bud (where auxin is concentrated) is removed.
- Gibberellins are produced in young leaves, root and shoot apical meristems, and developing seeds.
- They contribute to growth through both cell elongation and cell division.
- Gibberellins are essential for breaking seed dormancy and promoting germination.
Gibberellins are key to initiating growth from seeds and further elongating stems, playing a vital role in the plant's life cycle.
Gibberellins help seeds overcome their dormant state, allowing them to sprout when conditions are favorable.
- Abscisic acid (ABA) is produced in most plant organs and acts to inhibit growth.
- It protects plants from extreme conditions, earning it the name 'stress hormone'.
- ABA triggers leaf drop (abscission) and stomatal closure during drought, and induces seed dormancy.
Abscisic acid is critical for plant survival, enabling it to conserve resources and protect itself during unfavorable environmental conditions.
When a plant is low on water, ABA causes it to shed its leaves to reduce water loss and closes its stomata.
- Ethylene is the only plant hormone that exists as a gas.
- It is produced by most parts of the plant.
- Ethylene promotes fruit ripening by softening the fruit and also accelerates aging and shedding of leaves, flowers, and fruits under stress.
Ethylene's role in fruit ripening is essential for seed dispersal, while its stress-induced aging response helps plants manage adverse conditions.
Ethylene causes fruits like bananas to become softer and sweeter as they ripen.
- Traumalin is believed to be involved in wound healing by stimulating cell division to form protective tissue.
- Kalin is thought to regulate the formation and growth of specific plant organs.
- These hormones are considered hypothetical by some scientists, with traumalin found in damaged tissues and kalin categorized into types for root (rhizokalin), stem (caulokalin), leaf (phyllokalin), and flower (anthokalin) formation.
While debated, the proposed functions of traumalin and kalin suggest mechanisms for tissue repair and organogenesis within plants.
Traumalin is associated with the process of sealing a cut or injury on a plant stem.
Key takeaways
- Genes provide the fundamental genetic instructions for plant traits, while hormones act as chemical messengers to regulate growth and development.
- Auxin promotes cell elongation and directional growth (phototropism), while cytokinin promotes cell division and lateral branching.
- Gibberellins are crucial for breaking seed dormancy and stem elongation, whereas abscisic acid inhibits growth and manages stress responses like drought.
- Ethylene gas is primarily responsible for fruit ripening and can accelerate aging under stress.
- Plant hormones work in a complex interplay, often with opposing or synergistic effects, to finely tune growth and development.
- Understanding these internal factors helps explain why plants grow the way they do and how they adapt to their environment.
Key terms
GenesPlant HormonesAuxinCytokininGibberellinsAbscisic Acid (ABA)EthyleneApical DominancePhototropismCell DivisionCell ElongationSeed DormancyFruit Ripening
Test your understanding
- How do genes and hormones differ in their roles in plant growth and development?
- What is the primary mechanism by which auxin influences plant growth, and how does it lead to phototropism?
- Explain the contrasting roles of auxin and cytokinin in regulating plant branching.
- Under what environmental conditions does abscisic acid become particularly important for a plant's survival, and what specific actions does it take?
- How does ethylene contribute to both the natural life cycle of fruits and the plant's response to stress?