Bio 131 Handout 7 Seed Development and Germination

Seed development

Seed development

The process of maturation and germination of a seed, involving complex metabolic, enzymatic, morphological, and structural processes.

Maturation

The phase of seed development characterized by the fast formation/decline of monosaccharides and amino acids in the early phase, followed by the synthesis and polymerization of reserve carbohydrates and proteins.

Germination

The phase of seed development characterized by the activation of hydrolytic enzymes, production of de novo synthesized enzymes, and degradation of storage compounds in the endosperm. It involves the mobilization of starch and reserve proteins.

Soybean

A model plant for studying seed development, with a 120-day period divided into five stages:globular, heart, torpedo, maturation, and dormancy.

Cotyledons

The storage organ in soybean where the bulk of storage proteins are synthesized and deposited during the maturation phase.

Seed dormancy

The temporary inability of a viable seed to germinate, even under favorable environmental conditions. It is under endogenous control and requires a trigger before the embryo can resume growth.

Seed storage proteins

A unique class of proteins synthesized during seed formation, acting as a food reserve for the germinating seedling. They are rich in arginine, glutamine, glutamate, and asparagine and have different solubility properties in water or alcohol/detergent solutions depending on the plant species.

Protein bodies

Dense, crystalloid structures where storage proteins accumulate in the cytoplasm of cells.

Quiescence

A short period of dormancy induced by unfavorable environmental conditions, which can be overcome by exposure to favorable conditions.

Endogenous control

Regulation of dormancy by factors such as hormone levels, embryo maturity, and seed coat impermeability.

Dormancy

A state of suspended growth and development in seeds, characterized by reduced metabolic activity.

Abscisic acid (ABA)

A hormone that triggers seed dormancy and is involved in the regulation of various processes in plants.

Viviparous

Referring to seeds that germinate while still attached to the mother plant.

LEA genes

Late embryogenesis-associated genes that are expressed during the onset of seed dormancy and are regulated by abscisic acid.

Scarification

The process of breaking or weakening the hard seed coat to allow water to enter and initiate germination.

Imbibition

The uptake of water by a dry seed, leading to the resumption of metabolic activity.

Metabolism reactivation

The restart of metabolic processes, including the mobilization of food reserves and protein synthesis, during seed germination.

Radicle

The embryonic root of a plant that emerges from the seed during germination.

Long-lived mRNA

mRNA molecules that are synthesized during embryogenesis and stored in mature dry seeds, remaining translatable for long periods.

Radicle extension

The elongation of the radicle, marking the completion of germination and the beginning of seedling growth.

DNA synthesis

The process of creating new DNA molecules.

Radicle

The embryonic root of a plant.

Imbibition

The process of absorbing water by a seed.

Turgor-driven process

A process that is driven by the pressure of water inside plant cells.

Cell wall loosening

The process of making cell walls less rigid, allowing for cell expansion.

Expansins

Proteins that are involved in loosening cell walls during cell expansion.

XET (xyloglucan endotransglycosylate)

An enzyme that is involved in loosening cell walls during cell expansion.

Germination

The process of a seed sprouting and growing into a new plant.

Mechanical resistance

The ability of a structure to resist external forces.

Endosperm

The tissue that surrounds and provides nutrients to the embryo in a seed.

Hydrolysis

The chemical breakdown of a compound by reacting with water.

Proteases

Enzymes that break down proteins.

Lipases

Enzymes that break down lipids.

Amylases

Enzymes that break down starch.

Gibberellins

Plant hormones that play a role in seed germination.

Aleurone layer

The outermost layer of cells in the endosperm of a seed.

ER (endoplasmic reticulum)

An organelle involved in protein synthesis and processing.

mRNA

Messenger RNA, a molecule that carries genetic information from DNA to the ribosomes.

Abscisic acid (ABA)

A plant hormone that inhibits seed germination and promotes seed dormancy.

Transcription

The process of synthesizing RNA from a DNA template.

Antagonistically

In opposition to each other.

Seed dormancy

A period of inactivity in a seed before it can germinate.

Phytohormones

Plant hormones that regulate plant growth and development.

Auxin

A plant hormone that regulates cell elongation and growth.

Brassinosteroids

Plant hormones that promote cell elongation and growth.

Ethylene

A plant hormone that regulates fruit ripening and senescence.

GA biosynthesis

The process of producing gibberellic acid (GA), a plant hormone that plays a crucial role in seed germination.

Radicle

The embryonic root of a plant.

Germination progression

The process of a seed sprouting and developing into a new plant.

GA metabolism genes

Genes that regulate the metabolism of gibberellic acid.

Gibberellin 3-oxidase I and II

Enzymes involved in the biosynthesis of gibberellic acid.

Water imbibition

The process of a seed absorbing water.

Seed dormancy

A state of suspended growth and development in a seed.

GA mutant

A plant with a genetic mutation that affects the biosynthesis of gibberellic acid.

Testa

The seed coat.

Endosperm

The tissue surrounding the embryo in a seed.

GA-ABA balance

The balance between gibberellic acid (GA) and abscisic acid (ABA) in the embryo and surrounding layers of a seed.

Environmental factors

Factors such as light and temperature that can influence seed germination.

Priming

A technique used to enhance seed germination by pre-treating seeds with certain substances.

Exogenous application

The application of a substance from an external source.

Phytohormones

Plant hormones that regulate various physiological processes.

Nitrogen-containing compounds

Compounds that contain nitrogen and can stimulate seed germination.

α-amylase activities

The activities of an enzyme called α-amylase, which is involved in the breakdown of starch during seed germination.

Adenosine triphosphate (ATP) production

The production of ATP, a molecule that provides energy for cellular processes.

Biostimulants

Substances or microorganisms that positively alter a plant's physiological processes to promote growth.

Seaweed extracts

Extracts derived from seaweed that can contain important phytohormones.

Humic substances

Organic compounds found in soil that can act as biostimulants.

Hydrolyzed proteins

Proteins that have been broken down into smaller peptides or amino acids.

Microorganisms

Small living organisms that can have beneficial effects on plant growth.

Epigeal germination

A type of germination where the cotyledons emerge from the soil along with the plumule.

Hypogeal germination

A type of germination where the cotyledons remain in the soil while the epicotyl elongates to push the plumule out.

Coleorhiza

A sheath that covers the radicle in monocot seeds.

Coleoptile

A sheath that covers the shoot in monocot seeds.