Plant Physiology: Seed Structure and Germination

Vocabulary flashcards covering key concepts related to seed structure, germination, and plant growth responses.

Germination

Germination is the emergence of the embryo from the seed, beginning with imbibition, where the seed absorbs water and swells. This is followed by metabolic processes activating the seed's stored nutrients, leading to the growth of the radicle, which is the first root structure to emerge. Successful germination requires optimal conditions such as sufficient moisture, appropriate temperature, and adequate oxygen availability. It marks the transition from a dormant seed to a growing plant, initiating its life cycle.

Endosperm

Food reserve stored in seed, can be endospermic (located outside seed) or non-endospermic (cotyledon acts as food source).

Germination

Emergence of the embryo from the seed; begins with imbibition, leading to metabolic processes and radicle emergence.

Dormancy

Temporal delay in germination process, which can be primary (induced during maturation) or secondary (due to environmental conditions).

Auxin

Plant hormone that promotes cell elongation and is involved in directional growth responses (tropisms).

Thigmotropism

Directional growth response of plants to touch, such as tendril bending toward a support.

Gravitropism

Growth response to gravity; roots grow downward while shoots grow upward.

Aleurone

Protein found in maturing seeds that secretes enzymes to mobilize nutrients during germination.

Imbibition

Absorption of water by seeds, marking the beginning phase of germination.

Scarification

Process of weakening or altering seed coat to promote germination, often using mechanical or chemical means.

Cytokinin

Plant hormone that promotes cell division and differentiation, particularly in conjunction with auxin.

Coleoptile

Modified leaf that protects the first leaves of monocots during growth in soil.

Hypocotyl

Embryonic stem found in seeds, developing into the part of the plant that separates root and shoot.

Radicle

Embryonic root that emerges during germination.

Vivipary

Germination of seeds while still attached to the parent plant.

ABA (Abscisic Acid)

Hormone that inhibits germination and promotes seed dormancy by signaling during seed maturation.

GA (Gibberellin)

Hormone that promotes germination by initiating metabolic processes in the seed.

Pericarp

Fruit wall derived from the ovary wall that encloses the seed.

Cotyledon

Embryonic leaf in seeds; monocots have one (scutellum) and dicots have two.

Primary Dormancy

Dormancy induced by abscisic acid during seed maturation.

Non-hair cell fate

Cell fate determined by the transcription factor WER, leading to the development of non-hair cells on roots.

Fertilization

Process by which male and female gametes fuse to form a zygote, initiating the development of a seed.

Pollination

Transfer of pollen from the male anthers to the female stigma, crucial for fertilization.

Seed Dispersal

Mechanism by which seeds are spread from the parent plant to reduce competition and colonize new areas.

Photosynthesis

Process by which green plants convert sunlight, carbon dioxide, and water into glucose and oxygen.

Chlorophyll

Green pigment in plants that absorbs light energy for photosynthesis.

Transpiration

Loss of water vapor from plant leaves to the atmosphere, crucial for water and nutrient uptake.

Root Hair

Extensions of root cells that increase surface area for water and nutrient absorption.

Photosystem

Complexes of proteins and pigments in chloroplasts that capture and convert light energy.

Stomata

Microscopic pores on leaves that regulate gas exchange and transpiration.

Mycorrhizae

Symbiotic association between fungi and plant roots that enhances nutrient absorption.

What is a seed?

A seed is an embryonic plant enclosed in a protective covering developed from a ripened ovule after fertilization.

What is endosperm?

Endosperm is a food reserve stored in the seed that can be either endospermic (located outside seed) or non-endospermic (cotyledon acts as food source).

What is germination?

Germination is the emergence of the embryo from the seed, starting with imbibition, followed by metabolic processes and radicle emergence.

What defines dormancy in seeds?

Dormancy is a temporal delay in the germination process, which can be primary (induced during maturation) or secondary (due to environmental conditions).

What role does auxin play in plants?

Auxin is a plant hormone that promotes cell elongation and is involved in directional growth responses (tropisms).

What is thigmotropism?

Thigmotropism is the directional growth response of plants to touch, such as tendril bending toward a support.

How does gravitropism affect plant growth?

Gravitropism is a growth response to gravity, causing roots to grow downward and shoots to grow upward.

What is the function of aleurone in seeds?

Aleurone is a protein found in maturing seeds that secretes enzymes to mobilize nutrients during germination.

What is imbibition in the context of seeds?

Imbibition is the absorption of water by seeds, marking the beginning phase of germination.

What is scarification in seed germination?

Scarification is the process of weakening or altering the seed coat to promote germination, often using mechanical or chemical means.

Seed Coat

Protective outer layer of a seed that encases the embryo and endosperm.

Fruit

Ripened ovary of a flower that contains seeds and aids in their dispersal.

Monocots

Plants with one seed leaf (cotyledon), examples include grasses and lilies.

Dicots

Plants with two seed leaves (cotyledons), examples include beans and sunflowers.

Translocation

Movement of nutrients and photosynthates within a plant from source tissues to sinks.

Siphonogamy

Pollination process wherein pollen grains are transported to the ovule through a pollen tube.

Stigma

Part of the female reproductive organ of a flower that receives pollen.

Plumule

Embryonic shoot of a seed that develops into the aerial part of the plant.

Seed Dispersal Mechanisms

Methods by which seeds are spread from the parent plant, including wind, water, animal ingestion, and mechanical means.

Photosynthesis Equation

The chemical equation for photosynthesis: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2.

Role of Chlorophyll

Chlorophyll absorbs light energy, primarily in the blue and red wavelengths, essential for photosynthesis.

Phloem Function

Phloem transports sugars and nutrients produced by photosynthesis from leaves to other parts of the plant.

Xylem Function

Xylem transports water and minerals from the roots to the rest of the plant.

Role of ABA in Plants

ABA (Abscisic Acid) regulates water loss and promotes seed dormancy during unfavorable conditions.

Effects of Gibberellin

Gibberellin stimulates stem elongation, seed germination, and flower development in plants.

What is vivipary?

Vivipary is the process where seeds germinate while still attached to the parent plant.

Germination Conditions

Optimal conditions for germination include moisture, suitable temperature, and oxygen availability.

Seedling

A young plant that has emerged from a seed and is in its early stages of development.

Root System Types

Plants can have taproot systems (one main root) or fibrous root systems (numerous small roots).

Seed Stratification

A pre-germination treatment that involves exposing seeds to cold and moist conditions to break dormancy.

Nitrogen Fixation

The process by which nitrogen in the atmosphere is converted into ammonia by certain bacteria.

Pollinators

Organisms, such as bees and butterflies, that transfer pollen from one flower to another, aiding in fertilization.

Gibberellin Effects

Gibberellins promote seed germination, stem elongation, and flowering in plants.

Soil Fertility

The ability of soil to provide essential nutrients to plants, affected by organic matter, pH, and microbial activity.

Hydroponics

A method of growing plants in nutrient-rich water without soil.

Transpiration Pull

The process by which water is drawn up through a plant due to evaporation from the leaves.

Photosynthesis rate

The speed at which photosynthesis occurs, affected by light intensity, carbon dioxide levels, and temperature.

Chloroplasts

Organelles in plant cells where photosynthesis takes place, containing chlorophyll.

Xylem

Vascular tissue in plants that transports water and dissolved minerals from roots to leaves.

Phloem

Vascular tissue that transports sugars and nutrients produced by photosynthesis to various parts of the plant.

Transpiration rate

The amount of water vapor lost by a plant through stomata, influencing water uptake and nutrient transport.

Hydroponics

A method of growing plants without soil, using nutrient-rich water to supply essential elements.

Soil pH

A measure of the acidity or alkalinity of soil, affecting nutrient availability and microbial activity.

Nitrogen cycle

The series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms.

Plant hormones

Natural substances that regulate plant growth and development, including auxins, gibberellins, and cytokinins.

Asexual reproduction

A reproductive process by which offspring arise from a single organism, lacking genetic fusion, such as vegetative propagation.