Plant Hormones and Signal Transduction in Physiology

Signal transduction

Activation of receptors triggers cellular biochemical responses.

Signal hyposensitive mutation

Mutation resulting in reduced or no response to signals.

Signal hypersensitive mutation

Mutation causing constant response regardless of signal presence.

Chemical signals

Molecules coordinating plant morphogenesis and physiology.

Hormones

Chemical messengers regulating plant growth and development.

Auxin (IAA)

Hormone promoting cell elongation and growth.

Cytokinin

Hormone stimulating cell division and growth.

Gibberellin (GA)

Hormone involved in stem elongation and seed germination.

Ethylene

Hormone regulating fruit ripening and stress responses.

Abscisic acid (ABA)

Hormone regulating seed dormancy and stress responses.

Brassinosteroid

Hormone promoting stem elongation and cell division.

Dormin

Hypothetical hormone regulating seed and bud dormancy.

Etiolation

Growth in absence of light resulting in elongated stems.

De-etiolation mutant (DET2)

Mutant showing light-like growth in darkness.

Brassinolide

Active form of brassinosteroid essential for plant growth.

Stomata

Pores in leaves regulating gas exchange and water loss.

Vivipary mutant

Mutant exhibiting premature germination within seed.

Isoprenoid

Class of compounds including several plant hormones.

Cytosolic Ca2+

Messenger triggering physiological changes in response to stress.

Phototropism

Plant growth response to light direction.

Indole-3-acetic acid (IAA)

Most abundant and active form of auxin.

Optimal auxin concentration

1-10 μM for effective cell elongation.

Abscission

Process of shedding plant parts like leaves or fruits.

Skotomorphogenesis

Growth pattern in darkness, characterized by elongated stems.

Hormone balance (ABA:GA)

Determines seed dormancy and germination timing.

Brassinosteroid synthesis

Occurs in cytosol, crucial for plant development.

Cytokinin synthesis

Occurs in cytosol and chloroplasts, promoting growth.

Gibberellin synthesis

Involves multiple steps in plant hormone biosynthesis.

Hormonal signaling

Regulates physiological responses to environmental changes.

Meristem Cells

Undifferentiated cells responsible for new growth.

Differentiation

Process where cells specialize for specific functions.

Wounding Response

Cells regain division capacity to heal injuries.

Gottlieb Haberlandt

Proposed chemical substance for plant cell division.

Plant Tissue Culture

Indefinite cultivation of plant cells in medium.

Auxin

Hormone that promotes cell elongation and growth.

Bioassay

Test to measure biological activity of substances.

Philip White

Discovered coconut milk promotes cell division.

Murashige and Skoog Medium

Plant growth medium named after its developers.

Kinetin

Synthetic cytokinin derived from degraded DNA.

Zeatin

Dominant cytokinin derived from maize endosperm.

IPT

Key enzyme in zeatin biosynthesis.

Fasciation

Abnormal growth of plant tissues in meristems.

Agrobacterium tumefaciens

Bacteria causing tumor-like tissue in plants.

Gall

Tumor-like tissue formed by infected plant cells.

Ti Plasmid

Plasmid responsible for tumor formation in plants.

T-DNA

DNA transferred to plant cells by A. tumefaciens.

Octopine

Compound utilized exclusively by A. tumefaciens.

Gibberellins

Hormones promoting stem elongation in plants.

Gibberella fujikuroi

Fungus causing 'foolish seedling' disease in rice.

Gibberellic Acid

Purified compound promoting plant growth.

Parthenocarpy

Fruit development without fertilization.

Stenospermocarpy

Fruit develops but seeds abort early.

Climacteric Fruits

Fruits that ripen with increased respiration and ethylene.

Yang Cycle

Process involving CO2 in fruit ripening.

Autocatalytic Effect

Positive feedback loop enhancing ethylene production.

Non-Climacteric Fruits

Fruits that do not exhibit respiration spikes.

Véraison

Onset of ripening in grapevines.

Kinase

Enzyme that adds phosphate groups to proteins.

Phosphatase

Enzyme that removes phosphate groups from proteins.

MAPK Cascade

Signal amplification through sequential phosphorylation.

GPCR

G protein-coupled receptors absent in plants.

Two-Component System

Prokaryotic signaling system in plants.

Ubiquitination

Targeted protein degradation mechanism in cells.

E1 Enzyme

Ubiquitin-activation enzyme that loads ubiquitin.

E2 Enzyme

Transfers ubiquitin to substrate proteins.

E3 Enzyme

Specifies substrate proteins for ubiquitination.

SCF Protein

Common E3 enzyme with SKP, Cullin, F-box.

PYR

Abscisic acid receptor identified through screening.

SnRK2

Kinase activated by ABA signaling.

BSU1

Phosphatase involved in brassinolide signaling.

BIN2

Kinase involved in brassinolide signaling.

BZR1/BES1

Transcription factors regulated by brassinolide.

Lodging

Crop loss due to bending stems.

DELLA Protein

Regulates growth response to gibberellins.

Rht Mutation

GA-insensitive dwarf mutant in wheat.

Dr. Norman Borlaug

Nobel Prize winner for wheat production advances.

GID1

GA receptor involved in dwarf phenotype.