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HORMONES IN PLANTS (AKA PHYTOHORMONES) - Coggle Diagram
HORMONES IN PLANTS (AKA PHYTOHORMONES)
CHARACTERISTICS
NOT SPECIFIC, BUT HAS WIDE RANGE OF RESPONSES
TEND TO INTERACT WITH EACH OTHER IN CONTROL OF GROWTH
AT CERTAIN CONC., THE EFFECT MIGHT BE TO STIMULATE, BUT AT DIFF CONC., IT MIGHT HAVE AN OPPOSITE EFFECT
TYPES
AUXINS (IAA)
PRODUCED AT APICAL MERISTEMS & YOUNG LEAVES, TRANSPORTED TO ROOTS VIA PHLOEM
EG: INDOLE ACETIC ACID (IAA, NATURAL AUXIN) & 2,4-D (2,4-DICHLOROPHENOXYACETIC, SYNTHETIC AUXIN)
GIBBERELLIN (GA)
PRODUCED IN YOUNG APICAL LEAVES, DEVELOPING BUDS, ROOT TIPS & GERMINATING SEEDS
PROMOTES CELL ELONGATION
CYTOKININS
FOUND IN MOSTLY FRUITS & SEEDS
IN MATURE PLANTS, PRODUCED IN THE ROOTS & MOVES TO SHOOTS VIA XYLEM
PROMOTES CELL DIVISION
INCREASE OF CYTOKININ LEADS TO GROWTH OF SHOOT BUDS, INCREASE OF AUXIN INDUCES ROOT FORMATION
ABSISSIC ACID (ABA)
AKA STRESS HORMONE, AS IT PROMOTES CHANGE IN PLANT TISSUES THAT HAVE BEEN STRESSED / EXPOSED TO UNFAVOURABLE CONDITIONS
PRODUCED IN LEAVES, STEMS, ROOTS, SEEDS & TRANSPORTED IN PHLOEM
PROMOTES SEED & BUD DORMANCY
PROMOTES CLOSING OF STOMATA DURING WATER STRESS (WILITING)
ETHENE
GASEOUS HORMONE RELEASED DURING FRUIT RIPENING
PRODUCED BY MOST PLANT ORGANS
PHYTOCHROME & FLOWERING
PHYTOCHROME - BLUE-GREEN PIGMENT THAT ACTS AS A PHOTORECEPTOR, ABSORBING CERTAIN WAVELENGTHS OF LIGHT & AFFECTS FLOWERING
TWO INTERCONVERTIBLE FORMS
PR / P660 THAT ABSORBS RED LIGHT
PFR / P730 THAT ABSORBS FAR RED LIGHT
DURING THE DAY, SUNLIGHT CONTAINS MORE RED LIGHT, THEREFORE PR IS CONVERTED INTO PFR (CONVERSION DEPENDS ON LIGHT INTENSITY)
PFR (THE ACTIVE FORM OF PHYTOCHROME) THEN CARRIES OUT FLOWERING
AT NIGHT, PFR IS MORE UNSTABLE & SLOWLY CONVERTS BACK TO PR
PHOTOPERIODISM
PHENOMENON WHERE PLANTS RESPOND TO RELATIVE LENGTHS OF DAYLIGHT & DARKNESS
3 GROUPS OF CLASSIFICATION
SHORT-DAY PLANTS
PFR INHIBITS FLOWERING, THEREFORE PLANTS NEED A LONG NIGHT BEFORE IT CAN FLOWER
A LONG NIGHT ENSURES ALL PFR IS CONVERTED INTO PR & THERE IS NO PFR INSIDE THE PLANT TO INHIBIT FLOWERING
IF PLANT EXPOSED TO RED LIGHT DURING NIGHT, IT WILL NOT FLOWER, AS PR IS CONVERTED BACK INTO PFR
PLANT WILL FLOWER IF PERIOD OF DARKNESS > CERTAIN CRITICAL PERIOD
USUALLY FLOWERS IN AUTUMN / EARLY SPRING
EG: STRAWBERRIES, POTATOES
LONG-DAY PLANTS
PFR PROMOTES FLOWERING, THEREFORE PLANTS NEED A SHORT NIGHT BEFORE IT CAN FLOWER
SHORT NIGHT ENSURES NOT ALL PFR IS CONVERTED INTO PR & THERE IS PFR INSIDE OF PLANT TO PROMOTE FLOWERING
PLANT WILL FLOWER IF PERIOD OF DARKNESS < CERTAIN CRITICAL PERIOD
USUALLY FLOWERS IN SUMMER / LATE SPRING
EG: MAIZE, CLOVER, SPINACH
DAY-NEUTRAL PLANTS
PLANT DOES NOT DEPEND ON PHOTOPERIODISM FOR FLOWERING
EG: SUNFLOWERS, TOMATOES, DANDELIONS, MOST TROPICAL PLANTS