Answer:
Hormone
Positive Effects
Negative Effects
Ethylene
Promotes
horizontal/transverse growth.
Inhibits longitudinal growth.
Makes stem positively
geotropic.
Decreases sensitivity to
gravity. i.e., root become apogeotropic
Promotes apical dominance.
Enhances senescence of leaves
and flowers, fruits.
Breaks seed and bud
dormancy.
root initiation.
Prolongs dormancy of lateral
buds.
Mediates formation of ABA
under water stressed conditions.
Abscissic Acid
4- ABA is used as anti
transpirant, by reduce sing water requirement and during irrigation (by
partial closure of stomata).
Promotes abscission of flower
and fruits.
Also, induces flowering and
root
initiation in some plants.
Stimulates senescence of
leaves by stopping protein and RNA synthesis.
Used in prolonging dormancy
of
buds and seeds.
Promotes bud and seed dormancy.
Retards cambial activity by stopping mitosis in vascular strands and cambium.
Increases resistance of
plants, to cold and other types of stresses thus also known as stress hormone.
Act as antagonist to
gibberellins and counteracts the effect of other growth hormones (IAA and cytokinin).
Inhibits seed germination and
growth of embryos in them.
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