Plant hormones are naturally occurring organic substances that affect physiological processes. There are five major groups of plant hormones, such as auxins, gibberellins, cytokinins, abscisic acid and ethylene. In this presentation describes about abscisic acid with its biosynthesis, transport, pathways and physiological effects.

1. Abscisic acid
Dr. Emasushan Minj
Assistant Professor
Department of Botany
St. Xavier’s College,
Mahuadanr, Latehar
Nilamber Pitamber University

2. Introduction
• Abscisic acid (ABA) is a
• It is the only member.
• It was first identified and chemically characterized by
while
studying abscission of cotton fruits.
• It was originally called
• It plays a .

3. Biosynthesis and transport
• ABA is a
• It is synthesized almost in all
cells that contain chloroplast
and other plastids.
The pathway starts-

4. Physiological effects
• During the stress, ABA concentration increases dramatically in
plant leaves, which leads to stomata closure.
• Stomatal closure is driven by a reduction in guard cell turgor
pressure caused by a large efflux of potassium ion and anions (such
as chloride and malate ions).
• The effect of ABA on
.
•
in two ways:
▫ By influx of calcium ions through plasma membrane.
▫ By release of calcium ions into the cytosol from internal
compartment, such as ER and vacuole.

5. • ABA has different
of
the plant.
• Under low water potential,
• And negative effect on the shoot growth.

6. • High level of ABA in .
• Many types of dormant seeds germinate when ABA is
removed or inactivated.
• The
(Hormone balance
theory).
• ABA
(such as α-amylase) that is essential for the breakdown of
storage reserves in seeds.
• The role of ABA in buds dormancy is less known.

7. • ABA-deficient embryos may
• Vivipary is the germination of mature seed winthin the fruit on
maternal plant (Ex.– Mangroves).
• The phenomenon of
• of ABA can lead to precocious
germination and vivivpary.
• ABA increases the hydraulic conductivity (decreasing the
resistance to water movement across the membrane) and ion flux
of root in response to water stress.

8. Thankyou