A plant hormone (C₁₅H₂₀O₄)
and weak acid that generally acts to inhibit growth,
induces dormancy, and helps the plant tolerate stressful
conditions by closing stomata. Abscisic acid was
named based on a belief that the hormone caused the
abscission (shedding) of leaves from deciduous trees
during the fall.
At times when a plant needs to slow down growth
and assume a resting stage (dormant), abscisic acid is
produced in the terminal bud, which slows down
growth and directs the leaf primordia to develop scales
that protect the dormant bud during winter. Since the
hormone also inhibits cell division in the vascular cambium,
both primary and secondary growth is put on
hold during winter.
This hormone also acts as a stress agent, helping a
plant deal with adverse conditions. For example, ABA
accumulates on leaves and causes stomata to close,
reducing the loss of water when a plant begins to wilt.
In 1963 abscisic acid was first identified and characterized by Frederick Addicott and colleagues. In 1965 the chemical structure of ABA was defined, and in 1967 it was formally called abscisic acid.
The molecular weight of abscisic acid is 264.32 g·mol−1 , density 1.193 g/mL, melting point 163 °C.
The molecular weight of abscisic acid is 264.32 g·mol−1 , density 1.193 g/mL, melting point 163 °C.