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Probing hormone action in developing seeds by ABA-deficient and -insensitive mutants

1992; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-94-011-2458-4_5

0924-1949

C. M. Karssen, L.C. van Loon,

Seed Germination and Physiology

Exogenous application of plant growth regulators, combined with determination of endogenous hormone contents, has provided circumstantial evidence for various roles of ABA in plants. Mutant plants deficient in ABA synthesis or showing reduced sensitivity to its presence offer a direct test of these assumptions. The main benefit of mutants for the physiological analysis of hormone action is that they do not suffer from artefacts occurring when hormone synthesis is inhibited by chemical means or upon isolation of plant parts. Thus, studies of ABA mutants validated the role of ABA in regulating stomatal aperture and in inducing seed dormancy but negated, for instance, the proposed action of ABA in gravitropism. Deficient mutants have also contributed extensively to the clarification of the biosynthetic pathways of ABA. Recently, the physiological analysis of ABA mutants has been extended to the biochemical and molecular level, shedding light on the mechanism of action of the hormone. Since recent studies with ABA mutants were focused mainly on the role of ABA in developing seeds this chapter will be restricted to progress in that area of research.