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What is the role of ABA accumulation in leaf growth under water deficits?
Thorne, Eleanor*,1, Jackson, Alison2, Burbidge, Alan3, Thompson, Andrew2, Taylor, Ian3, Sharp, Robert1, 1 University of Missouri-Columbia, Columbia, MO2 Horticulture Research International, Wellesbourne, UK3 University of Nottingham, Sutton Bonington, UK
ABSTRACT- Leaf growth is very sensitive to water deficits. Abscisic acid (ABA) accumulates in water-stressed plants, and its role in the leaf growth response is a longstanding question. ABA is generally regarded as an inhibitor of leaf growth. However, using ABA-deficient mutants and methods to avoid variation in plant water status due to low ABA, normal ABA levels were shown to maintain leaf growth in well-watered tomato plants by restricting ethylene production (Sharp RE et al., 2000, J Exp Bot 51:1575-1584). These approaches are being extended to study the role of ABA accumulation in leaf growth under water deficits. Because the growth impairment of well-watered controls would confound interpretation of responses to ABA deficiency under stress, a partially-complemented line of the notabilis mutant of tomato was developed, which exhibits normal ABA levels and growth when well-watered, yet is deficient in stress-induced ABA accumulation. This strategy enables specific investigation of the role of increased ABA levels during water deficit. Experiments are in progress to test the hypothesis that ABA accumulation functions to maintain rather than inhibit leaf growth in water-stressed plants.
KEY WORDS: water relations, drought, leaf growth, ABA