Hormonal Modulation of Citrus Responses to Flooding
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In this work, variations in endogenous levels of several hormones were measured in citrus under conditions of continuous flooding following a time-course design. The use of three genotypes differing in their ability to tolerate waterlogging has allowed the discrimination between common and specific hormonal responses. Data suggest an essential involvement of the aerial part in the regulation of tolerance to flooding, whereas in roots more general responses were detected. The progressive increase in leaf abscisic acid (ABA) correlating with the different tolerance of genotypes confirms the involvement of this hormone in plant responses to stress. The late increase in 1-aminocyclopropane-1-carboxylic acid, concomitant with severe leaf injury, points to ethylene as a promoter of leaf senescence in citrus. Leaf putrescine increased in all flooded genotypes, suggesting a general protective role, whereas a higher protective ability of spermidine and spermine was enforced by their exclusive accumulation in the sensitive genotype. Leaf jasmonic acid (JA) increased rapidly and transiently under flooding, suggesting a role for this hormone in triggering downstream responses. In stressed roots, while indole-3-acetic acid increased, JA and ABA levels rapidly decreased to reach almost complete depletion in all flooded citrus genotypes. This suggests that not only should the increase in the so-called stress hormones be considered a signal but also their reduction. The results contribute to the understanding of the intricate set of connections between plant hormones that regulate physiologic responses to stress.
KeywordsAbscisic acid 1-Aminocyclopropane-1-carboxylic acid Indole-3-acetic acid Jasmonic acid Putrescine Spermidine Spermine Waterlogging
This work was supported by the Spanish Ministerio de Educación y Ciencia and Universitat Jaume I/Fundació Bancaixa through grants No. AGL2007-65437-C04-03/AGR and P1IB2006-02, respectively. Hormone determinations were performed in the central facilities (Servei Central d’Instrumentació Científica, SCIC) of Universitat Jaume I. Authors are grateful to Gerald Rix (M.D.) for proofreading the text.
- Azuma T, Hirano T, Deki Y, Uchida N, Yasuda T, Yamaguchi T (1995) Involvement of the decrease in levels of abscisic-acid in the internodal elongation of submerged floating rice. J Plant Physiol 146:323–328Google Scholar
- Else MA, Hall KC, Arnold GM, Davies WJ, Jackson MB (1995) Export of abscisic-acid, 1-aminocyclopropane-1-carboxylic acid, phosphate, and nitrate from roots to shoots of flooded tomato plants—accounting for effects of xylem sap flow-rate on concentration and delivery. Plant Physiol 107:377–384PubMedGoogle Scholar
- Else MA, Coupland D, Dutton L, Jackson MB (2001) Decreased root hydraulic conductivity reduces leaf water potential, initiates stomatal closure and slows leaf expansion in flooded plants of castor oil (Ricinus communis) despite diminished delivery of ABA from the roots to shoots in xylem sap. Physiol Plant 111:46–54CrossRefGoogle Scholar
- Ford HW (1968) Water management of wetland citrus in Florida. In: Proc 1st int citrus symp, vol 3, pp 1759–1770Google Scholar
- Hunter KJ (1998) A dansyl chloride HPLC method for the determination of polyamines. In: Morgan D (ed) Methods in molecular biology. Polyamine protocols. Humana Press, Totowa, NJ, pp 119–123Google Scholar
- Hurng WP, Lur HS, Liao CK, Kao CH (1994) Role of abscisic acid, ethylene and polyamines in flooding-promoted senescence of tobacco leaves. J Plant Physiol 143:102–105Google Scholar
- Olivella C, Biel C, Vendrell M, Save R (2000) Hormonal and physiological responses of Gerbera jamesonii to flooding stress. HortScience 35:222–225Google Scholar