Effect of osmotic stress on abscisic acid levels in xylem sap of sunflower (Helianthus annuus L.)

Abstract

Addition of an osmoticum (-12 bars) to the rooting medium of sunflowers (Helianthus annuus L.) caused an increase in the level of abscisic acid (ABA) present in xylem exudate subsequently collected from cut shoots. Using tall and dwarf plants it was shown that there was a time lag in the appearance of increased levels of ABA in tall plants when compared with dwarf plants. The results indicate that the leaves, rather than the roots are the site of synthesis of ABA present in the xylem sap of osmotically stressed sunflower plants.

The effect of growth regulators on the rooting of shoots of the peach rootstock Ishtara in in vitro conditions

“…It is not clear yet whether abscisic acid generated in the roots and with consequent transport through the xylem and regulation of leaf growth, plays the primary regulating role in the formation of adventitious roots (DAVIES et al 1994) or, on the contrary, whether abscisic acid is produced by the leaves and transported through the phloem into roots whose growth and development it influences (HOAD 1975). It is well known that a high level of ABA inhibits leaf growth (ALVES, SET-TER 2000) and stimulates elongation root growth at low water potentials and low ethylene production (SPOLLEN et al 2000).…”

Involvement of aerial organs on the ABA accumulation in roots of Citrus plants under water deficit

“…It is striking how those early works that demonstrated the crucial role of leaves in synthetizing ABA (Hoad, 1973(Hoad, , 1975Milborrow et al, 1973) and its transport to roots (Hocking et al, 1972;Shindy et al, 1973;Bellandi and Dorffling, 1974) were mostly ignored during the following decades. Indeed, the role of the leaves as a key organ in ABA biosynthesis during dehydration was mostly accepted by researchers after three decades due to the use of reciprocal grafting of tomato ABA-deficient mutants (Holbrook et al, 2002).…”

“…In fact, this basipetal-transport model has been mainly ignored and only sporadic references are found in the literature (Cornish and Zeevaart, 1985;. However, both models do not need to be mutually excluding (Hoad, 1995), since ABA that reach the roots from the aerial tissues could be redistributed again to the aerial tissues mainly by the xylem sap as demonstrated under high salinity conditions (Hoad, 1975;.…”

“…Once in roots, ABA plays several relevant functions such as modification of root architecture (Jung and McCouch, 2013;Boursiac et al, 2013;Harris, 2015) and root hydraulic conductivity (Thompson et al 2007;Ruiz-Lozano et al 2009) to increase water uptake (Aroca et al, 2012). Once in roots, ABA could be degraded to catabolic metabolites such as DPA or even dumped into the xylem, where ABA could be recirculated to aerial tissues (Hocking et al, 1972;Hoad, 1975;.…”

Conductancia Hidráulica en Patrones De Cítricos

“…Una de estas señales es la producción de ácido abscísico (ABA) en las raíces, el cual es transportado a través del xilema a las hojas (Zeevaart y Boyer 1984, Zhang y Davies 1987, 1989a Gómez- Cadenas et al 1996). Existen estudios que confirman esto, realizados tanto en plantas expuestas a condiciones de déficit hídrico (Zhang y Davies 1989a) como en plantas tratadas con Polietilen Glicol (PEG) (Hoad 1975, Neales et al 1989, Davies y Zhang 1991, Neales y McLeod 1991, Comstock 2002). El incremento de la concentración de ABA en la savia del xilema de plantas con estrés hídrico puede ser rápido (Hoad 1975) y el cierre estomático se puede producir incluso antes de que se detecte cualquier cambio en el contenido relativo de agua o en el potencial de turgencia de la hoja (Gollan et al 1986, Gowing et al 1990, Zhang y Davies 1990, Trejo y Davies 1991.…”