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Title: Calcium partitioning and allocation in tomato plants and fruit in response to abscisic acid application

item TONETTO DE FRIETAS, SERGIO - University Of California
item McElrone, Andrew
item SHACKEL, KEN - University Of California
item MITCHAM, BETH - University Of California

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2013
Publication Date: 11/1/2013
Citation: Tonetto De Frietas, S., Mcelrone, A.J., Shackel, K., Mitcham, B. 2013. Calcium partitioning and allocation in tomato plants and fruit in response to abscisic acid application. Journal of Experimental Botany. 65:235-247.

Interpretive Summary: Abscisic acid (ABA), a plant hormone, applications have been proposed across a wide range of crops as a means to improve crop water use efficiency and drought resistance by limiting water loss from leaves. Here, we evaluated the combined effects of ABA applications on water use in tomatoes and on blossom end rot and fruit development. Whole plant ABA applications not only decreased the incidence of blossom end rot, but increased fruit yield and reduced water use by the plants. Our results suggest that whole plant ABA application can be used to maintain or even improve tomato fruit production while using less irrigation by altering calcium transport to the developing fruit.

Technical Abstract: Although Ca2+ is believed to move in the plant exclusively through the xylem, the mechanisms regulating Ca2+ partitioning and allocation in tomato plants and fruit remain poorly understood. The objectives of this study were to determine Ca2+ partitioning and allocation in tomato plants and fruit in response to whole plant and fruit specific ABA treatments, as well as to analyze the effect of changes in Ca2+ partitioning and allocation on fruit susceptibility to blossom-end rot (BER). Tomato plants cultivar Ace 55 (Vf) were grown in a greenhouse and exposed to low Ca2+ conditions during fruit growth and development. Starting one day after pollination (DAP), the following four treatments were initiated: 1) whole plants were sprayed weekly with deionized water (control) or 2) with500 mg l-1 ABA; or fruit on each plant were dipped weekly 3) in deionized water (control) or 4) in 500 mg l-1 ABA. Blossom-end rot was completely prevented at 15 DAP by whole plant and fruit specific ABA treatment, and at 30 DAP by whole plant ABA spray treatment. Conversely, water control plants reached 36 to 40% BER incidence at 30 DAP. The whole plant ABA spray reduced leaf stomatal conductance, whole plant water loss, xylem sap flow rates into the leaves and leaf Ca2+ concentration while maintaining higher stem water potentials. In the fruit, the whole plant ABA spray also increased xylem sap flow rates, Ca2+ concentration in the xylem sap, apoplastic solution, and fruit tissue. Both ABA treatments maintained a higher number of functional xylem vessels at 15 DAP, while only the whole plant ABA spray increased fruit growth rate and fruit size. The results indicate that whole plant ABA spray shift xylem sap flow and Ca2+ from the leaves into the fruit, resulting in higher fruit tissue and water soluble apoplastic Ca2+ concentrations and preventing BER development. Although fruit specific ABA treatment had no effect on xylem sap flow rates or Ca2+ movement into the fruit, it increased fruit tissue water soluble apoplastic Ca2+ concentrations and reduced fruit susceptibility to BER to a lesser extent.