Publications - Faculty - Recently Submitted Faculty Publications 2008

Syvertsen - Irrigation Science

Physiological and Growth Responses of Swingle Citrumelo Citrus Rootstock Seedlings to Partial Rootzone Drying and Regulated Deficit Irrigation

J.C. Melgar, J. Dunlop and J.P. Syvertsen

Abstract. The study determined the potential for drought stress from partial rootzone drying (PRD) and regulated deficit irrigation (RDI) to trigger root-to-shoot signaling mechanisms (ABA) that induce partial stomatal closure and increase water use efficiency without reducing growth of citrus rootstock seedlings in a greenhouse. For the PRD study, root systems of six month-old Swingle citrumelo were split in half and grown in adjacent pots filled with native Candler sand. There were three irrigation treatments: well watered Control (100% ET, half on each pot); PRD 50-0 (50% ET by weight applied to only one half of plant root zone); and PRD 25-25 (25% ET applied to the both root halves). Although net CO2 assimilation rate of leaves and leaf WUE were significantly lower in the PRD 25-25 treatment, PRD did not affect any growth characteristics. Leaf N and K were increased in the 50% ET treatment while saving water. Leaf ABA was increased by PRD 50-0 but was unaffected by PRD 25-25. Similar plants with intact roots in a single pot were used for the RDI experiment using three irrigation treatments: well watered Control (100% ET), 75% ET and 50% ET. All plants were irrigated every other day. Deficit irrigation decreased growth but increased leaf N, K and ABA. Although a considerable amount of water was saved with both PRD and RDI, PRD saved water without reducing growth whereas RDI limited growth.