TitleTotal soil water content accounts for augmented ABA leaf concentration and stomatal regulation of split-rooted apple trees during heterogeneous soildrying
Publication TypeJournal Article
Year of Publication2012
AuthorsEinhorn, TC, Caspari, HW, Green, S
JournalJournal of Experimental Botany
Type of ArticleJournal Article

A split-rooted containerized system was developed by approach grafting two, 1-year-old apple (Malusxdomestica Borkh. cv 'Gala') trees to investigate the effect of soil moisture heterogeneity and total soil moisture content (.v) on tree water relations, gas exchange, and leaf abscisic acid (ABA) concentration [ABAleaf]. Four irrigation treatments comprising a 2 x 2 factorial experiment of irrigation volume and placement were imposed over a 30-day period: control (C) [> 100% of crop evapotranspiration (ETc)] applied to both containers; PRD100 (> 100% ETc) applied to one container only; and two treatments receiving 50% ETc applied to either one (PRD50) or both containers (DI50). Irrigation between PRD (partial rootzone drying) root compartments was alternated when.v reached 35% of field capacity. Maximum daily sap flow of the irrigated roots of PRD100 exceeded that of C roots throughout the experimental period. Pre-dawn water potential (.pd) was similar between C and PRD100; however, daily water use and mid-day gas exchange of PRD100 was 30% lower. Slightly higher [ABAleaf] was observed in PRD100, but the effect was not significant and could not explain the observed reductions in leaf gas exchange. Both 50% ETc treatments had similar, but lower.v,.pd, and gas exchange, and higher [ABAleaf] than C and PRD100. Regardless of treatment, the container having the lower.v of a split-rooted system correlated poorly with [ABAleaf], but when.v of both containers or.v of the container possessing the higher soil moisture was used, the relationship markedly improved. These results imply that apple canopy gas exchange and [ABAleaf] are responsive to the total soil water environment.

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