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An empirical model predicting xylem sap ABA concentration from root biomass and soil moisture distribution in plants under partial root-zone drying

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Publication date22/03/2016
Host publicationXXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposia on Water, Eco-Efficiency and Transformation of Organic Waste in Horticultural Production
EditorsR. L. Snyder, S. Ortega-Farias, W. R. Carlile, M. Raviv, M. Nichols, B. Clother, I. Goodwin, R. Gentile
Number of pages7
ISBN (print)9789462611061
<mark>Original language</mark>English

Publication series

NameISHS Acta Horticulturae
ISSN (Print)0567-7572
ISSN (electronic)2406-6168


Partial root-zone drying (PRD) is predicted to increase ABA concentration in the xylem sap ([X-ABA]) without changing leaf water status, thus partially closing the stomata which may enhance plant water use efficiency. Predicting ([X-ABA]) from soil moisture and root distribution data are essential to optimize the application of this technique. Bean (Phaseolus vulgaris) plants were grown in split pots, designed to allow a wide range of root mass distribution to either compartment, and PRD was applied. [X-ABA] was best predicted with an exponential model using the weighted (by root water uptake fraction - RWUF) average of root ABA concentration ([R-ABA]) in each compartment. This confirmed previous results reporting that a model accounting for RWUF is the best predictor of [X-ABA]. RWUF was equal to root mass fraction (RMF) when soil volumetric water content (θv) in the dry compartment was above 0.18 cm3 cm-3, linearly related to RMF when θv<0.18 and RMF>0.7, and null otherwise. [R-ABA] in the dry side had basal values (of 100-150 ng g-1 DW) when θv>0.18 and increased linearly with RMF above that threshold. Therefore, the proportion of roots in dry soil affected [X-ABA] by increasing both root water uptake fraction and ABA accumulation. [R-ABA] in the wet side was also stable when the dry side had θv>0.18 but was linearly related to local θv above that threshold and not to RMF. Simulation modelling showed that irrigating more than 1/3 of the total root mass during PRD had little impact on [X-ABA].