Grapevine water relations in Oakville, CA: root demographics and physiology in response to plant water deficit

PhD in Horticulture, 2007

Current Position: Assistant Professor, Cornell University

Collaborator, D.R. Smart, U.C. Davis

Taryn has been funded by the Viticulture Consortium (West), American Vineyard Foundation, Fellowships in 2004 and in 2005 from the American Wine Society Education, the Plant Science Department and the College of Agricultural Sciences

Plants must cope with strong spatial and temporal heterogeneity in soil moisture. While numerous physiological studies have examined the effects of localized soil moisture deficits in potted seedlings, relatively few physiological studies have examined the effects of localized soil moisture deficits in mature plants grown in unrestrictive soil volumes in the field. Of interest in the field environment are patterns of root growth, maturation and death to variation in soil moisture in different soil layers over the growing season. Within a root system, if significant hydraulic resistance exists among the various root elements then significant variation in root water potentials and other indicators of root stress may be exhibited. I hypothesize that root survivorship and growth under soil moisture deficits will decrease and root maturation (as assessed by lignification & pigmentation) will be accelerated under localized soil moisture deficits. I also predict that localized soil moisture deficits decrease root water and osmotic potentials and increase ABA concentrations and cortical cell death. However, it is also quite possible that root systems mitigate localized soil moisture deficits by redistributing water to roots under the greatest moisture stress. Indeed, recent evidence suggests that roots in moist soil can redistribute water to those in dry soil, possibly preventing appreciable water stress.

Drip irrigation creates marked spatial heterogeneity in soil water distribution which in turn may profoundly affect the vine. In order to gain a better understanding of how a root system responds to heterogeneous supply of soil water, I chose to work with two grape rootstocks that differ in overall vigor (1103P, V. berlandieri X V. rupestris and 101-14 Mgt V. riparia X V. rupestris) under different amounts of drip irrigation in an established Merlot experimental block in Oakville, CA (in cooperation with UC Davis). The vineyard is about 4 yrs old and planted in Bale (variant) gravely clay loam with vines spaced 8 x 7.2 ft. and trained on a bilateral cordon with VSP. The entire experimental block covers 2.6 acres and is laid out in a completely randomized block design. Each vine has one emitter, located 50 cm from the trunk on one side of the vine. Three irrigation treatments (no irrigation, 40% ET (deficit irrigation), & 100% ET) have been randomly assigned to each rootstock within the vineyard. In all treatments, one minirhizotron tube was placed through the dripper zone while a second tube was placed in the unirrigated zone on the opposite side of the vine, both tubes are about 60cm from the trunk. Additional collapsible minirhizotron tubes will be added to collect roots of different ages at different soil layers at different times of the season.

While this research will provide a better fundamental understanding of how roots respond to different soil water deficits the results are also important to viticulturalists. Previous field investigations of the effects of wet and dry soil conditions on temporal vine water status have been largely restricted to the aboveground portions of the plant. Examination of the effects of deficit irrigation on grape not only provides information towards the conservation of water, but can also aid the vineyard manager in manipulating irrigation to improve fruit quality and control excessive vegetative growth without decreasing yield.


  • Bauerle T.L. 2007. Root dynamics in response to abiotic and biotic stressors. Ph.D. thesis. The Pennsylvania State University. 119 pp.
  • Bauerle T.L. , Eissenstat D.M., Granett J., Gardner DM, and Smart D.R. 2007. Consequences of insect herbivory on grape fine root systems with different growth rates. Plant Cell & Environment 30: 786-795.
  • Bauerle T.L. , Richards J.H., Smart D.R. & Eissenstat D.M. 2008. Importance of internal hydraulic redistribution for prolonging lifespan of roots in dry soil. Plant Cell & Environment 31:171-186
  • Bauerle, T.L. , Smart, D.R., Bauerle, W.L., Stockert, C., Eissenstat, D.M. 2008. Root foraging in response to heterogeneous soil moisture in two grapevines that differ in potential growth rate. New Phytologist 179:857-866