Location: Horticultural Crops Research UnitTitle: Moderate water stress from regulated deficit irrigation decreases transpiration similarly to net carbon exchange in grapevine canopies
|PEREZ-PEÑA, JORGE - Instituto Nacional Tecnologia Agropecuaria|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2015
Publication Date: 10/13/2015
Citation: Tarara, J.M., Perez-Peña, J.E. 2015. Moderate water stress from regulated deficit irrigation decreases transpiration similarly to net carbon exchange in grapevine canopies. Journal of the American Society for Horticultural Science. 140:413-426.
Interpretive Summary: Regulated deficit irrigation is used to manage soil water content to impose predetermined periods of plant water stress or soil water deficit that may elicit a desirable response in the plants. The objective of this work was to demonstrate how the timing and extent of water restrictions greater than that of standard industry RDI alter whole-vine transpiration and whole-vine water use efficiency in field-grown, mature grapevines in a semiarid climate.
Technical Abstract: To determine the effects of timing and extent of regulated deficit irrigation (RDI) on grapevine (Vitis vinifera) canopies, whole-canopy transpiration (TrV) and canopy conductance to water vapor (gc) were calculated from whole-vine gas exchange near key stages of fruit development. The vines were managed under three approaches to RDI: 1) standard industry practice (RDIS), or weekly replacement of 60% to 70% of estimated evapotranspiration (ET) for well-watered grapevines; 2) early additional deficit (RDIE), or one-half of RDIS applied between fruit set and veraison; and 3) late additional deficit (RDIL), or one-half of RDIS applied between veraison and harvest. Compared with RDIS, the additional deficits (RDIE, RDIL) reduced daily cumulative Trv by about 45% (RDIE) and about 48%. Diurnal patterns of gc indicated consistent moderate water stress in all RDI regimens. Under RDIE and RDIL, there were transient occurrences of severe water stress, indicated by gc declining below 50 mmol·m-2·s-1. Across the day, vines under RDIE and RDIL had lower gc than RDIS. Under all deficit regimens, TrV exhibited opposing hysteretic loops with solar radiation and vapor pressure deficit (VPD), with less sensitivity to VPD in RDIE and RDIL. For a given value of VPD, TrV was higher in the morning than in the afternoon. For a given value of PPF, TrV was higher in the afternoon than in the morning. Single-leaf measurements of transpiration overestimated TrV by an average of 45%. Instantaneous water use efficiency (WUE) declined during midday at the pre- and postveraison measurements for all RDI regimens. Whole-canopy daily integrated WUE (WUEd) did not differ among regimens during the additional deficits because daily cumulative values of whole-vine net carbon exchange (NCEV) and TrV changed proportionally: by about 43% to 46% in RDIE relative to RDIS. The case was less clear-cut for RDIL, where NCEv declined by 33% and TrV by 48% relative to RDIS. However, WUEd did not differ significantly between the two.