Plant Water Status Indicators for Irrigation Scheduling Associated with Iso- and Anisohydric Behavior: Vine and Plum Trees

Abstract

Plant water status indicators have been increasingly used for scheduling irrigation. Different variables may be used to do this, depending on personal preferences and the resources available. Many studies have suggested that selection of an indicator should take into account plant behavior in relation to isohydricity. In two Iberian studies, deficit irrigation (DI) was applied in a vineyard and in a plum orchard while plant water status and fluxes were monitored. These case-studies are discussed with special focus on the use of predawn leaf water potential (Ψ pd ) versus stem water potential (Ψ st ) to determine whether Ψ st performed better and would therefore be the preferred stress indicator for plants exhibiting anisohydric behavior. In contrast, in plants with isohydric behavior, Ψ pd would be generally preferred. This hypothesis seems to be supported by the present results obtained and by prior studies. The cultivars used and the intensity of stress applied have an important influence on the results. This suggests that, if no specific information is available from the existing literature, daily preliminary studies would be recommended prior to application in order to select the most appropriate plant water stress indicators.

Stress Coefficients for Soil Water Balance Combined with Water Stress Indicators for Irrigation Scheduling of Woody Crops

“…Irrigation should take place when the measured value of Ψ p corresponds (from the equation) to the selected Ks threshold. In anisohydric plants/conditions, Ψ stem can be used instead of the values at predawn [124].…”

Evaluation of the Effect of Irrigation on Biometric Growth, Physiological Response, and Essential Oil of Mentha spicata (L.)

“…At 70 DAT, growth regulation was not enough to sustain a good physiological behavior of stress plants, so the electron transport of I 0 was impaired (+31%), as well as P n (−38%), g s (−55%), and g m (−41%). These results suggest that the spearmint plants are experiencing a slightly isohydric behavior [39] having maintained midday leaf water potential in I 100 and also I 50 (relative comfort), not too different from I 0 (rainfed), by decreasing stomatal conductance as a necessary strategy to reduce the transpiration rate. Therefore, this research on the physiological response of mint to drying soils and subsequent water stress classifies its behavior, in the circumstances of the study as relatively isohydric, and not anisohydric.…”

Biot-Granier Sensor: A Novel Strategy to Measuring Sap Flow in Trees

“…Possibly, this was caused by stomatal closure, which reduced transpiration, therefore increasing . This mechanic stomatal closure, occurring soon after solar noon, is known to occur in olive trees as referred in [ 38 ], especially under stress conditions and vineyard [ 39 , 40 ]. The vineyard was not being irrigated on the days from 20 July to 28 August 2017, and it is likely to admit some water stress.…”