Sensitivity of Continuous and Discrete Plant and Soil Water Status Monitoring in Peach Trees Subjected to Deficit Irrigation

Abstract

<jats:p>To characterize tree responses to water deficits in shallow and deep rooted conditions, parameters developed using daily oscillations from continuously measured soil water content and trunk diameter were compared with traditional discrete monitoring of soil and plant water status in lysimeter and field-grown peach trees [<jats:italic>Prunus persica</jats:italic> (L.) Batsch `O'Henry']. Evaluation occurred during the imposition of deficit irrigation for 21 days followed by full irrigation for 17 days. The maximum daily available soil water content fluctuations (MXAWCF) taken at any of the four monitored root zone depths responded most rapidly to the deficit irrigation. The depth of the MXAWCF increased with time during the deficit irrigation. Differences relative to a fully irrigated control were greater in the lysimeter than the field-grown trees. Minimum daily trunk diameter (MNTD) and maximum daily trunk shrinkage (MDS) responded sooner than midday stem water potential (stem Ψ), predawn or midday leaf water potential (predawn leaf Ψ and leaf Ψ), or photosynthesis (A). Parameters based on trunk diameter monitoring, including maximum daily trunk diameter (MXTD), correlated well with established physiological parameters of tree water status. Statistical analysis of the differences in the measured parameters relative to fully irrigated trees during the first 10 days of deficit irrigation ranked the sensitivity of the parameters in the lysimeter as MXAWCF &gt; MNTD &gt; MDS &gt; MXTD &gt; stem Ψ = A = predawn leaf Ψ = leaf Ψ. Equivalent analysis with the field-grown trees ranked the sensitivity of the parameters as MXAWCF &gt; MNTD &gt; MDS &gt; stem Ψ = leaf Ψ = MXTD = predawn leaf Ψ &gt; A. Following a return to full irrigation in the lysimeter, MDS and all the discrete measurements except A quickly returned to predeficit irrigation levels. Tree recovery in the field-grown trees was slower and incomplete due to inadequate filling of the root zone. Fruit size was significantly reduced in the lysimeter while being minimally affected in the field-grown trees. Parameters only available from continuous monitoring hold promise for improving the precision of irrigation decision-making over the use of discrete measurements.</jats:p>

Daily variations in water relations of apricot trees under different irrigation regimes

“…It should be noted that the measurement of leaf water potential in non-transpiring leaves (stem water potential) will almost certainly produce a more intense signal than that observed in sun-exposed transpiring leaves (Goldhamer et al 1999, Ortuño et al 2006). More research is needed before we can confirm what is the best plant water stress indicator for adult apricot trees.…”

“…Gas exchange parameters, such as variations in stomatal conductance, have also been used as water status indicators (Harrison et al 1989). More recently, some sensors used to measure sap flow and trunk diameter fluctuation have provided useful information about water status because of the continuous nature of the measurements; they have also proved to be very robust (Goldhamer et al 1999, Remorini and Massai 2003, Ohashi et al 2006, Ortuño et al 2006.…”

Relationships Between Climatic Variables and Sap Flow, Stem Water Potential and Maximum Daily Trunk Shrinkage in Lemon Trees

“…In this sense, Pataki and Oren (2003) studied factors controlling transpiration of some trees species, and showed that Quercus rubra, Q. alba, Carya tormentosa and Fraxinus americana plants were responsive to vapour pressure deficit and presented saturation in increases in daily sap flux density with vapour pressure deficit, these responses being similar at different soil moisture levels. Moreover, considering that MDS respond sooner to water stress than other continuous and discrete plant and soil water status indicators (Goldhamer et al, 1999) and that MDS is a versatile indicator of transpiration stream intensity when the soil water content is not strongly depleted (Huguet et al, 1992;Ortun˜o et al, 2004a, b), the fact that when SF presented high and constant values (Figure 2c) MDS values progressively decreased (Figure 2b) indicated that lemon trees were not under a water stress situation.…”

“…These techniques permit continuous and automated registers of the plant water status, and an immediate, consistent and reliable response to water deficit (Goldhamer et al, 1999;Ortun˜o et al, 2004a, b), with a reduction in the labour needed for the measurement procedure. Goldhamer and Fereres (2004) obtained promising results using only maximum daily trunk shrinkage (MDS) for scheduling almond trees irrigation.…”

Stem and leaf water potentials, gas exchange, sap flow, and trunk diameter fluctuations for detecting water stress in lemon trees

“…Also, Goldhamer et al (1999) indicated that MDS responded sooner than stem to water stress, and Ortuño et al (2004b) showed that in young lemon trees continuously measured plant water status indicators were more immediate and sensitive than discretely measured indicators.…”