Changes in the physiological response between leaves and fruits during a moderate water stress in table olive trees

Abstract

© 2014 Elsevier B.V. Pit hardening period is the phenological stage when water stress is recommended in regulated deficit irrigation (RDI) in olive trees. In table olive trees, fruit growth is a very important process which could affect the final profit of the yield. RDI scheduling based on water status measurements could improve water management, but accurate threshold values are needed. Previous works in low fruit load conditions suggested -1.8MPa of midday stem water potential as >first step> of water stress level where no variations of fruit growth have been detected. The aim of this work is to describe the physiological response of table olive trees with a significant yield in a moderate water stress conditions during pit hardening period. Water relations of Control (no water stress) trees and Stressed trees were studied in a mature table olive orchard in Seville (Spain). Control trees were irrigated with 100% of ETc and values around field capacity were measured. Irrigation in Stressed trees was withdrawn during pit hardening period, and they were irrigated as Control in the rest of the experiment. Fruit growth was not affected until the last days of the deficit period, though midday stem water potential and maximum leaf conductance measurements reached minimum values a few days after the beginning of the water stress period. Such responses suggest two phases in the water stress period. At the beginning of the experiment, the physiological response of the trees (osmotic adjustment and trunk dehydration in the present work) compensated the decrease in water potential. In this phase, leaves and fruits are similar water sink in the shoots. During the last days of the drought period, the reduction of the osmotic adjustment and the greater decrease of fruit water potential transform fruits in more strength water sink than leaves. These changes produced a decrease in the fruit growth. The recovery, though it was not complete, increase fruit size as the same level than Control.Ministerio de Economía y Competitividad AGL2010-19201-CO4-03 y AGL2013-45922-C2-1-RAECID A1/035430/1

Moderate regulated deficit irrigation can increase olive oil yields and decrease tree growth in super high density ‘Arbequina’ olive orchards

“…These trees in the −2.0 MPa treatment also had similar leaf conductance values than the fully irrigated control (Moriana et al, 2012), indicating that SWP is more responsive to water stress than gas exchange measurements in olive trees (Moriana et al, 2002(Moriana et al, , 2012. In table olive, SWPs of around −2.5 MPa applied during pit hardening produced similar yields as a fully irrigated controls (Girón et al, 2015;Iniesta et al, 2009;Moriana et al, 2003a,b) however water stress levels above −3.0 MPa reduced fruit growth (Moriana et al, 2013). Thus, a consensus is forming in the literature of SWP values of between 2.0 and 2.5 MPa applied near pit hardening until harvest to maximize oil yields and decrease plant growth.…”

“…Reducing water applications by 50% between pit hardening and the onset of ripening resulted in no significant effects on 'Arbequina' oil production, but reduced water application by 20% (Gispert et al, 2013). In table olives, water stress significantly lowered fruit osmotic potential compared with a well-watered control, indicating that water-stressed trees increased sugar transport into fruits (Girón et al, 2015). Moreover, moderate water stress (70% of full water requirement) significantly increased oil yield in other crops such as chamomile (Farhoudi et al, 2014).…”

A Cultivar-Sensitive Approach for the Continuous Monitoring of Olive (Olea europaea L.) Tree Water Status by Fruit and Leaf Sensing

“…In addition, the positive relationship between RANGE diel and midday stem in MN ( Figure 8B) is determined by the lower fruit water exchanges at DI-0 levels (Figure 8G), which may be driven by lower fruit cell-wall elasticity in MN compared to NB. The different mechanisms in the two cultivars were observed in an -ON year, and it would be interesting to further study tree responses in -OFF years, as Dell'Amico et al 2012and Girón et al (2015) observed that in "Manzanillo" trees crop load influenced the ability of fruit and leaves to act as sinks for water. Changes in osmotic adjustments (Dichio et al, 1997(Dichio et al, , 2009Lo Bianco and Scalisi, 2017) and cell-wall elasticity (Xiloyannis et al, 1993;Bacelar et al, 2009) along water deficit gradients have been reported for leaves.…”

Criteria for HydroSOS Quality Index. Application to Extra Virgin Olive Oil and Processed Table Olives

“…In order to obtain a successful RDI, it is necessary to monitor the phenology of the crop and control the level of water stress achieved (using different methods such as the pressure bomb technique), and the duration of that water deficit. In olive trees, a moderate water restriction applied during pit hardening, when the resistance to the water deficit in the soil is higher [21][22][23], allows water saving, without affecting yield and fruit weight and maximizing growers' profit [22,24].…”