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

Alessio Scalisi,Giulia Marino,Francesco Paolo Marra,Riccardo Lo Bianco,Tiziano Caruso

doi:10.3389/fpls.2020.00340

Abstract

Sustainable irrigation is crucial to reduce water use and management costs in modern orchard systems. Continuous plant-based sensing is an innovative approach for the continuous monitoring of plant water status. Olive (Olea europaea L.) genotypes can respond to drought using different leaf and fruit physiological and morphological mechanisms. This study aimed to identify whether fruit and leaf water dynamics of two different olive cultivars were differently affected by water deficit and their response to changes of midday stem water potential (Ψstem), the most common indicator of plant water status. Plant water status indicators such as leaf stomatal conductance (gs) and Ψstem were measured in the Sicilian olive cultivars Nocellara del Belice (NB) and Olivo di Mandanici (MN), in stage II and III of fruit development. Fruit gauges and leaf patch clamp pressure probes were mounted on trees and their raw data were converted in relative rates of fruit diameter change (RRfruit) and leaf pressure change (RRleaf), sensitive indicators of tissue water exchanges. The analysis of diel, diurnal and nocturnal fluctuations of RRfruit and RRleaf highlighted differences, often opposite, between the two cultivars under water deficit. A combination of statistical parameters extrapolated from RRfruit and RRleaf diurnal and nocturnal curves were successfully used to obtain significant multiple linear models for the estimation of midday Ψstem. Fruit and leaf water exchanges suggest that olive cultivar can either privilege fruit or leaf water status, with MN likely preserving leaf water status and NB increasing fruit tissue elasticity under severe water deficit. The results highlight the advantages of the integration of fruit and leaf water dynamics to estimate plant water status and the need for genotype-specific models in olive.

Highlights

In recent years, sustainable irrigation has become a crucial aspect of orchard management to reduce inputs in agricultural systems
This study aimed to identify cultivar-specific relative rates of fruit diameter change (RRfruit)/RRleaf relationships to determine whether the genotypes under study preserve leaf or fruit water exchanges under increasing water deficit, as sink power for water might differ among genotypes
Temperature (T) and vapor pressure deficit (VPD) were the highest in the measured fraction of stage II, as it occurred in full summer (Jul 8 to Sep 8) (Figure 2A)

Summary

Introduction

Sustainable irrigation has become a crucial aspect of orchard management to reduce inputs in agricultural systems. Sensing Water Status in Olive more important in high-density systems in which growers tend to increase orchard productivity and reduce management costs by mechanizing operations. Irrigation management was commonly based on soil water status or environmental indices. Tree water status provides the most precise drought stress indices, in spite of soil and environmental conditions. Plants represent the intermediate component of the soilplant-atmosphere continuum, and their physiological responses are the result of an integration of both soil and environment. This implies an advantage of plant-based over soil-based methods for an accurate irrigation scheduling (Fernández, 2017)

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Conclusion