Whole-Plant Water Use in Field Grown Grapevine: Seasonal and Environmental Effects on Water and Carbon Balance.

Cyril Douthe,Esther Hernández-Montes,Ignacio Tortosa,Jose Mariano Escalona,Hipólito Medrano,Alicia Pou

doi:10.3389/fpls.2018.01540

Cyril Douthe, Esther Hernández-Montes + Show 4 more

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https://doi.org/10.3389/fpls.2018.01540

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Abstract

Water scarcity is a main challenge in vineyards sustainability in most of the grapevine areas now and even more in near future due to climatic change perspectives. In consequence, water use efficiency (WUE) measurements are of the highest interest to improve the sustainability of this crop. The vast majority of WUE measurements relays on measurements of leaf carbon and water fluxes at leaf-level. However, less data are available at the whole-plant level, and for the moment those data are not totally coincident with conclusions reached at leaf scale. In this study, we used whole-plant chambers able to enclose an entire plant of 12 years old to measure at the same time water and carbon fluxes under realistic field grown conditions. The main objectives were to identify the technical issues interfering the whole-plant measurements and track the environmental and other abiotic factors that can affect water and carbon balance, i.e., WUE at the whole-plant scale. To achieve those objectives, we measured whole-plant water and carbon fluxes in grapevine exposed to two different water regimes at three phenological stages [pea size (July), ripening (August), and harvest (September)]. In September, measurements were repeated under high CO2 to also check its effect at the whole-plant scale. The results indicate that water and carbon fluxes are well coordinated under both water availability treatments. Under drought conditions, both fluxes were drastically reduced, but surprisingly the estimated WUE resulted not improved but decreased, contrarily to what is shown at the leaf scale. The phenology (September) also strongly decreased both water and carbon fluxes when compared to measurements in July. We hypostatized that harvest load respiration rates could have an important weight on the whole-plant net carbon exchange (NCE). Finally, high CO2 measurements, after correction for leaks, indicated an increase of whole-plant NCE as well as increased whole-plant WUE, as expected. Several technical issues were identified, like 1/instability of [CO2] during the night period that prevent robust estimation of whole-plant respiration and 2/condensation during last night and sun-rise hours which may affect the estimation of daily plant transpiration.

Highlights

Water use efficiency (WUE) refers to the ratio of water used in plant carbon assimilation or in biomass production to water lost by the plant through transpiration (E) and it has become an important parameter to take into account in agricultural systems to increase yield production in semi-arid areas to get more crop per drop
We observed a progressive decrease of the maximum transpiration rate along the calibration session (5 days), since plants were not watered while being inside the chamber
At late stages, we suggest that the contribution of grapevine clusters to the total carbon balance by the whole berry respiration, might be high enough to greatly reduce the daily net carbon exchange (NCE), and to regulate total plant WUE

Summary

Introduction

Water use efficiency (WUE) refers to the ratio of water used in plant carbon assimilation (photosynthesis; AN) or in biomass production to water lost by the plant through transpiration (E) and it has become an important parameter to take into account in agricultural systems to increase yield production in semi-arid areas to get more crop per drop. Whole-vine photosynthesis expressed on a leaf area basis usually results below than expected extrapolating values from singleleaf measurements (Edson et al, 1993; Intrieri et al, 1997; Poni et al, 2009) Factors such as leaf light exposure and position on the shoot, leaf aging and the presence of organs like fruits, shoots, and trunks in a given canopy makes difficult to scaling up from single-leaf to whole-canopy photosynthesis (Alleweldt et al, 1982; Schultz, 1993; Intrieri et al, 1997; Poni et al, 1997; Petrie et al, 2000; Escalona et al, 2003). Other processes such as nocturnal water loss and respiration (Escalona et al, 2012, 2013) or possible changes in dry matter partitioning among different sinks (Tomàs et al, 2014) may explain a frequently reported lack of correlation between WUEi and WUE expressed as biomass accumulation per unit of water lost

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