Effects of Postharvest Water Deficits on the Physiological Behavior of Early-Maturing Nectarine Trees

Abstract

The physiological performance of early-maturing nectarine trees in response to water deficits was studied during the postharvest period. Two deficit irrigation treatments were applied, moderate and severe, and these were compared with a control treatment (fully irrigated). Stem water potential and leaf gas exchange (net CO2 assimilation rate, ACO2; transpiration rate, E; and stomatal conductance, gs) were measured frequently. Drought avoidance mechanisms included a decrease in stomatal conductance, especially in the case of the severe deficit treatment, which also showed a strong dependence of ACO2 on gs. Intrinsic water-use efficiency (ACO2/gs) was more sensitive than instantaneous water-use efficiency (ACO2/E) as an indicator to detect water deficit situations in nectarine trees. However, in contrast to the results obtained for other deciduous fruit trees, a poor correlation was found between ACO2/E and ACO2/gs, despite the important relation between E and gs. ACO2/E was also weakly correlated with gs, although this relationship clearly improved when the vapor pressure deficit (VPD) was included, along with gs as the independent variable. This fact reveals that apart from stomatal closure, E depends on the boundary layer conductance (gb), which is mediated by VPD through changes in wind speed. This suggests low values of the decoupling coefficient for this water-resilient species.

Impact of a DANA Event on the Thermal Response of Nectarine Trees

“…Before the occurrence of the DANA event, seasonal variations in leaf gas exchange were more pronounced than those observed for Ψ stem , with mean values for net photosynthesis (P n ) and stomatal conductance (g s ) of ≈ 17.5 µmol m −2 s −1 and 273.5 mmol m −2 s −1 for the CTL treatment, respectively ( Figure 2 A,B). These values agreed with those reported in early-maturing peach and nectarine trees under non-limiting soil water conditions by other studies [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. In the DRY treatment, the P n and g s values were around 28% and 36% lower than in the CTL treatment, respectively.…”

“…Plant water status was estimated by the midday stem water potential (Ψ stem ) ( Figure 2 A). Prior to the DANA event, the CTL treatment showed an average Ψ stem value of about −0.80 MPa, which was indicative of non-limiting soil water conditions, as has been widely described for peach and nectarine trees [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The lowest Ψ stem values were measured during the summer in response to the increased evaporative demand, when the maximum VPD values were recorded ( Figure 1 A and Figure 2 A).…”

“…Different relationships have been established to predict plant water status based on the Tc or CWSI values in fruit trees such as almond [ 15 , 16 ], peach and nectarine [ 17 , 18 ], apple [ 19 ], pistachio [ 20 ], sweet cherry [ 8 ] and papaya [ 21 ], among others. Nevertheless, in fruit trees, stomatal control of the canopy conductance and plant water status is highly sensitive to the vapor pressure deficit (VPD), as described in Conesa et al [ 22 ], varying throughout crop development and between cultivars [ 18 , 23 ]. Subsequently, CWSI requires the use of two baselines that relate the canopy temperature under maximum stress and non-water stress conditions with the vapor pressure deficit (VPD), using data on clear sunny days and in full-irrigated conditions [ 10 , 13 ].…”

5-Aminolevulinic Acid and 24-Epibrassinolide Improve the Drought Stress Resilience and Productivity of Banana Plants

“…The biosynthesis of ABA is important in promoting root growth and regulating shoot growth [ 143 ] via the regulation of transpiration (through stomatal closure) and photosynthesis [ 144 ]. The increased level of ABA also increased the activity of PAL [ 145 ]. The positive role of ABA on sugar content came from the accumulation of assimilates from the phloem into the fruit by strengthening the sink capacity [ 146 ]; however, it has been reported that the increase in ABA may be an indicator of the onset of plant senescence [ 147 ].…”

Deficit Irrigation to Enhance Fruit Quality of the ‘African Rose’ Plum under the Egyptian Semi-Arid Conditions

“…Previous research has reported an increase in the biosynthesis of anthocyanins and an increase in ABA signaling, associated with improved fruit color under drought conditions [89][90][91]. Similarly, an increase in phenylalanine ammonia-lyase has been shown to be responsible for the biosynthesis of phenols [92] from the increase in ABA levels [93].…”