Fruit and Leaf Sensing for Continuous Detection of Nectarine Water Status

Abstract

Continuous assessment of plant water status indicators provides the most precise information for irrigation management and automation, as plants represent an interface between soil and atmosphere. This study investigated the relationship of plant water status to continuous fruit diameter (FD) and inverse leaf turgor pressure rates ( p p ) in nectarine trees [ Prunus persica (L.) Batsch] throughout fruit development. The influence of deficit irrigation treatments on stem ( Ψ stem ) and leaf water potential, leaf relative water content, leaf stomatal conductance, and fruit growth was studied across the stages of double-sigmoidal fruit development in ‘September Bright’ nectarines. Fruit relative growth rate (RGR) and leaf relative pressure change rate (RPCR) were derived from FD and p p to represent rates of water in- and outflows in the organs, respectively. Continuous RGR and RPCR dynamics were independently and jointly related to plant water status and environmental variables. The independent use of RGR and RPCR yielded significant associations with midday Ψ stem , the most representative index of tree water status in anisohydric species. However, a combination of nocturnal fruit and leaf parameters unveiled an even more significant relationship with Ψ stem , suggesting a changing behavior of fruit and leaf water flows in response to pronounced water deficit. In conclusion, we highlight the suitability of a dual-organ sensing approach for improved prediction of tree water status.

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

“…Overall, this work confirms the advantages of combining fruit and leaf water dynamics for the prediction of plant water status in olive, whose suitability was just confirmed in a nectarine study (Scalisi et al, 2019c). Nevertheless, technologies that sense fruit and leaves water dynamics are still independent and need to be fit in a unique system for real-time monitoring.…”

“…The two cultivars showed different fruit shape (i.e., NB fruit were almost spherical whereas MN fruit were oblong in shape) from the beginning of fruit diameter measurements at stage II until harvest. Fruit size was also consistently greater in NB than in MN (Figure 3), with nearly no fruit growth during stage II in either cultivars, as expected in the pit hardening stage (Scalisi et al, 2019c). Stage III was characterized by a faster fruit diameter increment in MN compared to NB.…”

“…This work aimed to study olive fruit and leaf water dynamics in relation to tree water status. Our hypothesis was that, similarly to what found in nectarine (Scalisi et al, 2019c), the combination of RR fruit and RR leaf might provide an even more accurate identification of plant water status, rather than monitoring each parameter independently. In addition, this study aimed to identify cultivar-specific RR fruit /RR leaf 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.…”

“…White and black circles represent diurnal and nocturnal data in a diel interval, respectively. (Scalisi et al, 2019c), and in both cases (i.e., olive and nectarine), the relationship of RSD noct to stem was negative (RSD noct linear components in Eqs. 3, 4), suggesting that the variability of RR fruit at lower stem is higher than the one of RR leaf .…”

Detecting Mild Water Stress in Olive with Multiple Plant-Based Continuous Sensors

“…The different drought resistance mechanisms exhibited by the two cultivars are also well depicted by the analysis of fruit RGR. While in other species, such as peach, transpiration from the cuticle has a great influence on fruit shrinkage [ 39 ], in olive, the fruits have few stomata that are rapidly covered by wax at early stages of development, hence we can assume that loss of water from the cuticle is negligible. In such conditions, we suppose that the high rate of fruit shrinkage observed in the daytime in OM is highly related to water backflow to leaves [ 16 , 40 , 41 , 42 ].…”