Continuous detection of new plant water status indicators in stage I of nectarine fruit growth

Conventional irrigation management is often inefficient in responding to seasonal changes of tree water needs. The use of leaf- and fruit-based sensors might provide helpful insights on tree water status, although they have been poorly investigated so far. Fruit gauges and leaf patch clamp pressure (LPCP) probes were tested during stage I of nectarine fruit growth to evaluate if leaf turgor pressure and fruit size may serve as indicators of water deficit. This experiment was carried out in the 2017/18 season. Four irrigation levels were applied to ‘September Bright’ nectarine trees (100, 40, 20 and 0% of crop evapotranspiration, ETc) and data were collected during stage I of fruit growth. Tree size, fruit doubling, leaf chlorophyll concentration, stomatal conductance (gs), stem water potential (Ψstem), fruit diameter and canopy light interception were measured. Fruit gauges and LPCP probes were mounted on trees for a week interval in the second half of fruit growth stage I. Sensor outputs were expressed as fruit diameter and attenuated pressure of leaf patches (pp). Fruit diameter was reduced in deficit irrigated trees. As expected, gs and Ψstem responded to irrigation inputs. Continuous fruit diameter and pp were found to be both sensitive to water deficit, although they require different analytical approaches for data interpretation. Results of this study suggest that nectarine fruit growth and leaf turgor pressure can be used independently as continuous indicators of plant water status.