Study of the within-plant spatial variability of stomatal conductance on a young 'Arbequina' olive orchard under drip-irrigated and semi-arid conditions
For drip-irrigated olive orchards, plant water status monitoring is an important tool for irrigation management practices, as it determines final fruit and oil yield. However, plant water status monitoring using plant physiological measurements, such as plant water potential and stomatal conductance (g s) imposes a challenge because the selection of the measurement site inside the canopy must be representative of the whole plant trend. Therefore, the objective of the present work was to study the spatial variability of stomatal conductance at the within-plant scale on a young drip-irrigated olive orchard under semi-arid growing conditions. A field study was carried out on a commercial drip-irrigated olive orchard (Olea europea L. Arbequina') located in Pencahue valley, Maule Region, Chile (35º 23' S; 71º 44' W; WGS 84; 96 m.a.s.l.). Measurements of g s were done at four dates using an infrared gas analyzer (LI-COR, LI-6400, USA) during the 2011-2012 growing season. The results show that under mild to moderate water restriction (-1.5 to -2.2 MPa), intracanopy stomatal conductance variability was high and two sectors were identified, independent of the level of vegetative expression. In contrast, under moderate to strong water restriction (< -2.2 to -3.5 MPa), intra-canopy stomatal conductance variability was low for both high and low vegetative expression, with no sector detected. These considerations are relevant to select the more appropriate site within the canopy for plant water status and/or gas exchange measurements.