Effect of fruit development on turgor related measurememts in olive leaves

Abstract

Leaf turgor related measurements made with ZIM probes are being used for scheduling irrigation in hedgerow olive orchards with high plant densities. However, the suitability of this approach under changing environmental conditions and concerning the presence of fruits close to the leaves in which the ZIM probes are clamped, remains in doubt. The aim of this work was to clarify both aspects. Basically, we evaluated the influence of both the proximity of fruits and the environmental conditions on the maximum daily turgor (Ppmin), a reliable water stress indicator derived from ZIM records. Our data showed no differences on Ppmin due to the proximity of fruits, suggesting that ZIM probes can be clamped in any leaf, regardless of the distance to a cluster of fruits. Although our plants were under non-limiting soil water conditions, there was a daily and a seasonal pattern on Ppmin, caused mainly by the course of atmospheric demand. The Ppmin seasonal pattern was also markedly affected by the fruit development stage. More precisely, our data showed by a tight relationship (R2 = 0.77) between fruit growth and Ppmin from 7 to 12 weeks after full bloom, a period of maximum rate of pit hardening and marked fruit growth. Our findings suggest that Ppmin could be a useful water stress indicator to schedule irrigation in periods when the plant water status has a marked effect on fruit development and production.