In the Mediterranean culture of loquat (Eriobotrya japonica Lindl.), some
growers apply a summer water withholding cycle in order to achieve earlier
flowering and harvest in the next season. Generally, the first fruit that reach the
market have higher commercial value. It has been shown that the duration and
severity of the plant water stress imposed is a determinant factor in the flowering
time response. Stem water potential (stem), is a useful indicator of plant water
status. However, because this measurement cannot be automated it is important to
look for alternatives to determine plant water status with plant sensors. In many
fruit trees it has been shown that stem dendrometers could be employed as a plant
water status indicator. However, in Loquat trees, the usefulness of this technique has
not been yet investigated. The experiment was carried out in 2009 with ‘Cardona’
where control fully irrigated trees were compared with trees submitted to water
withholding during the summer. Results showed that under mild plant water stress,
daily trunk shrinkage (MDS) was a sensitive indicator of plant water status and
MDS was able to detect soil water deficit even before that clear differences in stem
could be detected. However, when plant water stress became more severe (stem
lower than -1.4 MPa), MDS did not increase further. Results suggest that growers
can use MDS as a sensitive indicator of the early stage of plant water stress.
However, once plant water stress becomes more severe (stem<-1.4 MPa), as it is
required to advance flowering, stem is a more useful indicator of plant water
stress.