Usefulness of Stem Dendrometers as Continuous Water Stress Indicators of Loquat Tree Water Status

Abstract

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.