Water status and gas exchange of pistachio trees under different irrigation levels

F.P. Marra, A.A. Roxas, R. Lo Bianco, G. Marino, T. Caruso
The aim of this study was to investigate the physiological responses of pistachio trees to varying water supply in the attempt to identify reliable parameters to manage irrigation. Three different irrigation regimes were applied to 25-year-old pistachio trees of cultivar 'Bianca' on P. terebinthus rootstock. Midday stem water potential (ΨSWP), leaf relative water content (RWC), light-saturated net CO2 assimilation (An), stomatal conductance (gs), and ambient conditions were monitored throughout the season, and light response curves of net photosynthesis were constructed. To reflect tree water status, trees were separated into three classes of ΨSWP, no deficit (ΨSWP › 
-1.5 MPa), mild deficit (-2 ≤ ΨSWP ≤ -1.5), and severe deficit (ΨSWP ‹ -2 MPa). A weak correlation existed between ΨSWP and RWC due to high variation among RWC measurements. A relationship between ΨSWP and An or gs was detected only during stage III of kernel filling, which was the most sensitive growth stage to water deficit. Well-watered trees had higher photosynthetic performance compared to mild and severe deficit trees. The results suggest that ΨSWP can be regarded as a useful physiological indicator of tree water status to manage water supply, especially during critical periods of high atmospheric water demand and greatest sink strength in pistachio.
Marra, F.P., Roxas, A.A., Lo Bianco, R., Marino, G. and Caruso, T. (2017). Water status and gas exchange of pistachio trees under different irrigation levels. Acta Hortic. 1177, 281-288
DOI: 10.17660/ActaHortic.2017.1177.40
Pistacia vera L., water relations, stem water potential, phenological phases, drought stress

Acta Horticulturae