Sweet orange acclimatisation to water stress: a rootstock dependency

Abstract

The diversification of rootstocks is of great importance for the survival of the citrus industry in order to reduce and mitigate risks caused by abiotic factors, primarily related to drought. The present study aimed to investigate the effects of ‘Pera’ sweet orange Citrus sinensis (L.) Osbeck interactions with eight rootstocks on soil water extraction, physiological responses and field productivity. Eight rootstocks combined with the ‘Pera’ sweet orange were evaluated in the field to study the effects on the following factors in response to soil water availability: matric potential (Ѱm) at depths of 0.25 m, 0.50 m and 0.90 m; physiological responses of the plants: leaf water potential (Ѱw), stomatic conductance (gs) and temperature (Lt); and plant productivity. Significant differences (p ≤ 0.05) were observed in the dry period for scion-rootstock interactions on the parameters Ѱm, Ѱw and gs. There were also significant differences for yield and productive efficiency (p ≤ 0.05). However, contrasting individuals concerning soil water extraction showed similar physiological responses in the driest periods. Different mechanisms of acclimatization to periods of drought stress that resulted in different soil water extractions and different physiological responses were not strongly related to plant productivity and were dependent on the characteristics of the deficit event. Water extraction from the shallow layer of soil is best correlated with plant water status Ѱw, it is not associated with the effective use of water in deeper soil layers for the scion-rootstock combinations studied, and explains the variation on productivities of genotypes. Scion-rootstock interactions that induce a smaller canopy volume and higher productive efficiency (kg fruit/volume canopy) and lower water use are more appropriated in high planting densities.