Diurnal and seasonal changes in the xylem water potentials of Grevillea and Myoporum plants during drought

Abstract

SummaryDrought is an irregular feature of World climate and has adverse effects on ornamental plants growing in urban environments. Grevillea ‘Moonlight’ and Myoporum elipticum are attractive native Australian species that are commonly used in parks and gardens and are generally regarded as being drought-tolerant. Diurnal and seasonal water relations during a drought cycle of G. ‘Moonlight’ and M. elipticum, growing together in a non-irrigated garden bed, were monitored during a Summer (wetter)-to-Winter (dryer) transition period using a pressure chamber. G. ‘Moonlight’ generally maintained higher xylem water potentials than M. elipticum. Pre-dawn xylem water potentials in drought-affected M. elipticum dropped to around –2.5 MPa, while G. ‘Moonlight’ maintained pre-dawn xylem water potentials of around –1.0 MPa. This difference suggests that, because pre-dawn xylem water potentials reflect soil water potentials, G. ‘Moonlight’ accessed a different or additional source of soil water to M. elipticum. This study demonstrates the utility of the pressure chamber for describing the diurnal and seasonal water relations of ornamentals in a mixed planting in urban horticulture.