Osmotic regulation in leaves and roots of olive trees during a water deficit and rewatering

Abstract

We evaluated the osmotic adjustment capacity of leaves and roots of young olive (Olea europaea L.) trees during a period of water deficit and subsequent rewatering. The trials were carried out in Basilicata (40 degrees 24' N, 16 degrees 48' E) on 2-year-old self-rooted olive plants (cv. 'Coratina'). Plants were subjected to one of four drought treatments. After 13 days of drought, plants reached mean predawn leaf water potentials of -0.45 +/- 0.015 MPa (control), -1.65 +/- 0.021 (low stress), -3.25 +/- 0.035 (medium stress) and -5.35 +/- 0.027 MPa (high stress). Total osmotic adjustment increased with increasing severity of drought stress. Trees in the high stress treatment showed total osmotic adjustments ranging between 2.4 MPa at 0500 h and 3.8 MPa at 1800 h on the last day of the drought period. Osmotic adjustment allowed the leaves to reach leaf water potentials of about -7.0 MPa. Active osmotic adjustment at predawn decreased during the rewatering period in both leaves and roots. Stomatal conductance and net photosynthetic rate declined with increasing drought stress. Osmotic adjustment in olive trees was associated with active and passive osmotic regulation of drought tolerance, providing an important mechanism for avoiding water loss.

Plant Water Relations: Absorption, Transport and Control Mechanisms

“…Nevertheless, some species of plants can absorb water soil at a potential much smaller than this limit. For example olive trees can set a water potential gradient between dry soil (-3 MPa) and leaf (-7 MPa) (Dichio et al, 2006). Similarly, Larrea divaricata may absorb water at -6.0 MPa soil water potential (Kirkham, 2005).…”

Response of a clingstone peach cultivar to regulated deficit irrigation

“…Drought stress in Citrus reduced stomatal conductance, leaf transpiration rate, and net CO 2 assimilation rate ). Furthermore, Dichio et al (2006) reported that stomatal conductance and net photosynthetic rate declined with increasing drought stress. Water stress induced a decrease in the quantum yield of PSII electron transport of wheat plants (Triticum aestivum L.), suggesting that water stress resulted in modifications in PSII photochemistry (Lu and Zhang, 1999).…”

Genetic and Molecular Aspects of Plant Response to Drought in Annual Crop Species

“…At cellular level, osmotic adjustment is an adaptive mechanism in which the accumulation of solutes helps to maintain a favourable gradient of water potential in the soil-plant-air system. It allows to maintain a sufficient water absorption from a relatively dry soil for sustaining photosynthetic and transpiration activity, and cell expansion for root growth (Mastrangelo et al, 2011a;Dichio et al, 2006). Regarding the importance of this trait in improving grain yield in water stressed environment, a positive correlation between osmotic adjustment and yield increases has been found in particular in conditions of severe water stress (Serraj & Sinclair, 2002).…”