that respond to the low water availability, such as osmotic adjustment (OA), which consists of reducing cellular damage by accumulating osmolytes or compatible solutes ( Chaves et al., 2003 ). The aforementioned osmolytes are metabolites that accumulate
metabolic processes even under cellular water deficit. Drought tolerance may be accomplished through various mechanisms such as osmotic adjustment (OA), which involves accumulation of solutes to maintain cellular turgidity. Drought tolerance has been
Abstract
Seasonal changes in the relationship between leaf conductance and total water potential in mature apple (Malus domestica Borkh.) shoot leaves were found to be mediated by osmotic adjustment, not changes in the total water potential–relative water content relationship. Leaves at the growing shoot tip were found to have a much higher (1.0 to 2.0 MPa) osmotic potential than mature leaves and showed no seasonal osmotic adjustment, while mature, fully expanded leaves on the same shoots did adjust osmotically. Leaf osmotic potentials differed little among exposed leaves on a shoot once fully expanded.
moved indoors for measurement. Leaf water potential was measured in a custom Scholander-type pressure chamber ( Ritchie and Hinckley, 1975 ) constructed at the University of Queensland and fitted with a digital readout. Osmotic adjustment in terms of
cold-acclimating woody plants. Among these are reduced growth ( Li et al., 2005 ), reduced tissue water content ( Anisko and Lindstrom, 1996 ), osmotic adjustment, defined as an increase in osmotic pressure of cell sap resulting from more organic and
the demand for water ( Nilsen and Orcutt, 1996 ). Another mechanism serving to increase drought tolerance is through osmotic adjustment, which allows plants to maintain leaf cellular hydration and sustain metabolic activities during drought ( Nilsen
, 1986 ). Osmotic potential. Leaf ψ S was decreased by salinity for all grafted plants. This may indicate that organic or inorganic matter was increased in cells for osmotic adjustment, which is essential for osmoregulation. The highest percentage
, 2008 ). On the cellular scale, osmotic adjustment is an acclimation response to drought that concentrates compatible solutes inside cells ( Sanders and Arndt, 2012 ; Serraj and Sinclair, 2002 ). This lowers Ψ L and maintains the Ψ gradient needed for
of regular physiological processes often associated with osmotic adjustment. Plant growth under drought stress is substantially reduced, partly because lower turgor pressure in cells affected by low water potential results in a slower cell expansion
, 2, and 3. Because osmotic adjustment (oA) was assumed to be an important adaptation mechanism influencing LER under drought stress conditions, osmotic potential (Ψ s ) of leaves from the well-watered and the stress treatment was measured in Expt. 2