stresses such as high and low temperatures, drought, and salinity ( Liu et al., 2017 ). Osmotic adjustment is a mechanism for the maintenance of water potential in plant cells during periods of heat and cold stress ( Zaher-Ara et al., 2016 ). Compatible
Growth-chamber studies were conducted to examine the ability of seven vegetable crops-`Blue Lake' bean (Phaseolus vulgaris L.), `Detroit Dark Red' beet (Beta vulgaris L.), `Burgundy' okra (Abelmoschus esculentus (Moench), `Little Marvel' pea (Pisum sativum L.), `California Wonder' bell pepper (Capsicum annuum L.), `New Zealand' spinach (Spinacia oleracea L.), and `Beefsteak' tomato (Lycopersicon esculentum Mill.)–to adjust osmotically in response to water-deficit stress. Water stress was imposed by withholding water for 3 days, and the adjustment of leaf and root osmotic potentials upon relief of the stress and rehydration were monitored with thermocouple psychrometers. Despite similar reductions in leaf water potential and stomata1 conductance among the species studied, crop-specific differences were observed in leaf and root osmotic adjustment. Leaf osmotic adjustment was observed for bean, pepper, and tomato following water-deficit stress. Root osmotic adjustment was significant in bean, okra, pea, and tomato. Furthermore, differences in leaf and root osmotic adjustment were also observed among five tomato cultivars. Leaf osmotic adjustment was not associated with the maintenance of leaf growth following water-deficit stress, since leaf expansion of water-stressed bean and pepper, two species capable of osmotic adjustment, was similar to that of spinach, which exhibited no leaf osmotic adjustment.
Osmotic adjustment in response to decreasing media water availability was observed for in vitro Chrysanthemum morifolium Ramat. cultivars Bright Golden Anne, Deep Luv, and Lucido. Water stress was induced by increasing sorbitol (0, 0.1, 0.2, 0.3, 0.4 M), mannitol (0, 0.1, 0.2, 0.3, 0.4 M), and sucrose (30, 45, 60, 75, 90 g·l-1) concentrations in modified MS media (2 mg·l-1 BA and 0.1 mg·l-1 NAA). Osmotic adjustment was evidenced by a significant reduction in measured cell sap osmotic potential (R2 = 0.78, 0.96, 0.91 for sucrose, sorbitol, and mannitol respectively) in all cultivars. Shoot length, weighted density (apparent mass), and proliferation were significantly reduced by sorbitol and mannitol treatments. Sucrose reduced shoot proliferation, increased length, and had an inconsistent effect on weighted density. Cultures grown on media without hormones showed tremendous increase in root number up to 60 g·l-1 sucrose. Sorbitol had a negligible effect on rooting at 0.1 M but no roots developed at higher sorbitol concentrations or in any mannitol treatments. Plants transferred to a non-water-stress media after they had experienced in vitro water stress exhibited no change in osmotic properties from the stress treatments.
Six-year-old trees were repeatedly conditioned by withholding irrigation until Ψpd (predawn) thresholds of either –0.9 (“mild”) or –1.4 MPa (“moderate”) were attained. After conditioning, trees were exposed to severe drought (Ψpd –2.0 MPa) and then to 10 days of well-watered conditions. Throughout the investigation, osmotic potential (Ψπ), leaf RWC, transpiration, and total water potential (Ψx) were measured. Water stress was quantified by integrating Ψx. Conditioning caused a significant, but modest, degree of osmotic adjustment (0.08 to 0.28 MPa), which persisted after a brief relief from stress and transpiration rates were reduced 35% to 50%. Osmotic adjustment was not significantly enhanced by more than one stress exposure or conditioning beyond the mild threshold of stress. During severe drought, the moderate group maintained less negative Ψx and lower transpiration rates (38%). After prolonged stress relief, Ψx was similar among all treatments and daily transpiration rates and Ψx gradually recovered. Thuja occidentalis appears to rely on increased stomatal resistance more than osmotic adjustment to tolerate drought stress.
Seedlings of ‘Halford’ peach [Prunus persica (L.) Batsch] maintained in a growth chamber and exposed to leaf water deficits as low as – 38 bars exhibited slight osmotic adjustment before turgor potential reached zero. This adjustment was inadequate to maintain high turgor potential, which decreased until reaching zero at a total leaf water potential of ca. —20 bars. Stomatal conductance was linearly related to total leaf water potential and independent of the average turgor potential of the leaf.
. Nonetheless, there are some commonalities. Tolerance (to high salt levels in plant tissues) almost always requires the combination of several different traits: accumulation and compartmentation of ions for osmotic adjustment; the synthesis of compatible
). The objective of this study was to evaluate the protective effect of EBR treatment on perennial ryegrass under salt stress condition and detect changes of osmotic adjustment and antioxidant defense system in perennial ryegrass. Materials and Methods
, osmotic adjustments, and saturation level of cell membrane lipids ( Huang et al., 2014 ; Shinozaki and Yamaguchi-Shinozaki, 2007 ), these responses can be overwhelmed during climatic extremes. Drought stress may inhibit photosynthesis and cause an energy
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