Specific leaf metabolic changes that underlie adjustment of osmotic potential in response to drought by four Quercus species

2020 ◽  
Author(s):  
Ismael Aranda ◽  
Estrella Cadahía ◽  
Brígida Fernández de Simón
Keyword(s):  
Drought Tolerance ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Quinic Acid ◽  
Molecular Processes ◽  
Leaf Habit ◽  
Leaf Osmotic Potential ◽  
Quercus Species ◽  
Metabolic Basis ◽  
Watering Treatment

Abstract Osmotic adjustment is almost ubiquitous as a mechanism of response to drought in many forest species. Recognized as an important mechanism of increasing turgor under water stress, the metabolic basis for osmotic adjustment has been described in only a few species. We established an experiment with four species of the genus Quercus ranked according to drought tolerance and leaf habit from evergreen to broad-leaved deciduous. A cycle of watering deprivation was imposed on seedlings, resulting in well-watered (WW) and water-stressed (WS) treatments, and their water relations were assessed from pressure-volume (P-V) curves. Leaf predawn water potential (Ψpd) significantly decreased in WS seedlings which was followed by a drop in leaf osmotic potential at full turgor (Ψπ100). The lowest values of Ψπ100 followed the ranking of decreasing drought tolerance: Q. ilex < Q. faginea < Q. pyrenaica < Q. petraea. The leaf osmotic potential at the turgor loss point (ΨTLP) followed the same pattern as Ψπ100 across species and treatments. The pool of carbohydrates, some organic acids, and cyclitols were the main osmolytes explaining osmotic potential across species, likewise to the osmotic adjustment assessed from the decrease in leaf Ψπ100 between WW and WS seedlings. Amino-acids were very responsive to WS, particularly γ-aminobutyric acid (GABA) in Q. pyrenaica, but made a relatively minor contribution to osmotic potential compared with other groups of compounds. In contrast, the cyclitol proto-quercitol made a prominent contribution to the changes in osmotic potential regardless of watering treatment or species. However, different metabolites such as quinic acid, played a more important role in osmotic adjustment in Q. ilex, distinguishing it from the other species studied. In conclusion, while osmotic adjustment was present in all four Quercus species, the molecular processes underpinning this response differed according to their phylogenetic history and specific ecology.

Accumulation of Glycinebetaine in Chloroplasts Provides Osmotic Adjustment During Salt Stress

1986 ◽  
Vol 13 (5) ◽  
pp. 659 ◽  
Author(s):  
SP Robinson ◽  
GP Jones
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Salt Stress ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Spinacia Oleracea ◽  
Resonance Spectroscopy ◽  
Leaf Osmotic Potential ◽  
Cellular Compartments ◽  
Isolated Chloroplasts

Glycinebetaine was determined in leaves and in isolated chloroplasts of spinach (Spinacia oleracea) by nuclear magnetic resonance spectroscopy. Some leakage of glycinebetaine from the chloroplasts occurred during the isolation so the concentration in chloroplasts in vivo could be up to 1.5 times higher than that measured in isolated chloroplasts. It was demonstrated that any contamination of the chloroplast preparations by glycinebetaine originating from other cellular compartments or from broken chloroplasts would have amounted to less than 10% of the measured values. Leaf osmotic potential of salt-stressed plants was -2.09 MPa compared to -0.91 MPa in non-stressed controls. This was accompanied by a sixfold increase in glycinebetaine content in the leaf but the levels of choline and proline were not increased. In chloroplasts isolated from control leaves the calculated glycinebetaine concentration was 26 mM which was 10-fold higher than the concentration in the leaf as a whole but only contributed 7% of the osmotic potential of the chloroplast. Chloroplasts from salt-stressed plants contained up to 300 mM glycinebetaine which was 20 times the concentration in the leaf as a whole. The glycinebetaine concentration in chloroplasts from salt-stressed leaves was equivalent to an osmotic potential of -0.75 MPa and this contributed 36% of the osmotic potential of the chloroplast and 64% of the decrease in osmotic potential induced by salt stress. At least 30-40% of the total leaf glycinebetaine was localized in the chloroplast. The results demonstrate that glycinebetaine accumulates in chloroplasts to provide osmotic adjustment during salt stress and provide support for the hypothesis that glycinebetaine is a compatible cytoplasmic solute which may be preferentially located in the cytoplasm of cells.

Osmotic Adjustment in Expanding and Fully Expanded Leaves of Sunflower in Response to Water Deficits

1980 ◽  
Vol 7 (2) ◽  
pp. 181 ◽  
Author(s):  
MM Jones ◽  
NC Turner
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Leaf Water ◽  
Similar Degree ◽  
Tissue Water ◽  
Predawn Leaf Water Potential ◽  
Leaf Osmotic Potential ◽  
Osmotic Potentials

Sunflower plants were grown in large volumes of soil and slowly water-stressed by withholding water. The tissue water relationships of leaves at various stages of stress and of leaves of equivalent well watered controls were studied by the pressure chamber technique. Plants were stressed either when leaf 17 was expanding or when it was fully expanded. When expanding leaves reached a moderate level of stress (predawn leaf water potential of -0.9 MPa), the osmotic potentials at full turgor and zero turgor were lower than the control values by 0.1 MPa and 0.2 MPa, respectively. When fully expanded leaves were stressed to a similar degree (predawn leaf water potential of - 1.1 MPa), the osmotic potentials at full turgor and zero turgor were lower than the control values by 0.2 MPa and 0.3 MPa, respectively. The development of more severe stress in the fully expanded leaves was not accompanied by any further osmotic adjustment. However, when the expanding leaves reached a predawn leaf water potential of -2.3 MPa, the values of leaf osmotic potential at full turgor and zero turgor were lower than the values for the well watered plants by 0.4 MPa and 0.6 MPa, respectively. In expanding leaves prestressed to a predawn leaf water potential of -2.3 MPa, the osmotic potential at full turgor was significantly less than the control values for at least 7 days after rewatering. Stress had no effect on the bulk modulus of elasticity. It is concluded that both expanding and fully expanded sunflower leaves show osmotic adjustment.

Osmotic Adjustment of Sorghum and Sunflower Crops in Response to Water Deficits and Its Influence on the Water Potential at Which Stomata Close

1978 ◽  
Vol 5 (5) ◽  
pp. 597 ◽  
Author(s):  
NC Turner ◽  
JE Begg ◽  
ML Tonnet
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Water Deficits ◽  
Rate Of Increase ◽  
Leaf Osmotic Potential ◽  
Response To Water

The soil and plant water status of irrigated and unirrigated sorghum [Sorghum bicolor (L.) Moench cv. TX610] and sunflower (Helianthus annuus L. cv. Hysun 30) crops were compared on several days from the late vegetative to the early grain-filling stages of development. Additionally, the stems of plants from the irrigated and unirrigated plots of both species were cut near their base; this caused the plants to quickly dry until the stomata closed. The leaf water potential and leaf osmotic potential were measured when the stomatal resistance reached 6 s cm-� to give the water potential for stomatal closure and to provide osmotic potentials at equal turgor. Carbohydrate and potassium levels of leaves were also monitored. The mean daily minimum leaf water potentials in the irrigated sorghum and sunflower did not decrease below - 1 7 MPa and - 2.0 MPa, respectively, but decreased to - 2.1 MPa in the unirrigated sorghum and -2.6 MPa in the unirrigated sunflower. The osmotic potential at stomatal closure in the rapidly dried plants decreased with increasing leaf water deficit in both sunflower and sorghum: in both species the osmotic potential decreased approximately 0.6 MPa for each megapascal decrease in leaf water potential. The results indicate that both sorghum and sunflower adjusted osmotically in response to water deficits and that adjustment occurred at a rate of at least 0.1 MPa per day. The lowering of osmotic potential persisted less than 9 days after the relief of stress in both sunflower and sorghum. The soluble sugar concentration increased linearly in both sunflower and sorghum with osmotic adjustment: the rate of increase of soluble sugars was significantly greater in sunflower than sorghum. No changes in potassium concentration were observed during osmotic adjustment. The water potential at which the stomata closed varied from - 1.5 to -2.6 MPa in sorghum and - 1.7 to -2.7 MPa in sunflower: the water potential that induced stomatal closure decreased as the osmotic potential decreased. Stomatal closure occurred at a mean turgor of -0-5 MPa in both species: systematic error in the measurement of osmotic potential on frozen and thawed leaf tissue is considered the reason for the low turgor potentials at stomatal closure. The adaxial stomatal closed before the abaxial stomata in the sorghum and unirrigated sunflower but, since the leaf water potential initially fell rapidly and then became stable before the adaxial stomata closed, both the adaxial and abaxial stomata closed at the same leaf water potential.

Evidence for Osmotic Adjustment in Phalaris tuberosa L. cvv. Australian and Sirosa

1985 ◽  
Vol 12 (5) ◽  
pp. 481 ◽  
Author(s):  
E.Y Sambo ◽  
M.J Aston
Keyword(s):  
Water Stress ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Pasture Grass ◽  
Leaf Osmotic Potential

The temperate pasture grass Phalaris tuberosa L. (cvv. Australian and Sirosa) was grown in soil under glasshouse conditions. When water was withheld, leaf xylem potential (�) decreased at the rate of 0.02 and 0.05 MPa per day in cvv. Australian and Sirosa, respectively, between 7 and 17 days, and reached a dawn value -0.25 (� 0.02) MPa and -0.56 (�0.08) MPa in the respective cultivars. These plants were moderately stressed. Between 17 and 23 days, when the experiment was terminated, stress developed more rapidly and � at dawn reached final values of -2.1 (�0.09) and -2.2 (�0.08) MPa in Australian and Sirosa phalaris, respectively. These plants were severely stressed. The leaf osmotic potential (��) decreased at similar rates as � in the stressed plants, thus maintaining the turgor potential (�*p) relatively constant with increasing water stress. Osmotic adjustment (��100/�) was judged by comparing �� at full turgor (�100/�) in stressed plants which had been rewetted, with �100/� of control unstressed plants. ��100/� of moderately stressed plants was 0.46 and 0.48 MPa in Australian and Sirosa phalaris, respectively. In severely stressed plants, the respective ��100/� values were 0.67 and 0.85 MPa.

scholarly journals The Role of Carbohydrates in Active Osmotic Adjustment in Apple under Water Stress

1992 ◽  
Vol 117 (5) ◽  
pp. 816-823 ◽  
Author(s):  
Zhongchun Wang ◽  
Gary W. Stutte
Keyword(s):  
Water Stress ◽  
Malus Domestica ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Soluble Sugars ◽  
Sugar Alcohol ◽  
Apple Trees ◽  
Mature Leaves ◽  
Leaf Osmotic Potential

Greenhouse grown 2-year-old potted `Jonathan' apple trees (Malus domestica Borkh.) were subjected to various levels of water stress in February. Midday leaf water potential (ψW), leaf osmotic potential (ψS), soluble sugars, and starch contents of mature leaves were measured throughout the development of water stress to determine whether active osmotic adjustment could be detected and whether carbohydrates were involved. Active adjustments of 0.6 MPa were observed 3 and 5 days, respectively, after water stress was initiated. Leaf turgor potential (ψP) could not be maintained through the osmotic adjustment when ψW dropped below -1.6 MPa. Sorbitol, glucose, and fructose concentrations increased while sucrose and starch levels decreased significantly as water stress developed, strongly suggesting that sugar alcohol and monosaccharide are the most important osmotica for adjustment. Sorbitol was a primary carbohydrate in the cell sap and accounted for > 50% of total osmotic adjustment. The partitioning of newly fixed W-labeled photosynthates in mature leaves was not affected by water stress immediately after the 30-min 14CO2 treatment. All the W-labeled carbohydrates decreased in the labeled leaves very rapidly after 14CO2 labeling. The decrease in 14C-sorbitol was greater than the decrease in other carbohydrates under both well-watered and stressed conditions. After 24 hours of water stress, however, the percentage of 14C-sorbitol increased while the percentages of sucrose, starch, glucose, and fructose decreased significantly with increasing levels of stress. The ratio of 14C-sorbitol in leaves with ψW = -3.5 MPa to leaves with ψW = -0.5 MPa was significantly higher than that of 14C-sucrose, 14C-glucose, W-fructose, or 14C-starch.

scholarly journals 405 Glycinebetaine Accumulation in Red Beet under Salinity

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 513E-513
Author(s):  
Guntur V. Subbarao ◽  
Raymond M. Wheeler ◽  
L.H. Levine ◽  
Gary W. Stutte
Keyword(s):  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Dry Weight ◽  
Hydroponic System ◽  
Red Beet ◽  
Leaf Osmotic Potential ◽  
Sodium Toxicity ◽  
Relative Water ◽  
The Mean ◽  
External Salinity

Accumulation of glycinebetaine occurs in Chenopodiaceae members and is thought to assist in osmotic adjustment and protect cytoplasm from sodium toxicity. Red beet has an ability to tolerate high tissue sodium levels, which may result in increased glycinebetaine production. To test this hypothesis, two cultivars of red beet ['Scarlet Supreme' (SS) and `Ruby Queen' (RQ)] were grown under nonsaline (4.75 mM Na) and saline (54.75 mM Na) conditions in a recirculating hydroponic system for 42 days at elevated CO2 (1200 μmol•mol-1) in a growth chamber. Leaf glycinebetaine level, relative water content, and osmotic potential were measured at weekly intervals. Leaf glycinebetaine levels increased with plant age and reached a maximum of 67 μmol•g-1 dw under nonsaline and 101 μmol•g-1 dry weight (dw) under saline conditions at 42 days in SS; in RQ, the glycinebetaine levels reached a maximum of 91 μmol•g-1 dw under nonsaline and 121 μmol•g-1 dw under saline conditions by 26 days. The mean glycinebetaine levels were increased over two-thirds under saline conditions in both the cultivars. RQ accumulated significantly higher (37% more under nonsaline, and 46% more under salinity) glycinebetaine than SS. The turgid leaf osmotic potential of RQ was consistently higher than SS under nonsaline (2.23 MPa in RQ vs. 1.82 MPa in SS) and saline (2.48 MPa in RQ vs. 2.02 MPa in SS) conditions. The results indicate that higher glycinebetaine levels in the leaf could result in better osmotic adjustment, and glycinebetaine accumulation in red beet can vary among cultivars and is strongly affected by external salinity.

Seasonal and clonal variations in drought tolerance of Populusdeltoides

1991 ◽  
Vol 21 (6) ◽  
pp. 910-916 ◽  
Author(s):  
G. Michael Gebre ◽  
Michael R. Kuhns
Keyword(s):  
Drought Tolerance ◽  
Osmotic Potential ◽  
Weight Fraction ◽  
Dry Weight ◽  
Weather Conditions ◽  
Injury Index ◽  
Eastern Cottonwood ◽  
Leaf Osmotic Potential ◽  
Favorable Weather ◽  
Osmotic Potentials

Water relations of three field-grown eastern cottonwood (Populusdeltoides Bartr.) clones were compared for the 1989 growing season. Clonal and seasonal variations in leaf water potential, leaf osmotic potential, dry weight fraction, and injury index were measured. The injury index was calculated from conductivity changes due to electrolyte leakage during rehydration of dehydrated and nondehydrated leaves. When samples were measured after dry periods, dry weight fraction increased and injury index and predawn osmotic potential declined. There were significant negative correlations between dry weight fraction and osmotic potential for all clones. There were no significant differences between clones from Nebraska (Platte) and Indiana (Tippecanoe) throughout the season in osmotic potential and injury index. The clones Platte and Tippecanoe had significantly lower osmotic potentials than a clone from Ohio (Ohio Red) on most sample dates. When injury index values increased following favorable weather conditions, Platte and Tippecanoe had a significantly lower injury index than Ohio Red. Since all clones had lower osmotic potential, higher dry weight fraction, and lower injury index during dry periods, it was concluded that all had drought hardened during the period, indicating that all clones have some degree of drought tolerance.

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