Mechanisms of drought resistance in grain legumes I: Osmotic adjustment

SUMMARYAdult early maturing peach trees (Prunus persica(L.) Batsch cvar Flordastar) grafted ontoP. persica×Prunus amygdalusGF-677 peach rootstock, were subjected to low water availability (water stress) and recovery periods for 28 and 7 days, respectively, during summer 2009. Control plants were irrigated daily at 1·3 estimated crop reference evapotranspiration (ETC) in order to obtain non-limiting soil water conditions. Active osmotic adjustment was observed at the end of the stress period. However, the magnitude of this osmotic adjustment (0·18 MPa) was not sufficient to modify the leaf water potential at turgor loss point. The observed active osmotic adjustment that maintained turgor was in contrast to other results in potted peach trees, where no osmotic adjustment was observed, and highlights the importance of field studies in which water stress is developed gradually over a prolonged period. Relative apoplastic water content (RWCa) values were high and decreased as a result of water stress. The rapid decrease in leaf conductance from the beginning of the stress period, together with the delay in stomatal reopening after rewatering, indicated that stomatal behaviour was not a simple passive response to water deficit. The results indicate that drought resistance in early maturing peach trees is based both on avoidance mechanisms, such as stomatal control and tolerance mechanisms, including active osmotic adjustment and high RWCa.

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Physiological Mechanisms of Drought Resistance in Four Native Ornamental Perennials

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.119.2.299 ◽

1994 ◽

Vol 119 (2) ◽

pp. 299-306 ◽

Cited By ~ 18

Author(s):

Douglas S. Chapman ◽

Robert M. Augé

Keyword(s):

Drought Resistance ◽

Osmotic Adjustment ◽

Relative Water Content ◽

Stomatal Closure ◽

Echinacea Purpurea ◽

The Other ◽

Dehydration Tolerance ◽

Drought Avoidance ◽

Relative Water ◽

Monarda Didyma

Understanding physiological drought resistance mechanisms in ornamentals may help growers and landscapers minimize plant water stress after wholesale production. We characterized the drought resistance of four potted, native, ornamental perennials: purple coneflower [Echinacea purpurea (L.) Moench], orange coneflower [Rudbeckia fulgida var. Sullivantii (Beadle & Boynt.) Cronq.], beebalm (Monarda didyma L.), and swamp sunflower (Helianthus angustifolius L.). We measured a) stomatal conductance of leaves of drying plants, b) lethal water potential and relative water content, and c) leaf osmotic adjustment during the lethal drying period. Maintenance of stomatal opening as leaves dry, low lethal water status values, and ability to osmotically adjust indicate relative drought tolerance, with the reverse indicating drought avoidance. Echinacea purpurea had low leaf water potential (ψL) and relative water content (RWC) at stomatal closure and low lethal ψL and RWC, results indicating high dehydration tolerance, relative to the other three species. Rudbeckia fulgida var. Sullivantii had a similar low ψL at stomatal closure and low lethal ψL and displayed relatively large osmotic adjustment. Monarda didyma had the highest ψL and RWC at stomatal closure and an intermediate lethal ψL, yet displayed a relatively large osmotic adjustment. Helianthus angustifolius became desiccated more rapidly than the other species, despite having a high ψL at stomatal closure; it had a high lethal ψL and displayed very little osmotic adjustment, results indicating relatively low dehydration tolerance. Despite differences in stomatal sensitivity, dehydration tolerance, and osmotic adjustment, all four perennials fall predominantly in the drought-avoidance category, relative to the dehydration tolerance previously reported for a wide range of plant species.

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Physiological attributes associated with drought resistance of wheat cultivars in a Mediterranean environment

Australian Journal of Agricultural Research ◽

10.1071/ar9900799 ◽

1990 ◽

Vol 41 (5) ◽

pp. 799 ◽

Cited By ~ 91

Author(s):

A Blum ◽

Y Pnuel

Keyword(s):

Drought Stress ◽

Linear Regression ◽

Heat Tolerance ◽

Drought Resistance ◽

Osmotic Adjustment ◽

Grain Filling ◽

Yield Stability ◽

Yield Reduction ◽

Linear Regression Method ◽

Low Precipitation

Twelve spring wheat (Triticum aestivum L.) cultivars were planted in 16 trials which received seasonal rainfall (including irrigation) ranging from 230 to 755 mm year-l. Under low rainfall conditions, drought stress occurred during the period of stem elongation when the ears grew. Grain filling was largely free of stress. Variation in precipitation explained 75% of the variation in mean yield among trials, and the main yield component responsible for yield reduction at low precipitation was ear number, as affected by tiller survival rate. The larger-yielding cultivars sustained a higher kernel number per ear in compensation for the reduced number of ears under stress. The yield stability of cultivars under low precipitation was defined by both the joint linear regression method and by the linear regression of yield on precipitation, both of which gave very similar predictions. The magnitude of the intercept of the latter regression was taken as indicator of drought resistance in terms of yield. The variations among cultivars in this intercept was well explained by corresponding variations in osmotic adjustment, heat tolerance and canopy temperature. Grain filling from stem reserve mobilization was not important in this respect, evidently because grain filling was not subjected to drought stress in these trials. Early-heading cultivars had a relative yield advantage only when precipitation were less than about 300 mm and grain yield was less than about 350 g m-2. Both early heading and heat tolerance were positively correlated with osmotic adjustment across cultivars. It was therefore concluded that the main physiological attribute associated with yield stability under conditions of drought stress during the period of ear growth was the capacity for osmotic adjustment, which apparently allowed sustained ear growth under drought stress.

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