scholarly journals The risk-takers and -avoiders: germination sensitivity to water stress in an arid zone with unpredictable rainfall

AoB Plants ◽  
2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Corrine Duncan ◽  
Nick L Schultz ◽  
Megan K Good ◽  
Wolfgang Lewandrowski ◽  
Simon Cook
Keyword(s):  
Water Stress ◽  
Seed Germination ◽  
Water Potential ◽  
Water Availability ◽  
Cold Climate ◽  
Arid Zones ◽  
Water Potentials ◽  
Risk Takers ◽  
Hydrotime Model ◽  
Germination Traits

Abstract Water availability is a critical driver of population dynamics in arid zones, and plant recruitment is typically episodic in response to rainfall. Understanding species’ germination thresholds is key for conservation and restoration initiatives. Thus, we investigated the role of water availability in the germination traits of keystone species in an arid ecosystem with stochastic rainfall. We measured seed germination responses of five arid species, along gradients of temperature and water potential under controlled laboratory conditions. We then identified the cardinal temperatures and base water potentials for seed germination, and applied the hydrotime model to assess germination responses to water stress. Optimum temperatures for germination ranged from 15 to 31 °C under saturated conditions (0 MPa), and three species had low minimum temperatures for germination (<3 °C). A small proportion of seeds of all species germinated under dry conditions (Ψ ≤ −1 MPa), although base water potential for germination (Ψ b50) ranged from −0.61 to −0.79 MPa. Species adhered to one of two germination traits: (i) the risk-takers which require less moisture availability for germination, and which can germinate over a wider range of temperatures irrespective of water availability (Casuarina pauper and Maireana pyramidata), and (ii) the risk-avoiders which have greater moisture requirements, a preference for cold climate germination, and narrower temperature ranges for germination when water availability is low (Atriplex rhagodioides, Maireana sedifolia and Hakea leucoptera). High seed longevity under physiological stress in H. leucoptera, combined with a risk-avoiding strategy, allows bet-hedging. The hydrotime model predicted lower base water potentials for germination than observed by the data, further supporting our assertion that these species have particular adaptations to avoid germination during drought. This study provides insights into the complex physiological responses of seeds to environmental stress, and relates seed germination traits to community dynamics and restoration in arid zones.

The effect of ecological disturbance on competition between Crinipellis perniciosa and other tropical fungi

1988 ◽  
Vol 94 ◽  
pp. 159-166 ◽  
Author(s):  
Elizabeth Bravo-Velasquez ◽  
John Hedger
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Tropical Forests ◽  
Water Availability ◽  
Tropical Fungi ◽  
Soil Horizons ◽  
Ecological Disturbance ◽  
Crinipellis Perniciosa ◽  
Water Potentials

SynopsisIsolates of the tropical fungus Crinipellis perniciosa obtained from cocoa and lianas in Ecuador were grown on media ranging from −0.45 MPa to −9.0 MPa water potential and their responses compared to those of other agarics and Xylaria species isolated from cocoa. Antagonism between mycelia of C. perniciosa and these isolates was also assessed over the same range of water potentials. It is hypothesised that C. perniciosa and other canopy inhabiting fungi of tropical forests are adapted to water stress, but are not competitive with fungi which colonise later, following litterfall, from lower litter and soil horizons, where water availability is higher. Xylaria spp. proved to be aggressive antagonists of C. perniciosa over a range of water potentials.

scholarly journals Unexpected relationships between δ13C and wine grape performance in organic farming

OENO One ◽  
2013 ◽  
Vol 47 (4) ◽  
pp. 269 ◽  
Author(s):  
Edoardo Antonio Costantino Costantini ◽  
Alessandro Agnelli ◽  
Pierluigi Bucelli ◽  
Aldo Ciambotti ◽  
Valentina Dell’Oro ◽  
...  
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Soil Water ◽  
Organic Farming ◽  
Water Availability ◽  
Stress Conditions ◽  
Soil Water Availability ◽  
Wine Grape ◽  
Stem Water Potential ◽  
Stem Water

<p style="text-align: justify;"><strong>Aim</strong>: To evaluate the relationship between carbon isotope ratio (δ<sup>13</sup>C) and wine grape viticultural and oenological performance in organic farming.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The study was carried out for four years in the Chianti Classico wine production district (Central Italy), on five non irrigated vineyards conducted in organic farming. The reference variety was Sangiovese. Eleven sites were chosen for vine monitoring and grape sampling. The performance parameters were alcohol and must sugar content, sugar accumulation rate, mean berry weight, and extractable polyphenols. δ<sup>13</sup>C, stem water potential, and soil water availability were also monitored. Finally, soil nitrogen as well as yeast available nitrogen in the must were measured. δ<sup>13</sup>C was directly related to stem water potential and soil water deficit, and indicated a range of water stress conditions from none and moderate to strong. However, its relationship with viticultural and oenological results was contrary to expectation, that is, performance linearly increased along with soil moisture. On the other hand, the worst performance was obtained where both water and nitrogen were more limiting.</p><p style="text-align: justify;"><strong>Conclusions</strong>: The unexpected relationship between δ<sup>13</sup>C and Sangiovese performance was caused by low nitrogen availability. The studied sites all had low-fertility soils with poor or very poor nitrogen content. Therefore, in the plots where soil humidity was relatively higher, nitrogen plant uptake was favoured, and Sangiovese performance improved. Macronutrient being the main limiting factor, the performance was not lower in the plots where soil water availability was relatively larger. Therefore, the best viticultural result was obtained with no water stress conditions, at low rather than at intermediate δ<sup>13</sup>C values.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Water nutrition is crucial for wine grape performance. δ<sup>13</sup>C is a method used to assess vine water status during the growing season and to estimate vine performance. A good performance is expected at moderate stress and intermediate δ<sup>13</sup>C values. A better knowledge of the interaction between water and nutrient scarcity is needed, as it can affect the use of δ<sup>13</sup>C to predict vine performance.</p>

scholarly journals A conceptual dynamic vegetation-soil model for arid and semiarid zones

2008 ◽  
Vol 12 (5) ◽  
pp. 1175-1187 ◽  
Author(s):  
D. I. Quevedo ◽  
F. Francés
Keyword(s):  
Soil Moisture ◽  
Water Stress ◽  
Water Balance ◽  
Water Availability ◽  
Leaf Biomass ◽  
Soil Conditions ◽  
Model Parameters ◽  
Arid Zones ◽  
Soil Model ◽  
Arid And Semiarid

Abstract. Plant ecosystems in arid and semiarid climates show high complexity, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development and its dynamic evolution. The available water-soil content results from the water balance in the system, where the key issues are the soil, the vegetation and the atmosphere. However, it is the vegetation, which modulates, to a great extent, the water fluxes and the feedback mechanisms between soil and atmosphere. Thus, soil moisture content is most relevant for plant growth maintenance and final water balance assessment. A conceptual dynamic vegetation-soil model (called HORAS) for arid and semi-arid zones has been developed. This conceptual model, based on a series of connected tanks, represents in a way suitable for a Mediterranean climate, the vegetation response to soil moisture fluctuations and the actual leaf biomass influence on soil water availability and evapotranspiration. Two tanks were considered using at each of them the water balance and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process, whereas the second one models the evolution of moisture by the upper soil. The model parameters were based on soil and vegetation properties, but reduced their numbers. Simulations for dominant species, Quercus coccifera L., were carried out to calibrate and validate the model. Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years. On the other hand, the model shows the adaptation of the vegetation to the variability of climatic and soil conditions, demonstrating that in the presence or shortage of water, the vegetation regulates its leaf biomass as well as its rate of transpiration in an attempt to minimize total water stress.

Hydrothermal time analysis of tomato seed germination at suboptimal temperature and reduced water potential

1994 ◽  
Vol 4 (2) ◽  
pp. 71-80 ◽  
Author(s):  
Peetambar Dahal ◽  
Kent J. Bradford
Keyword(s):  
Seed Germination ◽  
Water Potential ◽  
Time Course ◽  
Hydrothermal Time ◽  
Tomato Seed ◽  
Time Model ◽  
Germination Time ◽  
Radicle Emergence ◽  
Time Courses ◽  
Hydrotime Model

AbstractBoth temperature (T) and water potential (ψ) have consistent and quantifiable effects on the rate and extent of seed germination (radicle emergence). Germination at suboptimal T can be characterized on the basis of thermal time, or the T in excess of a base (Tb) multiplied by the time to a given percentage germination (tg). Similarly, germination at reduced ψ can be characterized on a hydrotime basis, or the ψ in excess of a base (ψb) multiplied by tg. Within a seed population, the variation in thermal times to germination for a specific percentage (g) is based upon the normal distribution of ψb values among seeds (ψb(g)). Germination responses across a range of suboptimal T and ψ might be accounted for by a general hydrothermal time model incorporating both T and ψ components. We tested this hypothesis for tomato (Lycopersicon esculentum Mill.) seeds of two genotypes differing in germination rates and tolerance of suboptimal T and ψ. For combinations of T (10−25°C) and ψ (0 to −0.9 MPa), a general hydrothermal time model accounted for approximately 75% of the variation in times to germination within the seed populations of both genotypes, and over 96% of the variation in median germination rates. However, ψb(g) distributions were sensitive to both the T and ψ of imbibition, resulting in a poor fit of the model to specific time course data. Analysis of germination timing separately for low and high ψ ranges within a given T resulted in specific models accounting for 88−99% of the variation in individual germination times and >99% of the variation in madian germination rates. Thus, for a given T and ψ range, the hydrotime model closely matched tomato seed germination time courses. Accumulated hydrothermal time accounted well for germination rates at ψ> −0.5 MPa across suboptimal T if ψb(g) was allowed to vary with T. Germination did not show a consistent response to T at ψ < −0.5 MPa, and estimated Tb values varied over different T ranges. Generalization of the hydrothermal time model across the entire range of suboptimal T and ψ was limited by physiological adjustments of the seeds to their current environment. The hydrothermal time model detected and quantified these adjustment processes that would otherwise not be evident from inspection of germination time courses. Temperature and water potential influence the time to germination via physiological mechanisms that reciprocally interact.

Effects of water potential on germination of lettuce, sunflower, and citrus seeds

1969 ◽  
Vol 47 (11) ◽  
pp. 1761-1764 ◽  
Author(s):  
Merrill R. Kaufmann
Keyword(s):  
Polyethylene Glycol ◽  
Water Stress ◽  
Water Potential ◽  
Cellulose Acetate Membrane ◽  
Lettuce Seeds ◽  
Water Potentials ◽  
Citrus Seeds ◽  
Germinating Seeds ◽  
Polyethylene Glycol 6000 ◽  
Selection Of

The effect of nearly constant water potential on germination of citrus, sunflower, and lettuce seeds was studied. Water potential equilibration was achieved by placing soil above a cellulose acetate membrane which was in contact with a solution of polyethylene glycol-6000. Selection of solute potentials in the solution resulted in controlled water potentials in the soil over a range of 0 to −14.9 bars for citrus and 0 to −8.0 bars for sunflower and lettuce. The water stress experienced by germinating seeds in this system is largely the result of a matric effect rather than a solute effect.Citrus seeds germinated at water potentials as low as −4.7 bars and lettuce at −4.1 bars, but sunflower germinated at −8.0 bars. Sunflower germinated as rapidly at −4.1 bars as lettuce at −2.3 bars, both reaching 50% germination at about 8 days. Citrus germinated much more slowly, requiring 26 days at 0 bars.

Effect of Water Stress on Stomatal Conductance and Leaf Water Relations of Leaves Along Current-Year Branches of Peach

1989 ◽  
Vol 16 (6) ◽  
pp. 549 ◽  
Author(s):  
SL Steinberg ◽  
MJ Mcfarland ◽  
JC Miller
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Water Status ◽  
Stomatal Closure ◽  
Water Flux ◽  
Leaf Water ◽  
Leaf Water Status ◽  
Mature Leaves ◽  
Water Potentials

A gradation, that reflects the maturity of the leaves, exists in the leaf water, osmotic and turgor potential and stomatal conductance of leaves along current and 1-year-old branches of peach. Predawn leaf water potentials of immature folded leaves were approximately 0.24 MPa lower than mature leaves under both well-watered and dry conditions. During the daytime the leaf water potential of immature leaves reflected the water potential produced by water flux for transpiration. In well- watered trees, mature and immature unfolded leaves had a solute potential at least 0.5 MPa lower than immature folded leaves, resulting in a turgor potential that was approximately 0.8 MPa higher. The turgor requirement for growth appeared to be much less than that maintained in mature leaves. As water stress developed and leaf water potentials decreased, the osmotic potential of immature folded leaves declined to the level found in mature leaves, thus maintaining turgor. In contrast, mature leaves showed little evidence of turgor maintenance. Stomatal conductance was lower in immature leaves than in fully mature leaves. With the onset of water stress, conductance of mature leaves declined to a level near that of immature leaves. Loss of turgor in mature leaves may be a major factor in early stomatal closure. It was concluded that osmotic adjustment played a role in maintenance of a leaf water status favorable for some growth in water-stressed immature peach leaves.

scholarly journals Canopy temperature and heat stress are increased by compound high air temperature and water stress and reduced by irrigation – a modeling analysis

2021 ◽  
Vol 25 (3) ◽  
pp. 1411-1423 ◽  
Author(s):  
Xiangyu Luan ◽  
Giulia Vico
Keyword(s):  
Heat Stress ◽  
Water Stress ◽  
Water Potential ◽  
Soil Water ◽  
Air Temperature ◽  
Water Availability ◽  
Plant Traits ◽  
Soil Water Potential ◽  
Canopy Temperature ◽  
Threshold Temperature

Abstract. Crop yield is reduced by heat and water stress and even more when these conditions co-occur. Yet, compound effects of air temperature and water availability on crop heat stress are poorly quantified. Existing crop models, by relying at least partially on empirical functions, cannot account for the feedbacks of plant traits and response to heat and water stress on canopy temperature. We developed a fully mechanistic model, coupling crop energy and water balances, to determine canopy temperature as a function of plant traits, stochastic environmental conditions, and irrigation applications. While general, the model was parameterized for wheat. Canopy temperature largely followed air temperature under well-watered conditions. But, when soil water potential was more negative than −0.14 MPa, further reductions in soil water availability led to a rapid rise in canopy temperature – up to 10 ∘C warmer than air at soil water potential of −0.62 MPa. More intermittent precipitation led to higher canopy temperatures and longer periods of potentially damaging crop canopy temperatures. Irrigation applications aimed at keeping crops under well-watered conditions could reduce canopy temperature but in most cases were unable to maintain it below the threshold temperature for potential heat damage; the benefits of irrigation in terms of reduction of canopy temperature decreased as average air temperature increased. Hence, irrigation is only a partial solution to adapt to warmer and drier climates.

Germination, and Seedling and Rosette Development of Flodman Thistle (Cirsium flodmanii)

Weed Science ◽  
1984 ◽  
Vol 32 (6) ◽  
pp. 768-773 ◽  
Author(s):  
Robert G. Wilson ◽  
Melvin K. McCarty
Keyword(s):  
Seed Germination ◽  
Gibberellic Acid ◽  
Water Potential ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Plant Water ◽  
Germination Medium ◽  
Water Potentials ◽  
Average Plant ◽  
Osmotic Potentials

Maximum germination of flodman thistle [Cirsium flodmanii(Rydb.) Arthur ♯3CIRFL] occurred at alternating temperatures of 10 to 20 and 20 to 30 C. Seeds germinated (20%) in 1.7 M NaCl. Light was important in seed germination; however, its absence could be overcome by adding 8.6 × 10-5M GA3(gibberellic acid) to the germination medium. The greatest seedling emergence occurred when seeds were planted on the soil surface and was lower when seeds were buried at any depth in the soil. Osmotic potentials at −0.5 MPa and greater reduced germination, but 3% of the seeds germinated at −1.3 MPa. Flodman thistle seedlings tolerated average plant water potentials of −0.9 and −1.1 MPa, but they died when the water potential was decreased to −1.5 MPa. Flodman thistle seedlings 43 days old and with four true leaves resprouted after topgrowth removal. Regrowth was evident on 75% of the clipped plants 13 days after initial topgrowth removal. Flodman thistle rosettes spread more rapidly and rosette survival was enhanced more in a weed-free nursery than in a weedy pasture.

Incubation under fluctuating temperatures reduces mean base water potential for seed germination in several non-cultivated species

2005 ◽  
Vol 15 (2) ◽  
pp. 89-97 ◽  
Author(s):  
Roberto Huarte ◽  
Roberto L. Benech-Arnold
Keyword(s):  
Seed Germination ◽  
Water Potential ◽  
Osmotic Potential ◽  
Quantitative Description ◽  
Maximum Temperature ◽  
The Mean ◽  
Hydrotime Model ◽  
Total Seed ◽  
Base Water Potential ◽  
Fluctuating Temperatures

Seeds ofCarduus acanthoides,Cynara cardunculus,Cirsium vulgare,Brassica campestris, andSisymbrium altissimumwere incubated at a range of decreasing osmotic potentials (Ψo) under fluctuating temperatures or the median temperature of the fluctuation cycle. Fluctuating temperatures promoted total seed germination in water and at reduced osmotic potential. Total germination was reduced as the Ψodecreased. However, this trend was smallest under fluctuating temperatures, signalling a higher tolerance of seeds to reduced osmotic potential. Effects of osmoticum and temperature were modelled with the hydrotime model. The parameters estimated from the model, the hydrotime constant (θH), the mean base water potential Ψb(50) and its standard deviation (σΨb) gave good descriptions of germination time courses. For all species, incubation under fluctuating temperatures shifted Ψb(50) values downwards without modifying their distribution substantially. This accounted for the greater tolerance of germination to reduced Ψounder fluctuating temperatures. To confirm that these effects were mediated by temperature fluctuationsper se, the behaviour ofC. acanthoidesandC. cardunculusincubated at the minimum, the mean and the maximum temperature of the fluctuation cycle was also analysed. Constant maximum and minimum temperatures of the cycle did not stimulate germination, nor did they shift Ψb(50) towards more negative values. The hydrotime model provides a physiologically based quantitative description for germination promotion due to fluctuating temperature.

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