Drought Impact on the Morpho-Physiological Parameters of Perennial Rhizomatous Grasses in the Mediterranean Environment (original) (raw)
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Biomass production and water use efficiency in perennial grasses during and after drought stress
GCB Bioenergy
Drought is a great challenge to agricultural production, and cultivation of drought-tolerant or water use-efficient cultivars is important to ensure high biomass yields for bio-refining and bioenergy. Here, we evaluated drought tolerance of four C 3 species, Dactylis glomerata cvs. Sevenop and Amba, Festuca arundinacea cvs. Jordane and Kora, Phalaris arundinacea cvs. Bamse and Chieftain and Festulolium pabulare cv. Hykor, and two C 4 species Miscanthus 9 giganteus and M. lutarioriparius. Control (irrigated) and drought-treated plants were grown on coarse and loamy sand in 1 m 2 lysimeter plots where rain was excluded. Drought periods started after harvest and lasted until 80% of available soil water had been used. Drought caused a decrease in dry matter yield (DM; P < 0.001) for all species and cultivars during the drought period. Cultivars Sevenop, Kora and Jordane produced DM at equal levels and higher than the other C 3 cultivars in control and drought-treated plots both during and after the drought period. Negative correlations were observed between stomatal conductance (g s) and leaf water potential (P < 0.01) and positive correlations between g s and DM (P < 0.05) indicating that g s might be suitable for assessment of drought stress. There were indications of positive associations between plants carbon isotope composition and water use efficiency (WUE) as well as DM under well-watered conditions. Compared to control, drought-treated plots showed increased growth in the period after drought stress. Thus, the drought events did not affect total biomass production (DM total) of the whole growing season. During drought stress and the whole growing season, WUE was higher in drought-treated compared to control plots, so it seems possible to save water without loss of biomass. Across soil types, M. lutarioriparius had the highest DM total (15.0 t ha À1), WUE total (3.6 g L À1) and radiation use efficiency (2.3 g MJ À1) of the evaluated grasses.
2009
The drought adaptation of two annual legumes, Medicago minima (L.) Bartal and Onobrychis aequidentata (Sibth and Sm) D'Urv., was studied at the H 2 O and CO 2 efficient use level over the drought period investigating whether, besides the already known drought adaptation mechanism, annual legumes are dealing with drought by controlling stomatal and mesophyll conductance. O. aequidentata maintained higher leaf water potential and leaf hydraulic conductance than M. minima and consequently exhibited better water balance. The data revealed that these two legumes exhibit a completely different photosynthetic behavior. The photosynthetic rate in M. minima is mainly depended on stomatal conductance while in O. aequidentata seems to be depended both on stomatal and mesophyll conductance. O. aequidentata seems to be more efficient having significantly lower values of the ratio internal CO 2 concentration to stomatal conductance at the same value of leaf water potential compared to M. minima. This verifies the higher values of mesophyll conductance and consequently the higher values of carboxylation efficiency. Each one of the two species has different traits to cope with the adverse environmental conditions. The differentiation of drought adaptation mechanisms seems to be a major key for co-existence of several plants of the same life form in Mediterranean grasslands.
Effects of an extended drought period on physiological properties of grassland species in the field
Journal of Plant Research, 2012
A very high percentage (around 70%) of the agronomic area in Switzerland is covered by grasslands at various altitudes where environmental conditions, management, community structure and productivity vary widely. As heat waves and drought are predicted to increase in future climate, survival of plant species in grasslands is a major issue of concern in Central Europe. The effect of summer drought on representative grasslands in Switzerland was studied through drought experiments (using rain-out shelters avoiding natural precipitation) to understand the response of predominant species to changed climatic conditions. The physiological performance (gas exchange, leaf water potential) of selected species was investigated at three locations in Switzerland. The predawn leaf water potential of all species was lower (more negative) under the dryer conditions at the three sites. Net photosynthesis and stomatal conductance of forb and legume species did not show major changes under drought, while grass species showed large decreases at the lowland site. These differences between forb-legume and grass species were not observed at the pre-alpine and alpine site. The apparent drought tolerance of the forb-legume species seems to be due-at least partially-to increased water use efficiency under drought conditions.
Water use efficiency and drought survival in Mediterranean perennial forage grasses
Field Crops Research, 2011
In Mediterranean areas, water use efficiency (WUE) is mainly increased by maximising crop growth during the rainy seasons. Perennial forage species have a number of advantages in comparison to the predominantly used annuals. They can utilize water from autumn to spring, while annuals need to be sown or to germinate from the soil seed bank. Under Mediterranean annual rainfall pattern, perennial plants must grow from autumn to spring and survive under summer aridity. Drought survival can impact water use efficiency through plant mortality and stand recovery after autumn rainfalls. In order to enhance knowledge of physiological and agronomic traits associated with WUE and persistence, a 3-year study was conducted at two Mediterranean sites, comparing a range of accessions of two perennial species, cocksfoot (Dactylis glomerata L.) and tall fescue (Lolium arundinaceum (Schreb.) Darbysh). Within the accessions of predominantly Mediterranean origin, we defined four major functional types, i.e. groups of accessions with similar response to summer drought. One type (FT1) is represented by the only cultivar of a semi-arid cocksfoot (Kasbah) that is completely summer dormant, with high persistence under the most arid situations but with low WUE. The type FT2 all cocksfoot cultivars (Currie, Delta-1, Jana, Medly, and Ottava) that are not or less summer dormant, with good perenniality and intermediate productivity at rainy seasons. The type FT3 includes the cultivars of tall fescue (Centurion, Flecha, Fraydo, and Tanit) that combine an incomplete summer dormancy, a deep rooting system and the highest WUE from autumn to spring. The type FT4 is represented by a cultivar of tall fescue (Sisa) with no summer dormancy, therefore less persistent and also less productive. Dehydration avoidance in tall fescue and cocksfoot and summer dormancy in cocksfoot were the main strategies contributing to persistence under summer drought. WUE in autumn was highly correlated with sward recovery after drought. Seasonal and total WUE were also highly correlated with biomass production over the same period and with depth and density of the root system. Parameterization of functional types of the major species of forage grasses will enhance future modelling work to test the effects of a range of environments and future climate scenarios.
Journal of Arid Environments, 2000
Growth, photosynthesis and water use efficiency of two Sahel dominant C4grasses:Schoenefeldia gracilis Kunth and Dactyloctenium aegyptium (L) P. Beauv were studied under well-watered and drought conditions. D. aegyptium had a faster rate of development than S. gracilis and responded to water-deficits by decreasing leaf area in the earlier stages of development. However, under water-stress the overall reduction of leaf area suffered by S. gracilis was greater than in D. aegyptium. The decrease in net photosynthesis observed under water-deficits resulted mainly from stomatal closure. Analysis of correlation between long-term water-use efficiency and several physiological, structural and growth characteristics shows that long-term water-use efficiency in D. aegyptium was positively correlated with relative growth rates. The reduction in growth resulting from water-deficits was compensated by an increase in the short-term water-use efficiency associated with stomatal closure. In S. gracilis, the long-term water-use efficiency under moderate water-deficits increased but was not positively correlated with relative growth rate; it was associated with a high allocation to non-photosynthetic (support and vascular) tissues. The possible implications of this behaviour for the different ‘strategies’ for plant survival in the arid climate of the Sahel are discussed.
SUMMARY - Because of the climatic characteristics of the Mediterranean Basin, most of the world's water problems can be found in this area. This fact and the future prospects of the Climate Change make it necessary for more efficient forages and grasslands to be used in order to obtain environmental quality benefits. For these reasons, the main objective of this work is to review the ecophysiological strategies of herbaceous species to overcome water deficit under Mediterranean conditions, paying special attention to their ability to survive a summer drought period and to produce biomass under restricted and unpredictable water availability.
Biotechnology for biofuels, 2015
Switchgrass (Panicum virgatum L.) is a warm-season C4 grass that is a target lignocellulosic biofuel species. In many regions, drought stress is one of the major limiting factors for switchgrass growth. The objective of this study was to evaluate the drought tolerance of 49 switchgrass genotypes. The relative drought stress tolerance was determined based on a set of parameters including plant height, leaf length, leaf width, leaf sheath length, leaf relative water content (RWC), electrolyte leakage (EL), photosynthetic rate (Pn), stomatal conductance (g s), transpiration rate (Tr), intercellular CO2 concentration (Ci), and water use efficiency (WUE). SRAP marker analysis determined that the selected 49 switchgrass genotypes represent a diverse genetic pool of switchgrass germplasm. Principal component analysis (PCA) and drought stress indexes (DSI) of each physiological parameter showed significant differences in the drought stress tolerance among the 49 genotypes. Heatmap and PCA d...
Wild Miscanthus Germplasm in a Drought-Affected Area: Physiology and Agronomy Appraisals
Agronomy
Predictions of future climate scenarios indicate that yields from perennial biomass crops (PBCs) growing in the Mediterranean region are likely to decline due to prolonged drought. Among PBCs, Miscanthus grasses with C4 photosynthesis combine high yield potentials and water use efficiencies. However, the standard commercial clone M. x giganteus (Mxg), with minimal stomatal regulation, is too sensitive to drought for reliable yields in the Mediterranean regions. This paper screened a diverse panel of thirteen Miscanthus genotypes (M. sinensis, M. floridulus, M. sacchariflorus and Mxg) to identify which types could maximize yield under summer drought conditions typical in the South Mediterranean climate. In the second growing season, significant differences were observed for plant height (from 63 to 185 cm), stem number (from 12 to 208 stems plant−1), biomass yield (from 0.17 to 6.4 kg DM plant−1) and whole crop water use efficiency (from 0.11 to 7.0 g L−1). Temporal variation in net ...