Browsing by Author "García-Favre J"

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    18O isotopic labelling and soil water content fluctuations validate the hydraulic lift phenomena for C3 grass species in drought conditions
    (Elsevier B.V., 2024-02-29) Oliveira BA; López IF; Cranston LM; Kemp PD; Donaghy DJ; Dörner J; López-Villalobos N; García-Favre J; Ordóñez IP; Van Hale R
    Hydraulic lift is a functional characteristic observed in some plant species, often associated with their ability to withstand drought conditions. It involves capturing water from deep soil layers and redistributing it to shallower soil layers through the plant's roots. Bromus valdivianus Phil., Dactylis glomerata L., and Lolium perenne L. may perform hydraulic lift at varying rates. Using both direct (isotopic labelling - δ18O) and indirect (soil water content sensors) techniques, the study assessed and validated the hydraulic lift under extreme drought conditions on the soil top layer (below permanent wilting point), maintaining the bottom layer at high (20–25% filed capacity [FC]) and low (80–85% FC) levels of soil water restriction. Above- and below-ground biomass growth and morpho-physiological responses were evaluated. All species displayed some degree of hydraulic lift, with significant differences observed in the isotopic analysis and soil water content (p > 0.05). This illustrates that water was redistributed from the deep to shallower soil layer and validates that the hydraulic lift phenomenon is occurring in these C3 grasses. Bromus valdivianus presented the highest δ18O values (25.05‰) and highest increases in soil water content (µ=0.00626 m3 m−3; five events). Bromus valdivianus had a dry matter ratio of approximately 4:1 (0–20cm:20–40 cm). In contrast, L. perenne and D. glomerata had approximately 6:1 and 5:1, respectively. This difference in root morphology may explain the higher rate of hydraulic lift observed in B. valdivianus relative to L. perenne and D. glomerata. This paper validates the occurrence and provides initial insights into the hydraulic lift process occurrence of temperature grass species.
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    Aboveground Structural Attributes and Morpho-Anatomical Response Strategies of Bromus valdivianus Phil. and Lolium perenne L. to Severe Soil Water Restriction
    (MDPI (Basel, Switzerland), 2023-12-01) Zhang Y; García-Favre J; Hu H; López IF; Ordóñez IP; Cartmill AD; Kemp PD; Głab T
    Grass species have a range of strategies to tolerate soil water restriction, which are linked to the environmental conditions at their site of origin. Climate change enhances the relevance of the functional role of anatomical attributes and their contribution as water stress tolerance factors. Morpho-anatomical traits and adjustments that contribute to drought resistance in Lolium perenne L. (Lp) and Bromus valdivianus Phil. (Bv), a temperate humid grass species, were analysed. The structure of the leaves and pseudostems (stems only in Lp) grown at 20–25% field capacity (FC) (water restriction) and 80–85% FC (control) were evaluated by making paraffin sections. In both species, water restriction reduced the thickness of the leaves and pseudostems, along with the size of the vasculature. Bv had long and dense leaf hairs, small and numerous stomata, and other significant adaptive traits under water stress, including thicker pseudostems (p ≤ 0.001), a greatly thickened bundle sheath wall (p ≤ 0.001) in the pseudostem to ensure water flow, and a thickened cuticle covering on leaf surfaces (p ≤ 0.01) to avoid water loss. Lp vascular bundles developed throughout the stem, and under water restriction the xylem vessel walls were strengthened and lignified. Lp leaves had individual traits of a ribbed/corrugated-shaped upper surface, and the stomata were positioned to maintain relative humidity outside the leaf surface. Water restriction significantly changed the bulliform cell depth in Lp (p ≤ 0.05) that contributed to water loss reduction via the curling leaf blade. This study demonstrated that the two grass species, through different morphological traits, were able to adjust their individual tissues and cells in aboveground parts to reach similar physiological functions to reduce water loss with increased water restriction. These attributes explain how both species enhance persistence and resilience under soil water restriction.
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    Decreasing Defoliation Frequency Enhances Bromus valdivianus Phil. Growth under Low Soil Water Levels and Interspecific Competition
    (MDPI (Basel, Switzerland), 2021-07-01) García-Favre J; Zhang Y; López IF; Donaghy DJ; Cranston LM; Kemp PD
    Bromus valdivianus Phil. (Bv) is a water stress-tolerant species, but its competitiveness in a diverse pasture may depend on defoliation management and soil moisture levels. This glasshouse study examined the effect of three defoliation frequencies, based on accumulated growing degree days (AGDD) (250, 500, and 1000 AGDD), and two soil water levels (80–85% of field capacity (FC) and 20–25% FC) on Bv growth as monoculture and as a mixture with Lolium perenne L. (Lp). The treatments were applied in a completely randomised block design with four blocks. The above-ground biomass of Bv was lower in the mixture than in the monoculture (p ≤ 0.001). The Bv plants in the mixture defoliated more infrequently (1000 AGDD) showed an increase in root biomass under 20–25% FC compared to 80–85% FC, with no differences measured between soil water levels in the monoculture. Total root length was highest in the mixture with the combination of infrequent defoliation and 20–25% FC. Conversely, frequent defoliation treatments resulted in reduced water-soluble carbohydrate reserves in the tiller bases of plants (p ≤ 0.001), as they allocated assimilates mainly to foliage growth. These results provide evidence that B. valdivianus can increase its competitiveness relative to Lp through the enhancement of the root growth and the energy reserve in the tiller base under drought conditions and infrequent defoliation in a mixture.
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    Pasture brome and perennial ryegrass characteristics that influence ewe lamb dietary preference during different seasons and periods of the day
    (Elsevier BV on behalf of the Animal Consortium, 2023-07) García-Favre J; Cranston LM; López IF; Poli CHEC; Donaghy DJ; Caram N; Kemp PD
    Under the current scenario for climate change, Bromus valdivianus Phil. (Bv), a drought-resistant species, is an option to complement Lolium perenne L. (Lp) in temperate pastures. However, little is known about animal preference for Bv. A randomised complete block design was used to study ewe lamb's preference between Lp and Bv during morning and afternoon grazing sessions in winter, spring, and summer by assessing the animal behaviour and pasture morphological and chemical attributes. Ewe lambs showed a higher preference for Lp in the afternoon in winter (P < 0.05) and summer (P < 0.01), while no differences were found in spring (P > 0.05). In winter, Bv, relative to Lp, had both greater ADF and NDF (P < 0.001), and lower pasture height (P < 0.01) which negatively affected its preference. The lack of differences in spring were due to an increase in ADF concentration in Lp. In summer, ewe lambs showed the typical daily preference pattern, selecting Lp in the morning to ensure a greater quality and showing no preference during the afternoon to fill the rumen with higher fibre content. In addition, greater sheath weight per tiller in Bv could make it less desirable, as the decrease in bite rate in the species was likely due to a higher shear strength and lower pasture sward mass per bite which increased foraging time. These results provided evidence on how Bv characteristics influence ewe lamb's preference; but more research is needed on how this will affect preference for Lp and Bv in a mixed pasture