Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Effect of Water Restriction and Supplementary Nitrogen on the Growth Dynamics of Bromus valdivianus Phil(MDPI (Basel, Switzerland), 2025-09) López IF; Rodríguez A; Cartmill AD; Dörner J; Calvache I; Balocchi O; Sanders D; Liu YDecreasing summer precipitation is negatively affecting global productivity of grassland plant species. This study evaluated the effect of three levels of soil plant available water [80–90% PAW-H (high), 50–60% PAW-M (medium), and 20–30% PAW-L (low), which were soil water restriction (SWR) equivalent to (v/v%) 10–20%, 40–50%, and 70–80%, respectively] and nitrogen (N 0 and 110 kg ha−1) on growth and nutritional quality of Bromus valdivianus Phil. (Bv) mini-swards (MS; 125 L containers), arranged in three blocks. Total lamina length (TLL), leaf expansion rate (LER; cm d−1), phyllochron (Phy) expressed as “days” and “°C day”, tiller mass (TM, g tiller−1), number of live leaves (NLL), number of dead leaves (NDL), and accumulated herbage mass [AHM, g DM (dry mass) m2] were measured. Defoliation events, leaving 5 cm residual height, were carried out every 320 GDD (using a base growth temperature of 5 °C), and foliage samples for nutritive quality [DM, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), water-soluble carbohydrates (WSC), and metabolic energy (ME)] were collected. Reducing PAW to 20–30% decreased the AHM by 60.7%, TLL by 52.7%, LER by 50%, and TM by 50%, with significant interaction between the main effects for AHM, TLL, and LER. The addition of N increased the AHM by 31.6%, LER by 21.6%, and TLL by 19.6%. The Phy remained undisturbed by decreasing PAW and increasing the N rate. Nutritive quality was generally not statistically different for the interaction or between N levels. However, low PAW levels resulted in statistically (p < 0.05) lower ME and higher concentrations of NDF. In general, growth, AHM, and nutritional quality of Bv during the summer period were driven by PAW levels and by the availability of N. Plant available water levels of 50% to 60% at 20 cm soil depth, with the addition of N, allowed Bv to reach its highest production.Item Belowground Structural Attributes and Morpho-Anatomical Response Strategies of Bromus valdivianus Phil and Lolium perenne L to Soil Water Restriction(MDPI (Basel, Switzerland), 2025-05) Zhang Y; García-Favre J; Hu H; López IF; Ordóñez IP; Cartmill AD; Symonds V; Kemp PD; Vergine MThe effect of soil water restriction on the root structure and morpho-anatomical attributes of Lolium perenne L. (Lp) and Bromus valdivianus Phil. (Bv) was investigated. The anatomical structure of roots from plants grown under two water restriction conditions (20–25% and 80–85% field capacity (FC)) were assessed using paraffin embedding and thin sections. These sections were examined to assess anatomical traits, including root diameter (root D), stele diameter (stele D) and cortex thickness (cortex T), and xylem vessel of Lp and Bv roots. Tiller population, shoot herbage mass, and the shoot-to-root ratio were also determined. Under water restriction, biomass and tillers were significantly decreased (p < 0.001), while the root-to-shoot ratio significantly increased, indicating a higher proportion of Bv roots than shoots when compared to Lp. The root D and stele D, and cortex T, were larger in Bv than in Lp (p < 0.001), indicating a greater adaptation of Bv for water uptake and storage compared to Lp. Xylem vessels were wider in Lp when compared to Bv (p < 0.01), indicating greater water flow within the plant. Water restriction generated a decrease in root D, stele D, and cortex T (p < 0.01). Canonical variate analysis showed that the pith cell wall had a strong positive relationship with water restriction in both Bv and Lp; lignified xylem and the endodermis wall had a close relationship with Lp under water restriction. The findings demonstrate that Lp and Bv have individual structural and morpho-anatomical response strategies to increasing water restriction.Item 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 PDBromus 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.