The role of nitrogen sources in enhancing drought resilience of tropical tree seedlings

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Vithya Krishnan, Nicole Robinson , Jennifer Firn , John Herbohn , and Susanne Schmidt

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Global temperatures are expected to increase by 1.5°C in the next 20 years from pre-industrial periods due to anthropogenic activities. Rising temperatures induce drought stress and mortality in trees, which is pertinent to restoration efforts as seedlings that are drought resilient have a higher chance of survival in water limited environments. Drought-related studies discount the role of nutrients, particularly nitrogen, in conferring drought survival. When exposed to high quantities of nitrogen, plants increase shoot growth at the expense of root growth and consequently require more water to recoup losses from increased transpiration. Most studies focus on inorganic nitrogen (i.e., ammonium and nitrate) as the main source for plant growth. However, plants can take up organic nitrogen (e.g., amino acids) for growth. The effect of organic nitrogen on the hydraulic properties of plants is unknown. The aim of our study was to determine if organic nitrogen (e.g., arginine) versus inorganic nitrogen confers drought resilience in pioneer Australian rainforest seedlings Acacia mangium and Alphitonia petriei, exposed to drought conditions in the glasshouse. Seedlings were grown from seed in 2L pots containing peat and sand for three months from September 2020. The treatments comprised of two inorganic N sources (Osmocote and ammonium nitrate), and two organic N sources (ArGrow and arginine) with 20 replicates per treatment. In December 2020, drought was induced (45-50% water holding capacity) in 10 replicates per treatment while the rest remained well watered. Pots were weighed and watered daily to maintain water holding capacity. Xylem pressure, total biomass, specific leaf area, root volume, and stem density to be determined and analysed in late January 2021.

Resource Type:
Conference Presentation, SER2021

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