DAY 1Wednesday, 13 November 2024

Crop plants are often exposed to environmental stress conditions which poses a serious threat to food security and sustainable development. Expected increases in atmospheric CO₂ and air temperature will further aggravate the detrimental impacts of the stress conditions on crop production. A strong body of evidence shows that balanced mineral nutrition is highly effective in mitigating the adverse effects of environmental stress conditions on crop productivity, especially in case of drought stress, extreme temperatures, excess light, aluminium toxicity and diseases. Optimal mineral nutrition is essential to support a range of physiological functions which enable plant adaptation to changing environment and to maintain yield under stressful environments. This presentation will highlight examples of the effect of plant nutrition on plant adaptation to stress with a focus on the role of nutrient elements in cell wall and membrane stability, the production of bioactive and antioxidative compounds, stomatal regulation, stress-signalling mechanisms, carbon allocation, and rhizosphere microbiome. This presentation will also discuss how an understanding of plant mineral nutrition is critical for the effective use of biostimulants in cropping systems.

Seaweed (ascophyllan nodosum) extracts (SWE) are widely used for active components in plant biostimulant products. The foliar application of SWE has been shown to improve plant tolerance to various abiotic and biotic stresses such as drought, heat, and cold temperature. The beneficial effects of SWE on plant stress tolerance have mainly been attributed to its hormone (especially cytokinin and auxin) components. By using bioassays and GC-MS/MS, the hormonal activity of SWE has been analyzed. Studies were carried out to prove the role of hormonal activity is an important factor responsible for the positive effects of SWE for improving abiotic stress tolerance by using bioassay and GC-MS/MS analysis of hormones in the SWEs. Physiological and metabolic analysis showed that SWE could improve plant stress tolerance by multiple regulatory pathways, including relating hormonal balance, enhancing antioxidant defense, and osmotic adjustment, protecting photosynthetic function, and improving root growth and viability. Recent research also showed that SWE could regulate nitrate reductase activity, plant antioxidant and hormone-related gene expressions. The SWE application in interaction with other biostimulants for enhancing plant abiotic stress tolerance will also be presented.

To satisfy global food markets with continuous supply of fruits and vegetable crops during the whole season, growers in arid and semi-arid regions have increased the use of salinized water in irrigation regimes1. While plant biostimulants have been reported to be an effective solution to tackle salinity stress in different crops, the key genes and metabolic pathways involved in these tolerance processes remain unclear2-4. This study focused on integrating phenotypic, physiological, biochemical and transcriptome data obtained from different tissues of tomato plants (cv. Micro-Tom) subjected to a saline irrigation water program for 61 days (EC: 5.8 dS/m) and treated with a protein hydrolysate and Ascophyllum nodosum-derived biostimulant. The biostimulant application was associated with the overexpression of transporter genes related to ion homeostasis (e.g., HKT1;2), restricting Na+ translocation from roots to leaves and promoting K+ accumulation in roots. It allowed the maintenance of higher K+/Na+ ratios in both leaf and root tissue. A more efficient osmotic adjustment was characterized by a significant increase in RWC, which was associated with osmolyte accumulation and upregulation of genes related to aquaporins (e.g., PIP2.1). Higher content of photosynthetic pigments, increased expression of genes involved in photosynthetic efficiency and chlorophyll biosynthesis (e.g., LHC) and enhanced primary C and N metabolic mechanisms were also observed, leading to higher fruit yield and fruit number (47.5% and 32.5%, respectively). Overall, it can be concluded that this novel biostimulant can provide long-term protective effects on salinity stressed tomato plants through a well-defined mode of action in different plant tissues.