Oil palm crops are the most important determinant of the agricultural economy within the segment of oilseed crops. Oil palm growing in their natural habitats are often challenged simultaneously by multiple stress factors, both abiotic and biotic that limit crop productivity and are major constraints to meeting global food demands. The stress-tolerant oil palm crops that mitigate the effects of abiotic stresses on crop productivity are crucially needed to sustain agricultural production. Basal stem rot threatens the development of the industry, and the key to solving the problem is to breed new oil palm varieties resistant to adversity. This has created a need for genetic improvement which involves evaluation of germplasm, pest and disease resistance, earliness and shattering resistance, quality of oil, varieties for different climatic conditions, etc. In recent years, insights into physiology, molecular biology, and genetics have significantly enhanced our understanding of oil palm response towards such stimuli as well as the reason for varietal diversity in tolerance. In this review, we explore the research progress, existing problems, and prospects of oil palm stress resistance-based physiological mechanisms of stress tolerance as well as the genes and metabolic pathways that regulate stress response.

Nitrogen addition can alter soil microbial communities and regulate nitrogen cycling processes. However, the role of nitrogen-induced soil acidification in modulating nitrogen cycling in macadamia orchard soils remains poorly understood. Based on a 3-year field fertilization experiment, this study established three treatments: no-nitrogen (N0), medium-nitrogen (N1), and high-nitrogen (N2). We systematically investigate the effects of nitrogen addition on soil chemical properties, the abundance of nitrogen cycling genes, enzyme activities, microbial community structure, and co-occurrence networks. The results showed that nitrogen addition significantly increased the contents of alkaline hydrolyzable nitrogen (AHN) and nitrate nitrogen (NO ₃ ^– -N), altered soil stoichiometric ratios, and exacerbated soil acidification. Quantitative PCR (qPCR) analysis revealed that nitrogen addition significantly decreased the abundance of nitrification genes (AOA- amoA ), ammonification gene ( ureC ), and denitrification genes ( narG , nirK , nosZ ), while no significant changes were observed for AOB- amoA or nirS . 16S rRNA gene sequencing demonstrated that nitrogen addition altered the succession of microbial communities towards a copiotrophic (R-strategy) state and altered the predicted carbon-metabolism functional profiles. Co-occurrence network analysis showed that the N2 treatment reduced network complexity but enhanced modularity, suggesting that microbial communities may respond to nitrogen addition through functional modular reorganization. The asynchronous changes between key enzyme activities and their corresponding gene abundances revealed the complex regulatory mechanisms of the nitrogen cycle. Furthermore, correlation analyses identified pH, electrical conductivity (EC), and NO ₃ ^– -N were important environmental factors affecting nitrogen cycle function gene groups. These findings provide new insights into the response mechanisms of the nitrogen cycle in the soil ecosystem of Macadamia orchards.