Changes in the Root Architecture of Oil Palm Seedlings in Response to Nitrogen Starvation

Oil palm (Elaeis guineensis) is a widely cultivated crop known for its high oil yield. It is cultivated extensively across tropical regions, notably in Southeast Asia, Africa, and Latin America. It plays a vital role in global vegetable oil supply, meeting approximately 35% of the world’s demand. However, the expansion of oil palm plantations often involves the utilization of degraded soils where nutrient availability, particularly nitrogen, is limited, posing challenges to plant growth and productivity. Roots are crucial in responding to nitrogen deficiency by adjusting their growth and distribution; however, research on root system distribution patterns in oil palm still needs to be completed. This study analyzes the root system architecture using RhizoVision Explorer, a 2D root image processing software while assessing its relationship with nitrogen availability across two commercial cultivars: Deli × La Mé of African oil palm (Elaeis guineensis) and the interspecific hybrid O×G Coari × La Mé. Our findings reveal significant associations between eight root traits in oil palm seedlings and treatments with and without nitrogen availability. Notably, total root morphology (length, surface area, and volume), rotation angle, solidity, and hole characteristics decreased under nitrogen deprivation, whereas surface angle frequency increased. We highlight the variability of these traits across cultivars, suggesting genetic dependence and potential utility in breeding programs. Moreover, interactions observed in primary root morphology and hole size indicate greater differences between control and nitrogen-treated groups in C × LM than in D × LM cultivars. On the other hand, cultivar differences, regardless of nitrogen availability, influenced lateral root morphology, while nitrogen availability, irrespective of cultivar, affected inclined angle frequency. Significant differences were observed in growth and development parameters such as root and shoot biomass, root-to-shoot ratio, and leaf emission numbers between nitrogen-optimal and nitrogen-starved conditions. Nitrogen significantly affects root architecture and plant growth in oil palm, particularly in the C × LM cultivar during the nursery stage.