THE DYNAMICS AND PHYSIOLOGICAL ROLE OF THE SUGARCANE ROOT SYSTEM

Abstract

This study is aimed to understand how root system growth and function influence sugarcane productivity. Sugarcane root systems have been described as comprising highly branched superficial roots, downward-oriented buttress roots and deeply penetrating agglomerations of vertical roots, known as rope roots. Root distribution in sugarcane follows an expected exponential decline with depth, with maximum values for root length density reaching as high as 5 cm/cm3. Maximum root depth could exceed 6 m and there is evidence of root activity below 2 m, supported using 32P as a tracer. The root system is not entirely replaced during ratooning. The below-ground carbon budget is uncertain regarding carbon allocation and energy cost associated with the sugarcane root system. Stomatal and root hydraulic conductance have been found to be correlated in both pot and field-grown sugarcane crops, suggesting a homeostatic regulation of leaf water potential. This indicates that stomatal response to root water status may be mediated by a chemical signal transmitted through the xylem sap, potentially affecting assimilation. The effects of root water status on assimilation should be considered, particularly in situations where the system is subjected to compaction or drought. The extraction of water and nutrients from depth can lead to improved resource utilization and reduced off-site impacts. Advancements in yield through breeding have inadvertently compromised root development and the plant's capacity for water and nutrient uptake. A comparative analysis of old and new cultivars is required to determine if selection programs have led to declining application efficiencies (i.e., uptake per unit of resource applied) for water and nutrients. This study highlights the current knowledge gaps in understanding how root system growth and function influence sugarcane productivity. It underscores the need for further research and the importance of considering root-related factors in sugarcane models and management practices to optimize resource utilization and minimize potential off-site consequences.