Aeroponics to monitor root growth of longan trees

Abstract

Towards a holistic understanding of the plant-soil-air continuum, the root systems of fruit trees are still under researched. Knowledge about the roots' growth and functioning is essential for an understanding of the tree as a whole. In modern Thai longan-farming, flower induction by potassium chlorate is a common practice. Many studies on the effects of this substance on flowering shoot physiology, soil, environment and other issues have been carried out. However, a study of the direct effect of potassium chlorate on the root system of the plant has not yet been reported. Most methods to monitor root-growth are not appropriate for this special case, as the potential damage induced by potassium chlorate is localized due to the application technique. Thus, the tree survives at concentrations, that otherwise would be lethal. In this study two young longan trees have been cultivated as aeroponics. This is a system, where the root grows in the air in a dark container. Water and nutrients are applied to the root by a fogging technique. For observation/measuring purposes, the root can be brought to light for a limited period. The trees adapted well to this form of nutrition and developed a sound root system. Subsequently, flowering and flushing were observed. Potassium chlorate was applied to the roots in a similar concentration as it would be used in the field for flower induction to subsequently isolated parts of the root system. The detrimental effect on root growth could be visualized. Subsequent recovery of the root system started right after the substance was withdrawn from the root system.