Effect of CO2 Elevation on Root Growth and Its Relationship with Indole Acetic Acid and Ethylene in Tomato Seedlings

A hydroponic experiment was carried out to study the effect of elevated carbon dioxide (CO2) on root growth of tomato seedlings. Compared with the control (350 μLL−1), CO2 enrichment (800 μLL−1) significantly increased the dry matter of both shoot and root, the ratio of root to shoot, total root length, root surface area, root diameter, root volume, and root tip numbers, which are important for forming a strong root system. The elevated CO2 treatment also significantly improved root hair development and elongation, thus enhancing nutrient uptake. Increased indole acetic acid concentration in plant tissues and ethylene release in the elevated CO2 treatment might have resulted in root growth enhancement and root hair development and elongation.