Morphological and physiological differences between aeroponically and hydroponically grown sunflower plants

The effects of aeroponic (AP) and hydroponic (HP) conditions on growth rate, morphological traits, potassium uptake and redox activities were compared in sunflower seedlings. Higher growth rate was found under HP than AP conditions and morphological traits were also different. The thickness of AP grown roots increased and new lateral roots with thickened root hairs were formed while the length of AP roots was small. Microscopical studies on cross-sections of the embedded root segments showed that the diameter of cross-section, the diameter of stele and the width of cortex of AP grown roots were significantly higher than those of HP plants. The element composition of AP or HP grown plants also differed, due to the different ion uptake processes. Potassium (86Rb+) uptake of AP grown plants was low and it seemed to be a passive process, while in case of HP grown plants it was decreased by both dinitrophenol and ferricyanide suggesting that the uptake process was coupled to the proton gradient. Roots of AP grown plants showed high ferricyanide reductase activity and it was accompanied by an increased acidification of the medium.