Effect of Phytohormones, Phosphorus and Potassium on Cotton Varieties (Gossypium hirsutum) Root Growth and Root Activity Grown in Hydroponic Nutrient Solution

Modern agriculture using hydroponics allows in-depth study of root morphology and physiology. Two experiments were conducted to evaluate effectiveness of mineral nutrients, phosphorus (P) and potassium (K) and phytohormones, indole-3-acetic acid (IAA), gibberellic acid, (GA3 ) and zeatin ( Z) on cotton plant varieties root area, root volume and root activity. During the first cropping, Low P, low K and high PK treated plants significantly influenced total root absorption area, active absorption area, percentage active absorption area ratio, specific surface area and root volume. Furthermore, treatments applied did not favour root activity at the early growth stage but effects were known as from 104 to 148 days after transplanting. During the second experiment, however, cotton plants treated with hormones significantly affected active absorption area, percentage active absorption area ratio, root volume, specific surface area and root activity at 80 and 90 days after transplanting. In general, there was no relationship between the first cropping without hormones application and second cropping with hormones application except percentage active absorption area ratio (-0.999*) which was negatively correlated. This report shows effect of mineral nutrients and stimulatory tendency of hormones in root growth regardless of different cropping time between first and second cropping.