HYDRAULIC CONDUCTIVITY OF COTTON ROOTS AS INFLUENCED BY PLANT-AGE AND ROOTING MEDIUM

Models of water extraction by plant root systems often contain the basic assumption that hydraulic conductivity of the root system is a constant value. An experiment was conducted to determine if plant age or rooting medium environmental conditions affected hydraulic conductivity of cotton (Gossypium hirsutum L.) roots. Hydraulic conductivity was measured by the pressure outflow method at 12, 24, 36, and 48 d after planting (DAP) on roots grown in both hydroponics and sand. Hydraulic conductivity decreased 45% in nutrient-solution-grown and 57% in sand-grown roots from 12 DAP to the mean of 24, 36, and 48 DAP. Hydraulic conductivity of sand-grown roots was 4 to 10 times lower than that for roots grown hydroponically, whether conductivity was compared at equal DAP or at equal root length.