level of drought stress (P0 = fraction of transpirable
soil water (FTSW) 1/control), P1 = FTSW0.5/ mild stress and P2 = FTSW0.25 / severe stress) and level of purple nutsedge interference (T1 = 0 purple nutsedge per pot /control), T1 = three purple nutsedge per pot and T2 = six purple nutsedge per pot).
Response of whole plant water use to soil water availability has often been quantified with respect to fraction of transpirable
The fractions of available and transpirable
soil water have been widely documented (Wahbi and Sinclair, 2007).
The amount of soil water available for transpiration by plants, transpirable
water (TW), at pot capacity was defined as the difference between the pot-capacity weight and the pot weight when daily transpiration for water-deficit plants was [is less than] 10% of the well-watered plants (Ritchie, 1981; Sinclair and Ludlow, 1986).
For example, Sinclair (1986) found that the threshold for an initiation in the decline of [N.sub.2] fixation occurred at a fraction of transpirable
soil water (FTSW) of 0.50 in contrast to a lower threshold of soil water content of about 0.35 for inhibiting transpiration.
soil water (TSW) and average number of days to the end point of the drying cycle for three experiments.