the response of pearl millet root (pennisetum americanum l.) to drought stress and re-watering

to evaluate the effects of drought stress and re-watering on nodal roots initiation and growth, two glasshouse experiments were conducted in commonwealth scientific and industrial research organization (csiro) in australia during 2008-2009. the experimental designs in both experiments were factorial in a randomized complete block design with two factors. first factor was drought stress and second one was harvest time after re-watering (one day before re-watering and one, three and six after re-watering). drought stress treatments were control (no drought stress) and watering after 40% of control moisture reached (mild stress) and control (no drought stress) and watering after 25% of control moisture reached (severe stress) in the first and second experiment, respectively. in both mild and severe stress treatments, total dry matter (tdm) showed a reduction compared to control. in plants harvested six days after re-watering, tdm decreased by 37 and 52.3% in mild and sever stress, respectively. number, length and dry matter of nodal roots decreased in both drought stress treatments compared to control. the reduction in tdm of nodal roots in mild and sever stress treatments was 34 and 56 % compared to control, respectively. in conclusion, drought stress in any level could limit the initiation and growth of nodal roots and increasing in drought stress severity could delay the required period for recovery of plant.