Abstract

Abbreviation

The physiological and biochemical responses of pigweed under artificially simulated drought stresses were examined to provide a theoretical basis for medicinal plant cultivation and effectively increasing agricultural production in arid areas in this study. The results showed that the relative water content in leaves of the control, mild-stressed, moderately-stressed and severely-stressed plants were 94.07, 87.01, 76.35 and 64.03%, respectively. Under moderate drought stress, the relative water content (RWC) and free water content (FWC) in leaves were decreased, while the bound water content (BWC) was increased. The activities of superoxide dismutase (SOD) and peoxidase (POD) in leaves reached the highest level among the four treatments. Membrane permeability, malondialdehyde (MDA) content and the O₂  production rate in leaves declined, whereas, soluble sugars, proline, K⁺and Ca²⁺ in leaves accumulated rapidly, indicating that pigweed has the ability to adapt to drought stress by regulating the internal osmolarity and protecting the membrane. Under severe drought stress, however, the O₂ production rate and the MDA content increased remarkably, causing membrane damage and increasing membrane permeability of leaf cells. The activities of SOD and POD were initially increased as compared to those under the moderate drought stress and then declined; ascorbic acid (ASA) content was also decreased. These results suggest that severe drought stress could cause some damage on the pigweed.

Key words: Pigweed, drought stress, osmoregulatory molecules, membrane lipid peroxidation, protective enzyme.