Purpose To study the effects of polyethylene glycol (PEG) simulation of drought stress on the growth and physiological conditions of cassava.
Methods Cassava NZ199 was used asthe experimental material, and its root was immersed in PEG solutions with mass fraction of 0%, 5%, 10%, 15%, and 20% for a nine-day simulated drought stress experiment. Its growth, photosynthesis and physiological indexes were measured on the 3rd, 6th and 9th day, respectively.
Results With the increase of PEG mass fraction, the growth indexes of NZ199 showed a trend of increasing and then decreasing in the same period. The net photosynthetic rate, stomatal conductance and transpiration rate showed the promotion by low mass fraction and inhibition by high mass fraction, which was the highest in 10% PEG treatment at the early stage of the treatment (≤3 d), and 5% PEG treatment at the late stage (≥6 d). The soluble protein content showed a trend of increasing and then decreasing, and the highest content was found in 10% PEG treatment for the 6th and 9th day. The proline content of 15% and 20% PEG treatments was significantly higher than other treatments. The peroxidase activity showed a tendency of increasing and then decreasing, and was highest at the 6th day of 10% PEG treatment. The catalase activity gradually increased, and was highest at the 9th day of 20% PEG treatment. The malondialdehyde content gradually increased, and was highest at the 9th day of 20% PEG treatment, indicating that the stress level was the highest.
Conclusion At the seedling stage of NZ199, PEG simulated drought stress with appropriate mass fraction and duration can promote photosynthesis and facilitate assimilate accumulation in plants, but excessively high mass fraction will have a reverse effect on plants, showing that leaf photosynthesis decreases, and proline content, catalase activity and malondialdehyde content increase, that is, stress is caused to their growth physiology and stress resistance is weakened.
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