The comparison effect of drought and flooding stress on sweet pepper

Plants are continuously exposed to a variety of stress indices which is affected many aspects of the plant's genetic and bimolecular characteristics. water stress is one of the variables of climate change, which is characterized by a shortage or abundance of water which is affected the growth and development of the plant and causes morphological, physiological, molecular and biochemical changes in the plant. Aquaporin are the main proteins that facilitate the movement of water, CO2, and other small soluble substances through a plasma membrane. The purpose of this study was to investigate the physiological and biochemical changes of pepper (301Ps) and role of Aquaporin. A factorial experiment in a completely randomized design including drought stress in hydroponic culture with polyethylene glycol-6000 in five levels including control, -2, -3, -4, and -5 MPa, and flooding stress in non-oxygen condition.  All treatments applied in shock (2 days) and gradual (10 days). Results showed that proline content increased under drought-gradual, drought and flooding-shock. The phenolic and antioxidant content was gradually increased during the stress. The potassium concentration increased in drought-gradual stress and decreased in flooding- gradual stress. Chlorophyll fluorescence and chlorophyll index decreased in drought stress and flooding. The electrolyte leakage increased in drought and flooding stress. The most negative water potential of the pepper leaf was in flooding-gradual and in root water potential at drought-shock. The relative water content decreased in both drought and flooding stress when applied gradually. Carotenoids increased during shock time. Abscisic acid increased due to stresses and also affected the stomatal condition. In the root of pepper, the expression of PIP1 gene increased in drought-gradual and decreased in flooding stress at both shock and gradual.  Also, in pepper leaf, the expression of PIP1 gene increased in drought and flooding stress in both times. In general, due to changes in electrolyte leakage, water potential, chlorophyll fluorescence, and chlorophyll index, the most damage was observed in shock on the pepper. Also, under the shock time due to the lack of changes in the content of phenol and antioxidants and potassium concentration due to stresses were not observed. Due to increased phenolic, antioxidant, proline, potassium, carotenoid, abscisic acid and PIP1 gene expression in leaf and root, it was resistant to drought-gradual stress.