ABSTRACT
Portulaca oleracea grows in arid and semi-arid regions and is an important vegetable food and medicinal plant. Drought stress inhibits the growth of P. oleracea leaves and stems, and prolonged stress results in a reduced chlorophyll content affecting photosynthesis. P. oleracea actively closes stomata to reduce water loss and to maintain adequate biomass yield in response to drought stress. The plant regulates osmotic balance by synthesizing organic osmotic regulators, including proline, soluble sugars, polyols, urea and glycerol, etc., which regulate cellular osmotic balance in a “long-acting” manner. To cope with the damage caused by oxidative stress, non-enzymatic antioxidants such as flavonoids, betaine and phenolics are synthesized and the activity of superoxide dismutase (SOD) and peroxidase (POD) shows an increase to regulate the content of reactive oxygen species (ROS). Also, the application of exogenous plant growth regulators, including salicylic acid, improves the drought tolerance of P. oleracea. Based on physiology, transcriptomics and metabolomics, the physiological and molecular mechanisms of C4/CAM pathways have been studied. P. oleracea was revealed to have strong environmental adaptability and plasticity, and it has become an important drought-tolerant plant research model, that is gaining attention currently.
