Abstract
Paulownia fortunei is an important economic tree species that possesses numerous biological and economic traits, such as fast growth, strong stress resistance, and excellent wood properties. The cultivation of this species is pervasive across numerous regions of China. Epicauta ruficeps, a common pest species of P. fortunei, typically consumes the foliage of its host plant. However, there are currently no reported studies on the physiological and biochemical mechanisms underlying P. fortunei response to E. ruficeps feeding. In this study, we discovered that the enhancement of nitrogen assimilation and porphyrin metabolism directly contributes to the maintenance of the steady state of photosynthetic activity in P. fortunei leaves. Meanwhile, E. ruficeps feeding also leads to an increase in the level of reactive oxygen species (ROS) in P. fortunei leaves. As key signaling molecules, the elevated level of ROS activates the antioxidant system and phenylpropanoid metabolism, which in turn results in increased antioxidant enzyme activity, as well as increased contents of antioxidants and lignin. The aforementioned changes have the potential to reduce the degree of membrane lipid peroxidation and enhance the mechanical strength of leaf tissues. Consequently, this can assist in maintaining the steady state of photosynthesis indirectly. In summary, the present study elucidates the physiological and biochemical mechanisms underlying the maintenance of the steady state of photosynthetic activity in P. fortunei after being feeded by E. ruficeps from multiple dimensions. Simultaneously, it lays a theoretical foundation and provides data support for the subsequent comprehensive analysis of the molecular mechanisms involved in P. fortunei response to E. ruficeps feeding.