Effects of invasive Chenopodium ambrosioides L. volatile oil on stomatal movement and signal transduction of Vicia faba L., Arachis hypogaea L. and Pisum sativum L.
We studied the allelopathic stress of C. ambrosioides volatile oil using the epidermal strip bioassay, microscopy and histochemical techniques on stomatal movement in leaves from broad beans (Vicia faba L.), peanuts (Arachis hypogaea L.) and peas (Pisum sativum L.). We also studied the changes in vacuoles, microfilaments and signalling molecules ROS, NO and Ca2+ in guard cells. The stomatal aperture of 3-test legume species decreased significantly (P < 0.05) in volatile oil concentration-dependent manner. Compared with control, the applied volatile oil increased the numbers of vacuoles but decreased their volume in guard cells of all 3-test crops. Aggregation of microfilament skeletons, increased the in ROS, NO and Ca2+ concentrations. These effects could be alleviated, when related inhibitors (Cytochalasin B, AS, LaCl3 and L-NAME) were used with volatile oil. It is speculated that the dynamic changes in guard cell microfilaments caused by volatile oil of C. ambrosioides could lead to increased ROS and NO levels by activating the related enzymes, which increased the cytoplasmic free Ca2+ levels in guard cells. Thereby the ion channels in plasma membrane and vacuolar membrane were affected. The bigger vacuoles in guard cells were divided into smaller ones, turgor pressure was decreased and stomata were closed. The stomatal movement of broad bean was most sensitive to volatile oil of C. ambrosioides, which showed strong allelopathy.