Department of Plant Sciences

We investigated the effects of Fe nutrition on the stomatal behaviour and water relations of peach leaves (Prunus persica (L.) Batsch, cv. Miraflores), under field conditions. Transpiration rates, net photosynthesis and water use efficiency were significantly lower in chlorotic leaves than in healthy green leaves. In the course of the day, the water potentials in healthy leaves strongly declined to –2.0 MPa, whereas in chlorotic leaves the minimum water potential was only -1.0 MPa. The hydraulic conductivity of the supplying xylem system was found to be significantly lower in chlorotic leaves than in green leaves. Chlorotic leaves were found to experience a significant transient opening of stomata after leaf abscission (Iwanoff effect), which was ascribed to the morphological changes found in epidermal and guard cells. In contrast, after leaf abscission stomata from green leaves gradually closed and were found not to be Iwanoff-reponsible. In healthy leaves, exposure of previously darkened leaves to high irradiation or withdrawal of CO2 induced a rapid increase of stomatal conductance, whereas stomata of chlorotic leaves did hardly react. These results show that in peach leaves Fe deficiency causes a broad range of physiological effects, which include, in addition to the well-documented reduction in photosynthetic performance, disturbances of plant water relations and the functionality of stomata.