Effects of physical stresses on radish seed germination and growth

Abstract

In this work we explore the consequences on variable magnetic fields applied to radish seeds (Raphanus sativum L.) on germination and seedling growth. Three, different alternate magnetic fields have been tested having a high intensity, 40 mT, at very low frequency, 0.2 Hz (B0.2), a low intensity, 577 µT, at low frequency, 370 kHz (B370), and a very low intensity, about 250 nT, at ultra high frequency, 900 MHz (RF900). These last generate electromagnetic waves which are nowadays very used for mobile communications. Groups of uniform radish seeds were exposed to alternate magnetic fields at three duration time values: i) 120 h (BO.2/1), 260 h (B0.2/2) and 360 h (B0.2/3) at high intensity and very low frequency, 0.2 Hz; ii) 120 h (B370/1), 260 h (B370/2), 360 h (B370/3) at low intensity and low frequency, 370 kHz; iii) 120 h (RF/1), 260 h (RF/2), 360 h (RF/3) at very low intensity and ultra high frequency, 900 MHz. Furthermore, another group of seeds was treated by laser beams of 248 nm wavelength whose magnetic field is coupled to an electric field. These two fields, by the Planck theory, origin the quantum energy, expresses by photons. Therefore, in the laser-matter interaction photons are absorbed dependent on laser shots. Again, we performed experiments at three duration time values that applied: 30 kshots (KrF/1), 80 kshots (KrF/2) and 135 kshots (KrF/3) at 40 mJcm2/ fluence. The magnetic field and electric field presented by the laser beam are approximatively 250 kVm/ and 850 µT, respectively. All treatments were performed at room temperature. Both untreated seeds and each group of seeds exposed to the physical stresses were transferred in Petri dishes and followed for their germination and seedling growth up to 96 h. The results showed that all physical stresses induced by alternate magnetic fields, radiofrequency and laser radiations did not have effect on seed germination as well as on cell elongation growth of the radish hypocotyls in comparison to control seeds. On the contrary, all physical stresses showed a significate stimulation on root growth.