Application of infrared-pulsed laser radiation with wavelength L=904nm to stimulate the growth of wheat seeds

Recently microwaves and laser radiation have been applied to activate the growth processes of biological systems. Sae Shimizu-Sato et al. developed a gene promoter system that can be activated using short pulses of red light and can be deactivated using short pulses of infrared light, but the properties of the light and the pulses to activate the system were not specified. From previous publications it is possible to observe that the wavelength, the intensity and the exposition time are the most important parameters to produce activation of biological systems. The present work used an infrared-pulsed laser diode with wavelength λ=904nm and peak power of 6W to investigate the activation or deactivation of wheat seeds. The pulse repetition rate used for this laser was 1500Hz with pulse duration of 200ns. Wheat seeds were supplied by the National Institute of Forest, Agriculture and Livestock researches of Mexico (INIFAP). Wheat variety was Nahuatl F2000, developed by the institute above mentioned and the International Maize and Wheat Improvement Center (CIMMYT). To investigate the effects of laser radiation on wheat seeds, the stem length and the root length of wheat seedlings were measured. Wheat seeds were irradiated with one of the three intensities: 0.9mW/cm2, 1.8mW/cm2 and 3.6mW/cm2 for five different exposition times: 15s, 30s, 60s, 120s and 240s. For each laser treatment 400 wheat seeds divided into groups of 25 seeds according to the International Seed Testing Association (ISTA 2009) were used. The same quantity of non-radiated seeds was used as a control. The growth tests were carried out under laboratory conditions and according to guidelines issued by the International Seed Testing Association (ISTA 2009). The growth data were analyzed using the ANOVA test to detect differences between average values. Average values were compared using Tukey test (multiple comparisons) to detect differences between control and treated seedlings.