Photoacoustic Technique in the Study of Photosynthesis in Aquatic Lirium (Eichhornia Crassipes)
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Photoacoustic Technique in the Study of Photosynthesis in Aquatic Lirium (Eichhornia Crassipes) A. Calderón1*, A. Cardona1, G. Juárez Gracia1, E. Marín1 and Cesar Mora1 1
Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Av. Legaria # 694 Col. Irrigación, C.P. 11500, México D.F. México
ABSTRACT We report, for the first time, the application of the photoacoustic spectroscopy for monitoring the optical absorption spectra in aquatic lirium (Eichhornia Crassipes), before and after it was exposed to ultrasonic irradiations. We obtained a decrease in the amplitude of the bands of the chlorophylls a and b for the irradiated samples with ultrasound of 17 kHz and 1.5 mW/cm2 of power density, and therefore, damage in the centers producing the photosynthesis, due to the irradiation. These results show the utility of the ultrasonic irradiation, as well as, of the photosynthesis monitoring by means of the photoacoustic technique, for the elaboration and establishment of methodologies in the control of this aquatic plant, whose propagation causes many consequences extremely unfavorable for the environment, as well as for the diverse human activities that are developed in the bodies of water in the tropical and sub-tropical regions of the world. INTRODUCTION Aquatic lyrium or water hyacinth, is a free float plant native of the Amazon, Brazil, which by the beauty of its flowers has been propagated to almost all the tropical and sub-tropical regions of the world. This plant is a weed that causes many consequences extremely unfavorable for the environment and for the diverse human activities that are developed in the bodies of water [1,2]. Among the most used methods to control water hyacinth there are the herbicides, physical removal or drainage, and biological control, none of which has been entirely efficient or profitable [3,4]. Therefore, it is important to develop better methods for the control of this weed, technically effective, economically viable and environmentally friendly [5]. It is for these reasons that arises the need to incorporate other new technologies of control, being in this case the use of ultrasonic irradiations with certain values of frequency and intensity, in order to induce cavitation in the aqueous structure of the Aquatic Lirium, and consequently, to inhibit their photosynthetic activity, causing its death. When a powerful ultrasound (16 to 100 kHz) is applied to a liquid with enough intensity (more than 75 mW/cm2), the liquid undergoes compression and expansion alternately, forming bubbles that may contain steam from the more volatile components of liquid or gas dissolved in it. These bubbles have a very short lifetime and when they collapse the so-called "hot spots" of high temperature and pressure appear which produces energy that causes damage on the surfaces [6,7].
The leaves of aquatic plants are systems particularly useful for studying the effects of bubbles trapped within their structures. For this reason, in this work it was used the time reso
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