Plants constantly interact with environment, mainly, by means of photosynthesis and soil nutrition. The state of plant photosynthetic apparatus that reflects the general physiological state of a plant, can be analyzed remotely on a basis of laser-induced fluorescence using a fluorescence lidar. In this respect, a fluorescence lidar can be a technical means of remote sensing of the effects on vegetation including chemical soil pollution. Among a series of applications, of interest is development of a lidar technique for detecting the effects of oil products and mechanical disturbances. This paper is devoted to the application of the fluorescence lidar technique to monitoring mechanical and chemical impacts on the woody vegetation typical of Siberia. A physical basis of this technique is the red fluorescence of chlorophyll of green plants excited by the second harmonic (532 nm) of Nd:YAG laser. Red fluorescence of plants consists of two bands centered at 685 and 740 nm which is conditioned by functioning of two photosystems. As in situ experiments show, the indicated photosystems and, respectively, the fluorescence on these bands respond differently to feeding disturbances and mechanical impacts, making the increase in the fluorescence intensity informative. Time criteria of fluorescence characteristics were obtained at single and multiple effects on the vegetation. The paper describes a lidar system that meets the requirements for detecting the effects on vegetation.
The paper describes the fluorescent lidar created for monitoring of the atmosphere and for estimating the content of fluorescent components of organic aerosol. The lidar operation is based on the use of ultraviolet radiation of harmonics of Nd:YAG solid state laser for exciting the atmospheric fluorescence and the spectral analysis of the atmospheric fluorescence is used in the near ultraviolet and blue spectral range with the resolution of 2 nm. The lidar was found to be efficient for remote analysis of organic aerosol occurring as a result of vegetation emission of secondary metabolites to the atmosphere. Fluorescence spectra processing allows us to select some organic compounds, which molecules contain 7 and more carbon atoms.
Taking into account the availability of interconnection between organic aerosol and vegetation, in lidar the second harmonic of Nd:YAG laser is also used for exciting the fluorescence of vegetation covers. In this case the receiving system detects the fluorescence of vegetation in the red spectral range conditioned by the chlorophyll of vegetation. Simultaneous detection of the fluorescence from the atmosphere and from vegetation makes it possible to obtain data on the interaction of the atmosphere and underlying surface covered by vegetation. It has been found that a disruption in the vegetation feeding or the impact of pollutions on vegetation resulted in a sharp increase of the fluorescence intensity of vegetation chlorophyll in the red spectral range and in the simultaneous appearance of organic aerosol in the atmosphere adjacent to vegetation in the region of negative impact.
As a result of the accomplish experiments determine, that by a method of a laser-induced fluorescence of chlorophyll it is possible to spot for cedar an early stage of the stressful factor, bound with presence in ground ≪petroleum dirt≫. In our case the laboratory researches provided learning a quantitative contents chlorophyll for plants found in normal and stressful conditions on a basis spectrophotometrical of a method. Natural measurement the observations behind dynamics of a photosynthetic state means of wood plants in vivo enable. For an estimation of this state the fluorescence of chlorophyll on wavelength 685 and 740 nm was used. The optical model of a green leaf was developed for methods of a laser-induced fluorescence of chlorophyll. A experiments series on remote research of processes violation of mineral power supply and exchange in plants is carried spent. Was considered the change of the ratios of intensity of a fluorescence of chlorophyll and carotenoids at deficiency. Was designed technique for detection infringement processes of mineral nutrition and change surveyed acidity grounds on laser-induce fluorescent responses of deciduous plants.
Great attention is now paid to ecology of the environment, in whic plants are of great importance. However the present methods of biophysical analysis of plant states are very labor-intensive and require a lot of time. The structure of protein-pigment complexes is known to break in different dissolvents that results in the shift of maxima of chlorophyll absorption and fluorescence bands. That is why development of methods for remote diagnostics of plants is of great scientific and practical interest. They would make it possible to determine species and state of plants rather quickly and accurately. We have developed a setup and methods for optical diagnostics of the physiological state of plants to investigate the dynamics of the fastest part of fluorescence of plants in vivo. The method of laser-induced fluorescence makes it possible to observe the level of vegetative development of living plants, as well as their state under the impact of some stress factors.