Radiotracers in understanding plant processes

Nuclear and allied techniques have immense applications in the area of agricultural research. Radioisotopes have been exceptionally useful to understand the various physiological functions of the metabolic changes induced under varying growth environments and among different crops. These have helped in improving our understanding of crop variation in carbon influx and assimilation, source sink relationship, ion influx into apoplasm, nutrient uptake, interaction of ions, foliar uptake, transport, utilisation/assimilation. Isotopes yield an analytical advantage that they can be easily traced and measured in minute quantities and analysis remains uncomplicated by the presence of large cellular pools of the ions in question. In fact radioisotopes can be used effectively in developing modern agro-techniques for better understanding of the mineral fertilizer-, water-use and biological nitrogen efficiency. It is important to collate and critical analyze the available research knowledge and leads on the advances made in the field of plant mineral nutrition through the use of radioisotopes and stable isotopes. ¹⁴C can be used to assess source sink relationship and to measure the carbon exudates that are released by plant roots for ensuing rhizosphereic modifications. Radiotracers offer a unique advantage in terms of high sensitivity, their simplicity and small expense (compared to competing technologies such as mass spectrometry). In a well-designed experiment, the presence of radiotracers does not affect the system under study and any analysis is non-destructive. Radiotracers can be used to study the dynamic biological processes like the ion transport across cell membranes, turnover, intermediary metabolism, or translocation in plants that were earlier being studied indirectly with a greater degree of analytical error. Radiotracer technology also aids in identification of the rate determining step in any biological process. Innovative radiological tools like Positron Emission Tomography (PET) where short-lived positron-emitting radiation provide time-dependent data that are critical for developing models of metabolite transport and resource distribution in plants and their microenvironments or the real time radioisotope imaging for studying nutrient uptake and translocation are now an indispensable analysis tools in understanding the biological activity of plants. There is no doubt that radiotracers have a great future and will continue to better our understanding of the metabolic dynamism that the plants reveal under challenging condition. (author)