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Photoautotrophic (shoots) and heterotrophic (roots) organs are the main structural and functional parts of higher plants. Normal functioning of a plant as of a whole system depends on coordinated interaction of these two parts. The ratios of structural and functional parameters of photoautotrophic and heterotrophic organs may be the index of the coordination level of their functional activity. Pea, wheat, buckwheat cultivars different in stress resistance were grown under normal conditions, at iron deficiency and low pH (pH 3.0 and 4.0) in the nutrient media. Integral indexes of the functional activity and of the state of photoautotrophic and heterotrophic organs - the parameters of the growth and pH of tissues - were measured. The state of energy transduction systems in chloroplasts was evaluated according to activities of light induced proton uptake and ATP formation. Dynamics in disturbances in biosynthesis of cytochromes and ATP in chloroplasts was noted in iron deficiency variants.

It was demonstrated for a number of cultivars of the studied species that under normal growing conditions and good adaptation to stress-factors (iron deficiency, low pH) the ratio of the length of the photoautotrophic part of the plant to the length of the whole plant was equal to the ratio of the length of heterotrophic part to the length of photoautotrophic part and equal to 0.6 what corresponds to the golden section and to the ratio of numbers in Fibonacci series. It should be noted that in this proportion the size of the photoautotrophic part is the mean proportional value for the size of the whole plant and its heterotrophic part. However, at early stages of ontogenesis when the photosynthetic apparatus is not developed enough the size of the heterotrophic part may be the mean proportional value. Later on the size of the photoautotrophic part becomes the mean proportional value - the change in functional dominants and sink-source relations in plant take place. Position of the junction of photoautotrophic and heterotrophic tissues (root collar) at the golden section point makes it possible to consider it as an important regulatory zone. At poor adaptation of plants to stress-factors the ratios of structure-function parameters of photoautotrophic and heterotrophic organs are not equal to the golden section. In this case the place of junction of photoautotrophic and heterotrophic tissues is disposed not at the golden section point. It disturbs the regulation conditions in the whole plant system what leads to a functional disbalance in shoots and roots and to slowing down in plant growth. pH proportions of photoautotrophic and heterotrophic tissues of some cultivars of the studied plant species (for example, early maturating buckwheat cultivar with a high growth rate) also correspond to the golden section rule under normal conditions and adaptation to moderate iron deficiency. The existence of the golden section in proportions of structural and functional parameters of photoautotrophic and heterotrophic organs points to good functional coordination of these organs expressed in harmonic plant development. At poor adaptation of plants to the studied stress-factors deviation of the mentioned proportions from the golden section takes place. In this case acidosis of photoautotrophic and heterotrophic tissues, slowing down in growth of shoots and roots occurs. One of the reasons for it may be the enhancement of free radical oxidation. Under iron deficiency and low pH conditions activities of light induced proton uptake and ATP formation in chloroplasts decreased. Iron deficiency also caused a disturbance in cytochrome biosynthesis in chloroplasts. The value of deviation of the ratios of the measured parameters from the golden section was proportional to the degree of the observed disturbances in metabolism of plants.

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