Regulation of shoot growth, root development and manganese allocation in wheat (Triticum aestivum) genotypes by light intensity

The objective of this study was to assess effects of different light intensities on shoot growth, root development and allocation of root-borne solutes via the transpiration stream to various shoot parts of young wheat plants (Triticum aestivum L.). Hydroponic culture allowed direct access to the roots and shoots throughout the experiment. Under low light intensity (100 mu mol photons m(-2) s(-1)), shoot growth was restricted, less (but larger) leaves were produced at the main shoot and only a few tillers became visible as compared to plants under high light intensity (380 mu mol photons m(-2) s(-1)). The root system was indirectly also affected by the illumination of the aerial parts. A larger number of shorter roots were produced under high light leading to a denser root system, while only a small number of longer roots were present under low light. The distribution of Mn-54 (xylem-mobile, but essentially phloem-immobile in wheat) from the roots to the shoot lead to the conclusion that light regime strongly influences the distribution of root-borne solutes within the shoots. Labels introduced into the roots may allow a deeper insight into the transfer of solutes from the root system to the various shoot parts under different light regimes.