Institute of Plant Physiology in Sofia. In the course of many years he has been cultivating personal contacts with researchers from many laboratories abroad, especially in Germany and the USSR, as well as with the Institutes of the Agricultural Academy and the Academy of Sciences in Sofia. His several short or long lasting specializations in the USSR, DDR, BRD, etc. have also contributed to his high scientific erudition. He has taken part in numerous symposia, congresses, scientific-coordinating conferences etc., where he has presented more than 25 lectures. Prof. Ivan Yordanov has been successfully combining intensive research work with pedagogical activity. Since 1961 till 1997 he delivered a course of lectures on photosynthesis to students in biology. Besides, he delivered the main course in plant physiology at the Paisii Hilendarski University in Plovdiv in the course of 3 years and at the Higher Forestry University in Sofia for one year. It is difficult to enumerate all fundamental and applied scientific achievements of Prof. Ivan Yordanov. He has focused his attention mainly to the investigation of BULG.