ИСТИНА

Light and reactive oxygen species (ROS) are well known crucial factors that regulate plant growth and development. The intriguing topic is whether these factors interact during the plant development. It is known that superoxide is necessary for the root hairs tip growth and for the root elongation in Arabidopsis. These data typically obtained by studying mechanisms of the root growth in the completely illuminated plants. We suggested that mechanisms of the root growth and development in the dark may differ from those established for the light-grown plants. In 5 days-old Arabidopsis seedlings, grown in sterile conditions under 16/8 h photoperiod the typically root growth zones dependent nitroblue tetrazolium (NBT) distribution could be easily detected. NBT – is a widely used indicator, which forms a dark blue formazan precipitate in contact with superoxide. Surprisingly, we have not found NBT staining of the root elongation zone in the dark-grown seedlings. CuSO4 that typically result in increasing in the levels of ROS induce extensive root tip NBT staining in dark-grown seedlings. We propose that there is no superoxide production in the dark-grown Arabidopsis root tip. However, slight NBT staining was detectable in the region with the high density of the root hairs in the dark-grown plants. We suggest that different enzymes are responsible for the superoxide generation in the root hairs and in the cells of root elongation zone. We have shown that deetiolation of seedlings under white light cause the NBT staining of the root tip. The dark-grown seedlings exhibit extensive NBT staining of the root tip if kinetin in various concentrations was present in the growth medium. NBT staining was also observed in the root tip of seedlings grown in the dark in the presence of sodium nitroprusside - an NO donor that is known as a stimulator molecule in plant photomorphogenesis. We propose that photomorphogenetic changes result in the superoxide production in the root elongation zone in Arabidopsis.