TIP GROWTH OF <i>NEUROSPORA CRASSA </i>IN THE CONDITIONS OF THE RESOURCE DEFICIENCY: IMPAIRMENTS IN THE COHERENCE OF ELONGATION, BRANCHING, AND SEPTATION
With the aid of intracellular fluorescent probes, peculiarities of elongation, branching, septation, and nucleus morphology have been studied in isolated 400-μm-long apical fragments of <i>Neurospora crassa</i> hyphae growing for several hours without the influx of the nutrient materials from the mycelium. We found that: 1) the diameter and growth rate of newly developing branches decreased as compared to intact mycelium (from 10-20 to 6.5 ± 0.4 μm and from 24 ± 1 to 6.7 ± 0.5 μm/min, respectively), but the initial orientation of growth did not change; 2) the branching rhythm was altered; abnormally long internode distances appeared (up to 1471 μm), and the development of some side-branch buds ceased; 3) the character of the septation remained unchanged, as well as the hyphal segment length (68 ± 2 μm). In hyphae growing for 4.5-5.0 h in isolation from the whole mycelium, the distance between the tip and the first septum was 210 ± 15 μm, which was comparable with the respective value in intact mycelium, whereas the mean distance between the growth tip and the first side branch (492 ± 127 μm) and the dispersion of this parameter was considerably higher than in intact mycelium. In branches growing in isolation from the intact mycelium for 1.5-4.5 h, the length of the nucleus-free apical zones near the growth tip (from 5 to 33 μm) and the nucleus morphology were similar to the respective characteristics known for the <i>N. crassa</i> mycelium. The experimental model described here can be used for the investigations of molecular and genetic mechanisms regulating the interactions between intracellular structures involved in the tip growth of <i>N. crassa</i>.