Physiology of thegrowing hypha1.2.1

Physiology of the
growing hypha
1.2.1 Polarity of the hypha
By placing microscopic markers such as small
glass beads beside a growing hypha, Reinhardt
(1892) was able to show that cell wall extension,measured as an increase in the distance between
two adjacent markers, occurred only at the
extreme apex. Four years earlier, H. M. Ward
(1888), in an equally simple experiment, had
collected liquid droplets from the apex of hyphae
of Botrytis cinerea and found that these ‘fermentdrops’
were capable of degrading plant cell walls.
Thus, the two fundamental properties of the vegetative
fungal hypha
the polarity of both growth
and secretion of degradative enzymes
have
been known for over a century. Numerous studies
have subsequently confirmed that ‘the key to the
fungal hypha lies in the apex’ (Robertson, 1965),
although the detailed mechanisms determining
hyphal polarity are still obscure.