304
Chapter 7
Figure 7.20 Structure of a densely branched hyphal element with indication of apical, subapical, and
hyphal cells.
( z Л
^ A
«1
2+(Ma ~V)ZA
^
Zs
=
+M2
-Wj+C“s
- m )Zs
^
U3
fjZfJ
J
(4)
The rates of the metamorphosis reactions and the morphological variables have been shown to correlate
with specific measures of the hyphae (Nielsen, 1993). Thus, the hyphal diameter is given by:
^hyphae ~ a \ 7
( 5 )
^
A
where aa is a physiological constant determined by the water content and the density of the hyphae.
Equation (5) is based on the assumption that only precursors synthesized in the apical compartment
contribute to tip growth. For some species of filamentous microorganisms, precursor synthesized in the
subapical compartment may also be transported to the apex and incorporated in the hyphal wall, but the
contribution from the subapical compartment to the total precursor synthesis is assumed to be small and is
neglected in the model. The hyphal growth unit length may also be derived from the model:
(6)
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