Biology Reference
In-Depth Information
B
A
E
D
G
F
C
I
H
K
L
J
Figure 7:
Pattern of akinete formation in
Scytonema fritschii
. (A) a vegetative fi lament with an intercalary heterocyst (
lower
)
showing cells which are longer than wide and two fi laments (
upper
, indicated by arrows exhibiting cell division from nitrate-
free medium on 26th day; (B) two fi laments from late exponential growth phase; of the two fi laments, in the upper fi lament
the interheterocyst distance increased to 16 cells while the lower fi lament shows maturing akinetes sandwiched by heterocysts;
(C) a fi lament with two intercalary heterocysts showing an inter-heterocyst distance of 26 cells from nitrate-free medium on 6th
day; (D) a fi lament undergoing second phase of heterocyst differentiation with potential akinetes in between from nitrate-free
medium on 28th day; (E) magnifi ed portion of a fi lament with two heterocysts on either side of two cells undergoing akinete
differentiation from nitrate-free medium on 30th day; (F), (G) advanced stage of akinete differentiation showing deposition of
cell wall layers revealing a thick exine and a smooth intine from nitrate-free medium on 42nd day; (H) a chain of mature akinetes
from nitrate medium on 28th day; (I), (J) chains of maturing akinetes with heterocysts in between from nitrate medium on 28th
day; (K) fully developed germlings being released laterally or terminally from nitrate-free medium on 3rd day of seeding; (L)
advanced stage of akinete germination showing germlings still held by old walls of akinetes from nitrate-free medium on 5th
day of inoculation. The magnifi cation bar in all pictures represents 10 µm (From Sarma and Ghai, 1998).
8) Enzyme levels
:
The levels of enzymes such as α-amylase, catalase, peroxidase, glutamine synthetase
(GS) have been compared in cells undergoing akinete differentiation in
A
.
torulosa
(Sarma
et al
., 1977;
Swarn Kanta
et al
., 1978; Sarma and Swarn Kanta, 1982). Higher levels of catalase and peroxidase in
the maturation phase of akinetes of
A
.
torulosa
suggested that the akinetes with fairly higher levels
