الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
Tne present study was carried out to investigate the
effect of some ecological factors on the growth and
N2-fixation of both AzalIa pinnata and Azolla filiculoides.
The plan of work included the following experiments: study
for growing of ~ pinnata and A. filiculoides to define the
growth curve of each species, and to investigate the effect
of nitrogenous compounds, viz., urea and ammonium sulphate
at concentrations of 0, 10. 20, 30. 40. and SO ppm N on the
growth and N2- fixation of each AzalIa. The study also
included the effect of salinity in the form of sodium ,
chloride and sodium sulphate at concentrations of 0, 100,
200, 500, 800, 1000 and 1500 ppm on the growth and N2-
fixation of both the two species of AzalIa. The effect of
illumination periods, viz.~ 24, 12, 6, 0 hrs. on the growth
and N2- fixation of each species of AzalIa was also
investigated.
Further, the effect of different rates of nitrogen and
A. pinnata application on the rice yield was also investigated
as compared with different levels of urea-Nt viz .• 0,
20. 40 and 60 kg N/ fed. In this experiment. two procedures
of application of A. pinnata in the soil namely, surface
inoculation and soil incorporation were employed.
The results could be summarized as follows :
1- Data of comparative study experiment clearly indithat
there is a positive relationship between the
and the incubation period up to 36 days for A.
cated
growth
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Qin~~tA and 28 days tor A. fi~i~~~9j~e~ after which the
~rowth yield decreased. Nitrogen content of both Azolla was
found to follow the same trend similar to that of the dry
weight. The results of nitrogenase activities of the tested
Azolia species were not constant and exhibited fluctuations
during the incubation periods. It could be noticed that A.
pinnata and ~ filiculoides exerted maximum N2 fixing
capacity on the 28th and 11th days of incubation respectively
after which the nitrogenase activity decreased.
2- Two nitrogenous compounds, viz .• ammonium sulphate
and urea were used to investigate their effect on the•
growth, of both Azolla species. The data showed that the
highest increase was recorded on the 21th day of incubation
in presence of 50 ppm urea-N of A. pinnata and A.
filiculoides. The highest biomass was obtained when 50 ppm
urca-N- was used. The rate of increase was higher in case
of urea-N as compared with NH.-N. The data indicated that
the highest nitrogen accumulation by both A. pinnata and ~
tiliculoides can be obtained on the 21th day of incubation
in presence of 50 ppm nitrogen either in the form of NH.-N
or urea-No
The effect of addition of NH.-N and urea-N on nitrogenase
activity indicated -that both NH.-N and urea-N has a
depressive effect on the nitrogenase activity, and the
depressive effect of both forms of nitrogen was increased by
increasing nitrogen concentration.
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3- In this experiment sodium chloride and sodium
sulphate at different concentrations, namely, O. 100, ZOO.
500, 8UO, 15UO ppm were used. Results indicated that the
growth of both Azoll~ species in terms of fresh and dry
weights, decreased by increasing NaCI and NaS SO.
concentrations. A. filiculoides was found to be relatively
resistant to high concentrations of both salts, i.e., 1000
and 1500 ppm as compared to ~ ~nnata. The growth of A.
~innata was comnpletely inhibited on the Zlth day of
incubation in the presence of 1000 and 1500 ppm of both
salts.
f
The values of the total fixed nitrogen by both
Azolla species behaved similarly in accordance with the dry
matter content, the depression of N-accumulation was
increased by increasing salt concentration, such effect was
more pronounced in the case of ~ pinnata especially at the
concentrations of 1000 and 1500 ppm.
The maximal nitrogenase activity of both Azolla
species was detected in the absence of salts. By increasing
NaCl or Na2S0. concentration the nitrogenase activity
decreased.
4- In this experiment illumination periods namely, 24.
1Z, 6 and a hrs. of light were used. results showed that the
growth of A. pinnata and Azolia filiculoides was stimulated
by exposing the Azolla fronds to 12 brs. of light followed
by 12 brs. of dark the highest increase was recorded on the
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~lth day of incubation. More incubation of Azolla fronds in
the dark for 18 hrs. resulted in sharp decrease in the dry
weight. The growth of both ~zolla species was completely
inhibited on the 21th and 28th day when incubated in
complete darkness.
The N2- fixing capacity was highest when both Azolla
species were exposed to 12 hrs. light followed by 12 hrs.
dark. The N2- fixation of both Azol1a species reduced
sharply when exposed to 6 hrs. of light. At complete
darkness the N2-fixing capacity was completely inhibited by
both Azolia species. The maximal nitrogenase activities of
both Azolla species was detected when they were exposed to
12 hrs. of light followed by 12 hrs. of dark. By increasing
dark period the nitrogenase activities were decreased and
ceased in complete darkness.
5- Data of rice experiment showed generally that the
incorporation of ~ pinnata in the soil was better for
obtaining higher values of rice growth parameters than the
surface incubation. The maximum values of the rice growth
parameters were obtained by incorporating 40 kg/ fed. of
Az~lla-N in presence of 20 kg/ fed. of urea-No