الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY
The respent investigation was carried out in an
attempt to add some information about the growth ot
Azolla plnnata under variable concantrations of Oa
levels applied either with pre-subjection to EDT!
(chelating agent) or with the application of heavy
metals,i.e• Cd,Pb or Hg •
TQ approach this aim, two· detailed experiments
were carried out under semi-controlled conditions which
include;-
1- Effect of variable calcium levels on the growth
ot Azolla Einnata plants which pre-subjected to
EDT! for two or tour hours.
2- Azolla plant growth behaviour as affected by
Cadmium (Cd),Lead (Pb) and Murcury (Rg) with
the presence of variable calcium levels in
the growing media.
It could be Bummarized the obtained results as
tollows :-
A) Experiment I :
a) Growth behaviour :
1) Pre-subjection of AzalIa plants to the 0.01 I.
aquious solution 01’ EDTA decreased significantly
the biomass tresh and dry weights production.
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Such decrement was increased with increasing
the time of exposure from two to four hours.
Thus tit concluded th at EDTA hase anpartial
effect on fresh and dry weights.
2) The level of Oa in the growing media modified
the adverse effect of EDTA on fresh and dry
weights production of the biomass.
3) It could be concluded that EDTA seemed to
control the physiological activity of Azolla
biomass, and the presence ot Cs levels modified
such adverse effect •
4) EDTA stimulated the higher fragmentation of
Azolla plants. and the presence of Cs levels
affected significantly such stimulation effects
and that lead to the assumption that the
presence of Ca reverse the effect of EDTA on
,the fragmentation processes.
5) Both EDTA and Ca levels affected the size of
frond through the changes in its fresh and dry
weights. The time of exposure to EDTA affected
frond size.
6) Both EDTA and Oa levels affected significantly
the formation of roots and the root length.The
absence of Oa increased such absorption
portion o~ A~o11a plante.
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7) Calcium play an important role on Azolla plant
growth and its effects were differed according
to its presence level in the growing media,and
that was discussed on the bases that Oa affected
the structure and function of cell membranes,
but EDTA had a removal effects on the presence
of Ca from such membranes.
b) Chemical composition:
I} Both Ca and EDTA affected the sugars contents
in Azolla plants as concentration (mg./gr.dry
weight) or total contents in the biomass per
vessel or per one frond. Accordingly, it was
concluded that such chelating agent and the
presence of Ca levels seemed to have a regulatory
effects on sugars synthesis, assimilation
or utilization which take a part in plant
growth behaviour.
2) Both EDTA and different Oa levels affected
nitrogen fixation by AzolIa-Anabaena symbiosis.
The presence of Ca reduced such activity, and the
most suitable concentration of ea in the growing
medium was the normal 2/5 of Hoagland nutritive
solution in this respect. Higher of low~r Levels
of es over or under such Os level minimized the
nitrogen fixation activity.
3) Calcium seemed to have a role on the absorption
01 P,K,Oa and JIg by Azolla plants, and such
role modified by the pre-subjection to EDTA.
This conclusion was discussed on-the bases
that Oa affected the absorption of such
nutrients. Also the presence of one ion in the
growing media affected the absorption of another
one through the antagonistic effects.
B) Experiment II :
a) Growth behaviour :
1) jhe presence of Cd,Pb or Hg had an adverse
toxic effeta on Azolla growth,as fresh or dry
weights of biomass per vessel or per one frond.
Such adverse effect was greatest under Cd or Hg
than Pb.
2) The presence of Oa in the growing media in
different rates modified the toxic effects of
heavy metals on the growth behaviour of Azolla,
and the best level of Oa in this respect was
the normal of 2/5 Hoagland solution.
b) Chemical composition:
1) It could be revealed from the obtained results
that the toxic effect of heavy metals on plant
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growth was occurred as a result of their
adverse effects on the accumulation,utilization
and assimilation of sugars in plant tissues,
while the presence of Ca at ditfere~rates in
the gro~ng media modified the toxic effects
of heavy metals on sugars metabolism.
2) It canld be concluded from the different obtained
results that heavy metals depressed the nitrogen
fixation which lead to a lower accumulation of
nitrogenous compounds in plant tissues, and Ca
regulated and modified such adverse effects of
heavy metals.
J) Both heavy metals and CS affected the absorption
rates of P,K,Ca and Mg and that affected the
plant growth behaviour.
4) It was suggested that AzalIa may be used as an
indicator or monitors for the pollution with
heavy metals, as its growth behaviour reduced
greatly under the presence pt heavy metals and
finally the mortality at the tronds was
observed.
5) It was suggested also that the toxic mechanism
of action of the studied heavy metals (Cd,Pb or
Hg ) was greatly differed between the tested
heavy metals, as the differences in the
.obtained data were greatly variable under
the different treatments.