Physiological Studies Of Some Nutrient Elements On Some Aquatic Plants:

Hosny Mohammed Mohamed Abd El-dayem

The present investigation was carried out in an attemptto add some informatiom about the response of AzolIa pinnataand Spirodela polyrhiza to variable concentrations of someessential nutrient elements such as phosphorus, calcium andcobalt added to the nutrient media. Also, the effect of somedifferent levels of cadmium and lead as a toxic heavy metalswhich may contaminat the natural a queous media of these twogenera was studied under laboratory conditions.To approach this aim, two laboratory experiments werecarried out under semi-controlled conditions which include:A. Comparative studies on the effects of some concentrationsof phosphorus, calcium and cobalt on thegrowth behaviour and mineral accumulation in bothstudied genera as well as the contents of sugars,chloroplast pigments and amino acid fractions.B. Comparative studies on the toxic effects of someconcentrations of Cadmium and lead on growthbehaviour, mineral contents and the changes inchloroplast pigments, sugars and amino acid fractionsof the two studied genera.The results obtained could be summarized as follows:A) Experl.ent I:-184-1- Application of different P, Ca and Co levels seemed toregulate the growth of Azolla and Spirodela plants.Such regulation varied greatly within the tested plantgenera and according to the examined element and itslevel.2- The application of different P, Ca and Co levels affectedgreatly the concentrations and the uptake of N,P, K, Ca, Hg, Na, Fe, Hn, Cu and Zn by Azolla andSpirodela plants. This effects differed greatly withinthe tested plant genera and varied according to the examinedelement and its level. This may indicate thatthe response of the used genera to the application ofdifferent levels of P, Ca and Co was greatly differedand that may be related to the variable inheritancetendency.3- The proportion and the distribution of different elementsin AzalIa and Spirodela tissues was greatly influencedby variation of P, Ca and Co applicationlevels.4- Photosynthetic pigment concentrations changed greatlywith the variable change in the levels of P, Ca and Coin AzalIa and Spirodela plant tissues. Such changeseemed to affected the accumulation of sugars and aminoacid accumulations in plant tissues. The degree of suchchange was greatly differed between the studied genera.5- Sugars and total free amino acids contents in AzalIa-185-and Spirodela plant tissues werethe variable concentrations of P,greatly affected byCa and Co levels affeetedthe plant metabolism which varied according tothe inheritance tendency and the variable response ofthe used plant species.6- The proprtion of reducing - to non-reducing sugars waschanged greatly by the variable applications of P, Caand Co in Azolla and Spirodela .7- The application of P, Ca and Co seemed to regulate theaccumulation of different amino acid fractions inAzalIa and Spirodela plant tissues.8- The variable changes in the accumulation of differentnutrient elements, and different tested organic mattersin AzalIa and Spirodela plant tissues as related thevariations in P, Ca and Co levels take a role in plantgrowth responces.The dominant amino acids in Azolla are:Glutamic + Alanine followed by aspartic acid, leucine,arginine, lysine, Phenylalanine, isoleucine, glycine,serine, proline, threonine, valine, cystine, methionineand finally histidine in deascending order.The inhibiting effect of lack of (P) or (Ca) ontotal a~ino acids resulted mainly fro~ the concentrationof glutamic + alanine. Also (P) deficiency minimizedmost of the various amino acids, but (Ca)deficiency minimized only glycine, isoleucine,threonine, serine, cystine and phenylalanine. The absenceof (Co) slightly altered the amino acids picture.With regard to Spirodela plants, the absence or theexcess of (P), (Ca), or (Co) decreased the concentrations ofthe total amino acids, but shortage of (P) was superior inthis respect followed by (Co) and (Ca).The most abandant amino acids in $pirodela are glutamic+ alanine followed by: aspartic or leucine, arginine,cystine, threonine, valine, phenylalanine, isoleucine,proline, glycine, histidine, serine and cystine in deascendingorder.The negative effect of (P) deficiency occurred on theconcentrations of glutamic + alanine, leucine, threonine,serine, methionine, cystine, lysine, arginine, phenylalanineand histidine. Lack of (Co) minimized the concentrations ofglutamic + alanine besides threonine, methionine, cystine,lysine, arginine and histidine. The other amino acidsslightly increased or unchanged.B- Experiment II:1- Observation during growth, different concentrations of(Cd) or (Pb) changed the normal light green appearanceinto yellowish one. The proportional chlorosis appearanceincreased progressively in the frond withicreasing plant age and also with increasing (Cd) or(Ph) levels. Also (Cd) treatments seemed to enhance theabscission of lateral branches from the main axis ofthe mother fronds more than did (Ph) treatment. So bothAzolia and spirodeia could be used as an excellentbiological indicators or monitors for (Cd) or (Pb)water pollution, however, Spirodela plants are moresensitive than Azolla in this respect.2- Growth, the different levels of (Cd) or (Pb) decreasedsignificantly AzalIa pr Spirodela fresh weight anddaily percentage was also decreased. However number ofplants per one gram fresh weight was increased and thereduction increased with increasing (Cd) ar (Pb)concentrations. Also lead had less toticity on AzalIagrowth comparing to (Cd) effect.Azolla plant could absorb (Cd) from the naturemedia easily than that absorbed by Spirodela. Also underthe nature conditions in which AzalIa servives suchplant may be considered as (Cd) sink and could be usedfor removing such element from the very low contaminatedpolutant media.3- Different levels of (Cd) or (Pb) decreased mostly theconcentrations of H, P, K, Ca, Hg, Na, Hn and Cu inboth AzalIa and Spirodela, but (Fe) increased with increasingof (Cd) concentration. Also in case ofSpirodela, (Mn) and (Zn) concentrations increased withincreasing (Pb) concentration.4. Total accumulation of some nutrient elements:I- In Azolla plants:a. The different levels of (Cd) were very harmful tothe process of N- fixation and the reduction observedin N-accumulation increased withconcentration.b. The different levels of (Pb) were less harmful to Nincreasing(Cd)fixation than those of (Cd). Thus, the lower (Pd) concentrations(10,15 and 25 PPm.) increased of the toatalN- accumulated in plant tuisues, while the high (Pb)concentration (40 PPm.) decreased thise accumulationand this decrease was less than that caused by (Cd).c. Different levels of (Cd) or (Pb) decreased the accumulationsand/or the uptake of the different essentialelements, but (Pb) was less harmful in thisrespect than (Cd). The only exception in this respectwas (Fe) which showed continuous increase especiallyunder (Cd) treatments.d. The different levels of both (Cd) or (Pb) did noteffect the proportion but affected the balance of theessential elements in AzalIa tissues.2) In SDirodela plants:-a) The effect of (Cd) or (Pb) levels on the amounts ofthe essential elements was less in case of Spirodelathan in AZalIa and also the effect of (Pb) was lessthan that of (Cd) in this respect.b) The applied rates of (Cd) or (Pb) caused troubles inmineral accumulation and their uptake.c) Cadmium and lead reduced (Ca) accumulation in bothSplrodela and AZalIa and Such reduction was proportionalto the increase in (Cd) or (Pb) levels. Also(Cd) was more effective than (Pb) in this respect.5- The different levels of (Cd) or (Pb) decreased the concentrationsof the photosynthetic pigments In bothAzalIa and Spirodela .. SUch reduction was great with increasingconcentrations of (Cd) or (Pb). Also, (Cd) wasmore effective than (Pb) in this respect.6- Sugars, the different levels of (Cd) or (Pb) reducedgreatly the sugar accumulation in both AzalIa andSpirodela, and (Cd) ”as more effective than (Pb).All the tested rates of (Cd) or (Pb) disrurbed theproportion of reducing- or oon- reducing sugars as relatedto the total sugar amounts.7- Host of the different (Cd) or (Pb) levels increased theconcentrations of f:ree amino acids In both AZalIa andSpirodela and (Cd ) sel!aed to be more effective than(Pb) .The different levels of (Cd) lowered the accumula-tion of free amino acids in Azolla, while (Pb) enhancedsuch accumulation. On the other hand, the differentlevels of (Cd) or (Pb) enhanced such accumulation inSpirodela.8- In both AzolIa and ~pirodela the total amino acids concentrations(mg/g dry matter) decreased continuouslywith increasing the rates of (Cd) or (Ph). This reductionwas observed with every amino acid tested.In case of Azo]~ the different (Cd) or (Pb)levels changed the concentrations of most amino acidsand the most pronounced reduction was obtained withglutamic + alanine, leucine, lysine and Phenylalanine,amino acids were una.ffectedor may increased 51 ightly.In case of Spirodela, nearly all the tested ominoacids decreased with increasing the concentiation of(Cd) or (Pb).