DISCUSSION

Experiments were conducted to assess the effect of some micronutrients (Zn, Cu

and Fe) disorders in wheat crop (Triticum aestivum L.) using various culture methods

such as pot culture, sand culture as well as field experiments with variable soil conditions

at five different locations of Uttar Pradesh. In experiments (4.1 and 4.3) studies were

performed to observe the effects of various levels of Cu (0, 1, 5, 10 and 25.0 mg kg -1) and

Zn (0, 5, 15, 25 and 50 mg kg-1) amendment in soil and also these metals (Cu and Zn)

supplied in the form of water solution in sand culture. Experiments were performed to

assess the effect of with various doses of Cu and Zn on growth, biochemical responses,

reproductive yield, tissue concentration of metals and grain quality of wheat (Triticum

aestivum L.) plants. The experiment (4.2A and 4.2B) studies were carried out to find the

effect of Cu and Zn interactions on growth, biochemical responses, reproductive yield,

tissue concentration of metals and grain quality of wheat. The experiment 4.4 was

performed to study the effect of various soil conditions in Uttar Pradesh state (India) on

plant growth and reproductive yield under field conditions of five different locations viz.

Lucknow (L1), Barabanki (L2), Khalilabad (L3), Mohanlalganj (L4), Bakshitalab (L5).

In experiment 4.1, test plants were grown in soil which was mild calcareous and

have deficient DTPA- extractable available Cu (0.28 mg kg-1) and Zn (0.69 mg kg-1).

Agarwala and Sharma, 1979. Visible symptoms such as reduction in growth, reduced size

of leaf lamina and marginal yellowing and tip burning in wheat leaves were observed in

plants grown at native soil, could be developed due to deficiency of Zn and Cu in soil

(Sharma, 2006).

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In Experiment 4.1, visible Zn deficiency symptoms such as reduction in shoot

length, reduced size of leaf lamina, marginal yellowing and tip burning in wheat leaves

were observed, these symptoms were more prominent in plants grown at native soil and

extended to lower doses of Zn amendments in soil. Wheat plant grown in sand culture

experiment at lower dose of Zn supply also shows the Zn- deficiency symptoms. These

symptoms resembled with Zn- deficiency symptoms as reported earlier by Sharma et al.

(1987) in chickpea grown in Zn deficient soil. Ambler et al. (1970) reported that, Zn

inhibits Fe translocation, therefore causes chlorosis in leaves. Being as an essential

micronutrient, Cu and Zn are required for normal growth and development of plants

(Alloway 2004). Growth and biomass of wheat plants is affected by various factors

including soil conditions, micronutrients status of soil and fertilizers application in soil

(Ekiz et al., 1991), but these factors influences soil conditions are least effective on

availability of Zn to plants grown in sand culture (Agarwala and Sharma 1961).

The shoot length of wheat plants increased maximum by 27.5% with Cu and

54.9% with Zn amendment in soil at the rate of 10.0 and 50.0 mg kg -1 soil were observed.

The increase in wheat growth with respect to shoot length and dry matter yield due to

fertilization of Cu and Zn could be due to the essential role of Cu and Zn in biochemical

activities of plants (Sharma, 2006). In the soil culture experiment, up to a certain level of

Cu and Zn application ensure better plant growth and dry matter yield of wheat plant

while at higher levels both Cu and Zn showed negative effects on growth. These results

also inconsonance with the result of Imtiaz et al.(2003). With the increasing

concentration of Zn in soil the growth and biomass increased more significantly than the

Cu. Significant increase in growth and biomass were observed with increase in Cu and

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Zn concentration at lower doses but at high concentration there was no significant change

in growth and biomass yield, this might be due to the low availability of Zn and Cu

(Alloway, 2004). These results also supported by Kaya et al., (2002). Xu et al.(2005)

also reported that, Cu decreases the growth and biomass yield of plants at its excess

levels, but at low level Cu promoted growth and biochemical responses of plants.

Assimilated copper in wheat plants might be played important role in growth and

development of crop plants because of their active role in plant metabolic processes such

as respiration and carbohydrate synthesis (Chen et al.,1995). The results of present

investigation are also in concordance with the findings of Dod et al. (1989) in chilli and

Tamilselvi et al. (2002a) in tomato plants.

The dry matter yield was significantly increased by the application of copper up to certain

levels in both sand and soil growth medium. The increase in dry matter yield with copper

nutrition could be attributed due to increased copper availability in soil, enhanced vital

metabolic activities in plants Xu et al.(2005). Also optimum concentration of copper in

plants might have been utilized by enzymes for respiration and auxin synthesis, which

intern accelerated the chlorophyll synthesis in the test plants and helped for higher dry

matter production (Chew et al., 1979). Similar observation was made by Tamilselvi et al.

(2002a) in tomato plants. Bameri et al.(2012) had reported increase in plant height and

biomass production with Zn application in growth medium. Hart et al. (1998) reported Zn

uptake by wheat seedlings to be concentration dependent grown in alluvial soil amended

with 50 mg kg-1 Zn, the test plant produce maximum dry matter yield, could be attributed

due to the uptake of Zn in plants above critical deficiency level (Sharma, 2006). The

critical deficiency concentration of Zn ranges between 15 to 20 μg/g dry matter yields has

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been reported in most plants (Sharma, 1996). Sharma et al.(1987) also reported increased

dry matter yield in chick pea grown at 5 mg Zn kg -1 amended in alluvial soil which

accumulated 30 μg g-1 Zn dry matter yield.

In experiment 4.1A and 4.1B, at elevated levels of Cu and Zn amendment could

not show serious toxic effects on growth and biomass production of wheat grown in soil

culture medium, it could be due to the slow availability of nutrients to the plants or many

other factors which had been affected the growth and development of plants in such

conditions (Agarwala and Sharma, 1979). It may also be due to the optimum

concentration of copper in plant might have been utilized by enzymes and auxin

synthesis, which intern accelerated the synthesis of pigments, starch protein and

chlorophyll synthesis which promoted growth and yield (Kumar et al., 2009). But, in

sand culture experiments (4.3A and 4.3B) growth and biomass of wheat plants was

significantly increased at lower doses while at higher concentration of both metals (Cu

and Zn) it was significantly reduced. Present results are in accord with Shen et al. (1998)

reported Cu and Zn toxicity cause multiple direct and indirect adverse effect on the

process of physiological metabolism in plants, such as altering the catalytic function of

enzymes, damaging cellular membrane, inhibition of root growth. Similar finding has

been also reported by Souguir et al.(2008) who investigated the potential genotoxicity of

Cu2+ in Vicia faba and Pisum sativum.

In experiment 4.1 and 4.3 It was shown that the pigment contents (chlorophyll a,

b and total chlorophyll and carotenoids contents) in wheat leaves were significantly

increased with increase in Cu and Zn concentration in growth medium up to certain level,

while it decreased at excess level of metal application in growth medium. In soil culture

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experiments (4.1A and 4.1B) chlorophyll contents were found to be increased up to 10

mg kg-1 Cu application and 25 mg kg-1 Zn application in soil, it might be due to low Zn

levels acts as a structural and catalytic component and as cofactor for normal

development of pigments biosynthesis (Balashouri and Prameeladevi, 1995). It was

shown that Cu was more toxic than Zn in terms of chlorophyll inhibition. The results of

Zn application effect on pigment contents also reported by the Bassi and Sarma (1993).

The loss in chlorophyll content can consequently lead to disruption of photosynthetic

machinery. Decline in pigments content might be due to the accumulation of excess Zn

and Cu resulting in interference with synthesis of chlorophyll (Manivasagaperumal et al.,

2011). It was shown that, the amount of chlorophyll in the wheat plant tissue grown in Cu

amended soil were more or less similar to the plants grown in Zn amended soil, but there

are some differences in relative ratio of chlorophyll a and b contents. The various abiotic

stress decreases the chlorophyll content in plants has been reported (Ahamad et al.,

2007).

The increase activity of antioxidative enzymes were observed in wheat leaves

grown in Cu and Zn application in soil and sand culture experiments were found to be

increased with increase in concentration of Cu and Zn in growth medium at certain limits

but further activity of antioxidative enzymes significantly decreased. It could be due to

accumulation of metals (Cu and Zn) ions in plants cells might cause decrease in

peroxidase activity (De Vos et al., 1993). They suggested that, free radicals induce lipid

peroxidation is part of the overall expression of Cu2+, Zn2+ and Fe2+. The increased

catalase activity was indicative of defense against oxidative stress produced in plants, it

may be due to the excess Zn in tissue (Cakmak, 2000). Low activities of catalase in plants

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have been reported due to Zn deficiency in plants (Bisht et al., 2002). It was shown that,

as the concentration of Zn and Cu increased in growth medium it induces increased

activity of catalase and peroxidase. It was supported by other workers also (Singh and

Malik, 2011) suggesting that enhancement in enzyme activity of catalase and peroxidase

in a response to heavy metal stress.

In the experiment results indicated that, protein content increased with increase in

concentration of Cu and Zn in growth medium (soil as well as sand culture medium) but

at higher doses it was decreased. The decrease in protein content might be due to

bindings of metals with the sulfhydryl group of protein and causes deleterious effects in

normal protein formation (Chen et al., 2001). The exposure of higher concentration of Cu

appreciably reduces the protein content in wheat plants (Singh et al., 2007). In

experiments 4.1 and 4.3 it was shown that, protein content was lower in the plants treated

with Cu as compared to the Zn treated plants. Our results are in accordance with

Manivasagaperumal et al. (2011). It showed that, excessive Cu reduced protein amount

of many plants species (Singh et al., 2007).

Crop productivity is the rate at which a crop accumulates organic matter due to

the photosynthesis and conversion of light energy into chemical energy by green plants

(Reddy 2004). Yield of wheat plants depends on many components viz. number, length

and weight of inflorescence per plant, particularly weight and quality of grains. Data

presented in the experiments 4.1 and 4.3 indicate that, Cu and Zn caused significant

effects on reproductive yield of wheat plants, The positive effectiveness of Cu and Zn

doses on improving reproductive yield of wheat plants were observed. The wheat grain

yield was supported due to increase in length, numbers and grain per inflorescence. These

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results were in accord with earlier workers (Kalyal and Agarwala 1982; Tiwari and

Tiwari 1993). Kumar et al. (2009) also reported that, Cu in soil and plants increases the

grain yield of wheat at its sufficient levels. Weight of wheat grains was significantly

increased by copper nutrition, the reason might be due to the accelerated mobility of

photosynthates from source to sink as influenced by copper nutrition and absorbed copper

might have raised the efficiency of energy producing systems and enzymes essential for

metabolism directly involved in nitrogen fixation (Alloway, 2008). Similar findings were

also reported by Hazra et al. (1987) in okra and Barik and Chandel (2002) in soybean. In

the present investigation, yield differed significantly due to various levels of copper

nutrition. Further, increase in the dose of CuSO4 reduced the yield of wheat plant. The

improvement in grain yield could be attributed due to the soil application of Cu (Kumar

et al.,2012) which, played an important role in plant metabolism as well as in

biosynthesis of auxins which may also reduce the flowers and fruits drop (Tamilselvi et

al., 2002a).

The supplementation of Cu in both soil as well as sand as growth medium, at

optimum dose of Cu sufficiency might promoted more uptakes of other nutrients that

could helped to produce more vegetative as well as reproductive yield (Kumar et al.,

2009). By this, effective translocation of carbohydrate to reproductive parts could be

increased grain yield in wheat (Gangamrutha, 2008). The excess concentration of Cu in

growth medium consequently, accumulated in tissue at higher concentration might

caused toxicity, imbalance and scorching effect on plant parts (Pandey, 2006; Brun et al.,

2001). Experiments 4.1B and 4.3B were carried out to see the effects of various levels of

Zn on growth and reproductive yield of wheat. It was observed that, growth and

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reproductive yield was increased with increase in concentration of Zn in growth medium,

maximum positive result was found at 50 mg kg-1Zn amendment in soil. Our results are in

accordance with Hussain and Yasin (2004) who reported increase in wheat yield by 12%

with the application of 5 kg Zn ha-1. Similarly, Khan et al.,2007; Singh et al.,1999 and

Ravankar et al., 2003 also reported enhance in yield of wheat grain with application of

Zn. Kannaujiya et al. (2013) reported increase in grain yield with Zn amendment in soil.

This might be due to the enhanced accumulation of assimilates in the grain (Kobayashi et

al., 1998). Increase in crop yield could be due to the increase in concentration of Zn

which might increases the uptake of NPK in plant (Abbas et al., 2009). Similarly,

Pederson et al. (2002) observed nitrogen concentration highly correlated to increase with

P and Zn concentration in plants.

In experiment 4.2 test plants were grown in soil with sandy loam in texture, high

CaCO3 contents, high pH, low organic matter content and low level of DTPA extractable

available micronutrients (Cu, Zn and Fe). Experiments were carried out to study the

effects of interaction between various levels of Cu and Zn vice- versa on growth, yield

and tissue concentration of plant. In test plants visual deficiency symptoms of Cu and Zn

such as reduction in shoot length, reduced leaf lamina, profuse tillering ware observed in

plants grown in control (native soil without any fertilizer application), as native soil was

deficient in available Zn and Cu (Agarwala and Sharma 1979). These symptoms were

similar as reported by Sharma et al. (1987) in chick pea grown in Zn deficient soil.

Kumar et al. (2009) reported that, numbers of tillers were maximum in Cu deficient soil.

This might be due to the low copper had decreased height and profuse tillering which

could be attributed to the loss of apical dominance of the main stem (Grotz and Guerinot,

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2006). Similar effects of low Cu have also been described in different plants (Agarwala

and Sharma, 1979; Marschner, 1995). Wheat plants showed less visible symptoms of

toxicity as compared to other plants, it could be due to the high tolerance of wheat to

excess Zn (Bennett et al., 2003). In experiment 4.2A data presented in table reveled that

Zn application promoted the shoot length and biomass yield of plants, our result showed

increase in growth and biomass yield of plants, although the concentration of Cu was at

excess level as in earlier experiments the amendment of 25 mg kg -1 in soil showed

positive response in wheat plants for growth and yield of crop it could be due to the soil

conditions have alkaline pH, which may reduce the toxic effect of Cu (Lexmond, 1990).

Cu and Zn application ensure better plant growth, dry matter yield of wheat plant has

been reported (Imtiaz et al., 2003).

In experiment 4.2A a reciprocal effect for both Cu and Zn was observed with the

application of Zn, data presented in table showed increase in concentration of Zn both in

shoot and grain. Concentration of Cu in shoot and grain of wheat decreased with the

increase in concentration of Zn in soil, it could be due to the Cu has the ability to replace

Zn on exchange sites resulting in increased concentration of Zn in soil solution and their

uptake in plants (Pendias and Pendias 1992). According to Tani and Barrington (2005)

increased level of Cu significantly increases Zn uptake at lower level, but at higher levels

in soil it slightly decreases Cu uptake.

In experiment 4.2B, various levels Cu amended with an excess level of Zn (100

mg kg-1) in soil. Data presented in table shows that the application of Cu in soil with

excess level of Zn increased the level of Cu concentration both in plant shoot and grains,

the result was in accordance with the reports of Malhi et al. (2005) and Brennam and

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Bolland (2003). The lower concentration of Cu amendments in soil did not affected the

concentration of Zn in shoot and grains of wheat plants, but at higher concentration it

decreased the concentration of Zn in shoot and grains of wheat, this might be due to the

antagonistic effect of Cu and Zn on plants (Dangarwala, 2001). Pendias and Pendias

(1992) also reported the similar result as the Cu and Zn compete for the same exchange

sites in soil. Higher concentrations of Cu in the soil solution can reduce the availability of

Zn to the plants (and vice versa) due to competition for the same sites for absorption into

the plant root. This could occur after the application of Cu fertilizer. Imtiaz et al. (2003)

reported that, application of Zn had an adverse effect on the Cu concentration in the

tissue of wheat. There is a negative interaction between Zn and Cu due to antagonistic

effects and the same membrane transport protein (Moustakas et al., 2011; Mousavi,

2011).

In experiment 4.4 the study was carried out to investigate the effect of various soil

conditions (texture, pH, organic matter contents, CaCO3 contents, trace metals Zn, Cu and

Fe contents) on growth, reproductive yield and grain quality of wheat plants under field

conditions at five different locations of Uttar Pradesh state (India). Data presented in

experimental table revealed that maximum growth and reproductive yield of wheat plants

was found at location L2 (Barabanki), where soil conditions were in best favorable limits

for plant growth and yield. At location L2 the soil has clay loam texture, moderate bulk

density (1.78g/m3), moderately acidic pH (6.2), low CaCO3 content (0.98%), high value

of O.M. contents (2.64%) and higher value of trace metals Zn, Cu and Fe (0.75, 0.38 and

4.80 mg kg-1). At location L2 the DTPA extractable available Cu were found to be

sufficient considering the critical limits 0.20 mg kg-1 soil as suggested by Lindsay and

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Norvell (1978), Fe was also found sufficient but Zn was found to be deficient this might

be due to the low total Zn concentration in soil, low pH or might be due to organic matter

contents (Alloway, 2008). Several studies suggested different values of critical Zn level

in soil using DTPA soil test. This could be due to variation in the soil type and physic-

chemical nature of the tested soils (Lindsay and Norvell 1978). In all five different

locations soil properties greatly influenced the bioavailability of micronutrients, many

factors such as soil texture, pH, CaCO3 contents, E.C. and organic matter contents

affected the bioavailability of metals (Zn, Cu and Fe). At all five locations, concentration

of Zn, Cu and Fe varied from 0.48 to 0.75, 0.25 to 0.38 and 2.38 to 4.80 mg kg -1

respectively, it could be due to the variation in soil type and their physic-chemical

properties (Ekiz et al., 1991). The availability of Zn, Cu and Fe were highly affected with

soil pH (Kiekens, 1995; Sharma, 2006). The organic matter contents also influences the

availability of Zn, Cu and Fe in soil (Katyal et al., 1983). Organic matter contents

regarded as a very important parameter of soil fertility influences nutrients availability

(Sarwar et al., 2008). It has number of important roles to play in soils, both in their

physical structure and as a medium for biological activity (Marschner, 1995). Organic

matter makes its greatest contribution to soil productivity provides nutrients to the soil,

improves its water holding capacity, and helps the soil to maintain good tilth and thereby

better aeration for germinating seeds and plant root development (Zia et al., 1993). High

pH >6, low organic matter and high CaCO3 contents fevers the Zn deficiency in soil

(Cakmak 1998; Nofal et al., 2013). The main factors which affected the amount of zinc in

soil at different study locations were pH, carbonate content, organic matter, soil texture

and interaction between zinc and other micro elements, such as Fe (Bukvic et al., 2003).

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The soils, with high pH, the solubility of micronutrients such as Cu, Zn and Fe is mostly

observed deficient in soil has been reported (Curtin and Naidu, 1998), and plants grow on

these soils often experiences deficiency of these trace elements (Sharma, 2006).

However, elemental deficiency is not always experienced (Qadir and Schubert, 2002)

because the soil binding agents, especially soil organic matter and hydrous ferric and

manganese oxides as well as carbonate can also influence the phytoavailability of metals

(Sauve et al., 2000; Dumat et al., 2006). Metals (Cu, Zn and Fe) concentrations in wheat

plants reflected the amounts of the chemically available metals present in the cultivated

soil. The data obtained from experimental sites were found to be in the normal range as

described by Kabata-Pendias and Pendias (1992). They found that, 27–150, 5–30, and

50–250 mg kg-1 soil for Zn, Cu and Fe respectively, however, no limiting values were

recommended for Fe. Therefore, heavy metals concentration in wheat plants at harvest

period was observed within the range of sufficiency.

In general, soil conditions are one of the most important factors in controlling

growth and yield of plants. At location L2, all soil conditions studies were found

positively correlated with yield. This might be due to at location L2, all these factors

were favorable which returned maximum growth and grain yield of wheat plants,

maximum growth and grain yield of wheat crop could be achieved due to improved soil

conditions which enhanced plant growth and yield (Shaimma et al., 2012). At location L1

(Lucknow) plant growth and yield were poor in compression to other locations studies

the soil conditions at location L1 were highly unfavorable for growth and grain yield with

respect to texture, pH, CaCO3 contents, E.C. and organic matter contents, bioavailability

of metals (Zn, Cu and Fe) could be attributed poor yield (Sharma, 2006). At location L1

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soil conditions was sandy loam in texture, contained high level of CaCO3, low level of

organic matter contents and deficient in micronutrients contents. These unfavorable

conditions of soil properties, in their combination affected plant growth and yield of

wheat at location L1 (Brady 1990). Lower yield of wheat plant might be due to many

factors such as sandy loam soils with poor availability of micronutrients (Zn, Cu and Fe),

and high soil pH have been reported (Naidu and Rengasamy, 1993). Zn shows the most

common deficiency in soil and crop, particularly at high-pH soils with low Zn (Cakmak,

2004; Alloway, 2004). Tissue concentration of Cu, Zn and Fe in wheat shoot and grain

from different study locations are shown in table 4.4.4. The Cu, Zn and Fe contents in

shoot ranged from 11.5 to 17.0, from 23.8 to 31.6 and from 132.56 to 164.90 µg g-1 DW

in shoot, and in grains it was ranged from ranged from 7.6 to 12.4, from 17.4 to 23.40 and

from 21.32 to 27.80 µg g-1 DW respectively were observed. The Zn contents of wheat

grains was consistent with findings of Cakmak et al. (2004) who reported that Zn content

of wheat grain ranged from 8 to 34 mg kg-1. The results were also in accordance with

Erdal et al. (2004) and Ali Riza, (2009).

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