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Plant Archives
Vol. 19, Supplement 2, 2019 pp. 1402-1410 e-ISSN:2581-6063 (online), ISSN:0972-5210
THE ROLE AND IMPORTANCE OF AMINO ACIDS WITHIN PLANTS : A REVIEW
H.A. Baqir, N. H. Zeboon and A.A. J. Al-behadili
College of Agricultural Engineering Sciences, University of Baghdad, Iraq
Corresponding author: haderabid@yahoo.com mailto:najat.Zeboon@yahoo.com
Abstract
Agronomy is one of the sensitive aspects associated with product goodness and quality. According to the rapid development of the
population density and the necessity for healthy food to meet this increment in population either by the traditional agricultural methods or
using modern technology, it is necessary to adopt the characteristics the biological and biochemical energies to achieve that goal. Many
studies proved that amino acids play a positive role in enhancing the plant yield and quality when they are sprayed at different growth stages
especially the critical ones such as the tillering and flowering stages or under stress conditions (such as drought, high temperature, frost,
salinity, or pathogens), thus they contribute to reducing the stress effect of drought and salinity through the different physiological activities
by changing the osmotic potential of plant tissue as well as they greatly reduce injuries caused by bio stresses. They stimulate physiological
and biochemical processes and participate in protein and carbohydrate synthesis. It also believed that amino acids are accountable for cell
division and producing some natural growth hormones such as IAA and GA3 and consequently increasing the yield and improving the
quality.
Keywords : Amino acids, biochemical process, temperature, growth hormones.
Introduction
Amino acids can be defined as the essential unit
responsible for protein molecule formation. They are organic
carbon acids made up of the amine (NH
2
) and carboxyl
(COOH) groups in addition to the alkyl (R) group which is
specific to each amino acid and known as a side chain. It
binds at the carbon atom (α). There are 21 amino acids type α
found within proteins divided into two divisions: peptide and
protein (AL-Modhafer, 2009).
Fig. 1 : The general chemical formula of amino acids (AL-
Modhafer, 2009)
Amino acids are bio activators providing a plant with
energy to compensate for the losses caused by the respiration
and decomposition processes. They are characterized as
colorless ionic compounds soluble in cold water, hot water
and alcohol to varying degrees and have a high melting point
that is because they are hybrid ions. Amino acids are found in
plants either freely or in combination with each other to form
proteins and peptide compounds, however, the free form is
the common, as the free form decomposes the petite bonds
and makes the amino acids free, single, and easy to
penetrate (Abd EL hafez, 2011). Amino acids are also
largely found in mitochondria and chloroplast of organisms
as a result of the availability of ketonic acids resulted from
the assimilation of carbohydrate formed by carbon
assimilation during the Kreb cycle (Beavers, 1991). The
amount of amino acids varies from one plant to another
depending on the metabolic processes (Abed, 2007) which
can easily transmit through root hairs and pass through
vessels of plants. Amino acids play an important role in
many biotic processes whether they are free or as a
component of proteins; therefore, their importance and
effectiveness lie in the stages of plant growth. They
contribute to increasing the cell ability to uptake water and
solvent nutrients from growth media and then increasing the
vegetative growth; moreover, they increase synthesizing
proteins participating to the multiple functions of plant
metabolism and enhance the carbon assimilation rate leading
to increasing the total dry matter reflecting on the sink and
the yield (Abu-Dahi and Al-Younis, 1988; Dreccer et al.,
2000; Sharma-Natu and Ghildiyal, 2005). Amino acids form
a substance for synthesizing other materials such as vitamins,
nucleotides, and plant growth regulators thus they are
essential components of the living matter and protoplasm;
furthermore, they contribute to the synthesizing enzymes as
well as to the enzymatic reactions inside the cells (Kamar and
Omar, 1987). Amino acids are believed to be responsible for
enhancing protein contents, cell division, plant pigments, and
natural hormones such as IAA, GA3, and ethylene (Ahmed
and Abd El-Hameed, 2003; Ahmed et al., 2007 and 2014;
Madian and Refaai, 2011). Amino acids as bio inducers can
also enhance the grain quality of some crops since they
increase minerals absorption and enhance the use efficiency
nutrient elements, where amino acids play an important role
as a chelate material for each of iron, zinc, copper,
magnesium, and calcium as these elements can be absorbed
and passed through plant easily with helped by amino acids
(Vernieri et al., 2005). In addition, they balance the soil
microorganisms which improve the mineralization of the
organic matter resulting in fertilized well-structured soil
surrounding the plant roots (Ashmead, 1986). Amino acid
represents an important source for nitrogen, thus they greatly
affecting the crop growth (Näsholm et al., 2000; Persson and
Näsholm, 2002). Some studies reported that proline
accumulation is a mean used for gathering nitrogen from the
compounds resulted from protein analysis (Edrees, 2009).
Protein breaking down or inhibiting protein synthesis during
plant subjecting to water stress conditions contributes to
nitrogen aggregation that leads to formation poisonous
compounds causing damage for the plant, therefore, plants
have a special mechanism converting these compound into
soluble nitrogenous compounds such as amino acids, the
most important of which is proline. Studies proved that
amino acids can affect directly or indirectly the physiological
1403
activities where they participate to protein synthesis and
carbohydrate construction by constructing chlorophyll and
enhancing photosynthesis as well as they contribute to
stimulating the activity of many enzymes and coenzymes (El-
Shabasi et al., 2005; Mohamed, 2006; Al-Said and Kamal,
2008; Kowalczyk and Zielony, 2008; El-Ghamry et al., 2009;
Shafeek et al., 2012). These results were confirmed by Kandi
et al. (2016) who reported that spraying wheat plants by
amino acids limited the rapidity of the nutrient deficiency as
they are absorbed easily and used directly for protein
synthesis, where Glycine is a major component of building
chlorophyll within plant as it helps to increase chlorophyll
concentration leading to the highest degree of photosynthesis.
Some amino acids are characterized by containing sulfur as a
major element participating in many plant proteins and
keeping the stereoscopic structure or forming the active sites
of enzymes. Among sulfuric amino acids containing Sulphur
are Cysteine, Cysteine, and Methionine which are similar in
containing sulfur in the side chain of their structure (Coccoti,
1996; Yassen, 2001). Sulfur function in proteins is forming
the disulfide bonds (-S-S-) (sulfuric bonds) between
polypeptide chains and within them causing the protein to be
folded or wrapped. These bonds are important in determining
the shape and structure of the protein, and they are also
involved in the formation of protein enzymes (Mengel and
Kerby, 1984; Havlin et al., 2005). Some amino acids,
including proline and arginine, also play an important role in
resisting adverse conditions such as salinity, drought, and
high or low temperature, where proline is one of the amino
acids participating in protein synthesis. It is also observed
that proline amount within a plant is proportional to the stress
size, either biotic or non-biotic, that the plant subjected to, as
proline accumulates in the plant parts subjected to the stress.
Figure 2 illustrates briefly the role of amino acids in plant.
Points have to be considered during spraying amino
acids on plant
• Spraying the amino acids during the early morning.
• Avoid mixing compounds containing calcium and
sulfur with mineral oils.
• Spraying amino acids at the beginning of the critical
growth stages in order to enhance the root and shoot
growth.
• Sprayed plants should not be subjected to lack of
phosphorus.
• In the case of use of individual amino acids, it is
preferable to treat the lack of elements before spraying.
Fig. 2 : The role of amino acids in plants
Table 1: the role of amino acids and their structural formula.
Amino acid Symbol
Amino acid role within plant Formula Molecular
weight
Glycine Gly
Acti
vating photosynthesis and raising its efficiency as
it enhances chlorophyll formation and encourages
vegetative growth as well as it has a role in pollination
and fruitfulness.
75
Alanine Ala Affecting plant growth velocity and activati
ng
chlorophyll formation
89
Valine Val
Affecting the velocity of growth, root formation, and
seed production.
117
H.A. Baqir et al.
1404
Methionine
Met
Accelerates the fruit ripening as it enters the cycle of
ethylene formation and has a role in the root activation.
149
Isoleucine Lle Increasing the shoot system, growth, and early yield
131
Thereonine The Increasing plant tolerance to diseases
119
Cysteine Cys Increasing vital pr
ocesses and regulating them within
plants and increasing the disease resistance
121
Phenylalanine
Phe Improving plant cells and embryo formation
165
Serine Ser
Increasing plant tolerance to diseases, activating
c
hlorophyll, and has a role in hormone balance inside
plant
105
Tyrosine Tyr Increasing plant tolerance to diseases
181
Lysine Lys Increasing the shoot system, growth, and early yield
146
Leucine Leu
131
Glutamic
Acid Glu Increasing the shoot system, growth, and early yield
147
Aspartic Acid
Asp Enhancing plant resistance to diseases
133
Arginine Arg
Increasing tolerance to the hard co
nditions such as
heat, frost, drought, and salinity. It has a role in
chlorophyll formation and enhancing root formation as
well as cell division and poly amid formation (Hozayn
and Abd El-Monem, 2010).
174
The role and importance of amino acids within plants : A review
1405
Hydroxy
Proline
Hyp Increasing tolerance to
the hard conditions such as
heat, frost, drought, and salinity.
Proline Pro
Increasing tolerance to the hard conditions, activating
pollen grain germination, organizing osmosis potential,
maintaining the colloidal properties of the cel
l
protoplasm, and removing the negative effect of free
radicals.
115
Hydroxy
Lysine Hyl Increasing crop growth and early yield.
Histidine
Increasing crop growth, early yield, and enhancing
phosphorus action inside plant.
155
Tryptophan Try
Helping to the formation of active auxins IAA
necessary for plant growth and has a role in the early
yield.
204
Effect of some amino acids on the root and shoot systems
of Plant
Research results showed the positivity effect of amino
acid on stimulating growth and increasing yield when they
were used for many field crops. Studies illustrated that
spraying amino acids on plants with increased both the
vegetative growth and leaf area as they are easily absorbed
by leaves to create protein and increase the leaf chlorophyll
content resulting in improving the crop yield and quality
(Mccarthy et al.., 1990; Lozek and Fecenko, 1996; Neri et
al., 2002). Dromantiene et al. (2013) reported that the
absorption of amino acids by winter wheat plants did not
depend on the chlorophyll activity as plants can use these
materials directly and save the energy. Studies confirmed that
amino acids can affect the physiological activities of plant
growth and development directly or indirectly, however, they
affect positively and greatly reduce the damages caused by
non-biotic stresses (Kowalczyk and Zielony, 2008; Abd El-
Aal et al., 2010; Shalaby and El-Ramady, 2014). These
studies were consistent with those of (Mohamed, 2006; Zaki
et al., 2007) who referred to the beneficial role of amino
acids. Nikiforova et al. (2006) mentioned that spraying
amino acids stimulated the emergence of the root system and
activated the growth of plant parts above the soil surface.
These results were confirmed by the findings of Kandi et al.
(2016) who indicated that spraying a mixture of amino acids
and nitrogen fertilizers at the levels (166, 214, and 262
kgN.ha
-1
) on the wheat crop plants increased the plant height
by 23.29% as well as the chlorophyll concentration leading to
the highest degree of photosynthesis and increasing the grain
yield by 7.50% and straw by 10.90%. These results were
consistent with those of Ashoori et al. (2013) who referred to
that spraying an amino acid compound at the concentration
of 1gm.L
-1
with chemical fertilizer 45 and 65 days after
planting enhanced the plant functions. El-Naggar and El-
Ghamry (2007) found that spraying 2000 mg.L
-1
of amino
acids on wheat plants 55 and 75 days after sowing increased
the number of tillers, plant height, and chlorophyll content,
these results confirmed those of Meijer (2003) who reported
that spraying amino acids on wheat plants stimulates plant
growth and increases yield and protein content. Ramaih et al.
(2003) and Kandil and Marie (2017) mentioned that
Tryptophan is the major origin of IAA in most living
organisms. Martens and Fankenberger (1994) and Sarwar and
Frankenberger (1994) found that the treatment of spraying
Tryptophan at 10
-5
.L
-1
40 days after sowing wheat increased
the growth rate. EL-Bassiouny (2005) reported that spraying
25, 50, and 100 mg.L
-1
of Tryptophan on wheat plants 30, 45,
and 75 days after sowing increased the plant growth, where
the concentration of 100 mg.L
-1
produced the highest plant
height among them with no significant difference, while the
concentration of 25 mg.L
-1
was superior in giving the highest
number of tillers.m
-2
(605 tillers.m
-2
), the highest leaf area
(74.72 cm
-2
), and the highest plant dry weight (1049 g.m
-2
),
however, this concentration did not differ significantly from
50 mg.L
-1
in the traits of the number of tillers and plant dry
weight which were 583 tillers.m
-2
and 977 g.m
-2
respectively, while spraying 50 mg.L
-1
of Tryptophan
achieved the highest dry weight of tillers (488g.m
-2
), yet, the
Tryptophan concentration did not affect the harvest index. He
also indicated that spraying 50 mg.L
-1
of Tryptophan on
wheat plants increased the content of chlorophyll a and b
H.A. Baqir et al.
1406
significantly, while the change in carotenoids content was
insignificant. Results of El-Hosary et al. (2103) referred to an
increment in all growth traits except for the traits of the
number of tillers, plant height, number of leaves, plant dry
weight, plant fresh weight, and flag leaf area as a result of
foliar spray of Tryptophan and Cysteine at different
concentrations where the treatment of spraying 50 mg.L
-1
of
Tryptophan produced the highest number of tillers (6.01 and
7.56 tillers.plant
-1
) and leaves (23.14 and 26.35 leaves.plant
-
1
) in two seasons respectively, in addition to the dry weight
that was affected obviously by spraying Tryptophan at the
concentration of 50 mg.L
-1
recording 17.76 and 23.00
g.plant
-1
in the two seasons respectively. The treatment of
50mg.L
-1
Tryptophan recorded the highest length of the spike
in the second season (12.14 cm), whereas in the first season,
the best concentration was 100 mg.L
-1
producing length
spikes 9.43 cm in an average. The treatment of 150 mg.L
-1
Cysteine also recorded values of growth higher than the
treatment of 100 mg.L
-1
of this amino acid. The results were
also clarified that foliar application of the used
concentrations of Tryptophan and Cysteine led to a
significant increment in all wheat growth traits compared to
the control treatment. He referred to the total photosynthesis
pigments (chlorophyll a, chlorophyll b, and carotenoids)
were increased significantly affected by used amino acids
(Tryptophan at the concentrations 50 and 100 mg.L
-1
and
Cysteine at 100 and 150 mg.L
-1
). Tryptophan was more
effective when it was used at the concentration 50 mg.L
-1
recoding averages 1.229, 0.6101, and 04390 mg.g
-1
for the
chlorophyll a, chlorophyll b, and carotenoids respectively
compared to the control treatment recoding 0.666, 0.3028,
and 0.2219 mg.g
-1
respectively. This result confirmed what
El-Nabarawy et al. (2001) reported the necessity of amino
acids for chlorophyll synthesis. Results of Alaei (2011)
showed increasing the chlorophyll content in wheat plants
resulted in an increment in the grain yield which went in line
with the findings of Abd- El-Aal et al. (2010) and
Khayatnezhad et al. (2011) who referred that spraying amino
acids on wheat plants increased chlorophyll a and b. Azevedo
et al. (2006) noticed that the essential amino acids such as
tryptophan and lysine make maturity early, activate
chlorophyll and increase the amount of sugar. Results gotten
by Zahir et al. (2005) and Sivasankari et al. (2005) referred
that spraying 50 mg.L
-1
Tryptophan enhanced the root and
vegetative growth of different crops. Khatid et al. (1999)
found that spraying Tryptophan at 10
-4
molars produced the
highest plant height and number of tillers (99.60 cm and
545.00 tillers respectively) differing significantly from the
control that produced the lowest values (93.60 cm and 491.00
tillers respectively), while the two concentrations 10
-3
and 10
-
4
molar did not affect significantly the spike length, but they
showed high spike length averaged 11.90 and 12.00 cm
respectively compared to the control producing the lowest
spike length (11.20 cm). Nilesh et al. (2012) referred to
performing the best when spraying the high doses of cysteine
(0.02%) 40 days after sowing that gave the highest number of
tillers and plant height (301.12 and 306.46 tillers.m
-2
) and
(85.22 and 86.25 cm) in two seasons respectively with
significant differences compared to the control treatment
giving the lowest averages (250.39 and 255.19 tillers.m
-2
)
and (78.10 and 77.49 cm) respectively, however, results
showed also that the differences within the same treatment
were not significant; moreover, they mentioned that
biological regulators are a group of chemical substances
including cysteine, regulate plant activities such as physical
and physiological activities. Many studies have been
conducted to investigate the effect of biological regulators on
the yield quantity and quality as well as on the seeds.
According to Sharma et al. (2008), there was a significant
improvement as a response to the foliar spray of biological
regulators on wheat crop. Results of Govind et al. (2007)
referred that biological regulators enhance the plant growth
and photosynthesis efficiency; furthermore, they affect the
transpiration rate and alleviate the stress effect (Freeha et al.,
2008), as well tolerate crop lodging. Results of Aldesuquy et
al. (2012) illustrated that spraying Glycine betaine (GB) on
wheat plants affected the yield and its components positively
with a significant difference compared to the control
treatment and was significantly superior in most growth traits
including root system length, plant height, and spike length
which they were averaged 68.85, 84.378, and 15.52 cm
respectively compared to the control treatment producing
67.49, 82.66, and 15.17 cm respectively. Results of AL-Qaisi
et al. (2016) referred that arginine increased the seed
germination, germination velocity, germination stimulation
indicator, and seed vigor, root system, as well as increased
root system and seedling dry weight in maize significantly.
Results of Dawood and Glaim (2018) showed that spraying
200mg. L
-1
of arginine on maize increased the chlorophyll
index, leaf area, and plant height significantly reaching
10.17, 18.73, 10.57, and 8.27% respectively. Results also
showed that spraying 200 mg.L
-1
proline increased the
mentioned traits by 15.34, 27.13, 14.80, and 14.60 %
respectively. Haroun et al. (2010), when using 1, 2, 3, 4, and
5 ml of glutamic acid on Phaseolus vulgaris found that the
two concentrations, 1 and 2 mL, increased all growth criteria.
Results obtained by Mazher et al. (2011) who used 100 and
200 mg.L
-1
glutamic acid on Codiaeum variegatum L. plants
showed that increasing the concentration to 200 mg.L
-1
increased the growth criteria (plant height, number of leaves,
number of branches disk diameter, root length, plant dry
weight, fresh weight, and the plant content of carbohydrates
and N, P, and K) significantly. Results of Talat et al. (2013)
explained the superiority of spraying 100 mg.L
-1
proline on
two wheat varieties grown under the effect of saline stress in
the traits, plant height, fresh weight, total chlorophyll content
potassium concentration, sodium concentration, and
transpiration rate, compared to the concentration of 50 mg.L
-1
furthermore the control, while the concentration 50mg.L
-1
was superior in the dry weight and water use efficiency.
Effect of some amino acids on the traits of yield and its
components
Khatid et al. (1999) found that spraying 10
-3
and 10
-4
of
Tryptophan on wheat plants increased the grain yield
significantly reaching 3.34 and 3.39 Mg.ha
-1
as well as straw
yield to be 7.24 and 7.35 Mg.ha
-1
compared to the control
treatment giving the lowest averages of grain and straw
yields (3.04 and 6.21 Mg.ha
-1
) for both concentrations
respectively. The concentration 10
-4
gave the highest weight
of 1000 grains (36.60g) differing significantly from control
treatment producing the lowest weight (34.90 g). The two
Tryptophan concentrations 10
-3
and 10
-4
M L
-1
did not affect
the number of spikelets significantly, yet they produced
17.30 and 17.60 spikelets.spike
-1
respectively. EL-Bassiouny
(2005) reported that spraying Tryptophan at the
concentrations 25, 50, and 100 mg.L
-1
30, 45, and 75 days
after sowing wheat increased the grain yield where the
The role and importance of amino acids within plants : A review
1407
treatment of 50 mg.L
-1
the highest value of 1000 grains
(42.89g), grain yield (4.840 Mg.ha
-1
), and straw yield (8.609
Mg.ha
-1
), while spraying Tryptophan did not affect the
harvest index. El-Naggar and El-Ghamry (2007) referred that
spraying 2000 mg.L
-1
amino acids 55 and 75 days after
sowing increased the number of grains, the weight of 1000
grains, grain yield, and straw yield. He confirmed the
findings of (Meijer, 2003; Abd El-Aal, et al. 2010;
Khayatnezhad et al., 2011; Alaei, 2011) who reported that
spraying amino acids on wheat plants increased the traits of
yield and its components. Rūta et al. (2011) suggested that
spraying amide nitrogen contained different concentrations of
amino acids (0-3 %) at the milk maturity stage increased the
grain yield by 0.16 – 0.53%. The liquid fertilizer treatment of
nitrogen contained 1.5% amino acids gave the highest grain
yield averaged 6.46 Mg.ha
-1
. He reported also that wheat
crop correlated significantly to the concentration of amino
acids in the liquid fertilizer of amide nitrogen. Result of
Nilesh et al. (2012) referred to the best performance getting
from spraying high concentration of cysteine (0.02%) on
wheat plants 40 days after sowing reflecting on many traits
including, the highest grain yield (6.15 and 5.70 Mg.ha
-1
) in
two seasons respectively and the highest number of grains in
the second season (53.40 grain.spike
-1
) differing significantly
from the control treatment that produced the lowest values
(4.52 and 4.60 Mg.ha
-1
) and (48.40 and 49.20 grain. Spike
-1
)
in the two seasons respectively. The results obtained by the
same researchers didn’t refer to a significant difference
within the same treatment. Results of Aldesuquy et al. (2012)
illustrated that spraying Glycine betaine (GB) on wheat
plants affected the yield and its components positively
causing significant differences compared to the control
treatments as a response for using bio-stimulators. Grain
yield correlated strongly to the yield components (including,
spike dry weight, number of spiklets, number of grains per
spike weight of 1000 grains, grain yield, biological yield, and
harvest index) which were superior (3.17 g, 17.33 spikelets.
Spike
-1
, 54.33 grains.spike-1, 4.65 g, 3.92g, 8.14g, and
0.96% respectively) compared to the control treatment values
(3.07g, 17.01 spikelets. Spike
-1
, 53.17 grains.spike
-1
, 4.59g,
3.63g, 7.87g, and 0.85% respectively). Results of El-Hosary
et al. (2013) demonstrated that wheat plants foliar sprayed
with 50 mg.L
-1
Tryptophan produced the highest number of
spikes (3.92 and 5.56 spikes.plan
-1
) spike dry weight (4.39
and 6.42 g), grain weight (2.85 and 5.18 g), number of grains
per spike (55.48 and 69.44 grains.spike
-1
), and grain yield
(2.59 and 3.02 Mg.ha
-1
) in the two seasons respectively. The
treatment of spraying 150 mg.L
-1
Cysteine also recorded the
highest values for most traits of yield and its components
compared to the concentration 100mg.L
-1
. The results
obtained by the researchers also showed that spraying all
used concentrations of tryptophan and cysteine on wheat
plants increased all traits of yield and yield components
significantly compared to the control treatment. Results of
Dromantiene et al. (2013) showed that spraying nitrogen
fertilizers containing 0.5–3.0% amino acids on winter wheat
crop at the stage of ear emergence increased the grain yield
to 0.13 – 0.37 Mg.ha
-1
. Results obtained by Hammad and Ali
(2014) reported that treating wheat plants with 3mg.L
-1
amino acids increased the grain yield by 20.49% compared to
untreated plants. Results of Zahir et al. (2005) and
Sivasankari et al. (2014) showed that spraying 50mg.L
-1
tryptophan improved yields of different crops. Results of
Dawood and Glaim (2018) illustrated that spraying 200
mg.L
-1
proline on maize increased the plant yield per by
17.35% and spraying 2000 g.L
-1
arginine increased the plant
yield by 16.35%. Results of Baqir and AL-Naqeeb (2019)
Showed that Spraying 50mg L
-1
tryptophan improved yield
of wheat and its Componenets number of spikes (477.00 and
944.67 spikes m
-2
) weight of 1000 grains (32.01 and 33.55 g)
and yield (5.77 and 5.33 mg ha
-1
) in the two seasons. Results
of AL- Hamoudi (2011) showed the proline role in increasing
the yield of wheat growing under adverse conditions (water
stress) when it was sprayed at concentrations 20 and 40
mg.L
-1
at three levels of water stress (100, 50, and 25% of the
field capacity) where 20 mg.L
-1
proline was significantly
superior. Results of Hasan (2012) referred to the superiority
of spraying 75mg.L
-1
proline on the mung bean plants
affected by periods of thirsting compared to the other used
concentrations (25 and 125 mg) and to the control treatment.
Effect of some amino acids on some qualitative traits of
grains
The quality of good grains is an important component
of food production. The quality of wheat grains depends on
the chemical, biological and physiological processes that take
place in the plant during the developmental stages, and partly
on genetic factors and on a number of environmental factors
during the vegetative growth phase (Johansson et al., 2003;
Svec et al., 2006; Лёвкин et al., 2007). Results of Mccarthy
et al. (1990) and Lozek Fecenko (1996) and Neri et al.
(2002) referred to the positive role of amino acids in
enhancing the plant yield quality. EL-Bassiouny (2005)
found an increment in the protein content by 18.52 %
resulted from spraying 50 mg.L
-1
tryptophan, in attrition to
carbohydrate percentage increasing by 64% when 100 mg.L
-1
was used. These results confirmed those referred to by
Landry and Delhaye (1993) and Arshad et al. (1995) and
Hegazi et al. (1995). Alaru et al. (2003) and Meijer et al.
(2003) reported that spraying amino acids on wheat crop
plants stimulated protein synthesis. Dromantiene et al. (2009)
recorded an enhancement in the wheat grain quality resulted
from spraying 30kg.L
-1
liquid fertilizers of nitrogen amide
containing 0-3% amino acids at the booting stage where the
protein content increased from 0.63% to 0.73%. Rūta et al.
(2001) confirmed that spraying liquid fertilizer of nitrogen
amide containing 0-3% amino acids at the milk maturity
stage increased the protein content in grains from 0.52% to
0.87%. Results of Aldesuquy et al. (2012) showed that the
treatment of Glycine betaine (GB) increased significantly the
protein content in wheat grains. Nilesh et al. (2012) found
that the treatment of foliar spray of 0.01-0.02% cysteine on
the wheat plants 40 days after sowing enhanced the grain
quality. Results of Dromantiene et al. (2013) showed that
foliar fertilization of amide nitrogen containing 0.5- 2.0%
amino acids at the stage of spike emergence enhanced the
wheat grain quality where the protein content increased by
0.62 – 0.81% compared to the control and the highest protein
percentage was 13.96% found in the winter wheat sprayed by
amide nitrogen containing 0.5% Amino acids; moreover, the
gluten values increased by 1.1–1.7% as a result of amino acid
fertilization. The correlation and regression analysis referred
to a significant correlation (r= 0.70) between amino acids and
protein content in the winter wheat grains.
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