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International Research Journal <strong>of</strong> Applied and Basic Sciences
© 2013 Available online at www.irjabs.com
ISSN 2251-838X / Vol, 4 (7): 1683-1686
Science Explorer Publications
<strong>The</strong> <strong>alleviating</strong> <strong>effects</strong> <strong>of</strong> <strong>humic</strong> <strong>substances</strong> on
photosynthesis and yield <strong>of</strong> Plantago ovate in
salinity conditions
Hamideh Gholami 1* , Saeed Samavat 2 , Zahra Oraghi Ardebili 3
1. Department <strong>of</strong> agriculture, Garmsar Branch, Islamic Azad University, Iran.
2. Member <strong>of</strong> scientific board, Soil and Water Research Institute, Karaj, Iran.
3. Department <strong>of</strong> Biology, Garmsar Branch, Islamic Azad University, Iran.
* corresponding author email: h1.gholami@yahoo.com
ABSTRACT: With regard to the rise <strong>of</strong> concern about environmental issues, the aims <strong>of</strong> the present
research were the assessment <strong>of</strong> the salt induced changes in photosynthesis and yield <strong>of</strong> Plantago ovate,
an important medicinal plant, as well as evaluation <strong>of</strong> the possible impacts <strong>of</strong> the <strong>humic</strong> <strong>substances</strong> on
the photosynthesis especially in salinity conditions. <strong>The</strong> <strong>effects</strong> <strong>of</strong> three levels <strong>of</strong> <strong>humic</strong> acid (0, 50 and
100mgL -1 ), fulvic acid (0, 50 and 100 mgL -1 ) and salt (0, 50 and 100 mM) on plants in fifteen different
treatment groups were evaluated. In contrast to qN (non photochemical quenching c<strong>of</strong>ficient), salt stress
reduced the amounts <strong>of</strong> Fv/Fm (maximum quantum yield <strong>of</strong> photosystem II), qPSII (the actual quantum
yield), qP (photochemical quenching coefficient) and chlorophyll contents whereas the application <strong>of</strong>
<strong>humic</strong> acid and fulvic acid, especially the first one, had promoting <strong>effects</strong> and damages caused by salinity
conditions were significantly alleviated by the applied <strong>humic</strong> <strong>substances</strong>. In addition, the application <strong>of</strong>
<strong>humic</strong> acid and fulvic acid not only had enhancing <strong>effects</strong> on the thousand grain weight but also
<strong>alleviating</strong> ones on the salt induced reduction <strong>of</strong> yield.
Keywords: Holmic <strong>substances</strong>; Organic; photosynthesis; Plantago ovate; productivity; salt stress
INTRODUCTION
Salinity, is known as one <strong>of</strong> the major abiotic stresses, can damage the cellular ionic homeostasis, balance and
distributions (Niu et al. 1995; Wang et al. 2012) which substantially resulted in reduced yield <strong>of</strong> agricultural plants
and these losses are <strong>of</strong> crucial concern for most countries. Salinity is known as a limiting factor <strong>of</strong> crucial process
like photosynthesis, nitrogen assimilation (Parida and Das, 2005; Munns and Tester, 2008), the ion distributions in
plant (Wang et al., 2012) in vast verities <strong>of</strong> plant species.
Humic <strong>substances</strong> can improve nutrient availability and affect chemical, biological, and physical soil properties
(Khaled and Fawy, 2011). It is well known that <strong>humic</strong> <strong>substances</strong> have enhancing <strong>effects</strong> on plant growth,
development and productivity. <strong>The</strong> mentioned direct and indirect beneficial <strong>effects</strong> <strong>of</strong> <strong>humic</strong> <strong>substances</strong> on plant
growth and development are their <strong>effects</strong> on cell membranes which lead to the enhanced transport <strong>of</strong> minerals,
improved protein synthesis, plant hormone-like activity, promoted photosynthesis, modified enzyme activities,
solubilization <strong>of</strong> microelements and macro elements, reduction <strong>of</strong> active levels <strong>of</strong> toxic minerals and increased
microbial populations (Seyed bagheri, 2010). In addition, <strong>humic</strong> <strong>substances</strong> introduced as good accumulators <strong>of</strong>
toxic heavy metals (Sinha and Bhattacharyya, 2011).
In respect <strong>of</strong> the rise <strong>of</strong> concern about environmental issues, there is more interest in organic agriculture. <strong>The</strong>re
are not enough studies about the changes induced by the application <strong>of</strong> <strong>humic</strong> <strong>substances</strong> on plant structures and
process in abiotic stresses, especially salinity conditions.
Plantago ovate is known as an important medicinal plant. <strong>The</strong> aims <strong>of</strong> the present research were the
assessment <strong>of</strong> the salt induced changes in photosynthesis and yield <strong>of</strong> Plantago ovate as well as evaluation <strong>of</strong> the
possible impact <strong>of</strong> the <strong>humic</strong> <strong>substances</strong> on the photosynthesis especially in salinity conditions.

Intl. Res. J. Appl. Basic. Sci. Vol., 4 (7), 1683-1686, 2013
MATERIAL AND METHODS
<strong>The</strong> experimental design was completely randomized. Plantago ovate plants were grown at a mean
temperature cycle <strong>of</strong> 25°C (day)/15°C (night) and relative humidity <strong>of</strong> 35%. <strong>The</strong> <strong>effects</strong> <strong>of</strong> three levels <strong>of</strong> <strong>humic</strong> acid
(0, 50 and 100mgL -1 ), fulvic acid (0, 50 and 100 mgL -1 ) and salt (0, 50 and 100 mM) on plants were evaluated. Two
month old plants were fertilized two times with two week intervals by different mentioned concentrations <strong>of</strong> <strong>humic</strong>
and fulvic acid. Salt treatments were done two times with three day intervals three days after the last fertilization.
<strong>The</strong> details <strong>of</strong> the used soil analysis were presented in table 1. <strong>The</strong> seedlings were grouped in 15 different
treatment groups including control (C), S50, S100, F50, F50-S50 , F50-S100 , F100, F100-S50, F100-S100, H50,
H50-S50, H50-S100,H100, H100-S50,H100-S100 (H, F and S refer to the <strong>humic</strong>, fulvic and salt respectively and
the numbers show the used concentrations).
Chlorophyll fluorescence was measured from the last developed leaves using a fluorometer (PAM-2000, Walz,
Germany). Parameters including qPS II (the actual quantum yield in the light-adapted steady state), qP
(photochemical quenching coefficient), qN (non photochemical quenching coefficient) and Fv/Fm (maximum
quantum yield <strong>of</strong> photosystem II) were determined.
Chlorophyll contents were analyzed with chlorophyll meter (Minolta SPAD-502, Japan).
Plant yield was estimated based on thousand grain weight in each treatment group.
Analysis <strong>of</strong> variance was performed on all data using SPSS s<strong>of</strong>tware. Duncan test with probability <strong>of</strong> 0.05 was
applied to assess any significant differences between treatments.
Parameters
EC
PH
Organic matter
Organic carbon
P
K
N
Table 1. the details <strong>of</strong> the used soil.
Amounts
1.31 ds/m
7.72
1.2 %o/m
0.7%o/m
2.46 mgL -1
599 mgL -1
0.003 mgL -1
RESULTS AND DISCUSSION
As it was shown in table 2, salt stress had reducing <strong>effects</strong> on the amounts <strong>of</strong> Fv/Fm whereas the application
oh <strong>humic</strong> acid and fulvic acid, especially the first one, had promoting <strong>effects</strong> and the negative <strong>effects</strong> <strong>of</strong> salt stress
were significantly alleviated by the applied <strong>humic</strong> <strong>substances</strong>. Although the salinity conditions, especially the
second used level, resulted in the reduced qPSII, the application <strong>of</strong> <strong>humic</strong> acid and fulvic acid, especially the first
one, decreased detrimental <strong>effects</strong> <strong>of</strong> stress (table 2). <strong>The</strong> application <strong>of</strong> <strong>humic</strong> and fulvic acid individually were
ineffective to promote qP whereas effective to alleviate damaging <strong>effects</strong> <strong>of</strong> salt stress (table 2). In contrast to the
<strong>effects</strong> <strong>of</strong> salinity conditions on qP, qPSII and Fv/Fm, the amounts <strong>of</strong> qN were increased in salt treated plants
however, the applied treatments <strong>of</strong> <strong>humic</strong> acid and fulvic acid were significantly effective to ease the salt stress
(table 2). In comparison to the control samples, the decreased chlorophyll contents were observed in individually
salt treated plants, S50 and S100, whereas the enhanced ones were found in <strong>humic</strong> and fulvic treated groups and
the best results recorded in H50 and H100 (table 3). <strong>The</strong> results presented in table 2 and 3 indicated that damages
induced by salinity conditions were declined by the applied treatments <strong>of</strong> <strong>humic</strong> acid and fulvic acid, especially the
first one. As it was presented in table 3, the application <strong>of</strong> <strong>humic</strong> acid and fulvic acid not only had enhancing <strong>effects</strong>
on the yield but also <strong>alleviating</strong> ones on the salt induced reduction <strong>of</strong> thousand grain weight. However, <strong>humic</strong> acid
concentrations <strong>of</strong> 100 were not effective as much as 50. It seems that the enhanced nutrient uptakes and induced
physiological changes by the applied treatment <strong>of</strong> <strong>humic</strong> acid or fulvic acid, especially the first one, were
responsible for the obtained results in this study.
A declined photosynthetic quantum conversion is assessed by a decline in the values <strong>of</strong> the Chl fluorescence
ratio Fv/Fm (Lichtenthaler and Burkart, 1999). It has been reported that photosynthesis is extremely sensitive to
varieties <strong>of</strong> abiotic stresses (Sadder et al., 2013). Salt stress in sorghum plants resulted in the significantly reduced
maximum quantum yield <strong>of</strong> photosystem II (Fv/Fm), photochemical quenching coefficient (qP) and electron
transport rate (ETR) as well as increased photochemical quenching (Netondo et al. 2004). It has been stated that
sensitivity to salt stress in cereals may be correlated with decreases in PSII photochemical efficiency and elevated
qN, in order to dissipate the excess energy (Moradi and Ismail 2007). <strong>The</strong> declined photochemical reactions,
especially with the mediation <strong>of</strong> PSII, which is occurred in plants exposed to various stresses and accompanied by
the chlorophyll losses, may be caused by the destroyed chloroplast structure, destabilization <strong>of</strong> pigment protein

Intl. Res. J. Appl. Basic. Sci. Vol., 4 (7), 1683-1686, 2013
complexes, limited CO2 fixation and enhanced photorespiration (Sadder et al. 2013). <strong>The</strong> fast chlorophyll a
fluorescence transient analysis indicated that salt restricted the maximum quantum yield <strong>of</strong> PSII photochemistry
(F v /F m ), occurred in plants exposed stress was resulted from the damage at the receptor side <strong>of</strong> PSII (Shu et al.
2012). In addition, the microscopic analysis reflected that salt stress led to the damaged chloroplast envelope,
increased number <strong>of</strong> plastoglobuli along with abnormal thylakoid membranes (Shu et al. 2012). <strong>The</strong> results
presented here showed that the application <strong>of</strong> <strong>humic</strong> <strong>substances</strong> not only had promoting <strong>effects</strong> on chlorophyll
contents and photosynthesis but also <strong>alleviating</strong> ones on damages caused by the salt stress. It seems that the
<strong>effects</strong> <strong>of</strong> <strong>humic</strong> <strong>substances</strong> on plants may be selective and variable, depend on their concentration and the
medium pH (Nardi et al. 2002). Humic <strong>substances</strong> can facilitate respiration and photosynthesis processes via
modified functioning <strong>of</strong> mitochondria and chloroplasts (Orlov et al. 2005). <strong>The</strong> negative <strong>effects</strong> <strong>of</strong> the environmental
stresses on plants can be alleviated by the use <strong>of</strong> <strong>humic</strong> <strong>substances</strong> (Orlov et al. 2005). As it was shown by the
decreased thousand grain weight, it seems that the observed reduction in plant biomass can be due to a
combination <strong>of</strong> slower growth and development, caused by osmotic stress, inhibited photosynthesis process as
well as altered source-sink metabolism and relations. <strong>The</strong> limited plant yield in salinity condition has been attributed
to the osmotic stress, restricted photosynthesis mainly because <strong>of</strong> salt induced changes in photosynthetic
apparatus and sink capacity (Kato and Takeda 1996; Dionsio-Sese and Tobita 2000; Shani and Ben-Gal 2005).
Stomatal conductance, reduced sink activity, decreased Rubisco efficiency, displacement <strong>of</strong> essential cations,
changes in membrane permeability, excessive generation <strong>of</strong> reactive oxygen species (ROS) in chloroplasts and
swollen and disorganized grana are proposed as a possible reason for inhibiting <strong>effects</strong> <strong>of</strong> salinity on
photosynthesis process (Dionisio-Sese and Tobita 2000; Desingh et al. 2007; Moradi and Ismail 2007; Chaves et
al. 2009).
In conclusion, the obtained results from the present research indicate that the application <strong>of</strong> <strong>humic</strong> <strong>substances</strong>,
especially at suitable concentrations, may alleviate the damages induced by the stress, probably via the enhanced
nutrient uptakes and induced physiological changes.
Table 2. the <strong>effects</strong> <strong>of</strong> <strong>humic</strong> acid, fulvic acid and/or salt stress on different parameters related to the photosynthesis in Plantago
ovate.
Treatments
qPSII
qP
qN
Fv/Fm
C
0.64 abc
0.9967 a
0.26 ef
0.637 c
S50
0.5767 de
0.9133 ab
0.3933 b
0.448 d
S100
0.3933 h
0.8267 c
0.45 a
0.4d
F50
0.6233 abcd
0.9733 ab
0.22 g
0.705 ab
F50-S50
0.4967 g
0.9533 ab
0.3567 c
0.637 c
F50-S100
0.5233 efg
0.91 ab
0.4567 a
0.689 abc
F100
0.5833 cd
0.9833 ab
0.2633 fg
0.68 abc
F100-S50
0.5867 bcd
0.9733 ab
0.2967 de
0.678 abc
F100-S100
0.5167 fg
0.9033 b
0.31 d
0.674 abc
H50
0.65 a
0.9933 a
0.2033g a
0.72 a
H50-S50
0.5233 efg
0.9767 ab
0.28 de
0.655 abc
H50-S100
0.5 g
0.91 ab
0.2867 de
0.69 abc
H100
0.6433 ab
0.9867 ab
0.23 fg
0.71 a
H100-S50
0.6033 abcd
0.96 ab
0.2667 ef
0.69 abc
H100-S100
0.5667 def
0.9133 ab
0.2867 de
0.676 abc
*: Mean values followed by different letters are significantly different at P

Intl. Res. J. Appl. Basic. Sci. Vol., 4 (7), 1683-1686, 2013
ACKNOWLEDGEMENTS
This study was supported by the Islamic Azad University, Garmsar branch. Authors would like to thank Dr.
A Ladan Mogadam for his pr<strong>of</strong>essional and warming helps.
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