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Biostimulant activity of brown seaweed species from Strangford Lough: Compositional analyses of polysaccharides and bioassay of extracts using mung bean (Vigno mungo L.) and pak choi (Brassica rapa chinensis L.)

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The aims of this study were to characterise the composition of seaweed species and to evaluate the efficacy of aqueous extracts as plant biostimulants. Five species (Ascophyllum nodosum, Fucus serratus, Fucus vesiculosus, Laminaria hyperborea and Sargassum muticum) of seaweed were harvested from Strangford Lough, Northern Ireland for the evaluation of polysaccharides, indole-3-acetic acid (IAA), carbon, nitrogen, lipid, ash and mineral contents. The compositional analyses of the five species and their freeze-dried extracts were also carried out using thermogravimetric analysis, scanning electron microscopy and X-ray microanalysis. The concentration of IAA in the acid extracts of the five species ranged between 2.74 and 46.8ngg−1. The carbon, nitrogen, lipid and ash contents ranged between 25.0 and 38.6, 1.37%, and 3.16, 0.83%, and 3.98 and 18.10 and 47.68%, respectively. L. hyperborea and S. muticum contained the highest amounts of minerals. The biostimulant activities of acidic (pH3.0), neutral (pH6.5) and alkaline (pH9.0) extracts were determined by mung bean bioassay. The alkaline extracts from F. vesiculosus and A. nodosum stimulated significantly (P < 0.001) higher dry matter (DM, %) yield of the mung bean plants. The majority of the acidic extracts significantly (P < 0.001) enhanced root formation on the mung bean stem cuttings compared to alkaline or neutral extracts. The acidic extracts of the five species, water control and a commercial product were evaluated as foliar feeds for pak choi plants using a hydroponic production system. The interaction of species, e.g. A. nodosum and F. vesiculosus and the two treatment dilutions on DM yield increases of pak choi were significant (P < 0.05). KeywordsSeaweeds–Phaeophyta–Mung bean–Pak choi
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1 23
Journal of Applied Phycology
ISSN 0921-8971
Volume 24
Number 5
J Appl Phycol (2012) 24:1081-1091
DOI 10.1007/s10811-011-9737-5
Biostimulant activity of brown seaweed
species from Strangford Lough:
compositional analyses of polysaccharides
and bioassay of extracts using mung bean
(Vigno mungo L.) and pak choi (Brassica
rapa chinensis L.)
S.H.S.Sharma, G.Lyons, C.McRoberts,
D.McCall, E.Carmichael, F.Andrews, et
al.
1 23
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Biostimulant activity of brown seaweed species
from Strangford Lough: compositional analyses
of polysaccharides and bioassay of extracts using mung bean
(Vigno mungo L.) and pak choi (Brassica rapa chinensis L.)
S. H. S. Sharma & G. Lyons & C. McRoberts &
D. McCall & E. Carmichael & F. Andrews & R. Swan &
R. McCormack & R. Mellon
Received: 12 May 2011 / Revised and accepted: 30 September 2011 / Published online: 27 November 2011
#
Springer Science+Business Media B.V. 2011
Abstract The aims of this study were to characterise the
composition of seaweed species and to evaluate the efficacy
of aqueous extracts as plant biostimulants. Five species
(Ascophyllum nodosum, Fucus serratus, Fucus vesiculosus,
Laminaria hyperborea and Sargassum mut icum) of sea-
weed were harvested from Strangford Lough, Northern
Ireland for the evaluation of polysaccharides, indole-3-
acetic acid (IAA), carbon, nitrogen, lipid, ash and mineral
contents. The compositional analyses of the five species
and their freeze-dried extracts were also carried out using
thermogravimetric analysis, scanning electron microscopy
and X-ray microanalysis. The concentration of IAA in the
acid extracts of the five species ranged between 2.74 and
46.8 ng g
1
. The carbon, nitrogen, lipid and ash contents
ranged between 25.0 and 38.6, 1.37%, and 3.16, 0.83%,
and 3.98 and 18.10 and 47.68%, respectively. L. hyper-
borea and S. mut icum contained the highest amounts of
minerals. The biostimulant activities of acidic (pH 3.0),
neutral (pH 6.5) and alkaline (pH 9.0) extracts were
determined by mung bean bioassay. The alkaline extracts
from F. vesiculosus and A. nodosum stimul ated significantly
(P<0.001) higher dry matter (DM, %) yield of the mung
bean plants. The majority of the acidic extracts significantly
(P<0.001) enhanced root formation on the mung bean stem
cuttings compared to alkaline or neutral extracts. The acidic
extracts of the five species, water control and a commercial
product were evaluated as foliar feeds for pak choi plants
using a hydroponic production system. The interaction of
species, e.g. A. nodosum and F. vesiculosus and the two
treatment dilutions on DM yield increases of pak choi were
significant (P<0.05).
Keywords Seaweeds
.
Phaeophyta
.
Mung bean
.
Pak choi
Introduction
Seaweeds have a long tradition of being used in coastal
agriculture in the British Isles including Northern
Irelandasasoilconditionertoenhancecropgrowth
and productivity (Booth 1969). During the 1950s liquid
seaweed extracts were formulated for organic production
(Milton 1952) in Europe and North America and later, dry
formulations were developed for foliar applications
(Stephenson 1974). Research carried out during the
1960s demonstrated the chelating properties of t hese
extracts for improving the utilization of m inerals, e.g.
phosphorus in soil (Booth 1969;Lyn1972), the stimula-
S. H. S. Sharma (*)
:
G. Lyons
:
D. McCall
:
E. Carmichael
:
F. Andrews
:
R. Swan
Plant Health and Environment Protection Branch,
Agri-Food and Biosciences Institute,
Newforge lane, Belfast BT9 5PX, UK
e-mail: shekhar.sharma@afbini.gov.uk
C. McRoberts
:
R. McCormack
Food Chemistry Branch, Agri-Food and Biosciences Institute,
Newforge lane, Belfast BT9 5PX, UK
R. Mellon
Northern Ireland Environment Agency,
Belfast BT30 6JB, UK
J Appl Phycol (2012) 24:10811091
DOI 10.1007/s10811-011-9737-5
Author's personal copy
tion of plant grow th due to auxin-like activities (Blunden
1971) and the priming of seeds for increasing the rate of
germination Stephenson 1974.Booth(1969) reported that
the full impact of using seaweeds as fertilizer was not
only due to nitrogen, phosphorus and potash content but
also because of other trace minerals and metabolites.
Other researchers have also speculated as to the
mechanisms involved as well as the validity of the
findings (Beckett and van Staden 1989;Crouchetal.
1990; Hankins and Hockey 1990). During the past two
decades, the evidences for the presence of rooting f actors
in extracts, e.g. indole acetic acid (IAA, Sanderson et al.
1987;Stirketal.2004), the growth stimulation and the
uptake of minerals under stressful conditions were
reported, leading to a better understanding of the mech-
anisms involved in the c ontrol of abiotic and biotic
stresses (Crouch and van Staden 19 9 3;Khanetal.2009;
Rayorath et al. 20 0 7 ). Curr ently c ommerci al form ulati ons
are used w idely in tropical and Mediterranean regions to
alleviate abiotic stresses (e.g. temperature, water deficit
and high salinity) a nd also to modulate crop plants against
biotic stresses (Demir et al. 2006;Spinellietal.2010;
Zhang and Ervin 2004). Henry (2005) reviewed various
studies focused on the performance of alkaline and
nonalkaline extracts of seaweeds and concluded that the
two extraction protocols may have some value, as crop
treatments depending on the conditions of application.
Relatively few studies have directly compared different
extraction protocols for bioactivity.
Many species of green, brown and red algae are
available in and around Strangford Lough, Northern
Ireland. However commercially available species are mostly
brown algae of the Phaeophyta: Ascophyllum nodosum,
Fucus serratus, Fucus vesiculosus and Laminaria hyper-
borea (McLaughlin et al. 2006). Several reports on the
introduction of Sargassum muticum, a non-native species to
the British Isles including Strangford Lough have been
published (Gorham and Lewey 1984; McLaughlin et al.
2006). Seaweeds contain a diverse range of organic and
mineral fractions (Rioux et al. 2007; Sivasankari et al. 2006).
The first four species were studied in many countries for
polysaccharide fractions such as laminarin, fucoidan and
alginate (Marinho-Sorinano et al. 2006). However the
biology and composition of S. muticum have not been
reported widely (Gorham and Lewey 1984). S. muticum is
particularly interesting as few studies have been reported
on the composition, metabolite content and bioactivity of
the polysaccharides and growth hormones. The aims of
this study were to characterise the composition of these
five seaweed species in terms of their polysaccharide,
auxin and mineral content and to evaluate the efficacy of
acidic, alkaline and neutral seaweed extracts as plant
biostimulants.
Materials and methods
Seed material
Seeds of pak choi (Brassica rapa chinensis
, green, F1
hybrid) were obtained from Thompsons and Morgan seed
company (Ipswich, England). Mung bean (Vigno mungo L.,
KPS1) seeds used in the bioassay were supplied by Moles
Seeds (Colchester, England) . Seeds were stored in foil bags
until required.
Collection
Five species (A. nodosum, L. hyperborea, S. muticum, F.
vesiculosus and F. serratus) of seaweed were harvested
from the coastal area of Strangford Lough (54°2640 N
3540 W) during February and June 2009. The seaweeds
were handpi cked and was hed thoroughly with seawater to
remove unwanted debris, grouped according to species and
bulked to 2030-kg lots.
Extraction procedure
The algal materials w ere subsampled, washed with tap
water to remove epiphytes and encrusting materials,
followed by careful evaluation for morphological char-
acteristics for species identification. A part of the
samples were air-dried (20°C) for compositional analy-
ses, and the remaining fresh samples were cut to 10-cm
lengths to ease handling and processed using a blender
(Wari ng Commercial). Fresh material (500 g) was
homogenised with 500 mL of deionised and distilled
water in a blender for 5 min. The pH of the extract was
adjusted to either 3.0 or 9.0 with acetic acid (1 M) or
potassium hydroxide (2 N) or left u nadjusted (neutral
water control) and further homogenised for another
5 min. The final pH of the extract was adjusted if
necessary. The materials were stored in the laboratory
for 12 hours to stabilise and complete the extract ion
steps. The solid residue was separated first by using a
fine muslin cloth, later filtered using Whatman grade 1
paper, and this step requ ired 34 h to complete.
Subsamples of the acidic, alkaline and neutral extracts
were evaluated for pH, electrical conductivity (EC) and
freeze-dried for dry matter (%) yield determinations and
compositional analyses. Further removal of fine particles
present in the extracts were achieved by using a 0.2-μm
vacuum filtration unit (Nalgene), and materials stored
were frozen at 20°C in aliquots of 200 mL. The
sterilised liquid filtrate was taken as 100% concentration
of the fi ve seaweed species and samples further diluted
as per treatment. The seaweed samples from June 2009
were extracted using the acid protocol only.
1082 J Appl Phycol (2012) 24:10811091
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Compositional analyses
The air-dried seaweed samples were pulverised using a mill
(Tecator, model 1093) equipped with a mesh screen size of
0.5 mm. The milled seaweed samples were stored in plastic
jars at room temperature for further analyses. All determi-
nations were performed in triplicate unless specified.
Nitrogen and carbon contents were determined by elemental
analysis (LECO CN-2000) in duplicate. The ash contents
were estimated by heating the samples overnight in a muffle
furnace maintained at 600°C. Crude lipids were extracted
from the seaweed samples with chloroform to methanol
(Sanchez-Machado et al. 2004). The elemental (Ca, Cu, Fe,
K, Mg, Na and P) composition of the samples was quantified
by inductively coupled plasma-optical emission spectroscopy
(ICP-OES, Perkin Elmer).
Thermogravimetric analysis of the samples (seaweed and
freeze-dried) was carried out by combustion in air using a
Mettler Toledo (TGA/DSC1) analyser. A typical sample
mass of 3.1 mg was heated from 30 to 780°C at a heating
rate of 20°C min
1
in a flow rate of 50 mL min
1
air (Lyons
et al. 2008). The reference standards, alginic acid (A7003),
laminarin (L9634), mannitol (M4125) and fucoidan
(F5631), were obtained from Sigma-Aldrich (England).
The seaweed samples and extracted polysaccharide frac-
tions were also evaluated using scanning electron microscopy
(SEM; Quanta 200, FEI) equipped with an energy-dispersive
X-ray microanalysis system (Inca 300, Oxford Instruments).
This instrumentation was used to determine visual differences,
such as surface topography of the freeze-dried polysacchar-
ides and elemental composition of seaweed species. Internal
standards were used for semi-quantitative analysis of the
samples under similar microscope parameters. Unextracted
seaweed or polysaccharide samples were distributed on
adhesive carbon discs on SEM sample support stubs. The
samples were imaged at ×200 magnification in the SEM, and
ten particles were selected from each image. X-ray spectra of
the ten particles of unextracted seaweed samples were
collected from five different regions per sample (50 spectra
per sample). Results on I and S concentrations presented along
with elemental data determined by ICP-OES of the same
samples.
IAA was determined by liquid chromatographymass
spectrometry (LC-MS) modified from Hou et al. (2008). The
extracts were centrifuged at 769 g for 10 min and purified on
6 mL/500 mg Strata C18-U cartridges (Phenomenex, UK).
The cartridges were conditioned with 3 mL methanol
followed by 3 mL water. The centrifuged extract was applied
followed by washing with 2 mL water then 2 mL 20%
methanol. Cartridges were dried under vacuum and IAA
eluted with 2 mL 80% methanol. LC-MS was carried out
using a Quattro Ultima Pt triple quadrupole MS (Micromass
UK Ltd.) coupled with an Agilent 1100 LC-MS system
(Agilent UK Ltd.). LC separation was carried out using a
Luna phenylhexyl column (150×2 mm, 5 μm particle size,
Phenomenex UK Ltd.). Chromatography was performed
using 95% acetonitrile (channel A) and 5% acetonitrile
(channel B) with the following gradient programme: At
t=0 min, the mobile phase was 95% channel B, and this
washeldfor2min.Between2and6mintheproportionof
channel B was reduced to 5%. Mobile phase composition
was returned to 95% channel B between 9 and 11 min.
Quantification was carried out by comparison against
authentic IAA standards.
Mung bean bioassay
The aux in-like ac tivity (Kollarova et al. 2010) in the
seaweed extracts was determined by measuring root
formation and dry matter (DM) accumulation in mung
bean stem cuttings. Three experiments were carried out
during March, April and May 2009. The seeds were soaked
in deionised water for 2 h prior to sowing in boxes
containing sterilised perlitevermiculite mix (2:6 litre) to
generate 560 seedlings under similar conditions in the
glasshouse. Poor-quality seedl ings were discarded. The
boxes were covered with black polythene and removed
when the hook stage was visible after 23 days. The
seaweed extracts solutions were diluted (10
2
,3×10
2
,
10
3
;3×10
3
;10
4
;3×10
4
) with distilled deionised water.
Cuttings were excised from seedlings 10 days after sowing
by removing roots and cotyledons and placed in vials (five
plants/vial; four vials/dilution; size 6×2 cm) containing
dilute solutions of the extracts (4 mL). An indole-3-butyric
acid (IBA, Sigma) dilution series [1 M (inhibiting concen-
tration), 10
2
,10
3
,10
4
and 10
5
(stimulating concentra-
tion)] was prepared as standards, and buffer solutions of
half-strength Hoaglands nutrient solutions (Hoagland and
Arnon 1950) adjusted at pH 6.26.5 were used as controls.
All plants were incubated for 3 days in the test solutions,
and on day 4, test solutions were poured out from each vial
and 4-mL buffer solutions were added. The plants were
incubated in a growth room maintained at 15°C with 16 h
photoperiod (100 μmol photons m
2
s
1
) and 8 h dark
cycle. The plants were monitored regularly, and vials were
topped up with deionised water when necessary. After
10 days, the number of roots was recorded. The fresh and
dry matter weights were recorded after drying in an oven at
90°C overnight in triplicate.
Hydroponic production of pak choi
A single pak choi seed was placed in a small hole in a rock
wool cube that was presoaked in water to allow rapid
germination of the test seeds. The seeded rock wool blocks
were covered with a 1-cm layer of milled peat to main tain
J Appl Phycol (2012) 24:10811091 1083
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moisture content and placed on trays in a glass house
maintained at 25°C. After 14 days the healthy germinated
seedlings at the two leaf stage were divided randomly to
groups of 12 plants and primed with 20 μL drops of the
various acidic seaweed extracts on each of the two leaves or
water control (buffered) or a commercial seaweed extract
(A. nodosum; 1:150, AlgaGreen; Oilean Glas Teo, Ireland).
After priming, the plants were transferred to the hydroponic
channels along with the rock wool cubes. The two dilutions
(1:100 and 1:30) of the extracts (five species) were
prepared, using deionised sterile water, and surfactants
were not added to the test solutions.
The pak choi hydroponic cropping trials were carried
out during May, July and Se ptember 2009 in a
polytunnel, and each trial was replicated with two
randomised blocks. The acidified extracts from t he five
species were used as foliar sprays. Each block consisted
of 12 channels placed on a wooden frame and each
housing 12 plants with a total of 144 plants. Treatment
details are as follows: five extracts of two dilutions;
1:100 and 1:30, pH adjusted to 5.45.6; one control,
distilled w ater, pH adjusted to 5 .45.6; AlgaGreen
diluted at 1:150, pH not adjusted. The beneficial effects
of the extracts as foliar feed were tested using a
continuous flow solution culture where the nutrient
constantly flows past the roots of pak choi seedlings.
The temperature in the p olytunnel and nutrient contain-
ers were monitored daily and r ecorded. The adjustment
for pH, electrical conductivity and concentration of
Hoaglands nutrients solutions (Hoagland and Arnon
1950) were performed in a storage tank (250 L capacity)
which supplied nutrient to each of the 24 containers set at
the bottom of each channel. Each container was equipped
with a filter and a pump attached inside t o distribute 12 L
of nutrient solution around the plant roots over shallow
and gently sloping channels. A steady flow of nutrient
solution was maintained along the channel, and the roots
grew into dense mats, with a thin film of nutrient passing
over them. The nutrient solution for each channel was
monitoredforreductionofvolumeinthecontainerand
topped up, as required by maintaining pH between 6 and
7.5 and conductivity at 2,000 μScm
1
using Hoaglands
nutrient solutions. The treatments were applied as foliar
sprays using a 30-mL bottle equipped with a hand pump.
The volum e required f or spraying t he p lan ts were 0.5 to
2.5 mL per plant depending on maturity, and top shoots
were sprayed with even coverage. The total volume of
each treatment sprayed (three times) was approximately
44.5 mL per plant during the hydroponic trials. The
treatments were carried out on day 8, 15 and 20 from the
start of the trial. The plants w ere harvested after 25 to
Table 1 Comparison of seaweed species (A. nodosum, F. serratus, F.
vesiculosus, L. hyperborea and S. muticum) harvested in February (F)
and June (J) 2009 to show changes in nitrogen (% DM), ash (%), lipid
(%) and carbon (%), LSD at 5% level (n=3)
AN FS FV LH SM
Nitrogen
F 1.37 3.16 1.79 3.11 2.81
J 1.95 2.20 2.02 1.45 1.84
LSD 0.04* 0.02** 0.05** 0.02*** 0.14**
Ash
F 18.10 23.33 21.91 47.68 41.49
J 20.82 25.39 21.66 34.39 34.03
LSD 0.58** 1.5* ns 1.17** 0.57**
Lipid
F 3.98 1.93 3.00 0.83 1.08
J 2.41 2.70 2.23 0.89 1.25
LSD 0.90* 0.66** 0.72* ns ns
Carbon
F 38.6 36.1 36.8 25.0 27.3
J 37.2 34.9 36.9 28.6 29.5
LSD 0.48** 0.22** ns 0.68** 0.61***
AN A. nodosum, FS F. serratus, FV F. vesiculosus, LH L. hyperborea,
SM S. muticum, ns not significant
*P<0.05; **P<0.01; ***P<0.001
Table 2 Comparison of elemental composition (%) of the five species (mean of February and June samples) using air-dried samples, LSD
significant at 5% level (n=6)
Species Ca Cu Fe I K Mg Na P S
AN 1.42 0.07 0.07 0.13 3.44 0.87 3.10 0.12 2.64
FV 1.41 0.08 0.15 0.07 3.04 0.86 3.70 0.18 3.13
FS 1.39 0.06 0.13 0.03 4.63 0.88 3.70 0.23 1.54
LH 1.36 0.09 0.30 0.11 8.07 0.86 4.09 0.20 1.01
SM 1.24 0.08 0.29 0.02 7.91 1.88 3.60 0.23 1.28
LSD ns ns 0.14* 0.03** 1.7*** 0.46** ns ns 0.71**
ns not significant; *P<0.05; **P<0.01; ***P <0.001
1084 J Appl Phycol (2012) 24:10811091
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28 days from the start of experiments by individually
cutting at the base of each plant followed by weighing and
recording the position of plants in the channel. The
harvested plants (roots and shoot) were dried for 19 h in
an oven maintained at 90°C, and dry matter content was
determined for each replicate.
Statistical analysis
The differences between the harvested seaweed samples
from the two sampling dates were evaluated by analysis
of variance. The results from the mung bean and pak choi
experiments were analysed as factorial experiments
(GenStat Release 11.1, 2008). Comparisons of biomass
yield and root numbers were presented as the measure of
the least significance difference (LSD) at 5% level. The
calculated mean DM and root numbers for comparison
with the extracts w ere derived from the measured values
of the five IBA concentrations.
Results
Composition of seaweed species
The morphological characteristics of the samples were
recorded and compared with published descriptions. The
nitrogen (%) content (Table 1) varied between 1.45 and
3.11 in L. hyperborea to 1.371. 95 in A. nodosum,andthe
values were within the range reported (Stephenson 1974).
The ash (%) content which ranged from 18.1 to 47.68 for
all species was higher than the reported values (Marinho-
Sorinano et al. 2006; Ruperez 2002; Rioux et al. 2007),
and this can be explained by the inorganic salt in sea water
absorbed by the seaweeds or by the association of cations
Table 3 Comparison of seaweed extracts using acidic, neutral and
alkaline extraction protocols for pH, electrical conductivity (mS cm
1
)
and dry matter (%) content for February samples; LSD at 5% level (n=3)
pH AN FS FV LH SM
Acidic 3.11 3.20 2.94 3.09 2.98
Water 5.23 6.68 5.14 6.17 6.19
Alkaline 8.98 9.54 8.96 9.00 8.94
LSD 0.04*** 0.001*** 0.20*** 0.05*** 0.07***
EC
Acidic 14.48 17.67 11.07 19.71 20.2
Water 12.49 12.20 17.55 24.8 17.33
Alkaline 14.19 15.87 13.86 20.30 23
LSD ns 2.08* 2.4* 1.8* 2.6*
DM
Acidic 2.15 3.24 2.98 1.26 1.15
Water 2.75 2.66 3.03 1.64 1.45
Alkaline 2.85 2.87 3.48 1.75 1.72
LSD ns 0.32* 0.34* 0.15** 0.24*
ns not significant; *P<0.05; **P<0.01; ***P <0.001
Table 4 Comparison of
thermogravimetric analysis of
seaweed species harvested in
February and June sampling
dates (AN, FS, FV, LH and
SMTable 1) in air showing
weight losses (WL1WL4, %)
and residue in the four temper-
ature bands (30190°C, WL1
1
,
190450°C, WL2
2
; 450660°C,
WL3 and 660780°C WL4),
LSD significant at 5% level
(n=3)
ns not significant; *P<0.05;
**P<0.01; ***P<0.001
AN WL1 WL2 WL3 WL4 Residue
(%)
Peak Temp
(°C)
1
Peak Temp
(°C)
2
February 7.59 49.11 19.29 5.27 17.62 267.6 473.2
June 8.02 39.98 21.59 8.30 20.84 269.9 483.2
LSD 0.44* 1.20*** 0.98** 0.86** 2.00** 0.56** 6.30**
FS
February 5.89 39.16 25.25 6.04 22.54 270.0 491.9
June 5.42 39.15 22.54 4.88 26.95 278.5 492.1
LSD 0.12* ns 0.82** 0.81* 1.23** 0.74*** ns
FV
February 7.67 43.18 19.64 8.67 19.71 264.4 495.8
June 6.80 40.31 16.22 12.79 22.82 273.5 491.3
LSD 0.79* 2.00*** 0.48** 0.92** 1.98** 0.90** 3.90*
LH
February 4.33 22.16 17.31 1.93 52.97 274.0 485.8
June 4.75 36.29 20.11 3.72 34.07 260.2 488.2
LSD 0.37* 1.10** 0.78** 1.30* 1.50*** 0.39*** ns
SM
February 8.21 25.01 21.23 4.71 39.67 283.2 497.1
June 5.35 32.26 19.42 4.05 37.92 267.0 494.1
LSD 0.17** 0.95** 1.30* 0.64* 1.43* 0.73** 2.90*
J Appl Phycol (2012) 24:10811091 1085
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with algal polysaccharides (Marinho-Sorinano et al.
2006). The minimum (0.83) and maxim um values (3.98)
of lipid were within the range reported (Sanchez-
Machado et al. 2004; Marinho-Sorinano et a l. 2006).
The carbon content (%) of the five species ranged
between 25.0 and 38.6. The differences in nitrogen, ash,
lipid and carbon contents of the samples were significant
(Table 1).
Mineral content of seaweed
Two species, L. hyperborea and S. muticum, contained the
highest amounts of minerals (Table 2) compared to the other
three species consistent with the ash contents of the five species,
confirming high inorganic content. The analyses indicated
significant differences in the concentrations of Fe, I, K, Mg and
S in the five species. Sulphur content was the highest in A.
Ascophyllum nodosum
Mixed Standards
mgmin^-1
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
c
Fucoidan
Alginic Acid
mgmin ^-1
-0.55
-0.50
-0.45
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
-0.00
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
b
Mannitol
Laminarin
mgmin^-1
-1.8
-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
-0.0
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
a
Derivative weight loss (dw/dt)
Tem
p
erature (°C)
Fig. 1 ac Overlays of deriva-
tive thermograms: a laminarin
and mannitol, b fucoidan and
alginic acid and c a mixture of
the four components along with
unextracted cell wall material of
A. nodosum, analysed in the
presence of air to show differ-
ences in the combustion profiles
1086 J Appl Phycol (2012) 24:10811091
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nodosum and F. vesiculosus compared to the other three
species, and K content was the highest for L. hyperborea and
S. muticum. The range of mineral concentrations detected
agreed with a previous report (Ruperez 2002).
Compositional analyses of seaweed extracts
The differences in pH of the acidic, neutral and alkaline
extractions were significant for the five species (Table 3).
The EC and DM contents of the three preparations of the
five species were quantified, and the differences between
the means were significant for all species except for A.
nodosum. The pH of the aqueous extractions from the June
samples extended between 5.21 and 6.30, and mean value
of EC was 9.3 mS cm
1
and after acidification of the
blended materials (pH 4.0), EC increased to 16.64 mS cm
1
.
The DM (%) contents of the five acid extracts from June (A.
nodosum,5.29;F. vesiculosus,5.95;F. serratus,5.36;L.
hyperborea,5.15;S. muticum, 5.10) were higher than the
February samples (Table 3). Similar increase in DM yields
from winter to summer sampling periods has been reported
by Rioux et al. (2009). The AlgaGreen was also evaluated
for pH (5.45), EC (27.9 mS cm
1
) and DM content (9.1%).
A high concentration of IAA was detected in acid extracts
(June samples) of F. vesiculosus (46.84 ng g
1
)andA.
nodosum (40.96 ng g
1
) compared to lower concentrations
detected in extracts of S. muticum (2.74 ng g
1
), F. serratus
(10.58 ng g
1
)andL. hyperborea (5.9 ng g
1
). The range of
IAA concentration in seaweed samples agreed with previous
reports (Sanderson et al. 1987; Stirk et al. 2004).
Thermogravimetric analysis of seaweed species
The weight loss (WL1) in the 30190°C temperature band
was signifi cantly higher for samples collected in February
compared to June except for L. hyperborea and A.
nodosum. In both February and June, L. hyperborea and
S. muticum had the lowest weight loss for WL2, the highest
residue values compared to other species and the differ-
ences in WL2 and residue values were significant except
for F. serratus. The mean weight losses (WL3) in the 450
660°C decomposition band for all species were significant-
ly higher in June compared to February sampling date,
except for A. nodosum and L. hyperborea. The WL4 values
in the 660780°C were significantly different and a peak at
near 700°C could be attributed to the decomposition of
stable char (Anastasakis et al. 2011; Ross et al. 2009). The
two peak decomposition temperatures (PT1 and PT2)
associated with WL 2 and WL3 decomposition bands were
also significantly different between the two samp ling dates
(Table 4).
The major organic fractions in the seaweed species are
protein, lipid and carbohydrates which can be subdivided into
alginic acid, laminarin, mannitol and fucoidan (Anastasakis et
al. 2011; Hou et al. 2008;Rossetal.2009). Reference
samples of these carbohydrates were analysed under similar
conditions to a sample of A. nodosum to allow evaluation of
the combustion steps and to identify any overlap in the onset
of their decomposition profiles. This included the analysis of
a mixture (synthetic sample) of equal proportions of the four
carbohydrate fractions listed above. The derivative curves of
the reference samples analysed in the presence of air are
presented in Fig. 1, showing the characteristic combustion
profiles of (a) laminarin and mannitol and (b) fucoidan and
alginic acid.
The derivative curve of the synthetic sample was
compared with the thermal profile of A. nodosum to show
similarities and differences in the primary peak due to the
presence of lipid, protein and minerals in the unextracted
material (Fig. 1c). The freeze-dried polysaccharides result-
ing from the acidic and alkaline extractions exhibited
decomposition peaks between 150160 and 285290°C.
The peak at 155°C was absent in the neutral fraction but
associated with a minor peak at 470°C (Fig. 2). Thermog-
ravimetric analyses have shown significant differences
between the five species of seaweeds, mainly in the primary
Alkali
Acid
Control
mgmin^-1
-0.40
-0.35
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750
Derivative weight loss (dw/dt)
Tem
p
erature (°C)
Fig. 2 Overlays of derivative
thermograms of A. nodosum
polysaccharides extracted in
control (neutral), acidic and
alkaline pH showing combus-
tion peaks at 150°C, 290°C and
470°C
J Appl Phycol (2012) 24:10811091 1087
Author's personal copy
and secondary decomposition peaks (WL1WL4), indicat-
ing compositional variations in both organic and inorganic
fractions (Ross et al. 2009).
Evaluation of extracted polysaccharide
The freeze-dried polysaccharide fractions extracted by acid,
neutral and alkaline protocols were evaluated for surface
features and structural forms by SEM (Fig. 3ac). The
materials from the alkaline extractions were well degraded
(fine particle size), indicating depolymerisation during
extraction but formed a highly regular structure and pores
on the materials were not visible. The polysaccharides
extracted in acid pH exhibited granular structures with open
and porous form compared to materials derived from the
alkaline or neutral extraction protocols. The polysacchar-
ides extracted from F. s er r a tu s in acidic, neutral and
alkaline pH were very sticky and non-granular compared
to the other four species. Several species including F. serratus
can release phenolalginate compounds that exhibit adhesive
(a) 500 X
(b) 500 X
(a) 2000 X
(b) 2000 X
(c) 2000 X
(c) 500 X
Fig. 3 ac Typical scanning
electron microscope images of
freeze-dried polysaccharides
of A. nodosum after a acidic, b
neutral and c alkaline
extractions showing differences
in particle forms (×500
and ×2,000)
1088 J Appl Phycol (2012) 24:10811091
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properties to both hydrophobic and hydrophilic surfaces in
aqueous conditions (Berglin et al. 2004).
Mung bean bioassay
Mung bean stem cuttings were incubated in the test
concentrations of the five seaweed extracts and IBA. This
resulted in a significant (P<0.001) increase of DM content
of all treatments except for the acidic extract of F.
vesiculosus compared to the control (Table 5). The alkaline
extracts showed the highest DM yiel ds of the treated plants
(Table 5). A comp ar iso n of DM con ten t of the pla n ts
incubated in different dilutions (10
2
to 3×10
5
)ofthe
extracts revealed a gradual in crease of DM (9.67 to
10.56%) yield, indicating higher nutrient uptake with
alkaline compared to acidic. The dry matter contents of
mung bean plants, treated with IBA in 1 M, 10
2
,10
3
,10
4
and 10
5
solutions, were 8.06, 8.89, 8.83, 9.53 and 9.66%.
The treatment also resulted in a significant (P<0.001)
increase in root numbers for all seaweed species when
prepared in acidic pH, and F. vesiculo sus showed
significantly (P<0.001) higher root numbers compared to
the other four species (Table 6). The root numbers of
mung bean plants, treated with IBA in 1 M, 10
2
,10
3
,
10
4
and 10
5
solutions, were 2 1.27, 24.73, 29.93, 35.43
and 44.63%. The mean root numbers were higher for IBA-
treated cuttings compared with plants treated with seaweed
extracts (Table 6).
Pak choi production trial
The test solutions of seaweed extracts (e.g. acidic extracts of
the five species, water control and AlgaGreen) were adjusted
to pH 5.435.62 before application and consequently EC
increased after pH adjustments to 27.94 mS cm
1
.MeanDM
content of the acidic extracts and AlgaGreen preparations
were 2.17 and 9.12%, respectively, indicating significant
differences in the availability of potential nutrients for plants.
Furthermore the DM contents of the June samples were
higher at a mean value of 5.37%. During the pak choi trials,
the plants treated with acidic extracts (100×dilution) would
have received a lower dose of nutrients compared to
AlgaGreen (150×dilution) due to differences in the DM
content. Two weeks after the transplantation in the channels,
plant leaves from some of the treated (e.g. dark green colour)
and control plants were easily distinguishable by visual
evaluation. The foliar application of the extracts positively
influenced the vegetative growth of pak choi plants (Table 7).
The seaweed extracts, e.g. A. nodosum and F. vesiculosus
showed significant (P<0.05) differences in DM yield for the
two dilutions.
Discussion
Major components of the five species changed significantly
during the winter and summer months (Rioux et al. 2009).
The range of carbon, nitrogen, lipid, ash, minerals and IAA
concentrations in the samples agreed with previous reports
(Rioux et al. 2007; Ruperez 2002; Sanchez-Machado et al.
2004; Sanders on et al. 1987;Stephenson1974). The
changes in dry matter content, pH and EC of acidic,
Table 7 Comparison of dry matter (%) yield of pak choi plants (g)
treated with foliar applications of five acidic extracts at two
concentrations 1/100 and 1/30, water control and AlgaGreen (1:150
concentration), LSD significant at 5% level; seaweed treatments, n=
900; water control, n=90; AlgaGreen, n=90
Treatment Concentration 1/100 Concentration 1/30
AN 5.06 4.54
FS 4.72 4.95
FV 4.60 4.97
LH 4.66 4.65
SM 4.93 4.72
Water control 4.72
AlgaGreen (1/150) 4.69
LSD species×concentrations=0.34
Table 5 A comparison of dry matter (%) content of mung bean plants
treated with five extracts prepared as acidic, neutral, alkaline and
control (IBA), LSD significant at 5% level (270 replicates for seaweed
extracts and 15 replicates for control); control IBA value mean of five
IBA test concentrations
Preparation AN FS FV LH SM Mean
Acidic 9.58 9.72 8.30 9.77 9.71 9.42
Neutral 10.13 9.97 10.10 9.80 9.94 9.98
Alkaline 10.46 10.09 10.41 10.35 10.07 10.28
Control (IBA) 8.99
LSD preparation=0.36; LSD species =0.46; LSD preparation×species
=0.79
Table 6 A comparison of root numbers of mung bean plants treated
with acidic, neutral and alkaline seaweed extracts and control, LSD
significant at 5% level (270 replicates for seaweed extracts and 15
replicates for control); control IBA value mean of five IBA test
concentrations
Preparation AN FS FV LH SM
Acidic 11.09 11.21 14.04 10.40 9.95
Neutral 9.43 9.78 12.37 9.29 9.59
Alkaline 10.76 9.72 10.20 9.12 9.28
Control (IBA) 31.20
LSD species=1.13; LSD preparation=0.88
J Appl Phycol (2012) 24:10811091 1089
Author's personal copy
alkaline and neutral extractions indicated affects on the
bioactivity of the extra cts (Booth 1969; Henry 2005).
The analysis of reference standards (e.g. alginic acid,
fucoidan, laminarin and mannitol) and the synthetic sample
demonstrated the changes in the rate of decom position of
some components of the mixture due to a catalytic effect of
alginic acid. Since alginic acid is composed of two types of
uronic acids,
D-mannuronic (M) acid and L-guluronic (G)
acid, the M/G ratio will determine solubility and viscosity
(Mizuno et al. 1983). The M/G ratio is likely to determine
thermal profile and the shoulder at 225°C may be linked to
compositional differences. Peak combustion of the synthetic
sample occurred between 160 and 320°C with a shoulder
near 220°C indicating decomposition of fucoidan and/or
alginic acid followed by the pr imar y peak at 250° C
representing laminarin. At 275°C a shoulder to the main
peak was observed which could be linked to combustion of
mannitol and the earlier onset of combustion for all fractions
indicated a catalytic effect caused by the acid group in
alginic acid (Anastasakis et al. 2011; Roman and Winter
2004). The next combustion step was a two-stage char
formation at 350°C and 450°C followed by a minor shoulder
at 520°C possibly linked to decomposition of residual
carbon/inorganic fractions (Anastasakis et al. 2011).
The pyr olysis profile of polysacc harid es present in
different seaweed species has been reported (Anastasakis
et al. 2011). Thermogravimetry can be used as a semi-
quantitative protocol for comparing compositional differ-
ences between mannitol, alginic acid, fucoidan and
laminarin fractions of seaweeds including the catalytic
effect of alginic acid. In this study similar results were
observed for both the synthetic sample and A. nodosum,
indicating a reduction in temperature of the primary peaks
from laminarin and mannitol by nearly 100°C (Fig. 1c).
The thermal profiles of the extracted polysaccharides
showed the influence of the extraction process demon-
strated by the higher weight loss below 200°C in the
acidic and alkaline extracts (Fig. 2).
The acidic preparations showed significantly increased
root numbers in four of the five species and a previous
study demonstrated that auxin-like compounds were present
in higher concentration compared to alkaline extracts
(Crouch and van Staden 1993; Stirk and van Staden
1977). The acidic extracts from A. nodosum and F.
vesiculosus showed high IAA content compared to the
other three species (Sanderson et al. 1987; Stirk et al.
2004). The presence of bioactive substances can enhance
efficiency of stomatal uptake of nutrients and minerals
compared to the untreated plants (Mancuso et al. 2006).
Many researchers (Demir et al. 2006; Rathore et al.
2009; Spinelli et al. 2010) have reported positive effects that
seaweed extracts have on seed vigour as a result of priming
and the productivity, and alleviation of biotic and abiotic
stresses in field crops. Key examples are the role of plant
growth regulators and polyols (e.g. mannitol) for alleviating
abiotic stresses, the development of protocols for determining
growth hormones and the identification of specific genes in
Arabidopsis thaliana linked to the signalling factors present
in A. nodosum extracts (Rayorath et al. 2008; Zhang and
Ervin 2004). Furthermore the results suggested that A.
thaliana could be used effectively as a rapid tool for testing
the bioactivity of seaweed extracts (Rayorath et al. 2008
).
Zhang and Ervin (2004) were one of the first to report that
the treatment of cool season grasses with seaweed extracts
and humic acids improved resistance to moisture deficit
conditions possibly by upregulation of plant defence systems
against oxidative stress. During our trials, the temperature
inside the plastic house reached 2530°C during at least
7 days and the evening temperatures averaged 48°C. The
abiotic conditions (e.g. high and low temperature) may not
have been stressful enough to the pak choi plants. Other
studies have shown that crop plants, e.g. potato, cucumbers
and onions are more likely to respond to foliar treatments
under stressful growing conditions (Kuisma 1989; McGeary
and Birkenhead 1984; Nelson and van Staden 1984).
In conclusion, this study has confirmed that carbon,
nitrogen, lipid, polysaccharides and mineral contents of the
species can change between winter and summer months.
The results from this study have provided supporting
evidence for improved uptake of nutrients leading to greater
DM yields of both mung bean and pak choi plants. The
alkaline extracts f rom F. vesiculosus and A. nodosum
stimulated higher DM yield of the mung bean plants. The
majority of the acidic extracts enhanced root formation on
the mung bean stem cuttings compared to alkaline or
neutral extracts. The interaction of species (A. nodosum and
F. vesiculosus) and the two treatment dilutions on DM yield
differences of pak choi plants were significant. The use of
plant biostimulants should be combined with precision
agriculture and innovative decision-making systems, for
maximizing yield and quality of crop plants.
Acknowledgements RS and FA would like to thank Dr. S Watson
for the statistical design of experiments and data analysis. The authors
also would like to thank Drs R Copeland and P Mercer and Mrs G
Nicholl for their contributions.
Conflict of interest The authors have declared no conflict of
interest.
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Seaweeds are an important component of the marine ecosystem and that can operate as an organic biostimulant for terrestrial plants. The biochemical ingredients of seaweed liquid organic biostimulant (SLB) produced plant have been improved, and their demand has recently increased due to multiple by-products. The present study deals with the effect of seaweed liquid organic biostimulant derived from Turbinaria ornata, Sargassum wightii and Halimeda opuntia at different doses like 10, 20, 30, 40, 50 and 100% on the growth and biochemical profile changes of common edible grain Vigna radiata. According to the findings, 20% of SLB from H. opuntia show the highest growth, proximate compositions, mineral contents, fatty and amino acid contents in V. radiata. The seed germination was obtained maximum in 20% SLB soaked seeds of V. radiata. The fatty acid contents were observed high in H. opuntia fertiliser fed V. radiata; palmitic acid (281.2 ± 0.04 mg/100 g) was found to be maximum in all treatment grown V. radiata. Saponins and terpenoids were highly present in T. ornata and S. wightii grown VR plant. The highest plant length (31.3 cm) was observed in T. ornata and lowest (17.1 cm) in S. wightii grown plants. Chlorophyll-a and b concentration was increased significantly (p < 0.01; p < 0.03) in T. ornata extract. The carotenoid content was increased significantly in S. wightii extract and decreased (p < 0.04) in chemical fertiliser grown plant V. radiata. The highest antioxidant activity (6.80 ± 0.01 mg/l) was observed in HO fed VR and the lowest (4.317 ± 0.03 mg/l) was recorded in TO fed VR. This technique can be used in organic farming for sustainable agriculture, which is a better alternative as an environmentally friendly approach. The current study revealed that SLB had certain environmental advantages over chemical fertilisers. Seaweed liquid organic biostimulant, if used on a wider scale, might have a substantial positive environmental influence on agricultural production. Seaweed extract with superior benefits at lower concentrations should be used at very high dilution rates in the agricultural field to increase seed germination rates while without impacting the native beneficial microorganisms present in the soil.
... Since ancient times, seaweeds and seaweed crude extracts have been used as biostimulants and have proven to be effective on multiple crops. Many species of seaweeds and numerous extraction methods have been used [9][10][11][12][13]. For example, enhanced tomato germination and growth were recorded following biostimulation with various green seaweed extracts such as Ulva lactuca 13,14 . ...
... The FTIR peaks (Fig. 1a) are comparable with previously published data for ulvan from various Ulva sp. [9,11] The dominating monosaccharides in the powder were rhamnose (111.1mg/g) and glucuronic acid (194.4mg/g), followed by xylose (23.6mg/g), and glucose (54.6mg/g) ( Table 2), as expected for crude ulvan extracts [33] (Fig. 1b). ...
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Seaweed-derived extracts hold the promise of providing novel biostimulants to sustainably increase crop yields. The objective of this work was to determine whether ulvan crude extract could be used as a biostimulant for terrestrial plants. Herein we show that the crude extract of ulvan, extracted from cultivated Ulva sp., promotes growth of Arabidopsis thaliana. Ulvan’s stimulative effect is both dose- and light intensity-dependent. We tested the effects of supplementation of 6 crude ulvan extract concentrations in the 0.01mg/ml - 1.43mg/ml range on A. thaliana growth for 3 weeks after sowing on agar plates under 90μmol m⁻² sec⁻¹ and 320μmol m⁻² sec⁻¹ light intensities. The addition of 0.07mg/ml ulvan extract to plant growth media for 3 weeks under 320μmol m⁻² sec⁻¹ light intensity led to an increase of 174% in root length, 83% in root dry weight, 54% in shoot dry weight, and 62% of total plant dry weight compared to untreated controls. The addition of 0.07mg/ml ulvan extract to plant growth media for 3 weeks in 90μmol m⁻² sec⁻¹ led to an increase of 120% in root length; no effect was observed on the total plant, shoot, or root weights compared to untreated controls. These results have applicative importance, as the use of biostimulants, such as ulvan, could potentially reduce the use of harmful agrochemicals, thus mitigating their negative environmental impacts, while increasing crop yield and contributing to global food security.
... The antimicrobial potential of seaweed extracts are heavily reliant on the extraction process and the types of solvents employed to maximize the recovery of various bioactive compounds. The chemical constituents of the extract, as well as its efficacy, may be affected by seaweed species, season, and raw seaweed harvest site [30,31]. ...
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Growing concern about environmental safety and the global desire for chemical residue-free food has sparked an interest in plant disease control. At present, tapping seaweed as a potential biopesticide to manage pests and diseases is getting increasingly popular. It offers plants immunity, thereby indirectly reducing the invasion of pathogens. The chapter reviews the economic value of seaweed in organic agriculture, its antimicrobial components, and its potential for phytopathogen management. It also analyzes the present policy gaps and limits in Sri Lanka's organic agriculture, as well as potential solutions using seaweed. Seaweed is recognized as an exceptional marine bio-resource as it contains various bioactive components such as carbohydrates, polysaccharides, sulfated polysaccharides, carotenoids, bioflavonoids, amino acids, and polyunsaturated fatty acids which have antiviral, fungicidal, nematocidal, and bactericidal properties. Antifungal and antiviral effects are achieved by inhibiting mycelial growth and microsclerotia formation in fungal pathogens and particle aggregation in viral pathogens, respectively. Also, it triggers systemic acquired resistance (SAR) or induced systemic resistance (ISR) in infected plants via induced activities of defense-related enzymes and upregulates the defense marker genes. However, the antimicrobial efficacy of seaweed extracts varies with the extraction methods and solvents used to recover the bioactive components, seaweed species, season, and location where it is cultivated. Moreover, the policies on organic agriculture in Sri Lanka emphasize the minimal use of synthetic pesticides. But, utilizing plant and marine resources to manufacture biopesticides is given less importance. Therefore, it could be recommended to initiate a public-private partnership (PPP) in seaweed farming in Sri Lanka, thereby ensuring the production of biopesticides, organic fertilizers, and other value-added products.
... The weekly foliar and basal application of Ascophyllum nodosum extracts were found to increase leaf number, weight and plant height in mint and basil (Elansary et al. 2016), while in the present study, at the tested doses, no significant differences with respect to the control were detected in these parameters. Although the beneficial effects of seaweed extracts are known since the early 1940s (Craigie 2011), several researches have highlighted the variable nature of these products, which frequently do not have reproducible effects on plants (Chojnacka et al. 2012;Sharma et al. 2012;Goñi et al. 2016;Yakhin et al. 2017;Boukhari et al. 2020). According to a recent transcriptomic study, two extracts obtained from A. nodosum resulted in dysregulation of 4.47 and 0.87% of the transcriptome of Arabidopsis thaliana, which implies an important variability in the responses elicited (Goñi et al. 2016). ...
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In the coming years biostimulants will play a key role in the sustainable intensification of agriculture due to their capacity to improve crops quality, nutrient use efficiency and tolerance to abiotic stresses. Cyanobacteria are nowadays considered one of the most promising sources of new biostimulants; however, in vivo studies using cyanobacteria are still scarce and often limited to a few genera. In this work the biostimulant activity of five cyanobacterial hydrolysates was evaluated on Ocimum basilicum L. grown in hydroponics. Plants were treated weekly with foliar applications of the cyanobacterial hydrolysates and of two commercial products. Three of the tested cyanobacterial hydrolysates, administered at the concentration of 1 g L⁻¹, were effective in increasing plant growth (up to +32%), and number (up to +24%) and fresh weight (up to +26%) of the leaves compared to controls. Moreover, the cyanobacterial hydrolysates performed better than the commercial biostimulants. The biochemical characterization of the hydrolysates suggests that the observed bioactivity can be related to a high carbohydrate content. Our results indicate that cyanobacteria-based biostimulants can be an effective tool for sustainably enhancing plant growth and yields.
... As referred to above, seaweed products contain a wide variety of substances, which are related to the specific source of the seaweed, time of collection, and extraction process [42,44,103,104]. Early reports indicate that the use of an Ascophyllum nodosum seaweedbased product in sweet cherry cv. ...
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Due to the increasing global population and the continued need to sustainably increase agricultural production, the agricultural sector requires innovative strategies to increase productivity and efficiency in the use of resources. Biostimulants have emerged as new, promising, and environmentally friendly products to promote the overall sustainability of production systems. Humic and fulvic acids, protein hydrolysates, seaweed extracts, chitosan and other biopolymers, inorganic compounds, beneficial fungi, and bacteria are widely accepted categories of biostimulants, with proven potential in improving plant growth, increasing crop production, and quality of the final product. Some of them also have the capacity to enhance nutrient uptake and improve stress tolerance of the crop. Sweet cherry is a highly appreciated fruit, with a significant economic value, linked to production yield and quality attributes influencing consumer acceptability. However, this fruit presents several undesirable characteristics, such as physiological disorders (e.g., fruit cracking) and a short shelf-life. Several approaches are used to enhance not only sweet cherry production, but also cherry quality, with the latest efforts being placed in biostimulants. The present review focuses on the most recent findings on the use of biostimulants in sweet cherry production.
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In agriculture, agrochemicals play a vital role in enhancing yield and productivity of crops under optimal and suboptimal conditions. In recent times, different innovations have been projected to reduce the use of fertilizers and pesticides and enhance sustainable agricultural production. An environment-friendly technique has been proposed which include the use of natural plant biostimulants. Biostimulants boost the growth and development from germination to maturity throughout the life cycle of a crop, increase the plant metabolism efficiency for higher yield and crop quality, increase tolerance against abiotic stresses, facilitates nutrient use efficiency and translocation, improves the quality of produce (colour, total sugar content, fruit seeding), efficient use of water, and improves the physiochemical properties of the soil. Plant bio stimulants include the substances which are applied to soil, plant, or seed in precise formulations to alter the physiological processes which, in turn, enhance the growth and development, fruit set, nutrient uptake, and stress responses in plants. Various extracts from algae or plant, protein hydrolysates, humic acid, fulvic acid, and other mixtures are used as biostimulants in plants. These substances can be directly added to soil in the form of soil preparations or as liquid foliar application products. Plant biostimulants were earlier used only in organic production, but now they are also used in conventional and integrated crop production systems.
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Drought continues to be a major limiting factor for creeping bentgrass (Agrostis palustris Huds. A.) quality and persistence on golf course fairways, greens, and tees. Little breeding specifically aimed at improving bentgrass drought resistance has been completed. However, a number of reports indicate that treatment with natural products such as seaweed extracts and humic acids improve cool-season grass drought resistance possibly by hormonal up-regulation of plant defense systems against oxidative stress. This study was conducted to determine the response of exogenous natural product treatment of three creeping bentgrass cultivars subjected to drought. 'Penn G-2', 'L-93', and 'Penncross' creeping bentgrass were treated with seaweed extract (SWE) at 0.5 kg ha -1, humic acid (HA; 80% a.i.) at 1.5 kg ha-1, alone or in combination, and maintained in a greenhouse at approximately field capacity (-0.01 MPa) or allowed to dry until near the permanent wilting point (-1.5 MPa). Unashed samples of SWE and HA contained 66 μg g-1 and 57 μg g-1 zeatin riboside (ZR), respectively, while ashed samples contained no detectable cytokinins as determined by enzyme-linked immunosorbent assay (ELISA). There were no significant differences between cultivars in response to drought, except for ZR concentration, which was higher in Penn G-2 than in L-93 or Penncross foliage. Turf quality and photochemical efficiency began to decline 14 d into the dry-down for the control and at 21 d in the natural product-treated bentgrass. The combination of HA + SWE enhanced root mass (21-68%), and foliar α-tocopherol (110%) and ZR (38%) contents. This is the first known report indicating that these natural products contain cytokinins and that their application resulted in increased endogenous cytokinin levels, possibly leading to improved creeping bentgrass drought resistance.
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The effect of foliar application of commercial seaweed extract on potato growth was studied in long-day conditions (60° 10' N 25°00' E) characterized by a cool and short growing season. The results showed that neither the doses, 0, 5, 10, 20 l/ha nor the spraying 24, 45, 58 days after the emergence had any remarkable influence on potato growth and yield if the other preconditions of production are in order. Only small, although insignificant benefit could be obtained with application done three weeks after emergence, clearly before tuber initiation.
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The ratios of mannuronic acid (M) to Guluronic acid (G) were determined in sodium alginate preparations from brown seaweeds. The M/G ratios widely varied according to the species of seaweed, ranging between 0.34 and 1.79. The M/G ratio of alginic acid preparation did not correlate with the intrinsic viscosity of its sodium salt solution, suggesting that the M/G ratio is not associated with the conformation of sodium alginate. On the other hand, the M/G ratios clearly correlated with its yield from a brown seaweed.
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Liquid seaweed products were introduced in 1950 and now enjoy a world-wide reputation. The manurial value of these products is not related to their N. P. K. content and they show unusual properties such as enhanced germination of seeds, increased frost resistance and they induce resistance to fungal and insect pests. The relevant literature is reviewed together with supporting evidence from other sources. The manufacture and use of these products is discussed. Iii my first contacts with (the late) Tony Stephenson, I discounted many of the claims he made for «Maxicrop» and I was surprised when a second product, «Baby Bio», was launched on the British Market. A demand for these products was soon apparent; one to the retail market and the other in commercial horticulture. The story of this unusual venture has now been published in a book (STEPHENSON, 1968) which outlines the manufacture and uses of these extracts. By 1958, export sales began to develop and Tony and I discussed ways of producing a dried extract for the export market and the type of publicity and research needed to foster further development. As a matter of fact, the first dried seaweed extract was exported early in 1959. At this time, the use of seaweed fertilizers was unorthodox and several factors contributed to my deviation from the tradional views of soil chemistry. The first was an analysis of my soil which was found to give unusually high figures for potash and «available» phosphorus.
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