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Marine algal seaweed species are often regarded as an underutilized bioresource, many have been used as a source of food, industrial raw materials, and in therapeutic and botanical applications for centuries. Moreover, seaweed and seaweed-derived products have been widely used as amendments in crop production systems due to the presence of a number of plant growth-stimulating compounds. However, the biostimulatory potential of many of these products has not been fully exploited due to the lack of scientific data on growth factors present in seaweeds and their mode of action in affecting plant growth. This article provides a comprehensive review of the effect of various seaweed species and seaweed products on plant growth and development with an emphasis on the use of this renewable bioresource in sustainable agricultural systems.
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Seaweed Extracts as Biostimulants of Plant Growth
and Development
Wajahatullah Khan ÆUsha P. Rayirath ÆSowmyalakshmi Subramanian Æ
Mundaya N. Jithesh ÆPrasanth Rayorath ÆD. Mark Hodges Æ
Alan T. Critchley ÆJames S. Craigie ÆJeff Norrie Æ
Balakrishan Prithiviraj
Received: 24 October 2008 / Accepted: 18 March 2009 / Published online: 8 May 2009
Springer Science+Business Media, LLC 2009
Abstract Marine algal seaweed species are often regar-
ded as an underutilized bioresource, many have been used
as a source of food, industrial raw materials, and in ther-
apeutic and botanical applications for centuries. Moreover,
seaweed and seaweed-derived products have been widely
used as amendments in crop production systems due to the
presence of a number of plant growth-stimulating com-
pounds. However, the biostimulatory potential of many of
these products has not been fully exploited due to the lack
of scientific data on growth factors present in seaweeds and
their mode of action in affecting plant growth. This article
provides a comprehensive review of the effect of various
seaweed species and seaweed products on plant growth and
development with an emphasis on the use of this renewable
bioresource in sustainable agricultural systems.
Keywords Seaweed Biostimulants Plant growth
Plant development Biotic and abiotic stresses
Plant-microbe interactions
Seaweeds form an integral part of marine coastal ecosys-
tems. They include the macroscopic, multicellular marine
algae that commonly inhabit the coastal regions of the
world’s oceans where suitable substrata exist. It has been
estimated that there are about 9,000 species of macroalgae
broadly classified into three main groups based on their
pigmentation (for example, Phaeophyta, Rhodophyta, and
Chlorophyta; or the brown, red, and green algae, respec-
tively). Brown seaweeds are the second most abundant
group comprising about 2,000 species which reach their
maximum biomass levels on the rocky shores of the tem-
perate zones. They are the type most commonly used in
agriculture (Blunden and Gordon 1986) and, among them,
Ascophyllum nodosum (L.) Le Jolis is the most researched
(Ugarte and others 2006). Besides A. nodosum, other brown
algae such as Fucus spp., Laminaria spp., Sargassum spp.,
and Turbinaria spp. are used as biofertilizers in agriculture
(Hong and others 2007).
The benefits of seaweeds as sources of organic matter
and fertilizer nutrients have led to their use as soil condi-
tioners for centuries (Blunden and Gordon 1986; Metting
and others 1988; Temple and Bomke 1988). Some
15 million metric tonnes of seaweed products are produced
annually (FAO 2006), a considerable portion of which is
W. Khan U. P. Rayirath S. Subramanian
M. N. Jithesh P. Rayorath B. Prithiviraj (&)
Department of Plant and Animal Sciences, Nova Scotia
Agricultural College, P.O. Box 550, 58 River Road,
Truro, NS B2N 5E3, Canada
D. M. Hodges
Atlantic Food and Horticulture Research Centre,
Agriculture and Agri-Food Canada, 32 Main Street,
Kentville, NS B4N 1J5, Canada
A. T. Critchley J. S. Craigie J. Norrie
Acadian Seaplants Limited, 30 Brown Avenue,
Dartmouth, NS B3B 1X8, Canada
J. S. Craigie
Institute for Marine Biosciences, National Research Council of
Canada, 1411 Oxford Street, Halifax, NS B3H 3Z1, Canada
Present Address:
W. Khan
Department of Biochemistry, College of Science,
King Saud University, P.O. Box 2455, Riyadh 11451, Kingdom
of Saudi Arabia
J Plant Growth Regul (2009) 28:386–399
DOI 10.1007/s00344-009-9103-x
used for nutrient supplements and as biostimulants or
biofertilizers to increase plant growth and yield. A number
of commercial seaweed extract products are available for
use in agriculture and horticulture (Table 1).
Numerous studies have revealed a wide range of bene-
ficial effects of seaweed extract applications on plants, such
as early seed germination and establishment, improved
crop performance and yield, elevated resistance to biotic
and abiotic stress, and enhanced postharvest shelf-life of
perishable products (Beckett and van Staden 1989; Hankins
and Hockey 1990; Blunden 1991; Norrie and Keathley
2006) (Fig. 1).
Modes of Action of Growth Stimulatory Factors
in Seaweed Extracts
Seaweed products exhibit growth-stimulating activities,
and the use of seaweed formulations as biostimulants in
crop production is well established. Biostimulants are
defined as ‘‘materials, other than fertilizers, that promote
plant growth when applied in small quantities’’ and are also
referred to as ‘‘metabolic enhancers’’ (Zhang and Schmidt
1997). Seaweed components such as macro- and microel-
ement nutrients, amino acids, vitamins, cytokinins, auxins,
and abscisic acid (ABA)-like growth substances affect
cellular metabolism in treated plants leading to enhanced
growth and crop yield (Crouch and others 1992; Crouch
and van Staden 1993a; Reitz and Trumble 1996; Durand
and others 2003; Stirk and others 2003;O
¨g and others
2004). Seaweed extracts are bioactive at low concentra-
tions (diluted as 1:1000 or more) (Crouch and van Staden
1993a). Although many of the various chemical compo-
nents of seaweed extracts and their modes of action remain
unknown, it is plausible that these components exhibit
synergistic activity (Fornes and others 2002; Vernieri and
others 2005).
Chemical Components of Seaweed that Affect Plant
Carbohydrates, Minerals, and Trace Elements
Seaweeds, particularly the red and brown algae, are a
source of unusual and complex polysaccharides not present
Table 1 Commercial seaweed products used in the agriculture and horticulture industries
Product name Seaweed name Company Application
Ascophyllum nodosum Acadian Agritech Plant growth stimulant
Acid Buf Lithothamnium calcareum Chance & Hunt Limited Animal feed
Agri-Gro Ultra Ascophyllum nodosum Agri Gro Marketing Inc. Plant growth stimulant
AgroKelp Macrocystis pyrifera Algas y Bioderivados Marinos, S.A. de C.V. Plant growth stimulant
Alg-A-Mic Ascophyllum nodosum BioBizz Worldwide N.V. Plant growth stimulant
High Tide
Ascophyllum nodosum Green Air Products, Inc. Plant growth stimulant
Biovita Ascophyllum nodosum PI Industries Ltd Plant growth stimulant
Emerald RMA Red marine algae Dolphin Sea Vegetable Company Health product
Espoma Ascophyllum nodosum The Espoma Company Plant growth stimulant
Unspecified Inversiones Patagonia S.A. Biofertilizer
Ascophyllum nodosum MaineStream Organics Plant growth stimulant
Kelp Meal Ascophyllum nodosum Acadian Seaplants Ltd Plant growth stimulant
Kelpak Ecklonia maxima BASF Plant growth stimulant
Kelpro Ascophyllum nodosum Tecniprocesos Biologicos, S.A. de C.V. Plant growth stimulant
Kelprosoil Ascophyllum nodosum Productos del Pacifico, S.A. deC.V. Plant growth stimulant
Maxicrop Ascophyllum nodosum Maxicrop USA, Inc. Plant growth stimulant
Nitrozime Ascophyllum nodosum Hydrodynamics International Inc. Plant growth stimulant
ProfertDurvillea antarctica BASF Plant biostimulant
Sea Winner Unspecified China Ocean University Product Development Co., Ltd Plant biostimulant
Seanure Unspecified Farmura Ltd. Plant growth stimulant
Durvillea potatorum Seasol International Pty Ltd Plant growth stimulant
Soluble Seaweed Extract Ascophyllum nodosum Technaflora Plant Products, LTD Plant growth stimulant
Ascophyllum nodosum Acadian Agritech Plant growth stimulant
Synergy Ascophyllum nodosum Green Air Products, Inc. Plant growth stimulant
Ascophyllum nodosum Acadian Agritech Animal feed
J Plant Growth Regul (2009) 28:386–399 387
in land plants (Siegel and Siegel 1973; Painter 1983;
Blunden and Gordon 1986; Craigie 1990; Chizhov and
others 1998; Duarte and others 2001) (Table 2). For
example, the brown seaweeds Ascophyllum nodosum,
Fucus vesiculosus, and Saccharina longicruris contain the
polysaccharides laminaran, fucoidan, and alginate (Painter
1983; Lane and others 2006). Laminaran is a (1,3)-b-D-
glucan with b-(1,6) branching (Nelson and Lewis 1973;
Zvyagintseva and others 1999). Although the precise
structures of fucoidans are not fully established, fucoidan
from A. nodosum consists primarily of sulfated fucose
linked in a-(1,3) and a-(1,4) configuration (Chevolot and
others 1999; Chevolot and others 2001; Daniel and others
2001; Marais and Joseleau 2001). Alginate is a block
copolymer structure composed of D-mannuronic and L-
guluronic acids with b-(1,4)-glycosidic linkages. The
properties of the various alginates differ depending on the
position of each monomeric unit in the chain, the average
molecular weight of the polymer, and the nature of its
associated counter ions. The monomers may alternate in
some regions of the alginate (heteropolymeric), or they
may occur in contiguous groups to produce homopolymeric
sections with either monomer within the alginate molecule
(Painter 1983; Rioux and others 2007). Of these three
polysaccharides, laminaran and fucoidan exhibit a wide
range of biological activities (Rioux and others 2007).
Direct effects of fucoidan on plants have not yet been
reported but sulfated fucoidans from brown algae have
evinced biological activities in mammalian systems
(McClure and others 1992; Angstwurm and others 1995;
Mauray and others 1995). Laminarin has been shown to
stimulate natural defense responses in plants and is
involved in the induction of genes encoding various path-
ogenesis–related (PR) proteins with antimicrobial proper-
ties (Fritig and others 1998; van Loon and van Strien
Growth Hormones
The concentration of mineral nutrient elements present in
commercial seaweed concentrates (SWCs) alone cannot
account for the growth responses elicited by seaweed
extracts (Blunden 1972,1991). Beneficial effects observed
in various plant growth bioassays have led to speculation
that SWCs contain plant growth-regulatory substances
(Williams and others 1981; Tay and others 1985; Mooney
and van Staden 1986). Furthermore, the wide range of
growth responses induced by seaweed extracts implies the
presence of more than one group of plant growth-promot-
ing substances/hormones (Tay and others 1985; Crouch
and van Staden 1993a).
Cytokinins have been detected in fresh seaweeds (Hus-
sein and Boney 1969) and seaweed extracts (Brain and
others 1973). The cytokinins present in seaweed formula-
tions include trans-zeatin, trans-zeatin riboside, and dihy-
dro derivatives of these two forms (Stirk and van Staden
1997). Liquid chromatography/mass spectroscopy
(LC/MS) analysis of 31 seaweed species representing
various groups revealed that zeatin (Z) and isopentenyl (IP)
conjugates of cytokinins are the predominant cytokinins
Fig. 1 Schematic
representation of physiological
effects elicited by seaweed
extracts and possible
mechanism(s) of bioactivity
388 J Plant Growth Regul (2009) 28:386–399
(Stirk and others 2003). Seaweed concentrates also con-
tained aromatic cytokinins BAP (benzyl amino purine) and
topolin (6-[3-hydroxybenzyl-amino] purine) derivatives)
(Stirk and others 2004).
Marine algae are also reportedly rich in auxins and
auxin-like compounds (Crouch and van Staden 1993a). An
A. nodosum extract had as high as 50 mg IAA (indole
acetic acid) per gram of dry extract (Kingman and Moore
1982). Similarly, an extract of Ecklonia maxima exhibited
a remarkable root-promoting activity on mung bean, an
effect reminiscent of auxins (Crouch and van Staden 1991).
Gas chromatography/mass spectroscopy (GC/MS) analysis
of the extract revealed the presence of indole compounds,
including IAA in SWC (Crouch and others 1992).
Auxins have been detected in other algal species like
Porphyra perforata, but the levels found were low (Zhang
and others 1993). In higher plants IAA occurs as an inac-
tive conjugate with carboxyl groups, glycans, amino acids,
and peptides, which, upon hydrolysis, are converted to free
active IAA (Bartel 1997). Stirk and others (2004) found
four amino acid and three indole conjugates of IAA in the
extracts of two seaweeds, E. maxima and Macrocystis
pyrifera. Biologically active auxin-like compounds other
than IAA were reported in alkaline hydrolyzates of
A. nodosum,Fucus vesiculosus, and other seaweeds
(Buggeln and Craigie 1971).
The water-soluble growth inhibitors extracted from
Laminaria digitata and A. nodosum resulted in marked
inhibition of lettuce hypocotyl growth (Hussain and Boney
1973). One of these substances seemed to be similar to
ABA as revealed by bioassay, thin-layer, and gas-liquid
chromatography analysis. Presence of ABA in seaweeds
has also been reported by others such Tietz and others
(1989) (green algae) and Kingman and Moore (1982)
(A. nodosum).
Ascophyllum nodosum extracts contain various betaines
and betaine-like compounds (Blunden and others 1986). In
plants, betaines serve as a compatible solute that alleviates
osmotic stress induced by salinity and drought stress;
however, other roles have also been suggested (Blunden
and Gordon 1986), such as enhancing leaf chlorophyll
content of plants following their treatment with seaweed
extracts (Blunden and others 1997). This increase in
chlorophyll content may be due to a decrease in chloro-
phyll degradation (Whapham and others 1993). Yield
enhancement effects due to improved chlorophyll content
in leaves of various crop plants have been attributed to the
betaines present in the seaweed (Genard and others 1991;
Whapham and others 1993; Blunden and others 1997). It
has been indicated that betaine may work as a nitrogen
source when provided in low concentration and serve as an
osmolyte at higher concentrations (Naidu and others 1987).
Betaines have been shown to play a part in successful
formation of somatic embryos from cotyledonary tissues
and mature seeds of tea (Wachira and Ogada 1995; Akula
and others 2000).
As with many other eukaryotic cells, sterols are an essen-
tial group of lipids. Generally, a plant cell contains a
mixture of sterols, such as b-sitosterol, stigmasterol,
24-methylenecholesterol, and cholesterol (Nabil and Cos-
son 1996). Brown seaweed chiefly contains fucosterol and
fucosterol derivatives, whereas red seaweeds primarily
contain cholesterol and cholesterol derivatives. Green
seaweed accumulates mainly ergosterol and 24-methylen-
echolesterol (Ragan and Chapman 1978; Hamdy and
Dawes 1988; Govindan and others 1993; Nabil and Cosson
1996) (Table 3).
Table 2 Selected polysaccharide constituents of green, red, and
brown seaweeds
Seaweed Polysaccharides
Amylose, amylopectin
Complex hemicellulose
Sulfated mucilages
Rhodophyceae (Red) Agars, agaroids
Complex mucilages
Glycogen (floridean starch)
Xylans, rhodymenan
Complex sulfated heteroglucans
Fucose containing glycans
Lichenan-like glucan
J Plant Growth Regul (2009) 28:386–399 389
Effect on Soil Health
Soil Structure and Moisture Retention
Besides eliciting a growth-promoting effect on plants,
seaweeds also affect the physical, chemical, and bio-
logical properties of soil which in turn influence plant
growth. Seaweeds and seaweed extracts enhance soil
health by improving moisture-holding capacity and by
promoting the growth of beneficial soil microbes.
Brown seaweeds are rich in polyuronides such as algi-
nates and fucoidans. The gelling and chelating abilities
of these polysaccharides coupled with their hydrophilic
properties make these compounds important in food
processing and in the agricultural and pharmaceutical
industries (Cardozo and others 2007). Alginate occurs
in the cell walls of seaweeds as a mixed salt with the
major cations being Na, Ca, Mg, and K together with a
number of minor metal counterions. The molecular
mass of alginate isolated from A. nodosum,F. vesicu-
losus,andS. longicruris varies between 106.6 and
177.3 kDa (Rioux and others 2007). Alginates possess
unique and valuable properties attributable to the
varying proportions of their two monomeric units
(D-mannuronic acid and L-guluronic acid) that are
arranged in block copolymer structures. The free acid
form, alginic acid, is insoluble in water, as are alginates
of certain divalent and polyvalent metal ions. Knowl-
edge of these properties together with that of chain
lengths and copolymer composition are used to control
the gel structure and porosity of alginates for agricul-
tural, pharmaceutical, and industrial uses (Lewis and
others 1988; Skjak-Braek and others 1989). For exam-
ple, alginates are widely used in formulating slow-
release pharmaceuticals (Kim and others 2005;Chan
and Heng 2002; Wong and others 2002)andpesticides
(Vollner 1990; Davis and others 1996; Gonzalez-Pradas
and others 1999; Kumbar and others 2003). The wide-
spread interest in alginate is due in part to its biode-
gradable nature and the relatively non toxic nature of
this natural compound.
Salts of alginic acid combine with the metallic ions in
the soil to form high-molecular-weight complexes that
absorb moisture, swell, retain soil moisture, and improve
crumb structure. This results in better soil aeration and
capillary activity of soil pores which in turn stimulate
the growth of the plant root system as well as boost soil
microbial activity (Eyras and others 1998; Gandhiyappan
and Perumal 2001; Moore 2004). The polyanionic
properties of seaweeds and unicellular algae have proved
valuable in remediation of soils, especially those con-
taminated with heavy metals (Metting and others 1988;
Blunden 1991).
Table 3 Common sterol constituents of green, red, and brown
Seaweed Type of sterol
Chlorophyceae (Green) 22-Dehydrocholesterol
- Ergostenol
- Ergostenol
Rhodophyceae (Red) 22-Dehydrocholesterol
- Ergostenol
- Ketosteroids
Phaeophyceae (Brown) 22-Dehydrocholesterol
390 J Plant Growth Regul (2009) 28:386–399
Effect on Rhizosphere Microbes
Application of seaweeds and seaweed extracts triggers the
growth of beneficial soil microbes and secretion of soil-
conditioning substances by these microbes. As mentioned,
alginates affect soil properties and encourage growth of
beneficial fungi. Ishii and others (2000) observed that
alginate oligosaccharides, produced by enzymatic degra-
dation of alginic acid mainly extracted from brown algae,
significantly stimulated hyphal growth and elongation of
arbuscular mycorrhizal (AM) fungi and triggered their
infectivity on trifoliate orange seedlings. Extracts of vari-
ous marine brown algae [Laminaria japonica Areschoug
and Undaria pinnatifida (Harvey) Suringar] could be used
as an AM fungus growth promoter (Kuwada and others
2006). Kuwada and others (1999) previously showed that
methanol extracts of brown algae fractionated by flash
chromatography promoted in vitro AM hyphal growth as
well as improved root colonization by AM fungi on trifo-
liate orange, Poncirus trifoliate (Linn.) Raf., seedlings.
Indigenous AM fungi demonstrated a 27% improvement in
root colonization, while spore number was increased about
21% over the controls when liquid fertilizer containing
tangle (L. japonica) extracts was applied via a sprinkler
system in a citrus orchard (Kuwada and others 2000).
Kuwada and others (2006) reported that organic fractions
(25% MeOH eluates) of red and green algae considerably
improved in vitro hyphal growth of AM fungi. Their results
showed that application of the 25% MeOH eluates of red
and green algal extracts to roots of papaya (Carica papaya
Linn.) and passion fruit (Passiflora edulis Sims.) improved
mycorrhizal development more than the control treatment.
Kuwada and others (2006) implied that both red and green
algae have AM stimulatory compounds which play a part
in mycorrhizal development in higher plants.
Limited research has been conducted on the effects of
seaweed extracts on other beneficial AM fungi.
Effect on Plant Growth and Health
Root Development and Mineral Absorption
Seaweed products promote root growth and development
(Metting and others 1990; Jeannin and others 1991). The
root-growth stimulatory effect was more pronounced when
extracts were applied at an early growth stage in maize, and
the response was similar to that of auxin, an important root-
growth-promoting hormone (Jeannin and others 1991).
SWC applications reduce transplant shock in seedlings of
marigold, cabbage (Aldworth and van Staden 1987), and
tomato (Crouch and van Staden 1992) by increasing root
size and vigor. SWC treatment enhanced both root:shoot
ratios and biomass accumulation in tomato seedlings by
stimulating root growth (Crouch and van Staden 1992).
Similarly, wheat plants treated with SWC Kelpak
(Table 3) exhibited an increase in root:shoot dry mass
ratio, indicating that the components in the seaweed had a
considerable effect on root development (Nelson and van
Staden 1986). This stimulatory activity was lost on ashing,
suggesting that the active principles in the seaweed extract
were organic in nature (Finnie and van Staden 1985). The
root-growth-promoting activity was observed when the
seaweed extracts were applied either to the roots or as a
foliar spray (Biddington and Dearman 1983; Finnie and
van Staden 1985). The concentration of kelp extract is a
critical factor in its effectiveness as Finnie and van Staden
(1985) showed for tomato plants in which high concen-
trations (1:100 seaweed extract:water) inhibited root
growth but stimulatory effects were found at a lower
concentration (1:600). Biostimulants in general are capable
of affecting root development by both improving lateral
root formation (Atzmon and van Staden 1994; Vernieri and
others 2005) and increasing total volume of the root system
(Thompson 2004; Sla
`vik 2005; Mancuso and others 2006).
An improved root system could be influenced by
endogenous auxins as well as other compounds in the
extracts (Crouch and others 1992). Seaweed extracts
improve nutrient uptake by roots (Crouch and others 1990),
resulting in root systems with improved water and nutrient
efficiency, thereby causing enhanced general plant growth
and vigor.
Effect on Shoot Growth and Photosynthesis
Seaweeds and seaweed products enhance plant chlorophyll
content (Blunden and others 1997). Application of a low
concentration of Ascophyllum nodosum extract to soil or on
foliage of tomatoes produced leaves with higher chlorophyll
content than those of untreated controls. This increase in
chlorophyll content was a result of reduction in chlorophyll
degradation, which might be caused in part by betaines in the
seaweed extract (Whapham and others 1993). Glycine
betaine delays the loss of photosynthetic activity by inhib-
iting chlorophyll degradation during storage conditions in
isolated chloroplasts (Genard and others 1991).
In a recent study (Rayorath and others 2008), extracts of
A. nodosum have been shown to affect the root growth of
Arabidopsis at very low concentrations (0.1 g L
whereas plant height and number of leaves were affected at
concentrations of 1 g L
. Plants treated with extracts
showed growth enhancement effects over control plants;
for example, plants treated with A. nodosum extract were at
a more advanced developmental stage when compared with
untreated plants and the effect was concentration depen-
dent (Fig. 2; unpublished results).
J Plant Growth Regul (2009) 28:386–399 391
Although they may contain different levels of minerals,
biostimulants are unable to provide all the nutrients needed
by a plant in required quantities (Schmidt and others 2003);
however, their main benefit is to improve plant mineral
uptake by the roots (Vernieri and others 2005) and in the
leaves (Mancuso and others 2006).
Effect on Crop Yield
Seaweed concentrate triggers early flowering and fruit set
in a number of crop plants (Abetz and Young 1983;
Featonby-Smith and van Staden 1987; Arthur and others
2003). For example, tomato seedlings treated with SWC set
more flowers earlier than the control plants and this was not
considered to be a stress response (Crouch and van Staden
1992). In many crops yield is associated with the number of
flowers at maturity. As the onset and development of
flowering and the number of flowers produced are linked to
the developmental stage of plants, seaweed extracts prob-
ably encourage flowering by initiating robust plant growth.
Yield increases in seaweed-treated plants are thought to be
associated with the hormonal substances present in the
extracts, especially cytokinins (Featonby-Smith and van
Staden 1983a,b,1984). Cytokinins in vegetative plant
organs are associated with nutrient partitioning, whereas in
reproductive organs, high levels of cytokinins may be
linked with nutrient mobilization. Fruit ripening generally
causes an increase in transport of nutrient resources within
the developing plant (Hutton and van Staden 1984, Adams-
Phillips and others 2004) and the fruits have the capacity to
serve as strong sinks for nutrients (Varga and Bruinsma
1974; Adams-Phillips and others 2004). Photosynthate
distribution could be shifted, perhaps markedly, moving
from vegetative parts (roots, stem, and young leaves) to the
developing fruit, to be utilized in fruit development
(Nooden and Leopold 1978). Fruit treated with seaweed
extracts had higher concentrations of cytokinins compared
to untreated fruit in tomato (Featonby-Smith and van Sta-
den 1984). Cytokinins have been implicated in nutrient
mobilization in vegetative plant organs (Gersani and Kende
1982) as well as reproductive organs (Davey and van
Staden 1978). Such a response indicates that seaweed
extracts are involved either in enhancing the mobilization
of cytokinins from the roots to the developing fruit, or,
more likely, by improving the amount or synthesis of
endogenous fruit cytokinins (Hahn and others 1974).
Higher root cytokinin levels have also been found in sea-
weed extract-treated plants (Featonby-Smith 1984). This
increase in cytokinin availability will eventually result in a
greater supply of cytokinins to the maturing fruit. Devel-
oping fruits and seeds demonstrated increased endogenous
cytokinin levels (Crane 1964; Nitsch 1970; Letham 1994).
It has been reported that the increased cytokinin concen-
tration is associated with translocation of cytokinin from
roots to other plant parts (Stevens and Westwood 1984;
Carlson and others 1987).
Seaweed extract increased fruit yield when sprayed on
tomato plants during the vegetative stage, producing large-
sized fruits (30% increase in fresh fruit weight over the
controls) with superior quality (Crouch and van Staden
1992). The number of flowers and seeds per flower head
increased (as much as 50% over the control) (van Staden
and others 1994) when marigold seedlings were treated
with SWC Kelpak immediately after transplanting (Ald-
worth and van Staden 1987). Application of Maxicrop
enhanced harvestable yield in lettuce, whereas an increase
in the heart size of the florets and curd diameter was
observed in cauliflower (Abetz and Young 1983). Simi-
larly, a substantial increase in yield was achieved in barley
(Featon-Smith and van Staden 1987) and peppers (Arthur
and others 2003) after treatment with Kelpak.
Foliar application of seaweed liquid extract (Kelpak 66)
enhanced bean yield by 24% (Nelson and van Staden
1984). Kelpak 66 also had a similar effect on the yield of
wheat under potassium stress, although its application had
no significant effect on the plants receiving an adequate K
supplement (Beckett and van Staden 1989). Norrie and
Keathley (2006) have reported that A. nodosum extracts
showed positive effects on the yield of ‘Thompson seed-
less’ grape (Vitis vinifera L.) consistently over a 3-year
period. They observed that the A. nodosum-treated plants
always outperformed (in terms of berries per bunch, berry
size, berry weight, rachis length, and the number of pri-
mary bunches per plant) the controls maintained under the
regular crop management program, and resulted in
improved fruit size (13% increase), weight (39% increase),
and yields (60.4% increase over the control).
Vegetative Propagation
Seaweed products are exploited in conventional vegetative
propagation in many crop species (Crouch and van Staden
1991; Atzmon and van Staden 1994; Kowalski and others
1999). It is common practice to apply auxins exogenously
to enhance rooting in cuttings in certain species that are
difficult to root. It has been observed that treating cuttings
Fig. 2 Arabidopsis thaliana plants treated with different A. nodosum
extracts (1 g L
) showed growth enhancement effects over the
control plants 3 weeks after treatment
392 J Plant Growth Regul (2009) 28:386–399
of some flowering plants like marigold (Tagetus patula) for
about 18 h with 10% SWC Kelpak increased the number
and dry weight of roots (Crouch and van Staden 1991).
Similarly, Kelpak, when applied at a 1:100 dilution,
increased the number of rooted cuttings and improved the
vigor of the roots in difficult-to-root cuttings of Pinus pinea
(Atzmon and van Staden 1994). In another study, Leclerc
and others (2006) observed that foliar application of
commercial liquid seaweed extract from Ascophyllum
nodosum (Acadian Seaplants Limited), supplemented with
BA and IBA, enhanced the number of propagules (crown
divisions) per plant in the ornamental herbaceous perennial
Hemerocallis sp.
Resistance to Environmental Stresses
Effects of SWCs in Alleviating Abiotic Stress in Crop
Abiotic stresses such as drought, salinity, and temperature
extremes can reduce the yield of major crops (Wang and
others 2003) and limit agricultural production worldwide.
For example, salinity and drought are becoming wide-
spread in many regions of the world, with an estimated
50% of all arable lands possibly being salinized by 2050
(Flowers and Yeo 1995). Many abiotic factors such as
drought, salinity, and temperature are manifested as
osmotic stress and cause secondary effects like oxidative
stress, leading to an accumulation of reactive oxygen
species (ROS) such as the superoxide anion (O
) and
hydrogen peroxide (H
) (Mittler 2002). These are known
to damage DNA, lipids, carbohydrates, and proteins and
also cause aberrant cell signaling (Arora and others 2002).
Seaweed extracts from Ascophyllum nodosum have been
shown to contain betaines, including gamma-aminobutyric
acid betaine, 6-aminovaleric acid betaine, and glycine
betaine (Blunden and others 1986). To test whether the
increased chlorophyll content in leaves caused by seaweed
extract treatment may be due in part to the betaines present
in the extract, the effects of Algifert 25, an alkaline extract
of A. nodosum, were compared with those of a mixture of
known betaine constituents of A. nodosum (Blunden and
others 1997). Blunden and others (1986) used a betaine
mixture in the same concentrations as those present in
the diluted seaweed extract (gamma-aminobutyric
acid betaine, 0.96 mg L
; 6-aminovaleric acid betaine,
0.43 mg L
; glycine betaine, 0.34 mg L
). Results
showed that similar leaf chlorophyll levels were recorded
in both seaweed- and betaine-treated plants. Sixty-three
and 69 days after application of SWC, leaf chlorophyll
contents, as expressed in SPAD (soil-plant analysis
development; Minolta Corporation, Japan) units, were
27.70 and 26.48, respectively, for seaweed extract and
27.30 and 23.60, respectively, for the betaine treatment.
Both treatments resulted in higher chlorophyll levels versus
controls measured on both days. The results imply that the
enhanced leaf chlorophyll content of plants treated with
SWC might depend on betaines present in the extract
(Blunden and others 1997).
Plants sprayed with seaweed extracts also exhibit
enhanced salt and freezing tolerance (Mancuso and others
2006). Commercial formulations of Ascophyllum extracts
) improved freezing tolerance in grapes. Grape-
vines sprayed with Seasol (0.8%) showed a reduction in
leaf osmotic potential, a key indicator of osmotic tolerance.
The treated plants showed an average osmotic potential of
-1.57 MPa after 9 days of seaweed extract treatment,
whereas it was -1.51 MPa in untreated controls (Wilson
2001). Field studies on winter barley (Hordeum vulgare cv
Igri) have shown that application of seaweed extract
(Maxicrop) improves winter hardiness and increases frost
resistance (Burchett and others 1998).
Taken collectively, these studies suggest that seaweed
products elicit abiotic stress tolerance in plants and that the
bioactive substances derived from seaweeds impart stress
tolerance and enhance plant performance. The chemistry of
bioactive compounds in the seaweed and the physiologic
mechanism of action of the compounds that impart this
tolerance are largely unknown. However, a number of
reports suggest that the beneficial antistress effects of
seaweed extracts may be related to cytokinin activity. For
example, Zhang and Ervin (2004) conducted experiments
to confirm the action of seaweed extracts (Ascophyllum
nodosum) on drought tolerance in creeping bentgrass.
Drought-stressed plants treated with a combination of
humic acid and seaweed extract had root mass enhanced by
21–68%, foliar tocopherol by 110%, and endogenous
zeatin riboside (ZR) by 38%. A systematic analysis of
cytokinins, namely, ZR and isopentenyl adenosine (iPA),
was then performed on A. nodosum extract using enzyme-
linked immunosorbent assay (ELISA). Seaweed extract
contained substantial amounts of cytokinins amounting to
66 lgg
as zeatin riboside. Ashing of the seaweed extract
reduced the effectiveness of the treatments suggesting the
organic nature of the bioactive compound (Zhang and Er-
vin 2004). Cytokinins mitigate stress-induced free radicals
by direct scavenging and by preventing reactive oxygen
species (ROS) formation by inhibiting xanthine oxidation
(McKersie and Leshem 1994; Fike and others 2001). It was
hypothesized that seaweed extract-induced heat tolerance
in creeping bent grass might be attributed largely to the
cytokinin components in the seaweed extracts (Ervin and
others 2004; Zhang and Ervin 2008). However, it has also
been reported that Kelpak seems to mediate stress tolerance
by enhancing K
uptake, although synthetic
J Plant Growth Regul (2009) 28:386–399 393
benzylaminopurine (BA), at a similar concentration to
natural cytokinin present in Kelpak, showed no effect on
yield, irrespective of the K
supply. Hence, the beneficial
effects of seaweed extract against abiotic stress could also
be partly elicited by bioactive chemicals other than cyto-
kinin (Beckett and van Staden 1989).
Reactive oxygen species (ROS) are a common factor in
many abiotic stresses such as salinity, ozone exposure, UV
irradiation, temperature extremes, and drought (Hodges
2001). Application of an A. nodosum extract (Tasco
unstressed turf grasses increased the activity of the anti-
oxidant enzyme superoxide dismutase (SOD), which
scavenges superoxide (Fike and others 2001). In another
study, tall fescue (Festuca arundinacea) treated with 0, 1.7,
or 3.4 kg ha
of A. nodosum extract exhibited increased
SOD activity in all 3 years of the study by an average of
approximately 30% (Zhang 1997). Similarly, Ayad (1998)
reported an increase in SOD, glutathione reductase (GR),
and ascorbate peroxidase (AsPX) activities in genetically
similar endophyte-infected and endophyte-free tall fescue
in response to 3.4 kg Tasco ha
. Thus, the primary effect
of Tasco application to tall fescue in these experiments
seems to be through an increase in antioxidant capacity
(Fike and others 2001).
Effect of SWC in Alleviating Biotic Stress
Seaweed extracts have been shown to enhance plant
defense against pest and diseases (Allen and others 2001).
Besides influencing the physiology and metabolism of
plants, seaweed products promote plant health by affecting
the rhizosphere microbial community.
Nematodes Seaweed extracts were found to have an
impact on the population of nematodes in the soil (Wu and
others 1997). Plants treated with seaweed extracts caused a
reduction in nematode infestation (Featonby-Smith and van
Staden 1983a; Wu and others 1997). Root knot nematode
infestation in tomato was reduced in soil amended with
commercial seaweed extracts from Ecklonia maxima (Feat-
onby-Smith and van Staden 1983a; Crouch and van Staden
1993b). Interestingly, seaweed extract treatment did not
affect the nematode population in the rhizosphere (Featonby-
Smith and van Staden 1983a) and did not show a direct
nematicidal effect. Taken together, these results suggest that
seaweed extract imparts nematode resistance possibly by
altering the auxin:cytokinin ratio in the plant. An in vitro
experiment in which excised maize roots were treated with
seaweed extract showed reduction in the reproduction of the
nematode Pratylenchus zeae by 47–63%. However, in a pot
experiment, the reproduction of P. zeae was not influenced
by seaweed extracts (De Waele and others 1988).
Fungal and bacterial pathogens Marine algae can serve
as an important source of plant defense elicitors (Cluzet and
others 2004). Plants protect themselves against pathogen
invasion by the perception of signal molecules called elici-
tors which include a wide variety of molecules such as oligo-
and polysaccharides, peptides, proteins, and lipids, often
found in the cell wall of attacking pathogens (Boller 1995;
´and others 1998). A variety of polysaccharides present
in algal extracts include effective elicitors of plant defense
against plant diseases (Kloareg and Quatrano 1988).
Although red algae typically contain agars and carrageenans
in their cell walls, extracts of brown algae contain alginates,
laminarans, sulfated fucans, and other complex mucilages,
and green algae (e.g., Ulva spp.) contain mucilages com-
posed of units such as rhamnose, uronic acid, and xylose
(Cluzet and others 2004). Laminaran, a linear b-(1,3)-glu-
can, and sulfated fucans from brown algae elicit multiple
defense responses in alfalfa and tobacco (Kobayashi and
others 1993; Klarzynski and others 2000,2003). Similarly,
carrageenans, a family of sulfated linear galactans, are
effective elicitors of defense in tobacco plants (Mercier and
others 2001). Foliar sprays of A. nodosum extract reduced
Phytophthora capsici infection in Capsicum and Plasmo-
para viticola in grape (Lizzy and others 1998). Soil appli-
cation of liquid seaweed extracts to cabbage stimulated the
growth and activity of microbes that were antagonistic to
Pythium ultimum, a serious fungal pathogen that causes
damping-off disease of seedlings (Dixon and Walsh 2002).
Seaweeds are a rich source of antioxidant polyphenols with
bactericidal properties (Zhang and others 2006). The
application of A. nodosum extract and humic acid to bent-
grass (Agrostis stolonifera) increased SOD activity, which
in turn significantly decreased dollar spot disease caused by
Sclerotinia homoeocarpa.
A study using extracts of Ulva spp. against Colletotri-
chum trifolii in Medicago truncatula showed disease
resistance without the elicitation of necrotic lesions (Cluzet
and others 2004). Ulva extract elicited the expression of the
PR-10 gene. The PR-10 gene belongs to the group of
pathogenesis-related genes (PR) important for active
defense against diseases following pathogen attack (van
Loon and others 2006). Treatment of alfalfa with the algal
extracts prior to pathogen challenge resulted in an
increased resistance to Colletotrichum. cDNA array
revealed that the algal extract caused upregulation of 152
genes, mostly plant defense genes such as those involved in
phytoalexin, PR proteins, cell wall proteins, and oxylipin
pathways (Cluzet and others 2004).
Bacterial quorum sensing and effect of seaweed on
quorum sensing Quorum sensing (QS) is a communication
mechanism used by bacterial populations that are depen-
dent on cell density which, in turn, triggers and controls
gene expression that regulates various physiologic func-
tions and responses (Brelles-Marino and Bedmar 2001;
Winzer and Williams 2001; Dong and Zhang 2005). This
394 J Plant Growth Regul (2009) 28:386–399
response is mediated by low-molecular-weight signal
molecules called acylated-homoserine lactones (acyl-
The virulence of pathogenic bacteria is under the control
of the QS system. Agents that affect the QS system can
potentially alter pathogenicity. The marine red alga Delisea
pulchra synthesizes halogenated furanones and enones that
are homologous to acyl-HSL. They bind to the LuxR in the
acyl-HSL binding site and prevent the binding of acyl-HSL
autoinducers, thereby inhibiting the process of QS. These
furanones in nature seem to interfere with QS in marine
bacteria such as Serratia liquefaciens,Vibrio fischeri, and
Vibrio harveyi (Rasmussen and others 2000; Manefield and
others 2002).
Other pests Aphids and other sap-feeding insects gen-
erally avoid plants treated with seaweed extracts (Ste-
phenson 1966; Hankins and Hockey 1990). Hydrolyzed
seaweed extracts sprayed onto apple trees reduced red
spider mite populations (Stephenson 1966), and 2–3 years
of seaweed extract application resulted in a level of control
similar to that of acaricides (Stephenson 1966). Futher-
more, it was observed that the use of Maxicrop on straw-
berry plants (Fragaria sp.) greatly reduced the two-spotted
red spider mite (Tetranychus urticae) population (Hankins
and Hockey 1990). It has been suggested that seaweed
extracts might contain chelated metals that have been
shown to reduce the population of red spider mites (Ter-
riere and Rajadhyaksha 1964; Abetz 1980).
Conclusions and Future Perspectives
Seaweeds and seaweed products are increasingly used in
crop production. However, the mechanism(s) of actions of
seaweed extract-elicited physiological responses are lar-
gely unknown. As genomes of a number of plants are now
completely sequenced or nearing completion, it is possible
to look at the effects of seaweed extracts and components
of the seaweeds on the whole genome/transcriptome of
plants to better understand the mechanisms of action of
seaweed-induced growth response and stress alleviation.
For example, the use of model plants Arabidopsis thaliana
and Medicago truncatula could potentially unravel the
molecular mechanism(s) of action of seaweed extracts
(Rayorath and others 2008). The recent challenges to food
production due to the increasing occurrence of biotic and
abiotic stresses is likely due to climate change and will
further reduce yields and/or will have an impact on crops in
the 21st century (IPCC 2007). Therefore, research into
developing sustainable methods to alleviate these stresses
should be a priority. Recent studies have shown that sea-
weed extracts protect plants against a number of biotic and
abiotic stresses and offers potential for field application.
Further, seaweed extracts are considered an organic farm
input as they are environmentally benign and safe for the
health of animals and humans.
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... It is well documented in the literature that seaweeds are a potential source of biostimulants [49]. Seaweeds such as A. nodosum, Ecklonia maxima, Fucus sps., Laminaria sp., Sargassum sp., Durvillaea potatorum especially belonging to the brown algal group (Ochrophyta) have been extensively used for this purpose. ...
... However, several other seaweeds such as K. alvarezii, G. edulis, Caulerpa sps., Ulva sps., belonging to phylogenetically diverse groups of algae have also been commercially exploited for biostimulant production [4]. The various commercial products available in markets worldwide have been well documented elsewhere [7,20,49,85]. Some of the commercial seaweed-based biostimulants products available in India are given in Table 12.2. ...
... In addition, several other active principles have also been identified ranging from quaternary ammonium compounds like betaines [63], phenolic compounds [78]; various carbohydrates ranging from simple sugars like mannitol [58], to oligosaccharides of carrageenan [87] and finally polymers like alginic acid, fucoidan, laminarin, etc. [92]. The modes of action and growth stimulatory factor in seaweed biostimulants have been reviewed by [49] as well as [4]. These active principles are thought to function either alone or synergistically manner during plant response. ...
... Plant biostimulants are formulations that contain either a single or a combination of microbes, vitamins, amino acids, algal, seaweed extracts, and hydrolyzed proteins, which are applied either as foliar or to the rhizosphere of the plant and amplify the processes to increase crop quality and production, by augmenting nutrient uptake and nutrient usage efficiency, as well as improving the crop resistance to environmental stress [7][8][9][10][11]. In recent years, seaweeds are more and more being utilized as a biostimulant, which has phytohormones, polysaccharides, minerals, proteins, fatty acids, and polyphenols that enhance plant performance even under stress conditions [12][13][14][15]. ...
... The 15.00 (KR3) mL of Kendal Root in 5 L of water and applied as soil drenching by pouring 100 mL of prepared biostimulant solution per plant on the root zone by digging the soil around the plants ( Figure 1). The biostimulant treatments were given at two stages i.e., 15 and 60 days after transplanting (DAT). ...
... The biostimulant treatments were given at two stages i.e., 15 and 60 days after transplanting (DAT). The plant growth and physiological attributes were measured at 30, 45, and 60 DAT (15,30, and 45 after first application of biostimulants). Three plants per replication were selected for measuring the growth and physiological parameters of tomato (3 leaves from each plant). ...
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Biostimulants are innovative organic tools, which promote the growth, plant development, production, and quality of various crops without harming the environment; however, the effects of biostimulants on the production of tomato needed to be explored further under open field conditions. Based on this view, this study’s objective was to assess the impact of Kendal Root, a biostimulant-containing seaweed, Ascophyllum nodosum, and plant extracts on the phytomorpho-physiological, yield, and quality of tomato. Three doses of Kendal Root (2.5, 5.0, and 10 L ha−1) were given as soil drenching, and the results were compared with control. Generally, the Kendal Root treatments positively improved the growth, physiological, yield, and quality attributes of tomato. However, among the three different concentrations, Kendal Root 5.0 L ha−1 significantly improved the plant growth and physiological aspects of tomato, such as plant height, leaf area, shoot and root dry weight, SPAD value, and gas exchange parameters. Considering the yield traits, the Kendal Root 5.0 L ha−1 application significantly improved the tomato fruit number, yield per plant, and yield per hectare. Conversely, flower number per plant and average fruit weight was not remarkably improved by Kendal Root 5.0 L ha−1. Moreover, Kendal Root 5.0 L ha−1 positively improved the quality traits of tomato, including total soluble solids, ascorbic acid content, lycopene, and total sugars than the titratable acidity content of tomato fruits. Hence, the integration of Kendal Root biostimulant in tomato production could be an effective way to boost plant growth, production, and quality of tomato.
... Among the many biostimulants currently on the market, those containing A. nodosum are presently considered the most interesting and most popular due to their numerous effects on some crops [10,11]. Seaweed extracts obtained by A. nodosum contain chelators [12] and, between them, alginates which contribute to the soil aeration and water-holding capacity [13,14]. Due to the little-known mechanism of these molecules and the different formulations of A. nodosum-based biostimulants on the market, the outcome of using these biostimulants on crops in the open field is disputed [15,16]. ...
... Nevertheless, the slight and insignificant effect on some parameters is again due to the variability induced by the type of treatment (foliar or soil application) [35] and soil texture [36]. Seaweed extracts have two kinds of action when applied to the soil, as in our case, they promote the growth and yield capacity of the crop and, since they are also chelators, can contribute directly to soil health [12]. This mechanism is due to the alginic acids, the principal constituent of the algal cell wall. ...
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Among the innovative practices of dry-farming in recent years, the possibility of the combined use of biostimulants and soil conditioners is assuming an important role. In a preliminary pot experiment, this study aimed to verify the combined effects of Ascophyllum nodosum-based biostimulant and zeolite applied to the soil on gas-exchange and spinach growth. We also monitored the soil water content to study the effect on spinach soil water uptake. Pots were filled with soil to which zeolite and an Ascophyllum nodosum-based biostimulant were added. Spinach plants grew into pots and were subjected to four treatments: (1) soil plus zeolite at a percentage of 1%, (2) soil plus the biostimulant, (3) soil plus zeolite at 1% and biostimulant, (4) bare soil as control. The use of the zeolite and the A. nodosum-based biostimulant led to a higher (+10%) soil water content, highlighting the positive role in allowing a good water uptake by the spinach plant. Plant growth was not changed, while only photosynthesis showed an increase equal to 6% in spinach plants. These results are discussed with the soil water content variation according to modification induced by treatments. The combined use of zeolite and A. nodosum-based biostimulant can be considered a strategy to improve water storage and, at the same time, improve spinach cultivation in terms of sustainability.
... These products are not classified as fertilizers or pesticides, but they are able to increase plant growth, yield, and tolerance to abiotic stresses [22]. Among the different categories of biostimulants, seaweed extracts are one of the most widely used in agriculture [21], in particular, brown algae, such as the Ascophyllum nodosum (L.) extract, has been reported to promote the growth yield quantity and quality of many crops [23,24]. Among beneficial fungi, Trichoderma is one of the most studied, used as a biopesticide and biofertilizer to protect plants and enhance vegetative growth [25][26][27]. ...
... After manually placing the mulching films, the tomato plants were transplanted on 14 April 2021 at a density of 33,000 plants per hectare (row-to-row spacing within the paired row of 60 cm; spacing between the row pairs of 180 cm; plant-to-plant space on the single row of 33 cm). Ordinary soil fertility management was adopted with background fertilization carried out at two times: before the transplant, with an organ-mineral fertilizer (NP: [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], and at the transplant, with diammonium phosphate (NP: 18-46) per a total of 100 kg N ha −1 . During the crop cycle, nitrogen was provided in fertigation, as ammonium nitrate (26%) per a total of 200 kg ha −1 applied over 7 times. ...
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Tomato is a great source of bioactive compounds, is important for human health, and is cultivated worldwide. However, the high inputs required for its cultivation must be sustainably managed in order to limit yield losses, thus obtaining high-quality and environmentally friendly production. In this perspective, we compared four biostimulant treatments, i.e., Ascophyllum nodosum extract-Bio; microbial biostimulant containing the microorganism Trichoderma afroharzi-anum-Mic; a combination of both-M-B; not treated-Control) and three mulch treatments (biode-gradable film Ecovio-ECO; biodegradable film MaterBi ®-NOV; bare soil-BS) and evaluated their effects on yield and quality traits in processing tomato. Both biodegradable films elicited a 27.0% yield increase compared to plants grown on bare soil, and biostimulants determined a 23.7% increase over the Control, with the best performance recorded for M-B (+24.8%). Biodegradable Ma-terBi ® film (NOV) was associated with higher total soluble solids (TSS) and firmness values (average of 4.9°Brix and 1.30 kg cm −2 , respectively), even if a significant effect of biostimulants was observed only for the second element. Carotenoid content was higher in non-treated plants grown on bare soil as well as hydrophilic antioxidant activity (AA), but in this case, no differences between bi-ostimulant treatments were recorded. The lipophilic AA in NOV-treated plants was about six and four times higher than observed in BS and ECO treatments, respectively; NOV also caused a 38.7% increase in ascorbic acid content over the Control but was not different from ECO. All biostimulant treatments elicited a 30% increase in phenol content compared to Control plants. Our findings highlight that microbial biostimulants based on A. nodosum extract and T. afroharzianum (both applied singularly and combined) can be considered a sustainable tool for increasing yield and improve some quality traits of processing tomato; in addition, we also confirmed the capability of biodegradable mulches, in particular, MaterBi ® , to enhance the agronomic performance of tomato.
... The addition of P. protegens CHA0 also had a marked effect on root growth, while the overall effects on shoot growth were more limited. ANE is well known for its biostimulant activity [29,[77][78][79][80], including improved seed germination, seedling vigor, and plant growth [14,19]. Mannitol is naturally synthesized in numerous bacteria, fungi, algae, and land plants, and functions as an osmolyte, energy storage, and antioxidant [34,81,82]. ...
... The concentration of ANE was adjusted to 0.1% [23], while that of fucoidan, alginate, and mannitol were adjusted to 0.01%, considering that the proportion of these compounds in brown seaweed extracts ranges between 2 and 10% [29][30][31][32]. All biochemical assays were performed as mentioned in the previous sections. ...
Full-text available
Abiotic stresses, including salinity stress, affect numerous crops, causing yield reduction, and, as a result, important economic losses. Extracts from the brown alga Ascophyllum nodosum (ANE), and compounds secreted by the Pseudomonas protegens strain, CHA0, can mitigate these effects by inducing tolerance against salt stress. However, the influence of ANE on P. protegens CHA0 secretion, and the combined effects of these two biostimulants on plant growth, are not known. Fucoidan, alginate, and mannitol are abundant components of brown algae and of ANE. Reported here are the effects of a commercial formulation of ANE, fucoidan, alginate, and mannitol, on pea (Pisum sativum), and on the plant growth-promoting activity of P. protegens CHA0. In most situations, ANE and fucoidan increased indole-3-acetic acid (IAA) and siderophore production, phosphate solubilization, and hydrogen cyanide (HCN) production by P. protegens CHA0. Colonization of pea roots by P. protegens CHA0 was found to be increased mostly by ANE and fucoidan in normal conditions and under salt stress. Applications of P. protegens CHA0 combined with ANE, or with fucoidan, alginate, and mannitol, generally augmented root and shoot growth in normal and salinity stress conditions. Real-time quantitative PCR analyses of P. protegens revealed that, in many instances, ANE and fucoidan enhanced the expression of several genes involved in chemotaxis (cheW and WspR), pyoverdine production (pvdS), and HCN production (hcnA), but gene expression patterns overlapped only occasionally those of growth-promoting parameters. Overall, the increased colonization and the enhanced activities of P. protegens CHA0 in the presence of ANE and its components mitigated salinity stress in pea. Among treatments, ANE and fucoidan were found responsible for most of the increased activities of P. protegens CHA0 and the improved plant growth.
... It can also be treated with marine algae, which may contribute to increasing the yield and components of maize due to its nutritional content. Micronutrients such as Ca, Cu, Zn, Fe, B, and Mn are also important components of seaweed extract [27,28]. ...
Full-text available
A field experiment was conducted during the fall season 2022 to study the Conservation agriculure system and the role of Treatment foliar sprays (phosphorus and seaweed) in improve growth and productivity of maize. The Randomized Complete Block Design (RCBD) within the order of split plots including three replicates was used. The experiment included two levels of Conservation agriculture (Zero Tillage or Tillage) symbolized by T0, T1, that represented the main plots, while the subplots included the foliar spray six mixtures of liquid phosphorus and seaweed: without spray (control), Full recommendation of di ammonium phosphate (DAP) symbolized (P1), Half-recommended di ammonium phosphate (DAP), with spraying liquid phosphorous at concentration of 100 ml/L symbolized (P2), Half-recommended di ammonium phosphate (DAP) with spraying liquid phosphorous at concentration of 200 ml/L symbolized (P3), Half recommended di ammonium phosphate (DAP) with spraying liquid phosphorus at concentration of 100 ml/L with seaweed at concentration of 50 ml/L symbolized (P4), and Half-recommended di ammonium phosphate (DAP) with liquid full-recommendation with 200 ml/L of with seaweed at concentration of 100 ml/L symbolized (P5). Results showed, Conservation agriculture negatively affected the vegetative growth characteristics, reduced Plant height and Leafy area, Crop growth rate Also, the characteristics of productivity were negatively affected, and the 500-Grains weight, decreased gave 77.81(g), and the Grain yield 3.18 (Mega ha). Foliar spraying improved and increased the growth characteristics and productivity of Maize, gave higher treatment (P5) for plant height and leaf area as well as the highest productivity. Conclude Conservation agriculture of Maize did not succeed in central Iraq and affected negatively in reducing the growth and productivity characteristics, and that foliar spraying led to improving and increasing the growth and productivity of Maize.
... It can also be treated with marine algae, which may contribute to increasing the yield and components of maize due to its nutritional content. Micronutrients such as Ca, Cu, Zn, Fe, B, and Mn are also important components of seaweed extract [27,28]. ...
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A field experiment was conducted during the fall season 2022 to study the Conservation agriculure system and the role of Treatment foliar sprays (phosphorus and seaweed) in improve growth and productivity of maize. The Randomized Complete Block Design (RCBD) within the order of split plots including three replicates was used. The experiment included two levels of Conservation agriculture (Zero Tillage or Tillage) symbolized by T0, T1, that represented the main plots, while the subplots included the foliar spray six mixtures of liquid phosphorus and seaweed: without spray (control), Full recommendation of di ammonium phosphate (DAP) symbolized (P1), Half-recommended di ammonium phosphate (DAP), with spraying liquid phosphorous at concentration of 100 ml/L symbolized (P2), Half-recommended di ammonium phosphate (DAP) with spraying liquid phosphorous at concentration of 200 ml/L symbolized (P3), Half recommended di ammonium phosphate (DAP) with spraying liquid phosphorus at concentration of 100 ml/L with seaweed at concentration of 50 ml/L symbolized (P4), and Half-recommended di ammonium phosphate (DAP) with liquid full-recommendation with 200 ml/L of with seaweed at concentration of 100 ml/L symbolized (P5). Results showed, Conservation agriculture negatively affected the vegetative growth characteristics, reduced Plant height and Leafy area, Crop growth rate Also, the characteristics of productivity were negatively affected, and the 500-Grains weight, decreased gave 77.81(g), and the Grain yield 3.18 (Mega ha). Foliar spraying improved and increased the growth characteristics and productivity of Maize, gave higher treatment (P5) for plant height and leaf area as well as the highest productivity. Conclude Conservation agriculture of Maize did not succeed in central Iraq and affected negatively in reducing the growth and productivity characteristics, and that foliar spraying led to improving and increasing the growth and productivity of Maize.
... It is well established that seaweed extracts can increase the yield and quality of many horticultural crops due to their biostimulant effects, including improvements in plant nutrient-use efficiency and tolerance of abiotic and biotic stresses (Khan et al. 2009;Mattner et al. 2013Mattner et al. , 2018Arioli et al. 2015;Brown and Saa 2015;Shukla et al. 2019;Hussain et al. 2021;Li et al. 2022). However, few studies on avocado have investigated whether seaweed extracts can increase yield (Morales-Payan and Candelas 2014;El-Shamma et al. 2017). ...
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Seaweed extracts are proven to increase productivity in many agricultural crops, but there is limited research on their use in avocado production. Therefore, we evaluated the effectiveness of a seaweed extract from Durvillaea potatorum and Ascophyllum nodosum on avocado yield, revenue and post-harvest fruit quality in a series of field experiments in Australia, and on seedling root growth in a pot experiment. The field experiments were conducted on commercial farms across three different locations in northern Queensland over four years and utilised avocado trees with different ages, cultivars (Hass and Shepard) and inoculum pressures from Phytophthora cinnamomi. Results showed that the application of the seaweed extract by fertigation significantly improved avocado yield (kg fruit per tree) by 38%, fruit firmness by 4% (skin) and 22% (flesh) and fruit skin colour by 1° (hue), and an upgraded visual ripeness score. The increases in yield were associated with greater number of fruits per tree (up to 42%) indicating the liquid seaweed extract improved fruit set and retention per tree. Regular soil application of the seaweed extract to young trees (cv. Hass) in pots increased the root fresh weight by 22%. Overall, the regular application of the seaweed extract to avocado trees was found to be practical and economically viable for improving fruit production and post-harvest quality in Australian orchards.
Seaweeds are important component in the marine ecosystem. In the global scenario, about 221 species are having commercial utility but only 10 species are being commercially cultivated and has a market value of 11.7 billion US$. Among the 10 species, Eucheuma sp. (35%), Laminaria japonica (27%), Gracilaria sp. (13%), Undaria pinnadifida (8%), Kappaphycus alvarezii (6%), and Porphyra sp. (4%), have a major share in global seaweed biomass production. Seaweeds are the only resources for commercially important phycocolloids such as agar, carrageenan, and alginic acid production. In 2015, seaweed’s phycocolloids production was 93,035 tons wt and had a market value of 1058 million US$. Hectare level cultivation of K. alvarezii (carrageenan yielding seaweeds) can sequester 643.80 tons CO2/ha/yr, whereas Gracilaria edulis and Gracilaria debilis (agar yielding seaweeds) can sequester 10.71 tons CO2/ha/yr. Seaweeds are an excellent biosorbent for the removal of heavy metal ions. Seaweed biochar, an effective adsorbent for wastewater treatment systems. For bioremediation of eutrophicated water, green seaweeds Ulva sp., Cladophora coelothrix, and Cladophora parriaudii; red seaweeds Porphyra sp. and Gracilaria sp. are used. Seaweed has high protein content as it is being used by many of the countries like Japan, China, Korea, Malaysia, Thailand, Indonesia, Philippines, and other South East Asia. Seaweeds like Ulva sp., Enteromorpha sp., Caulerpa sp., Codium sp., Monostroma sp., Sargassum sp., Hydroclathrus sp., Laminaria sp., Undaria sp., Macrocystis sp., Porphyra sp., Gracilaria sp., Eucheuma sp., Laurencia sp., and Acanthophora sp. are used in the preparation of soup, salad and curry, salad vegetable or as garnish material for fish. Ascophyllum, Ecklonia, and Fucus are the general species sold as soil additives and functioned as both fertilizer and soil conditioner. Red seaweeds K. alvarezii, G. edulis, a green seaweed Caulerpa spp. Ulva spp., etc., have been commercially exploited for biostimulant production and increase in crop yield was found in the range of 8–25% over control.
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Ornamental containerized transplant production needs high doses of controlled release fertilizers (CFR), but it is known that there is an environmental risk caused by inadequate fertilization management. To the best of our knowledge, amino acid-(AaB) and seaweed extract-(SeB) based biostimulant application, in ornamental transplant production, is still poorly studied. Therefore, the aim of this work was to assess the hypothesis that, under reduced nutrient supply, SeB and AaB applications, via foliar spray, can promote quality and sustainability in the production of high-quality ornamental seedlings with a 90-day growing cycle. The CRF incorporated into the peat-growing medium was Osmocote Exact Mini in formulation N:P:K = 15 + 9 + 11 (3 months). Six treatments were compared in two economically important potted (0.3 L in volume) ornamentals: Abelia × grandiflora and Lantana camara: T1 = conventional full CRF dose: 4 gL−1 per pot; T2 = limited CRF dose: 50% of T1; T3 = T2 + MC-Extra® [SeB 0.5 gL−1]; T4 = T2 + MC-Extra® [SeB 1.0 gL−1]; T5 = T2 + Megafol® [AaB 1.5 mL L−1]; T6 = T2 + Megafol® [AaB 2.5 mL L−1]. The research results showed that the application of 50% CRF plus biostimulant application resulted in plant performance greater than or equal to those raised under the conventional CRF full dose. In particular, S1 (Abelia × grandiflora ‘Edward Goucher’) and S2 (Lantana camara ‘Little Lucky’) behaved differently concerning the Megafol® dose under 50% CRF; compared to T1, in A. × grandiflora young transplants, T5 increased root morphological characteristics, as well as number of leaves, leaf area, and dry biomass accumulation; in L. camara, T6 achieved higher performance. The application of biostimulants under 50% CRF also improved, in both A. × grandiflora and L. camara, the physiological and agronomical Nitrogen Use Efficiency, compared to a full CRF dose. This study can support decision-making in terms of agronomic technique choices in line with the sustainable development of high-quality ornamental transplant production.
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High ultraviolet-B (UV-B; 290-320 nm wavelength) radiation may significantly contribute to the quality decline and death of kentucky bluegrass (Poa pratensis L.) sod during summer transplanting. Antioxidants and protective pigments may be involved in plant defense against oxidative stress caused by UV-B. Selected exogenous hormones may alleviate UV-B damage by upregulating plant defense systems. The objectives of this study were to determine if exogenous hormone or hormone-like substances could alleviate UV-B damage to 'Georgetown' kentucky bluegrass (Poa pratensis L.) under greenhouse conditions. The hormone salicylic acid at 150 mg(.)m(-2) and the hormone-containing substances, humic acid (HA) at 150 mg(.)m(-2) and seaweed extract (SWE) at 50 mg(.)m(-1), were applied to plugs of kentucky bluegrass and then subjected to UV-B radiation (70 mumol(.)m(-2.)s(-1)). The UV-B irradiation stress reduced turf quality by 51% to 66% and photochemical efficiency by 63% to 68% when measured 10 or 12 days after initiation of UV-B. Endogenous alpha-tocopherol (AT) and antioxidant enzymes (superoxide dismutase (SOD) and catalase) were reduced by UV-B stress. Anthocyanin content was increased from day 1 to 5 and then decreased from day 5 to 10 of continuous UV-B irradiation. Application of SA and HA + SWE enhanced photochemical efficiency by 86% and 82%, respectively, when measured 10 or 12 days after UV-B initiation. In addition, application of the hormonal supplements increased AT concentration, SOD, catalase activity, and anthocyanin content when compared to the control at 10 days after UV-B initiation. Bluegrass with greater AT concentration and SOD and catalase activity exhibited better visual quality under UV-B stress. The results of this study suggest that foliar application of SA and HA + SWE may alleviate decline of photochemical efficiency and turf quality associated with increased UV-B light levels during summer.
1. The overall implications of biological stress.- 2. Oxidative stress.- 3. Salt stress.- 4. Chilling stress.- 5. Freezing stress.- 6. Desiccation.- 7. Water and drought stress.- 8. Heat stress.- 9. Anaerobic stress - flooding and ice-encasement.- 10. Environmental pollution stress.- Epilogue.
Winter barley (Hordeum vulgare L. cv. Clipper) was grown in pots in a growth chamber providing 12-h photoperiods and diurnal temperatures of 17/10°C. Seaweed concentrate was applied as a foliar spray and soil drench at dilutions of 1:250 and 1:500 two weeks after seedling emergence and as a seed dip (1:250) prior to planting. Grain mass per plant was increased in the order of 50% irrespective of the concentration of seaweed concentrate applied or whether applied as a foliar spray or soil drench. The increase was largely due to a greater number of fertile spikelets per ear. The total nitrogen content of the seed produced by seaweed-treated plants remained within the parameters laid down by the malting industry.
Large quantities of green seaweed, linked probably to eutrophication, are cast ashore every summer on the Puerto Madryn beaches (Patagonia, Argentina, 42 degrees 5, 65 degrees W). This algal biomass interferes with recreational uses of the beach, and therefore must be periodically collected and disposed. Part of this algal biomass was composted with the objective to produce an amendment to improve physical and nutritional characteristics of some local soils used in intensive horticulture, and at the same time to find a way to reduce environmental pollution. The compost was then biologically evaluated by determining the growth rate of tomato plants cultivated on various substrata (washed sand, sandy loam soil, and sandy loam soil plus inorganic fertilizers) to which different doses of compost were added. Results showed that in all cases the addition of compost increased water holding capacity and plant growth. The increase of tomato plants (Licopersicum esculentum var. platense) was proportional to the compost doses. Also, plants grown on sustrata containing at least ten percent compost had significant benefits compared to control plants, improving growth and water stress resistance. Although the quality of this seaweed compost was limited by excessive amounts of sand and low nitrogen content, it proved to be a good amendment that improved both physical and nutritional characteristics of local sandy loam soils used in intensive horticulture. According to these results, composting is a useful technology both to solve environmental pollution problems and to produce a valuable organic fertilizer for soils.
This chapter reviews algal polysaccharides. Fossil evidence indicates that many of the algae have changed very little in the hundreds of millions of years and it may be somewhat reckless to assume that the evolution of algal glycan structures has proceeded exactly in parallel with morphology. As new fossil evidence comes continually to light, ideas about the phylogenesis of algae are constantly being revised and there are inevitably areas of disagreement among authorities. There is unanimous agreement that the blue-green algae (Cyanophyta) are by far the oldest and there is reasonable evidence that the red algae (Rhodophyta) appeared next and the brown algae (Phaeophyta) last. In view of the very primitive morphology of algae, one might expect that the structures of the glycans would also be simple. In fact, the reverse seems to be true. Many algal glycans surpass even the gum exudates of terrestrial plants in apparent complexity. Some disorder might perhaps be expected in the glycans of organisms that are low on the evolutionary scale, because it implies that the biosynthetic enzymes are low in specificity rather than large in number. The apparent structural complexity of some algal glycans is increased by a special feature of the reproductive cycle of many algae, whereby the organism passes successively through gametophytic (haploid, male and female) and sporophytic (diploid) forms. There is growing evidence that many algal glycans exist in the native state, at least partly, as proteoglycans and that accepted procedures for isolation usually entail some degradation of these more complex macromolecules, with the liberation of the glycan moiety.
Free radicals and other active derivatives of oxygen are inevitable by-products of biological redox reactions. Reactive oxygen species inactivate enzymes and damage important cellular components. The increased production of toxic oxygen derivatives is considered to be a universal or common feature of stress conditions. Plant and other organisms have evolved a wide range of mechanisms to contend with this problem. The antioxidant defence system of the plant comprises a variety of antioxidant molecules and enzymes. The effects of the action of free radicals on membranes include the induction of lipid peroxidation and fatty acid de-esterification. Both ethylene biosynthesis and membrane breakdown, which appear to be closely linked, seem to involve free radicals, although the sequence of events generating these free radicals is still poorly understood. It is clear that the capacity and activity of the antioxidative defence system are important in limiting oxidative damage and in destroying active oxygen species that are produced in excess of those normally required for metabolism. Transgenic plants offered us a means by which to achieve complete understanding of the roles of the enzymes involved in protection against stress of many types, environmental and induced. Studies on transformed plants expressing increased activities of single enzymes of the antioxidative defence system indicate that it is possible to confer a degree of tolerance to stress by these means. The advent of plant transformation has placed within our grasp the possibility of engineering greater stress tolerance in plants by enhancements of the antioxidative defence system.