ISSN 1021-4437, Russian Journal of Plant Physiology, 2017, Vol. 64, No. 2, pp. 198–206. © Pleiades Publishing, Ltd., 2017.
Role of 5-Aminolevulinic Acid on Growth,
Photosynthetic Parameters and Antioxidant Enzyme Activity
in NaCl-Stressed Isatis indigotica Fort.
X.-Q. Tang, Y. Wang, T.-T. Lv, and Y.-H. Xiao
College of Horticulture, Nanjing Agricultural University, Nanjing, China
Received February 6, 2016
Abstract− 5-aminolevulinic acid (ALA) is a key precursor for the biosynthesis of porphyrins such as heme and
chlorophyll. ALA alleviates salinity stress damage in germinating seeds and improves seedling growth. Exoge-
nous application of ALA at low concentrations has been shown to enhance salt tolerance in a number of plants.
In the present study, we studied the effect of exogenous application of ALA on enhancing salt stress tolerance in
Isatis indigotica Fort. (Anhui population as S1, Shanxi population as S2). A foliar application of 0, 12.5, 16.7,
25.0, and 50.0 mg/L ALA was given to the leaves of I. indigotica plants treated with 100 mmol/L NaCl. The fresh
weight of leaves and roots; chlorophyll relative content (SPAD value); photosynthetic parameters, such as net
photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci) and water
use efficiency of the treated plants were determined. The third leaf of each treated plant was used to determine
the activities of antioxidant enzymes. Superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), gluta-
mate synthase (GOGAT), nitrate reductase (NR) activities and the malondialdehyde (MDA) content increased
in response to 100 mmol/L NaCl in both S1 and S2 plants. However, the fresh weight of leaf and root, chloro-
phyll relative content, Pn, Gs, Ci decreased in response to salt stress in both S1 and S2 plants. In all foliar appli-
cation of ALA in S1 plants, the MDA content, and the activities of SOD and POD were the highest in response
to 50.0 mg/L foliar application of ALA. GOGAT and NR activities were the highest in response to 16.7 mg/L
foliar ALA. Chlorophyll content and Pn were the highest in S1 plants treated with by 25.0 mg/L ALA.
In S2 plants, plant fresh weight, chlorophyll relative content, SOD, CAT, NR activities and Pn treated with
16.7 mg/L ALA were higher than that of the control (CK0). POD, MDA, GOGAT activities in S2 plants treated
with 25.0 mg/L ALA were the highest among all treatments. Thus, our results showed that the optimal concen-
tration of ALA (16.7 ~ 25.0 mmol/L) increases the activity of antioxidant enzymes, which in turn helps to abate
the damage caused by salt stress in I. indigotica seedlings. Furthermore, ALA also results in an increase in chlo-
rophyll content, Pn and the activities of GOGAT and NR.
Keywords: Isatis indigotica, 5-aminolevulinic acid, growth, photosynthetic parameters, antioxidant enzymes
Saline water covers over 71% of the earth’s surface.
Approximately, 95 million hectares of land worldwide
are afflicted by high salinity due to secondary saliniza-
tion, alkalization and waterlogging . Salt-affected
soils cause great economic losses by causing a drastic
reduction in yield. Furthermore, in some cases, saline
soils prevent land utilization. Fresh water is important
for sustainable agriculture and is the key to food secu-
rity. With an increasing agricultural area being affected
by salinity, research on plant responses to salinity has
rapidly expanded in recent decades.
Isatis indigotica Fort. (sources of Radix isatidis and
Folium isatidis) is a biennial cruciferous plant and is
extensively cultivated across China as an important
traditional medicinal plant. However, soil salinization
is a major problem affecting the yield and quality of this
medicinal plant. The dried roots and leaves, named
“Ban-Lan-Gen” and “Da-Qing-Ye” in China, respec-
tively, are commonly used in traditional Chinese med-
icine for the treatment of influenza, pestilence, epi-
demic hepatitis and infections . Furthermore, phy-
tochemical and pharmacological studies have
illustrated that I. indigotica roots and leaves contain
various bioactive constituents including alkaloids, sul-
focompounds, glucosinolates, lignans, flavonoids,
ceramides, steroids, polysaccharides and organic
The article is published in the original.
Abbreviations: ALA—5-aminolevulinic acid; Pn—net photosyn-
thetic rate; Gs—stomatal conductance; Ci—intercellular carbon
dioxide concentration; Tr—transpiration rate; SOD—superox-
ide dismutase; POD—peroxidase; CAT—catalase; GOGAT—
glutamate synthase; NR—nitrate reductase.