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CITE THIS ARTICLE
Kalita M, Devi N. Lemon basil (Ocimum
africanum Lour.) a new distribution record
from North East India with notes on its
identity. Plant Science Today (Early Access).
https://doi.org/10.14719/pst.2762
Abstract
The odoriferous Citron basilika, also known as lemon basil, possesses a
distinctive lemony sweetness amidst all the Ocimum L. members. While
native to India, it has not been formally recognized in India's North Eastern
(N.E) region until now. This investigation marks the first documented
occurrence of lemon basil, specifically O. africanum Lour., in N.E India. This
new record has been established through meticulous investigation,
comparison, diagnosis, verification using herbarium specimens, and a
thorough review of existing literature. The report includes a morphological
description, careful scrutiny, identification keys, taxonomic notes, and
photographic images of the species. The previously existing confusion
regarding its identification alongside O. americanum L. and O. basilicum L.
has been clarified. This study aims to facilitate the accurate identification of
these three Ocimum L. species.
Keywords
basil; Ocimum africanum; distribution; keys; taxonomy; morphology
Introduction
Lemon basil, i.e., Ocimum africanum Lour., belongs to the tribe Ocimeae
Dumort within the subfamily Nepetoideae Burnett of the deadnettle, mint, or
sage family Lamiaceae Martinov (1). This species originated in East Africa and
was first documented by Loureiro (1790), typically thriving in uncultivated
habitats. Ocimum africanum (=Ocymum) is native to India and exhibits little
variation in its growth habit and physical characterization (2).
A nothospecies, Ocimum × africanum, has emerged through direct
hybridization between American basil (O. americanum L.) and sweet basil
(O. basilicum L.). Previously, Ocimum africanum was identified as Ocimum ×
citriodorum Vis. However, Paton and Putievsky (1996) proposed the correct
name for the latter as O. americanum sensu Pushpangadan and Sobti non-L.
(3). They concluded that the methyl chavicol chemotype of Ocimum ×
citriodorum resulted from a hybridization event involving the parent species
O. americanum and O. basilicum, aligning with the postulation made by
Pushpangadan and Sobti (1982) (4). The specific epithet citriodorum is
derived from the citrol and lemony flavor characteristic of this species. The
pronounced lemon aroma of O. africanum can be attributed to citral, a key
component of its essential oil (5). The lemony fragrance can be utilized in tea
infusions and as an antioxidant (6). Lemon basil contains bioactive
compounds such as caeic acid, flavonoids, rosmarinic acid, and linalool,
which exhibit anti-inflammatory, antioxidant, and antimicrobial properties
(7). The name O. africanum also refers to plants that are morphologically
similar, resulting from the doubling of the F1 chromosome number (3). The
parent species, O. basilicum, has developed numerous forms over time due
PLANT SCIENCE TODAY
ISSN 2348-1900 (online)
Vol x(x): xx–xx
https://doi.org/10.14719/pst.2762
HORIZON
e-Publishing Group
Lemon basil (Ocimum africanum Lour.) a new distribution record
from North East India with notes on its identity
Mamita Kalita* & Nilakshee Devi
Department of Botany, Gauhati University, Guwahati, Assam 781014, India
*Email: mamita.bot@gmail.com
RESEARCH ARTICLE
2 KALITA & DEVI
https://plantsciencetoday.online
to extensive cultivation practices. Bentham (1832)
suggested considering these forms as varieties originating
in gardens within the same species, possibly stemming
from O. basilicum L. var. pilosum and O. basilicum L. var.
glabratum (8). He placed Ocimum africanum within a
section designated as ‘species quoad genus vel sectionem
dubiae’, which includes ten other Ocimum (=Ocymum)
species of certain classification. Paton (1992)
acknowledged O. basilicum var. pilosum (Willd.) Benth. as
a type specimen of O. americanum var. pilosum (Willd)
Paton. Furthermore, he asserted that O. africanum and
O. americanum var. pilosum are synonymous species, while
proposing two varieties of O. americanum (var.
americanum and var. pilosum) based on dierences in
stem indumentum (9). Nevertheless, the latter variety has
been established as a separate species named
O. africanum and is now considered synonymous with
O. americanum var. pilosum (Willd.) Paton. (10). According
to Ryding (1994), these species have chromosome
numbers of 2n=48 or 64. Ryding also conducted a back
cross between O. americanum L. var. pilosum
(=O. africanum) and one of its parent species, O. basilicum,
resulting in sterile hybrids that produced only a few dwarf
seeds (11). Paton and Putievsky (1996) suggested a high
crossability percentage of 12.5 with O. basilicum L. var.
purpurascens producing viable seeds, whereas non-viable
seeds with var. diorme (3).The ability of O. africanum to
readily hybridize with a few varieties of O. basilicum,
therefore, depends on which variety of the latter is
involved as a parent. Suddee et al. (2005) reported that
intermediates of O. africanum are not uncommon, as they
can freely hybridize with O. basilicum in cultivation (10).
In India, seven species of Ocimum L. have been
documented (12). Among these, four species of Ocimum
(O. americanum L., O. basilicum L., O. gratissimum L., and
O. tenuiflorum L.) are naturally found in N.E India, while
O. africanum, O. filamentosum Forssk. and
O. kilimandscharicum Gurke are not. O. africanum had, at
the time, been classified as a variety (pilosum), such as
O. americanum var. pilosum and O. basilicum var. pilosum.
The varietal epithet pilose suggests a so hairy surface.
Notably, the staminal, floral appendages, and
inflorescences of O. africanum are densely covered in hairs
compared to O. americanum and O. basilicum, making
them distinguishable as distinct species. To clarify these
distinctions and alleviate confusion, we have provided a
detailed comparative analysis of all three species (Fig. 1).
Additionally, we have outlined the distinctive
characteristics of all three species (Table 1).
O. africanum has oen been confused with its
familial species viz. O. americanum and O. basilicum. Many
authors have used the name O. americanum to refer to
both O. americanum and O. africanum. Furthermore,
O. africanum Lour. has been insuiciently specified,
leading to misidentification where O. americanum was
mistakenly labelled as O. africanum by some authors
(13,14). In a recent publication, Misra et al. (2022)
erroneously reported the new distribution record of
O. africanum from Odisha, India, and indicated its presence
in Manipur and Tripura based on habit photographs (14).
However, the images they presented are of O. americanum.
It’s worth noting that lemon basil (O. africanum) has not
yet been reported from the North Eastern province of India
Figure 1. Habit and floral morphology of three Ocimum L. species. A Ocimum americanum L. (UGOA01). B Ocimum africanum Lour. (KMOAf01) and C Ocimum
basilicum L. (CCOB07) showing magnified view of inflorescence architecture and floral arrangement a, b c respectively. Each of the species have been
represented with its complete flower (a1,b1,c1), flower bract (a2,b2,c2), calyx (a3,b3,c3), corolla showing epipetalous stamen (a4,b4,c4), nutlets (a5,b5,c5),
gynoecium exhibiting gynobasic style and bifid stigma (a6,b6,c6). ©Mamita Kalita
3
Plant Science Today, ISSN 2348-1900 (online)
and is also absent from the Plants of World Online (POWO)
database (15). Despite its presence and common usage,
the taxonomic identity of O. africanum remains unclear.
The study aims to address this taxonomic uncertainty by
reporting the first distributional record of O. africanum
from the North Eastern part of India, based on collections
from three districts of Assam. This finding represents a
valuable addition to the flora of Assam and North East
India.
Materials and Methods
The species were collected during a comprehensive Ph.D.
field survey between 2019 and 2022 from the Goalpara,
Hojai, and Kamrup districts of Assam. The representatives
of O. africanum were collected in the flowering and fruiting
stages. Field photographs and GPS locations were
recorded using a digital camera. The micro-morphological
features were investigated using a Labomed CZM4 stereo
zoom binocular microscope. Further photo plates were
prepared using Adobe Photoshop 7.0. A complete
characterization was made with examination of all the
possible morphological characters. The species was
identified with the help of its type specimen available at
the Royal Botanic Gardens, Kew (K), K000911679. Further
regional and national herbaria, such as ARUN, ASSAM, CAL,
and GUBH, were consulted for airmation and
identification. Also, relevant literature (Floras, Journals,
and Revisions) and microfilms of specimens from online
herbaria databases BSI-IVH, G, JSTOR, KEW, LINN, MNHN,
MO, and NY were conferred for accurate identification. The
new distributional record of the species was confirmed
through verification of the taxonomic and other relevant
literature and herbarium specimens deposited in dierent
regional and national herbariums. The common and
vernacular names of the species are given in English (E),
Hindi (H), and Assamese (A).
Results and Discussion
Taxonomic treatment
Ocimum africanum Lour. Fl. Cochinch. 2:370.1790; DC,
Prodr. 42.1873; Merr. In Trans. Amer. Philos. Soc. 24 (2):
343 (1935); Suddee, Paton & Parnell. KB. 60:28.2005. —
Ocymum africanum Lour. Bentham, Lab. Gen. Specs.
16.1832. — Ocymum × pilosum Roxb. Asiat. Res. 11:
173.1810. — Ocymum pilosum Willd. Enum. Pl. 2:629.1809;
Wallich, Pl. Asiat. Rar. 2:13.1830; Roxb, Fl. Ind. 3:16.1832. —
Ocimum pilosum Willd. A. J. Paton, KB.47.3:426.1992. —
Ocymum americanum Auct. ex. Benth. Labiat. Gen.
specs. 13.1832. — Ocimum americanum var. pilosum
(Willd.) Paton KB. 47:426.1992. — Ocymum anisatum
Benth. Labiat. Gen. specs. 4.1832. — Ocymum citriodorum
Vis. Index. Seminum (PAD, Patavium) 9.1840. — Ocimum
citriodorum L. DC, Prodr. 39.1873. — Ocymum ×
graveolens A. Br. Flora 24:265.1841. — Ocymum
petitianum A. Rich Tent. Fl. Abyss. 2:176.1850.
Type Neotype (NT): Vietnam, 1868, Dr. Talmy–76
(K000911679), designated by Suddee and Paton, Kew
Bulletin, 60:28.2005. K!
Description
Annual herbs or sub-shrubs typically reaching heights of
20–70 cm. Stems are round to quadrangular and have a
puberulent texture. Leaves are arranged in an opposite
decussate pattern, ovate in shape, measuring 4–5 × 2–3
cm. They are acute at the tips, with nearly equal sides,
shallow serrations along the edges, and are smooth on the
upper surface while having pubescence along the veins on
the underside. The petioles are slender, 3–5 cm long, and
puberulent. The inflorescence is lax, measuring 8–12 × 2–3
cm, with verticils spaced approximately 1.5–3 cm apart.
The axis of the inflorescence is lanate. Bracts are ovate,
measuring 0.4–0.5 × 0.1–0.25 cm, and have acute tips,
covered in villous hairs. Pedicels are recurved and shorter
than the calyx, with a pubescent texture. The calyx is
campanulate, measuring 0.4–0.6 × 0.3–0.45 cm, and
covered in villous hairs. The posterior lip is rounded with
an apiculate tip and extends along the tube slightly. The
anterior lip has two median lanceolate teeth that are
acuminate and longer than the posterior lip. The lateral
tooth is broad and acute, nearly equal in size to the
posterior tooth. There are villous hairs at the throat. The
corolla is colorless or pinkish-white, measuring 0.4–0.8 ×
0.5–1.2 cm. The lobes are entire and villous on the back.
The anterior lip is boat-shaped, while the posterior lip has
two median oblong lobes and two lateral obovate lobes.
The tube is pubescent and straight. Stamens are
didynamous, measuring 0.4–1.5 cm long, with a villous
base on the posterior side. The gynoecium has two equal
lobes, and the style is bifid, measuring 0.8–1.2 cm long.
Nutlets are narrowly oblong, black, measuring 0.25–0.3 ×
0.1–0.15 cm, minutely tuberculate, and become
mucilaginous when wet (Fig. 2).
Characteristics O. americanum L. O. africanum Lour. O. basilicum L.
Aroma strong pungent odor lemony or citral sweet or spicy like sweet fennel/
aniseed
Inflorescence 10–15 cm long; verticils 0.8–1.5 cm
apart; moderately pubescent
8-12 cm long; verticils 1–3 cm
apart; pubescent
5–8 cm long; verticils 0.5–1.2 cm
apart; sparsely pubescent or
glabrous
Bract 0.48–0.65 cm long; thin hair
present; sub-sessile; bract stalk
less than 0.2 cm in length
0.45–0.6 cm long; pubescent;
bract stalk 0.1–0.3 cm in
length
0.5–0.7 cm long; glabrous; bract
stalk 0.15–0.35 cm in length
Flower pinkish or crimson white, smaller;
moderately hairy
colorless or pinkish white,
moderate size; densely
pubescent
crimson white; comparatively
larger; less hairy
Nutlets ovoid; 3–3.5 mm in length
oblong; 3–3.2 mm in length ovoid; 3.2–3.5 mm in length
Table 1. Characteristic dierences between three species of Ocimum L.
4 KALITA & DEVI
https://plantsciencetoday.online
Figure 2. Ocimum africanum Lour. (KMOAf01) A habit B adaxial and C abaxial view of leaf with leaf petiole (lp) D inflorescence E inflorescence tip F closure
view of inflorescence showing floral arrangement, bract (b) and floral bud (fb) G complete flower along with bract (b) and densely covered trichomes (t) H bract I
calyx having villous throat (vt) J corolla showing epipetalous stamen K gynoecium exhibiting gynobasic style (gs), and bifid stigma (bs) L transverse section of
ovary revealing ovules (ov), ovary wall (ow) and ovary placenta (op) M nutlets. ©Mamita Kalita
5
Plant Science Today, ISSN 2348-1900 (online)
Specimen Examined
Africa: Sudan, Kotchy, C.G.T. 30 Sept 1839. W0006986!
Mozambique, Mayotte, 30 March 1975, P. Coulon, Coll. No.
21. MNHN-P-P00184722! Cambodia: Kampong Cham,
Sopheas, 17 December 1965, J.E Vidal, Coll. No. 4746.
MNHN-P-P00131438! Madagascar: Toliara, 17 March 1994,
30-50m, 24° 49' 49"S, 46° 32' 15"E, M. Randriambololona et
al. Coll No. 93. MO-694054! USA: New York Botanical
Garden, S. Longmuir, 8 Sept 1943. NY 03066781! Vietnam:
Cochinchine, 1868, Dr. Talmy, Neotype (NT), Coll. No. 76.
K000911679! India, Gujarat: 24° 23' 17.5"N 72° 31' 43.86"E,
Priyanka Mikwana, 2 Nov 2013, BIOMTFR-HER-002458!
Assam: Hojai, Kurkut, 25° 56' 49.4"N 92° 49' 18.2"E, 79m,
25 August 2019, Mamita Kalita, Coll. No. 42 (HJOAf06);
Goalpara, Jobepara, 25° 56' 34.9"N 91° 7' 33.3"E, 58m, 13
July 2019, Mamita Kalita, Coll. No. 06 (GPOAf03); Kamrup
Metropolitan, Kallapara, 26° 3' 24.6" N 91° 36' 34.3"E, 56m,
18 June 2019, Mamita Kalita, Coll. No. 14 (KMOAf01).
Common names Citronbasilika, Hoary basil, Lao basil,
Lime/Lemon basil, Sweet lemon, Thai lemon basil (E),
Nimboo tulsi, and Lebu tulsi/toolsee (H).
Vernacular names Mayang, Lebu toolakhi, and Nemu
toolakhi (A).
Phenology The flowering and fruiting have been observed
from April to August.
Habitat Growing in disturbed ground, damp, and forest
floors.
Distribution Africa, China, Taiwan, Malaysia, Sri Lanka,
India (Andhra Pradesh, Bihar, Chhattisgarh, Goa, Gujarat,
Haryana, Jharkhand, Karnataka, Kerala, Madhya Pradesh,
Maharashtra, Odisha, Punjab, Rajasthan, Tamil Nadu,
Telangana, Uttar Pradesh, West Bengal); Assam (Goalpara,
Hojai, Kamrup, new distribution record reported for first
time here).
Note The specific epithet `africanum´ indicates its native
origin and widespread distribution in tropical Africa.
Historically, the species was annotated as `Ocymum´. In
1747, the earliest reference to O. africanum was made as
Ozimum citratum Rumph. (16). Louriero (1790) placed the
species in the ‘Calyces bilabiati’ section with a two-lipped
calyx within the class of Gymnospermia (2). As stated by
Paton (1992), O. kenyense Ayob. ex Paton can be easily
confused for O. africanum (9). However, the former can be
distinguished by its short petioles and obtuse leaves.
Regarding the type specimen (K000911679), Dr. Talmy
(1868) collected the species in Cochinchine, Vietnam, and
initially identified it as O. basilicum. Suddee (2001)
identified the same specimen as O. americanum L. var.
pilosum (Willd.) A. J. Paton, while in 2002, Paton himself
identified it as Ocimum × citriodorum (17). The correct
identification and designation as a neotype were
established by Suddee and Paton (2005) during their
taxonomic revision of the Ocimeae tribe in Southeast Asia
(10). The respective collectors have identified the
herbarium specimens MNHN-P-P00184722!, MNHN-P-
P00131438!, and MO-694054! under the name of O.
americanum L. var. pilosum (Willd.) Paton.
The first author was unable to locate any physical
herbarium specimens of O. africanum in ARUN, ASSAM,
CAL, and GUBH except for one specimen at CAL, collected
by T. Chowdhury (recorded as O. citriodorum, DDTC-317,
22-10-2015, from Dinajpur, West Bengal, without a CAL
accession number). We have confirmed its identity as
O. africanum. The present study marks the first-ever record
of this species in the N.E India province. As a result, it
represents a new distributional record for the flora of
Assam and North East India.
Key to the species of Ocimum L. in N.E India
1. Pedicel longer than ………………...O. tenuiflorum
1. Pedicel shorter than calyx
2. Fruiting calyx open; annual herbs; leaves 2–6 × 1–3 cm
3. Two median anterior lips are almost equal to the
posterior lip of calyx........O. africanum
3. Two median anterior lips are more prolonged than
the posterior lip of calyx
4. Inflorescence 7–12 cm; fruiting calyx 2.7–3.7 mm;
bract elliptic......................O. americanum
4. Inflorescence 5–9 cm; fruiting calyx 2.7–4.9 mm; bract
lanceolate….....................O. basilicum
2. Fruiting calyx closed; perennial shrubs or under shrubs;
leaves 5–13 × 3–5 cm ....................O. gratissimum
Conclusion
Lemon basil holds significant importance in the
pharmaceutical, chemical, and food industries. Its
potential to contribute to the economy through large scale
cultivation is noteworthy. A better understanding of its
identification and distinction can facilitate the
implementation of eective cultivation practices. The
recent documentation of the occurrence of Ocimum
africanum Lour. in Assam marks the first recorded instance
and adds to the flora of North East India. Our study aims to
elucidate the distinction between O. africanum and its
allied species, enabling the proper utilization and
management of these economically valuable plants.
Abbreviations
L./LINN–Linnaeus; F1–First filial generation; POWO–Plants
of the World Online; GPS–Global Positioning System; K/
KEW–Royal Botanic Garden, Kew; ARUN–Arunachal
Pradesh Regional Centre, Itanagar, Arunachal Pradesh;
ASSAM–Eastern Regional Centre, Shillong, Meghalaya; CAL
–Central National Herbarium, Howrah, West Bengal; GUBH
–Gauhati University Botanical Herbarium; BSI–Botanical
Survey of India; IVH–Indian Virtual Herbarium; G–
Conservatoire et Jardin botaniques de la Ville de Genève;
JSTOR–Journal Storage; MNHN–Muséum national
d'Histoire naturelle; MO–Missouri Botanical Garden’s
Herbarium; NY–New York Botanical Garden Herbarium.
Acknowledgements
The authors are thankful to herbarium curators/oicers of
herbaria, such as ASSAM, ARUN, CAL, and GUBH.
6 KALITA & DEVI
https://plantsciencetoday.online
Authors' contributions
MK has carried out the field work and collected the
specimen. ND has designed the study and contributed by
giving important suggestions. MK has draed the
manuscript and ND has made corrections. ND and MK have
finalized the manuscript for correspondence. Both
authors have read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest: Authors do not have any conflict of
interests to declare.
Ethical issues: None.
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