Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 December 2018 | 10(15):
13002–13005
On the reproductive biology of Salacia fruticosa Wall. ex M.A. Lawson - an endemic medicinal plant of the Western Ghats, india
K. Subin 1,
P.A. Jose 2 & T.V. Sarath
3
1,2,3 Sustainable Forest Management Division,
Kerala Forest Research Institute, Peechi, Kerala
680653, India
1 subink1993@gmail.com, 2 pajosekfri@gmail.com
(corresponding author), 3 sarathtv35@gmail.com
doi: https://doi.org/10.11609/jott.3069.10.15.13002-13005
Editor: V. Sampath
Kumar, Botanical Survey of India, Howrah, India. Date of publication: 26
December 2018 (online & print)
Manuscript details: Ms
# 3069 | Received 03 January 2017 | Final received 30 August 2018 | Finally
accepted 07 December 2018
Citation: Subin, K., P.A. Jose & T.V. Sarath
(2018). On the reproductive biology of Salacia fruticosa Wall. ex M.A. Lawson - an endemic medicinal plant of the
Western Ghats, india. Journal
of Threatened Taxa 10(15): 13002–13005; https://doi.org/10.11609/jott.3069.10.15.13002-13005
Copyright: © Subin et al. 2018.
Creative Commons Attribution 4.0 International License.
JoTT allows unrestricted use of this article in any
medium, reproduction and distribution by providing adequate credit to the
authors and the source of publication.
Funding: Kerala Forest Research Institute Plan Grant received through
Kerala State Council for Science,
Technology and
Environment, Thiruvananthapuram.
Competing interests: The authors declare no competing interests.
Acknowledgements: The authors thank the Director, Kerala Forest Research Institute, Peechi for approval of the plant grant and constant
encouragement provided throughout the study.
Abstract: Salacia fruticosa Wall. ex M.A. Lawson, an endemic species was studied for the reproductive biology as
this species showed reduced fruit set and natural regeneration. The stigma-anther proximity, an extremely low
number of pollen grains, a short period of pollen viability, a sparse incidence
of pollinators, protandrous and facultative autogamous nature of the flowers and a low percent in fruit
set were identified as biological constraints for the species. The incidence of seed pest was added to the
poor seed and seedling bank and accelerated rarity process of the species.
Keywords: Endemic, ex situ conservation, insect-pest, medicinal plant,
overexploitation, reproductive biology, Salacia
fruticosa.
Salacia L. belonging to the family Celastraceae, consists of about 200 species worldwide,
distributed in tropical America, Africa and Asia (Mabberley
2008) of which 21 species are reported from India (Ramamurthy & Naithani 2000). Out
of this, 15 species are reported from peninsular India and eight species from
Kerala itself (Udayan et al. 2012). The true raw drug, Ekanayakam
(Malayalam) / Pitika (Sanskrit) is extracted
from Salacia reticulata Wight, however, the species is so rare
and sparse for raw drug collection in situ.
The Salacia oblonga Wall. ex Wight & Arn., S.
fruticosa Wall. ex M.A.Lawson and S. chinensis L. are the substitutes used and all of them are overexploited and
facing a high threat in their habitats (Chithra et al.
2010).
Salacia fruticosa is a woody climbing shrub, endemic to Western Ghats, distributed
in the evergreen and semi evergreen forests and also in the plains. It has anti hyperglycemic properties (Venkateshwarlu et al. 2009). Endemism and fragmented distribution, over
exploitation, poor fruit set and seed infestation have led to the study of
reproductive biology of the plant in order to understand the reproductive
constraints of the species.
Material and Methods
Periodic dynamic changes in
reproductive phenological phases of the species Salacia fruticosa were monitored and recorded on a day to day basis at KFRI, Peechi with respect to bud initiation, development, anthesis, pollination behavior etc. as per the methods
suggested by different authors (Faegri & Pijl 1979; Armstrong & Drummond 1984; Sreekala et al. 2008; Jose & Pandurangan
2012, 2013). Stigma receptivity was
determined by the physical appearance of stigma such as turgidity, shine and
oily appearance and it is confirmed by using hydrogen peroxide (H2O2)
(bubble formation). The pollen-ovule
ratio was worked out as per the method suggested by Cruden
(1977). Pollen fertility test was
carried out using Acetocarmine staining method
(Sharma & Sharma 1980). Pollen
germination was carried out with 15% sucrose solution. Bagging experiment was conducted for
evaluating the pollination behavior.
Study area
The study was carried out in a
population of S.
fruticosa growing in the medicinal garden of the Kerala
Forest Research Institute, Peechi, situated between 10.5290N
& 76.3480E (Fig.1).
Results
In Salacia fruticosa, the flower bud takes one week to reach the full bloom stage. The opening of the flower takes place from
11.00–12.00 hr. The flowers are protandrous as the anther dehisces at 10.00hr while the stigma
is receptive only at 11.00hr. The stigma
was found to be receptive for about 30 hours.
Each flower has three anthers and 3-celled ovaries with 1 (rarely 2)
ovules in each cell. Pollen grains are
liberated through longitudinal slits of the anther. A single anther contains ~105 pollen grains,
thus one flower comprises around ~315 pollen grains. Hence, pollen-ovule ratio was worked out as
105 pollens per ovule (105:1). The
pollen grains are globose in nature and having 13µm
in diameter. Nearly 92% pollen grains
are found viable and 87% pollen germination was recorded at the time of anthesis. The pollen
viability and germination was found to decrease and a drastic decline was
recorded after three hours from anthesis though the
stigma was found receptive for 30 hours.
After around one-&-half months the fruits attain maturity and the
percentage of fruit set was found to be 25% (detailed floral characters are
given in Table 1 & Image 1). The
emasculated flowers with artificial pollination as well as flowers which are polybagged (with big holes) were found to be inefficient
for fruit set, that underlines the autogamous nature
of the species. Majority of the fruits on maturity were found to be infested
and the seeds were consumed by the caterpillars of the adult
butterfly, Bindahara moorei
Fruhstorfer. About 70–80 % matured
fruits were infested by this insect.
Discussion and Conclusion
Knowledge of reproductive biology
particularly the anthesis, pollen and stigma
viability, nature of pollination and fruit set are essential to understand the
causes of rarity of the species. The
dehiscence of anthers and release of pollen grains prior to the receptivity of
stigma is considered as an indicator for promoting facultative autogamy in the
species. The low number of pollen
grains, i.e., 105 pollen/anther was found to promote cross
pollination through insects but the incidence of pollinators during
blooming time was negligibly sparse. A
low count of pollens and a sparse incidence of pollinators are limiting the
species from both anemophily and entomophily.
According to Cruden (1977), plants with
pollen–ovule ratio lying between 31.9 to 396 support
facultative autogamy and signifies the above observations in the species.
Depending upon the population
history and reproductive features of the species, reduced pollinator service
may have several negative impacts on the plant population including
reproductive failure (Jennersten 1988) or decreased
effective population size through reduced gene flow and increased selfing (Bawa 1990). These altered reproductive patterns may cause
less of genetic diversity and/or reduced progeny fitness due to inbreeding
depression (Jain 1976; Barrett & Kohn 1991).
Self fertile individuals, however, may be at a
selective advantage in some particular habitats, if outcrossing is disfavored
because plant density is low or if pollinators are scarce or cross pollination
is inadequate (Jain 1976; Lloyd 1980).
Even though the stigma receptive for
30 hours, the drastic decline of pollen viability within three hours after anthesis reduces chances for effective pollination. The bagging experiment also underlines the
chances for self pollination in the species. The low rate of pollination reduced fruit set to 25% in the
species. The insect-pest incidence and
its extent of damage on the seed and seedling output accelerate endangerment of the species in the
near future.
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Table 1. Reproductive characters of Salacia fruticosa
|
Floral Characters |
Findings |
|
Flowering period |
Throughout the year |
|
Flower type |
Pentamerous, bisexual, actinomorphic |
|
Flower colour |
Yellow |
|
Flower opening time (anthesis) |
11.00–12.00 hr |
|
Floral nature |
Protandrous |
|
Anther dehiscence mode |
Longitudinal slit |
|
Anther dehiscence time |
10.00hr |
|
Average no. of
pollens/anther |
105 |
|
Mean no. of
pollen grains/ flower |
315 |
|
Mean no. of
ovules/flower |
3 |
|
Pollen shape |
Globular, smooth |
|
Stigma receptive time and period |
11.00hr onwards (up to 30 hours) |
|
Pollen - Ovule ratio |
105:1 |
|
Pollen diameter |
13 µm |
|
Pollen fertility |
92.3% |
|
Fruit development period |
45 days |
|
Percentage of fruit set |
25% |
