Pollination Ecology of Commelina Communis (Commelinaceae)
J H Wei
1
, L D Liu
1,*
, L Zhang
1
, J Sun
1
and C C Pan
2
1
School of Life Sciences, Ludong University, Yantai, Shandong, 264025, China;
2
Northwest Institute of Eco-Environment and Resources, Chinese Academy of
Sciences, Lanzhou, Gansu, 730000, China.
Abstract. The floral biology, pollen/ovule ratio, pollen v iability, flower visitors, pollination
process and fruit set of Commelina communis were observed, measured and recorded in
Kunyu Mountain, Shandong Province. The main results were as follows: The flowers of C.
communis came into blossom at 3:00~5:00am, full-blossom before 6:00 and petal-shut at
12:00~13:00. The life-span of single flower of C. communis was about nine hours. In the four
hours after flowering, the pollen viability was higher than 92%; six hours later, no pollen
viability was detected. The P/O was 321±13. The results showed that C. communis was
facultative autogamous. C. communis was pollinated by at least 4 species, of which syrphid
fly was the main flo wer visitor. Fruit set of the completely netted flowers accounted for
92.7% of that under natural conditions. These indicated that self-pollination predominated in
C. communis, xenogamy just played an auxiliary role in the breeding system.
1. Introduction
Commelina communis L. (Commelinaceae) is an annual, monoecious plant that is native to temperate
northeast Asia [1]. C. communis flowers are zygomorphic with three blue petals. C. communis
flowers can be divided into two types according to the existence of fertile stigmas or not: perfect
flowers and staminate flowers. Each C. communis flower contains three types of stamen: long(L),
medium(M) and short(S) typed stamens. The L-anther and M-anther produce fertile pollen; the S-
anther produce pollen of weak vitality [2]. The pollination ecology of C. communis was studied by
Song [3]. Song believed that the pollination syndrome of C. communis was autogamy and the mainly
flower visitor (Lasioglossum sp.) was the pollen thief. Morita [2] considered that C. communis was
self-compatible and could have delayed autogamy and bud pollination. Here we reported the
pollination ecology of C. communis in China once again.
2. Materials and methods
2.1. Study sites
The study site was located on Kunyu Mountain (37º14´51.5"N and 121º46´16.3"E) in the eastern end
of Jiaodong Peninsular at an average altitude of 923m above sea level in Shandong Province, PR
China. This region is characterized by a temperate and monsoonal climate with four clearly distinct
seasons. The annual precipitation is 815.6mm; the average temperature is 11°C. Vegetation is typical
carpophylile.
Wei, J., Liu, L., Zhang, L., Sun, J. and Pan, C.
Pollination Ecology of Commelina Communis (Commelinaceae).
In Proceedings of the International Workshop on Environmental Management, Science and Engineering (IWEMSE 2018), pages 539-544
ISBN: 978-989-758-344-5
Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
539

2.2. Floral biology
In the field, flowering period, flower lifespan, anther dehiscence was revealed. The stigma of buds
was cut off to examine the existence of pollen or not under microscope.
2.3. P/O
The perfect flowers were chosen to measure the pollen-ovule ratio. The P/O ratio was estimated
according to the method of Cruden
[4]
. The number of pollen grains was estimated basing on the
method of Anderson [5].
2.4. Pollen viability
The pollen viability was measured by TTC staining method. 20 flowers were chosen and scattered
the pollens on a clean glass slide. A drop of 0.5% TTC was quickly added and keep the slide at 37°C
in the dark for up to 2h. Then, three fields were randomly observed under an optical microscope, and
100 pollen grains were observed in each field. The number of pollen grains that were dyed red
(active) was counted and averaged.
2.5. Observations and collection of flower visitors
Flower visitors observations were carried out in the field during 8-10, August 2008. We observed the
area for 30 minutes every hour from 05:00 to 13:00. During observation periods, the species of each
flower visitor, the number of visits made by each flower visitor were recorded. The flower visitors
were captured and sent to specialists at Ludong University, Yantai, China, for identification.
2.6. Bagging experiments
To examine self-compatibility and contributions of autogamy in fruit set, two treatments for
pollination experiments were conducted: (1) open pollination- flowers were labeled and left
unbagged; (2) natural self-pollination- buds were bagged with nylon net. Two weeks later, remove
the net away to observe if there was any fruit-set and counted.
2.7. Statistical analysis
A goodness of fit analysis was performed to test if the proportion in fruit set result in completely
netting deviated significantly from the natural conditions.
3. Results
3.1. Floral biology
The flowers of C. communis are zygomorphy. The flowers began to blossom at 3:00~5:00 and in full-
blown before 6:00. Before wilting, the flower lasted about nine hours. At 9:30am, flowers began to
wilt. At 11:00~11:30, most flowers wilted, the pistils and long stamens rolled up, and flowers closed
up again at 12:00~13:00. The anther dehisced before the opening of the petals. When the petals were
about to open, pollen were found distributed on the stigmatic surface. Thirty hours later, most of C.
communis flowers turned into fruits, others shed.
3.2. P/O
As shown in Table 1, P/O of C. communis was 321±13. The breeding system was facultative
autogamous based on the criteria established by Cruden [4]. Our result was in line with that of other
reports.
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Table 1. The P/O ratios for Commelina communis.
Stamens
no./flower
Pollen grain
no./anther
Pollen grain
no./flower
Ovule
no./flower
P/O ratio
6
1285±53
7714±317
4
321±13
3.3. Pollen viability
The pollen viability gradually decreased with the progress of flower life. The pollen viability of C.
communis was higher than 92% at the beginning of flowering, and could last about four hours. Four
hours later, the pollen viability of C. communis brought down quickly. The fifth hour after blooming,
the pollen viability of C. communis decreased to 23.9%. After the sixth hour, no pollen viability of C.
communis could be detected (Figure 1).
0
20
40
60
80
100
0 1 2 3 4 5 6
Pollen viability (%)
Time (h)
Figure 1. Pollen viability of Commelina communis on sunny days.
3.4. Flower visitors
At least four insect species were observed to visit the flowers of C. communis (Table 2). Most visits
to flowers occurred before 8:30, no visits were observed after 8:30 (Figure 2). Syrphid flies were the
most common visitors, the others belonged to Hymenoptera were occasional visitors. As usual,
syrphid flies hovered several times above the flowers before foraging, and then landed on the fertile
anthers to graze pollen. All the visitors were concentrated towards gathering pollen because no nectar
was found in the flowers of C. communis. Pollen was the only rewards for visitors. The anthers of the
long stamens could touch the stigmatic surface when visitors were landing and foraging on perfect
flowers.
Table 2. Floral visitors and their rewards on flowers of Commelina communis
.Order
Family
Genus
Species
Reward
Hymenoptera
Apoidea
Habropoda
Pollen
Halictus
Lasioglossum calceatum
Pollen
Amegilla
Amegilla parhypate
Pollen
Diptera
Syrphid
Pollen
Pollination Ecology of Commelina Communis (Commelinaceae)
541

Figure 2. Visitation frequency of all insects to Commelina communis.
3.5. Bagging experiments
Fruits were produced by perfect flowers but staminate ones. Under natural conditions, fruit set was
53.4±6.3%. In the completely netted flowers, fruit set was 49.5±6.2%, accounting for 92.7% of that
under natural conditions. These results suggested that autogamy played a dominant role in fruit
production in C. communis.
3.6. Conclusions
Our results indicate that the pollen viability of C. communis gradually decreased with the progress of
anther dehiscence; 6h later, most pollen grains lost their viability. P/O ratio was 321±13. According
to Cruden, C. communis was facultative autogamous. Fruit set of the completely netted flowers
accounted for 92.7% of that under natural conditions. Autogamy played a dominant role in fruit
production in C. communis.
4. Discussion
Mutualism was formed between plants and their pollinators in the million years’ coevolution. The
plants benefit from pollinators when they are foraging on the flowers. Many factors such as floral
color, shape, floral size and density, and the distribution of nectar rewards can affect the foraging
behavior of a pollinator [6-9]. In this species, flowers without petals received fewer approaches by
flower visitors. The removal of S- and M- anthers did not decrease the approach frequencies of
flower visitors [10]. So it was the floral color and shape attracting the insects, and the aim of flower
visitors was pollen because no nectar was produced in this species.
The reliability of using pollen/ovule ratio and outcrossing index as directive parameters of
breeding system was ever doubted. But these were extensive used [11-15]. In these studies, the
results of P/O, OCI were consist with that of bagging experiments. In this paper, these two
parameters were also adopted to test the breeding system of C. communis, but the results were
contradict with that of bagging experiments.
The flowers of C. communis are zygomorphy. Bilateral symmetry in flowers was evolved from
radial symmetry [16-17]. The appearance of zygomorphy has led to the evolution of highly
specialized pollination systems seen in advanced families [18]. In C. communis, at least four species
were observed. But syrphid fly was the most common flower visitor and could carry pollen on their
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542

body. The other visitors’ appearance was very occasional. So we also believed C. communis was
syrphid fly-pollinated on Kunyu Mountain.
Species with zygomorphic flowers which were more commonly found in the Commelineae were
self-compatible [19]. Our results indicated that the pollination syndrome of C. communis was mainly
autogamy. Entomophily played a minor role in fruit production in this species. Autonomous self-
pollination had been classified into three types [20]: prior self-pollination, competing self-pollination
and delayed self-pollination. Delayed self-pollination provides an opportunity for cross-pollination
prior to flowers self-pollinating [21]. Pollination was completed only when pollen with viability
reached to receptive stigma. In C. communis, pollen viability was disappeared after six hours of
flowering. So, delayed self-pollination could not occur even when the flowers closed up again in the
noon. In the mating system of C. communis existed both selfing (prior pollination) and outcrossing
simultaneously. Several studies show that the corolla of C. communis and associated structures may
attract pollinators and pollinators might influence the size of floral organs [22-24]. However,
autogamy predominated in C. communis, xenogamy just played an assistant role in the breeding
system. This was different from that of Morita and Nigorikawa [2].
In the experiment, we found the staminate flowers could not set fruits although pollen was found
on the stigma surface. This needs for further study.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China
(41773086, 31400392) and China Postdoctoral Science Foundation funded project (2015T81068,
2014M552516).
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