Corresponding authors: Yu Ito (
Academic editor: Lorenzo Peruzzi
Myanmar (Burma) constitutes a significant component of the IndoMyanmar biodiversity hotspot, with elements of the Indian, the Indochina, and the SinoJapanese floristic regions, yet thus far only a few reliable sources of the country's flora have been available. As a part of a contribution for the floristic inventory of Myanmar, since it is important in a floristic survey to obtain as much information as possible, in addition to previous two reports, here we present three more chromosome counts in the aquatic monocots of Myanmar:
With its wealth of plant diversity, Myanmar (Burma) constitutes a significant component of the IndoMyanmar biodiversity hotspot with elements of the India, the Indochina, and the SinoJapanese floristic regions (ca, 13,500 vascular plants:
The aim of floristic research is not only to count the total number of species but also to evaluate the native flora’s evolutionary origins by comparing with related floristic regions. From this aspect, it is useful to obtain as much information as possible, e.g., chromosome data (
Aquatic plants, which is polyphyletically evolved in fern and fern allies, basal angiosperms, monocots, and eudicots, is known as having numerous chromosomal variation, thus an excellent model for this aim. Here, in addition to the previous contributions of chromosome counts for new or noteworthy aquatic plants from Myanmar (
Plant materials of
Root tips collected in the field were pretreated with 0.002 M 8hydroxyquinoline at 4 °C in 12 h, and fixed with freshly mixed Carnoy’s fixative (3: 1 ethyl alcohol: acetic acid) for at least 30 min, and then preserved at 4 °C in 12 h. For microscopic observation, root tips were soaked in 1 N HCl for 1 h followed by 10 min at 60 °C. After being immersed in tap water, the materials were stained in a drop of 1.5% orcein acetate solution on a slide glass in 5 min., and then squashed. Then somatic chromosome numbers of the three taxa were obtained by light microscopic examination. For each species, at least two cells were used to confirm the numbers.
Distribution for each species follows
Chromosome researches for aquatic monocots of Myanmar were reviewed with a broad focus on Myanmar and related floristic regions, i.e., the Indian, the Indochina, and the SinoJapanes floristic regions. The focal species include 45 nonhybrid aquatic monocots listed in
Native to Americas; naturalized to tropical Asia.
Chromosome counts: 2n = 20 (Fig.
Bangladesh, Bhutan, China (nationwide), India (nationwide), Indonesia (Borneo, Java, Sulawesi), Japan, Malaysia (Peninsular), Myanmar, Nepal, Pakistan, Philippines, Thailand; Oceania.
Chromosome counts: 2n = 22 (Fig.
India (Central, Southern), Myanmar, Sri Lanka.
Chromosome counts: 2n = 24 (Fig.
Bangladesh, China (Southern), India (Eastern, Northern, Southern), Myanmar, Nepal, Sri Lanka, Thailand, Vietnam; Yemen, and Sudan.
Chromosome counts: 2n = 16 (Fig.
Chromosome counts: 2n = 52 (Fig.
The chromosome counts given for 45 nonhybrid species of aquatic monocots of Myanmar as well as wellinvestigated two
Of 45 nonhybrid aquatic monocots and two interspecific hybrids among them, more than two thirds have no chromosome variation. Meanwhile, the following nine species have infraspecific chromosome variation, i.e.,
Thanks are due to the following personnel in Myanmar for their help in arranging our field work: U. Htun Paw Oo, Exdirector of Nature and Wildlife Conservation Division; U. Soe Win Hlaing, Exdirector General, Forest Department, Ministry of Environmental Conservation and Forestry. We also thank Prof. T. Koyama, director of the Kochi Prefectural Makino Botanical Garden (Japan), who initiated the MyanmarJapanese cooperative program to inventory the plants of Myanmar, and gave us the opportunities to study the Myanmar plants, Prof. J. Murata, curator of the University of Tokyo (Japan), who principally organizes the MyanmarJapanese inventory project, and Dr. T. OhiToma, assistant professor of the University of Tokyo (Japan), who helps the first author to use the facilities of the botanical gardens, the university of Tokyo.
Conceived and designed the study: YI NT. Collected the samples in the field: YI NT. Performed the chromosome observation: YI. Analyzed the data: YI. Wrote the paper: YI. Corrected and revised manuscript: NT.
Somatic chromosome of
Somatic chromosome of
Somatic chromosome of
Somatic chromosome of
Somatic chromosome of
The chromosome counts given for 45 nonhybrid species of aquatic monocots of Myanmar as well as wellinvestigated two
Order  Family  Species  Chromosome number  Floristic region  

Indian  Myanmar  Indochina  SinoJapanese  Others  


2n = 24 





2n = 35 




2n = 36 




2n = 44 




2n = 45 




2n = 66 




2n = 24 




2n = 36 




2n = 54 




n/a  


2n = 28  


n/a  


2n = 40 




2n = 20 




2n = 40 




2n = 60  


2n = 80 




2n = 40  


2n = 42 




2n = 80 




n/a  


2n = 14 




n/a  


2n = 20  This study 




2n = 22  This study  


2n = 40 




2n = 42 




2n = 74 




2n = 42 




2n = 72 




2n = 46  


2n = 48 




2n = 48 




2n = 16 




2n = 24 





2n = 32 





2n = 16 





2n = 12 




2n = 24  


2n = 36 




n/a  


2n = 12  


2n = 24 




2n = 24 




2n = 16 





2n = 44  


2n = 66 




2n = 68 




n/a  


2n = 20 




2n = 24 




2n = 30 




2n = 40  


n/a  


2n = 52 





2n = 56 




2n = 52 




2n = 52  This study  


2n = 52 




2n = 56 




2n = 52 




2n = 52 





2n = 52 




2n = 28  


2n = 52 




2n = 78 





2n = 84 




2n = 20 





2n = 40 




n/a  


2n = 32 




2n = 28 




2n = 80 




2n = 24  


2n = 48  


2n = 52 




2n = 30 




n/a 