My research interests centre primarily on the biology of the angiosperms of Singapore or Southeast Asia. Research topics for graduate studies are selected based on mutual enthusiasm and interest for graduate student and myself as I believe students cannot sustain their drive and persevere if they are not passionate about their research.
A novel method for measuring leaf toughness
Current methods of measuring leaf fracture toughness involve cutting a leaf, either with a guillotine , pair of scissors or a penetrometer, and measuring the energy required to make a unit area of cut. Such cutting techniques unavoidably require the use of two working surfaces moving against each other to effect a cut, and the friction between these surfaces could be very high. Although it is possible to subtract the work of friction from the work of cutting by repeating the test a second time with the specimen still in place, this is however complicated by the presence of debris generated during the cutting process. The debris can come from micro-fragments of the working surfaces as they abrade against each other or from the cell wall fragments of the cut leaf. This debris will tend to increase the friction between the working surfaces, resulting in an overestimation of friction. The frictional forces involved during cutting is also relatively large compared to the forces required just for cutting alone. This would result in a large noise-to-signal ratio which will in turn lower the sensitivity of the cutting tests. The aim of this project is to develop a new technique for measuring leaf fracture toughness, which will reduce the above-mentioned problems to a minimum.
This research is being carried out in collaboration with Prof. Peter W. Lucas (The George Washington University). Graduate student Ang Kai Yang is carrying out this research for his MSc degree.
Aerobiology, image analysis and allergenicity of pollen and spores in Singapore
Current projects involve monitoring of outdoor airspora (pollen, fern and fungal spores) in relationship to their allergenicity. Daily and yearly airspora calendars have been established. Image analysis work to differentiate and subsequently identify the different local airspora components has yielded promising results. This has led to the expansion of the project to include allergenic airspora worldwide. We also developed an automated airspora quantification system. An automated system is needed to replace the current conventional method, which is not only extremely time- and labour-intensive but also has a high error rate of more than 30%. With the availability of more data, accurate modelling of the local airspora for forecasting allergen load in the airspora will be possible. Work was also carried out to monitor the actual airspora allergen load instead of merely counts of pollen grains or spores alone by using a bead suspension assay with the ability to detect multiple types of allergens simultaneously in a single minute amount of sample. The allergenicity of local airspora is also being studied using an allergen multi-array developed in house is also being carried. This work has led us to the identification of possible new allergenic pollen types.
These studies are currently being developed in collaboration with the Adjunct Assoc. Prof. Lee Bee Wah (Department of Paediatrics), Assoc. Profs. Ong Sim Heng and Surendra Ranganath of Department of Electrical and Computer Engineering and departmental colleagues, Drs. Chew Fook Tim and Ong Tan Ching.
Airspora composition in Singapore
This study aims to capture and identify the total airspora composition that exist in the Singapore environment. It will involve sample collections of airborne pollen, fern and fungal spores from a number and variety of sites across Singapore at ground level. The sampling locations were chosen to encompass parks, housing estates, schools and trains stations. The airspora composition will be studied based on island wide distribution and niches. The effects of sampling heights will also be studied at three different locations. Thirty self-fabricated Durham traps are currently being used in this preliminary study.
These studies are currently being carried out by junior college students from Hwa Chong Institution, Ms Nang Su Wai, and Messrs. See Yee Yang and Wong Min Hao under the Science Research Programme of the NUS Faculty of Science in collaboration with departmental colleagues, Drs. Chew Fook Tim and Ong Tan Ching.
Airspora distribution in Singapore and pollen allergy
The airspora consists of the pollen and spores (fungal, cryptogamic) found in the atmosphere. This study involves sample collections of airspora from 30 sites across Singapore using self-fabricated Durham spore traps placed at 1.5 m above ground level. Identification work will be out by light microscopy by comparing the sampled airspora with reference slides. Pollen from the major airspora found from the distribution study will then be collected. A large panel of pollen types will then be screened using the allergen array to study the frequency of pollen allergy in the Singapore population. Foreign allergenic pollen types will also be included in the screens for further cross reactivity studies. Pollen types found to be the major allergy trigger from the allergen array screened will then be further characterised using enzyme-linked immunosorbent assay, inhibition assays, and 1- and 2-dimensional western blotting followed by mass spectrometry. The findings from this study will allow us to determine the airspora composition, the spectrum of allergenic airspora and the major local pollen allergens. This project continues from the project on the Airspora composition in Singapore.
These studies are currently being carried out by Ms Chen Huimin for her Honours Project in collaboration with departmental colleagues, Drs. Chew Fook Tim and Ong Tan Ching.
Analysis of the functions of the MADS-box genes, AGL6 and AGL13 from Arabidopsis thaliana
MADS-box genes are known to be transcription regulators that play important roles in the development of seed plants (angiosperms and gymnosperms), particularly in the initiation and specification of reproductive organs. To date, over a hundred MADS-box genes have been identified from the model plant, Arabidopsis thaliana. AGL6 and AGL13 are two of the many MADS-box genes that have been first described more than a decade ago, but their functions remain unclear. Preliminary studies indicated that AGL6 and AGL13 may be involved in the control of flowering time in Arabidopsis thaliana. The current project aimed to clarify the function of these genes by looking into their expression patterns, over-expression and dsRNAi. The genes will be further characterized using protein tagging techniques to identify interacting partners, ChIP to identify direct downstream genes, as well as GR-inducible system and genetic crossing to identify their location in the flowering pathways of Arabidopsis thaliana.
This project is done in collaboration with departmental colleagues, Assoc. Prof. Prakash P. Kumar, and Dr. Yu Hao. Teo Lai Lai is the graduate student carrying out this research for her PhD degree.
Auspicious and inauspicious plants of Singapore
This ethnobotanical project will survey the literature and involve interviews with all races of Singaporeans for the plants which Singaporeans consider lucky and unlucky. Research will involve identification of relevant plants, their auspicious and/or inauspicious quality(ies) and photography. This unprecedented compilation involves numerous plants of great commercial value, e.g., plants grown by the Chinese for the Lunar New Year celebrations are worth several thousand dollars per year.
This project is being carried out by Undergraduate Research Opportunities in Science student, Mr. Giam Xingli.
Establishment of strangler and climber fig species on trees: towards the non-drastic replacement of cultivated exotic street trees by native species
Plants used for landscape or street plantings in Singapore and elsewhere in the tropics, tend to be species from South America. In Singapore, most cultivated species are exotic or non-native species. There is a world-wide trend to plant native species, but replacement of exotics by cutting down trees to replant with native species is very drastic, as it is not environmentally friendly as even exotic species provide environmental and ecological services. There are many native strangler or climber fig (Ficus) species which grow well in street or urban conditions, and can grow on cultivated exotic street trees. Strangler and climber figs will ultimately engulf the host plant over time, so allowing the services to continue till the native species is sufficiently large. This horticultural and ecological project will determine the feasibility of establishing strangler and climber fig species on urban plantings, and the factors involved.
This project is being carried out by Undergraduate Research Opportunities in Science student, Ms Goh Gan Khing.
Floral developmental genes of holoparasitic plants
Holoparasitic plants, including the famous Rafflesia, are enigmatic organisms, having no visible vegetative organs and highly unusual flowers. Such angiosperms have been little researched, with few studies (either molecular or ecological) published in the past twenty years, partly due to their rarity and inaccessibility of their habitats. Due to their strange and interesting floral morphology, there is a lot of scope for research in the molecular biology of Rafflesia and Balanophora, in particular the MADS-box genes involved in floral formation. MADS-box genes encode transcription factors involved in plant development and signal transduction. The main objectives of this project are to identify and characterise MADS-box genes involved in flowering in holoparasitic plants, focusing on selected Balanophora and Rafflesia species.
This project is done in collaboration with departmental colleague, Assoc. Prof. Prakash P. Kumar. Edwin Phua Ek Kian is the graduate student carrying out this research for his MSc degree.
Herbivory of sun and shade leaves
It has long been recognized that sun and shade leaves are quite different in terms of their mechanical, structural and nutritional properties. These differences can be expected to affect their palatability to insect herbivores, resulting in different herbivory rates. This study aims to investigate how differences in leaf fracture toughness, leaf developmental time, and leaf chemical content in sun and shade leaves can affect the rates of herbivory in tropical rainforest understorey plants of Singapore’s nature reserves. Knowledge about the different herbivory rates in sun and shade leaves can shed vital insights into how the increased light levels in gaps can affect the rate of herbivory, and in turn, the fitness of the surviving understorey plants.
This research is being carried out in collaboration with Prof. Peter W. Lucas (The George Washington University) and Dr. Nathaniel J. Dominy (University of California at Santa Cruz). Graduate student Ang Kai Yang is carrying out this research for his MSc degree.
Molecular systematics and genetic diversity of the Joey palms, Johannesteijsmannia
Johannesteijsmanniais a mostly endemic palm genus of four species ranging from South Thailand, North Sumatra, Peninsular Malaysia and Western Borneo. J. lanceolata, J. magnifica and J. perakensis are confined to a few locations in Peninsular Malaysia, but J. altifrons is the most widespread covering the range of the genus. This project is to re-examine the morphology and combine this with data on molecular markers to improve current classifications for the genus as well as to examine the genetic variation within the species.
This research is being carried out in collaboration with Drs. John Dransfield (Royal Botanic Gardens, Kew), William J. Baker (Royal Botanic Gardens, Kew) and Saw Leng Guan (Forest Research Institute Malaysia) and departmental colleague, Assoc. Prof. Prakash P. Kumar. Graduate student Look Su Lee is conducting this research for her PhD degree.
Monitoring mangrove biodiversity via satellite imagery remote sensing
Remote sensing is increasingly recognized as an important tool for the large-scale monitoring of forest biodiversity. While some research has already been carried out on monitoring the tree flora of mangroves via remote sensing, very little of such research was carried out in the Southeast Asian region, which is considered a biodiversity hotspot. This project involves the creation and analysis of a database of mangrove plant spectral signatures, which are important in identifying and thus monitoring mangroves via remote sensing, as well as the setting up of a Geographical Information System (GIS) for the large scale monitoring of mangroves.
This research is being carried out in collaboration with Dr. Liew Soo Chin (Centre for Remote Image Sensing and Processing, National University of Singapore). Graduate student Wong Choong Min is conducting this research for his MSc degree.
Plant food allergenicity and cross-reactivity of plant foods in Singapore
Consecutive sera of Singaporean allergic patients were screened using a dot-blot assay for presence of specific IgE to 38 plant foods, the majority of which are commonly eaten locally. The patterns of reactions were analysed for possible cross-reactivity between the plant species tested. Plant species with significant reactions will be chosen, and their allergenic fraction(s) will be characterized and cloned. The main aim of this project is to identify major allergens in commonly eaten plant foods, with the ultimate goal of using these for therapeutic purposes.
This research is being carried out in collaboration with departmental colleague, Dr. Chew Fook Tim. Graduate student Lee Wan She is conducting this research for her MSc degree.
Population genetics of tropical lowland rainforest tree species in forest fragments in Singapore
Through massive deforestation since the founding of modern Singapore, tropical lowland rainforests now occur only in small patches in the midst of residential and industrial development. Theoretically, habitat fragmentation can bring about the loss of genetic variation and increased genetic divergence between populations. Hence, we are keen to find out the genetic diversity of individuals of selected tree species in different forest patches, as well as to observe for gene flow between these sites. The studied species are Calophyllum ferrugineum (bintangor), Sindora wallichii (sepetir), and Streblus elongatus (tempinis). Both adults and juveniles shall be sampled and classified according to their class sizes. The AFLP (amplified fragment length polymorphisms) technique shall be employed in this study.
Reproductive phenology and population genetics of the superb fig, Ficus superba
The figs (Ficus species) are well-known for specialized species-specific pollinator. Such specializations may have several important repercussions. They include the necessary existence of a minimum population size of each Ficus species for the maintenance of the pollinator, and the effectiveness of long distance dipersal of pollinators due to the usually low-density of Ficus individuals. Ficus superba was chosen for the current study as it is a coastal species, atypical of the genus usually found in forests. It will be interesting to find out if data gathered for this species are in line with what are known of the species from the more typical fig habitats.
This research is being carried out in collaboration with departmental colleague, Assoc. Prof. Prakash P. Kumar. Graduate student Yeo Chow Khoon is conducting this research for his MSc degree.
Reafforestation of Kent Ridge Forests