The Science Mentorship Program allows groups of high school students to do small research projects at universities in Singapore. Harini Manivannan, Hong Ying Ying and Wai Yan Aung from NUS High School of Math and Science took the opportunity to do a study with the Asian School of the Environment.
ASE’s Dr Anna Lagerstroem, with two of the NUS High students, Harini Manivannan and Hong Ying Ying
From March to early June the students spent about three hours per week designing and setting up and carrying out an experiment together with ASE researchers. Their study investigated effects of seed size and light availability on germination and seedling growth in five common tropical fruit species, namely papaya, ladyfinger (okra), jackfruit, durian and longan. That seed size and environmental conditions, like light availability, play a major role for the success of a seed is well documented, but most research has been done on temperate species. Also, in times of changing environmental conditions, we need more information on how plants respond to these changes.
A seed cannot see but it can perceive light availability and thereby acquire information about its environment (like canopy cover or distance to soil surface) and if it is suitable to germinate in. Previous studies have found seeds of smaller size to germinate fast because of thinner seed coats and less stored nutrients and moisture. However, some tropical species, like durian and jackfruit, have large seeds with high moisture content that don’t keep long.
Durian fruits
In addition, the students expected higher light levels to benefit germination rate, particularly in small seeds. Unexpectedly, seed size did not affect germination rate or survival of seedlings, and both durian and jackfruit did better in shade than in light treatment. Overall, the shade treatment seemed to be the most beneficial for germination in all species and though ladyfinger had the highest survival in light, durian had significantly better survival in shade, while jackfruit and longan had their highest survival in the shade and dark treatments. Light availability is in turn linked to temperature and moisture, and this study shows that more studies are needed to better understand the factors that regulate germination and early seedling growth of tropical species. Supervisors from ASE were Dr Anna Lagerstroem, Dr Kang Min Ngo and Dr Shawn Lum.
The different treatments carried out on the seeds