Sing Kong Lee

Toward a better future : education and training for economic development in Singapore since 1965

The Singapore economy has undergone significant stages of development since the 1960s. It has grown from its traditional role as a regional port and distribution center in the 1960s to an international manufacturing and service center in the 1970s and 1980s, and now into a center of science-based manufacturing and knowledge-intensive technical services. Much has been written to explain this success. Emphasis has been placed on the early adoption of an export-oriented strategy for industrialization, high savings and investment rates, a stable macroeconomic environment, and even socio cultural traits that support successful industrialization. This volume documents a less-explored aspect of Singapores economic development: it examines the transformation of the education and training system since the countrys independence in 1965 and how the process contributed to skills formation and, hence, economic change.

Hybrid status of kuwini, Mangifera odorata Griff. (Anacardiaceae) verified by amplified fragment length polymorphism

Mangifera odorata Griff. (Anacardiaceae), was suggested to be a hybrid between M. indica L. and M. foetida Lour. due to morphological intermediacy. Results from this study show that M. indica and M. foetida produced unique amplified fragment length polymorphism (AFLP) profiles. Mangifera odorata did not produce any unique bands. All the M. odorata samples additively inherit bands specific to M. indica and M. foetida, which strongly suggested the hybrid origin. Three major clusters were produced in the phenogram. All samples of M. indica, M. foetida and M. odorata segregated distinctly. Mangifera odorata was closer to M. foetida than to M. indica, indicating that backcrossing with M. foetida might have taken place. AFLP analysis therefore verified the hybrid status of M. odorata.

EFFECTS OF ROOT-ZONE TEMPERATURE ON THE ROOT DEVELOPMENT AND NUTRIENT UPTAKE OF LACTUCA SATIVA L. “PANAMA” GROWN IN AN AEROPONIC SYSTEM IN THE TROPICS

Lactuca sativa L. cv. Panama is a temperate plant, but can be grown in the tropics by only subjecting its roots to 20°C while its aerial portions are exposed to the hot, fluctuating temperatures in the greenhouse. This study showed that in Lactuca sativa L. cv. Panama grown at 20°C root-zone temperature (RZT) in the tropics, the roots were longer with a greater number of root tips and total root surface area, and smaller average root diameter as compared with those of ambient RZT (A-RZT) plants. In plants transferred from 20°C to A-RZT (20°C ⇒ A-RZT) when they were 3 weeks old, rate of increase in root length was decreased as was root tip number and surface area; root thickening was increased. The reverse was observed for plants transferred from A-RZT to 20°C-RZT (A ⇒ 20°C-RZT). Mineral nutrients such as NO3 −, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), and zinc (Zn) present in the plant shoot and root tissues were also determined. Generally, it was found that 20°C-RZT plants had higher leaf N and P concentrations on the basis of per unit dry weight compared with plants grown at A-RZT. Results also showed that total shoot and root NO3 −, K, Ca, Cu, Fe, Mg, Mn, and Zn accumulation of 20°C-RZT plants were more than A-RZT plants. 20°C ⇒ A-RZT plants suffered from a reduction of total mineral accumulation, and Ar ⇒ 20°C-RZT plants increased in total mineral accumulation. Relationships between RZT, root growth, and mineral composition of the experimental plants are discussed.

Relationship among photosynthesis, ribulose-1,5-bisphosphate carboxylase (Rubisco) and water relations of the subtropical vegetable Chinese broccoli grown in the tropics by manipulation of root-zone temperature

Abstract Photosynthesis, initial Rubisco activity, Rubisco protein, total soluble protein and water relations were studied in subtropical Chinese broccoli ( Brassica alboglabra ) grown aeroponically in a tropical (Singapore) greenhouse. Aerial parts of the plant were maintained at hot ambient (A) temperature, but with their roots exposed to two different root-zone temperatures (RZTs): a constant 25°C-RZT and a diurnally fluctuating ambient temperature (25–40°C). Plants grown at 25°C-RZT exhibited greater non-stomatal and stomatal limitation of photosynthetic rates (light- and CO 2 -saturated O 2 evolution, P max and light-saturated CO 2 assimilation, A sat ). Light saturated stomatal conductance ( g s sat ) was higher in 25°C-RZT than A-RZT plants. Initial Rubisco activity and Rubisco protein was significantly lower in A-RZT plants than 25°C-RZT. The total soluble protein per unit leaf area showed a marked decrease in plants grown at A-RZT compared to those grown at 25°C-RZT. Predawn and midday leaf water potential ( Ψ leaf ) were higher in 25°C-RZT than A-RZT plants. Reciprocal RZT transfer experiments were also conducted to study the relationship among photosynthesis, Rubisco and water relations. Immediate parallel decreases were observed in A sat , g s sat and Ψ leaf when plants were transferred from 25°C-RZT to A-RZT. However, significant increases in these parameters were observed after only 3 days of RZT transfer from ambient to 25°C. Decreases in non-stomatal limitation of photosynthesis, P max , initial Rubisco activity, Rubisco and total leaf soluble proteins were not detected until 4 or 5 days post-transfer, while decreases in total leaf soluble protein was observed 2 or 3 days after RZT transfer from 25°C to ambient temperature. When plants were transferred from A-RZT to 25°C-RZT, no significant changes in P max , initial Rubisco activity, Rubisco and total leaf soluble proteins were observed during the first 4 days of RZT transfer. These results indicate that the direction of RZT transfer determined the relative contributions of stomatal and non-stomatal limitations to photosynthesis and the importance of water stress.

Root-zone temperature effects on photosynthesis, 14C-photoassimilate partitioning and growth of temperate lettuce (Lactuca sativa cv. ‘Panama’) in the tropics

The effect of root growth temperature on maximal photosynthetic CO2 assimilation (Pmax), carbohydrate content, 14C-photoassimilate partitioning, growth, and root morphology of lettuce was studied after transfer of the root system from cool root-zone temperature (C-RZT) of 20 °C to hot ambient-RZT (A-RZT) and vice versa. Four days after RZT transfer, Pmax and leaf total soluble sugar content were highest and lowest, respectively, in C-RZT and A-RZT plants. Pmax and total leaf soluble sugar content were much lower in plants transferred from C-to A-RZT (C→A-RZT) than in C-RZT plants. However, these two parameters were much higher in plants transferred from A-to C-RZT (A→C-RZT) than in A-RZT plants. A-RZT and C→A-RZT plants had higher root total soluble sugar content than A→C-RZT and C-RZT plants. Leaf total insoluble sugar content was similar in leaves of all plants while it was the highest in the roots of C-RZT plants. Developing leaves of C-RZT plants had higher 14C-photoassimilate content than A-RZT plants. The A→C-RZT plants also had higher 14C-photoassimilate content in their developing leaves than A-RZT plants. However, more 14C-photoassimilates were translocated to the roots of A-RZT and C→A-RZT plants, but they were mainly used for root thickening than for its elongation. Increases in leaf area, shoot and root fresh mass were slower in C→A-RZT than in C-RZT plants. Conversely, A→C-RZT plants had higher increases in these parameters than A-RZT plants. Lower root/shoot ratio (R/S) in C-RZT than in A-RZT plants confirmed that more photoassimilates were channelled to the shoots than to the roots of C-RZT plants. Roots of C-RZT plants had greater total length with a greater number of tips and surface area, and smaller average diameter as compared to A-RZT plants. In C→A-RZT plants, there was root thickening but the increases in its length, tip number and surface area decreased. The reverse was observed for A→C-RZT plants. These results further supported the idea that newly fixed photoassimilates contributed more to root thickening than to root elongation in A-RZT and C→A-RZT plants.

Photosynthetic Utilization of Radiant Energy by Temperate Lettuce Grown Under Natural Tropical Condition with Manipulation of Root-Zone Temperature

Photosynthetic utilization of radiant energy was studied by chlorophyll (Chl) fluorescence and maximum photosynthetic O2 evolution (Pmax) in temperate lettuce (Lactuca sativa L.) grown under natural tropical fluctuating ambient temperatures but with their roots exposed to two different root-zone temperatures (RZTs): a constant 20 °C-RZT (RZT20) and a fluctuating ambient RZT (RZTa) from 23 to 40 °C. On a sunny day, irrespective of RZT, ΔF/Fm′ [ratio of the variable to maximal fluorescence under irradiation (the maximal photosystem 2 quantum yield with “actinic light”)] decreased and non-photochemical quenching (NPQ) increased parallel to the increase of photosynthetic photon flux density (PPFD). However, RZTa plants showed lower ΔF/Fm′ and higher NPQ than RZT20 plants. The electron transport rate (ETR) was much higher in RZT20 plants than in RZTa plants especially during moderately sunny days. There were no significant diurnal changes in Pmax although these values of RZT20 plants were much higher than those of RZTa plants. On cloudy days, no significant diurnal changes in ΔF/Fm′ and NPQ occurred, but ΔF/Fm′ was higher and NPQ was lower in RZT20 plants than in RZTa plants. Diurnal changes in ETR were also observed in all plants while Pmax values throughout the whole cloudy days in both RZT20 and RZTa plants were constant. Again, RZT20 plants had much higher values of Pmax than RZTa plants. During RZT transfer period, all Chl fluorescence parameters measured at midday fluctuated with PPFD. Impact of RZT on these parameters was observed 2–3 d after RZT transfer. ETR and Pmax measured with saturating PPFD in the laboratory did not vary with the fluctuating PPFD in the greenhouse but the effects of RZT on these two parameters were observed 3–4 d after RZT transfer. Thus RZT affects photosynthetic utilization of photon energy in temperate lettuce grown under natural tropical condition.

Effects of elevated root zone CO2 and air temperature on photosynthetic gas exchange, nitrate uptake, and total reduced nitrogen content in aeroponically grown lettuce plants

Effects of elevated root zone (RZ) CO2 and air temperature on photosynthesis, productivity, nitrate (NO3–), and total reduced nitrogen (N) content in aeroponically grown lettuce plants were studied. Three weeks after transplanting, four different RZ [CO2] concentrations [ambient (360 ppm) and elevated concentrations of 2000, 10 000, and 50 000 ppm] were imposed on plants grown at two air temperature regimes of 28 °C/22 °C (day/night) and 36 °C/30 °C. Photosynthetic CO2 assimilation (A) and stomatal conductance (gs) increased with increasing photosynthetically active radiation (PAR). When grown at 28 °C/22 °C, all plants accumulated more biomass than at 36 °C/30 °C. When measured under a PAR ≥600 μmol m−2 s−1, elevated RZ [CO2] resulted in significantly higher A, lower gs, and higher midday leaf relative water content in all plants. Under elevated RZ [CO2], the increase of biomass was greater in roots than in shoots, causing a lower shoot/root ratio. The percentage increase in growth under elevated RZ [CO2] was greater at 36 °C/30 °C although the total biomass was higher at 28 °C/22 °C. NO3– and total reduced N concentrations of shoot and root were significantly higher in all plants under elevated RZ [CO2] than under ambient RZ [CO2] of 360 ppm at both temperature regimes. At each RZ [CO2], NO3– and total reduced N concentration of shoots were greater at 28 °C/22 °C than at 36 °C/30 °C. At all RZ [CO2], roots of plants at 36 °C/30 °C had significantly higher NO3– and total reduced N concentrations than at 28 °C/22 °C. Since increased RZ [CO2] caused partial stomatal closure, maximal A and maximal gs were negatively correlated, with a unique relationship for each air temperature. However, across all RZ [CO2] and temperature treatments, there was a close correlation between maximal A and total shoot reduced N concentration of plants under different RZ [CO2], indicating that increased A under elevated RZ [CO2] could partially be due to the higher shoot total reduced N.

INTERACTION BETWEEN POTASSIUM CONCENTRATION AND ROOT-ZONE TEMPERATURE ON GROWTH AND PHOTOSYNTHESIS OF TEMPERATE LETTUCE GROWN IN THE TROPICS

Lactuca sativa L. plants were grown at three root-zone temperatures (RZTs): 25°C, 30°C and ambient RZT (A-RZT) on an aeroponic system. Three potassium (K) concentrations: −25% (minus K), control (standard K), and +25% (plus K) were supplied to plants at each RZT. Plants grown at the plus K and 25°C-RZT had the highest productivity, largest root system and highest photosynthetic capacity. The minus K plants at 25°C-RZT had the highest shoot soluble carbohydrate (SC) concentration, but they had the highest root SC concentration in the plus K plants at A-RZT. However, the highest starch concentration was found in both shoots and roots of the plus K plants at 25°C-RZT. The plus K plants had the highest shoot K concentration at 25°C-RZT, but they had the highest root K concentration at A-RZT. Highest proportion of absorbed K was partitioned to shoots when the plants were grown with the plus K at 25°C-RZT.

Effects of soil ageing on the accumulation of hydrogen sulphide and metallic sulphides in mangrove areas in Singapore

Abstract The effects of soil ageing on the accumulation of hydrogen sulphide and metallic sulphides were studied in reclaimed mangrove plots of increasing ages. The analysis was carried out using a low-cost electrochemical approach, utilizing a sulphide volatilization/trapping procedure followed by sulphide quantification with an ion-selective electrode technique. The results showed that the content of hydrogen sulphide in the soil increased with age. Initially, the content of metallic sulphides also increased with the age of the soil. However, once the supply of metallic soil components for sulphide precipitation had been exhausted, the sulphides generated in the soils existed as hydrogen sulphide. The reasons for these patterns of sulphide accumulation in the mangrove soil and their possible impact on the growth of different types of mangrove vegetation are briefly discussed.

Physiological responses of certain ornamental plants to sludge and artificial topsoils derived from flyash, sludge, and rengam series subsoil

Abstract In this study, four artificial topsoil mixtures were produced by mixing incinerator flyash, sewage sludge, and subsoil (from granite origin) in various proportions. Each mixture had a different heavy metal content. Both sludge and the artificial topsoils were used to grow certain ornamental plants, namely, Bougainvillea spectabilis, Ixora coccinea, and three Heliconia taxa; H. psithacorum x H. spathocircinata cv. “Golden Torch”;, H. rostrata and H. psithacorum cv. “Tay”;. Their physiological responses were monitored using chlorophyll fluorescence Fv/Fm ratio and their general appearance was also recorded. All the five plants grown in sludge were observed to show no symptoms of heavy metal toxicity. However, it was found that I. coccinea and all three Heliconias were susceptible to heavy metal toxicity when grown in all the four mixtures of artificial topsoil. Bougainvillea spectabilis is capable of tolerating the heavy metal present in the artificial topsoil with the least amount of heavy metals ...