A bioengineering technique is gradually being used as an alternative for slope stabilisation design. The effect of vegetation on soil strength, particularly in terms of root reinforcement aspects has therefore become a major interest. However, there is a lack of documentation on the root mechanical properties available especially in Malaysia. In this study, both pull-out and tensile strength of two tropical trees namely Leucaena leucocephala and Acacia mangium were investigated on different stem sizes. L. leucocephala performs the higher pullout strength than A. mangium. The results also show that pullout resistance is much affected by the root than the shoot profiles. In terms of tensile strength, the tensile strength decreases with increasing root diameter, implying the finer root diameter contribute to the higher tensile strength. In both parameters, L. leucocephala exhibits the highest value. The study suggests that L. leucocephala has an added value as a good potential slope plant for slope stabilization work as it exhibits outstanding root mechanical properties. Interestingly, the results also showed that the pullout force was much affected by the tensile strength. It can be concluded that some root and shoot properties do have a great impact on root mechanical properties such as tensile and pullout strengths.
Rapid development in hilly areas in Malaysia has become a trend that put a stress to the sloping area. It reduces the factor of safety by reducing the resistant force and therefore leads to slope failure. Vegetation plays a big role in reinforcement functions via anchoring the soils and forms a binding network within the soil layer that tied the soil masses together. In this research, three plant species namely Acacia mangium, Dillenia suffruticosa and Leucaena leucocephala were assessed in term of their soil-root shear strength properties. Our results showed that Acacia mangium had the highest shear strength values, 30.4 kPa and 50.2 kPa at loads 13.3 kPa and 24.3 kPa, respectively. Leucaena leucocephala showed the highest in cohesion factor, which was almost double the value in those of Dillenia suffruticosa and Acacia mangium. The root profile analysis indicated Dillenia suffruticosa exhibited the highest values in both root length density and root volume, whilst Leucaena leucocephala had the highest average of root diameter.
In this study, we investigated the effects of 2,4-Dichlorophenoxy acetic acid (2,4-D) treatment on selected physiological parameters and fruit quality of wax apple fruits under field conditions. Foliar spray of 2,4-D at 0, 5, 10 and 20 mg L-1 concentrations were used from bud stage to the 3rd week of fruit development. Physiological parameters determined included net photosynthesis, stomatal conductivity, chlorophyll content and chlorophyll fluorescence. Net photosynthetic rate and photosynthetic efficiency via chlorophyll fluorescence significantly (p≤0.05) increased with 5 and 10 mg L-1 2, 4-D treatments. Furthermore, 5 mg L-1 2,4-D reduced bud and fruit drop, increased fruit weight and dry matter content in leaves. An improved fruit set, enhanced fruit growth, faster color development and advanced maturity were also recorded in treated plants. In addition, fruit yield increased by 39 and 48% with 5 and 10 mg L-1 2,4-D treatments, respectively. Fruit K+ content, total sugar, protein content and chalcone synthase (CHS) activities increased with 2,4-D treatments. Increased leaf soluble protein and elevated sucrose phosphate synthase (SPS) activity were also observed in 5 mg L-1 treated plants. Positive correlation between photosynthesis rate and SPS activity of leaves (R2=0.98) and between CHS activity and color development of fruits (R2=0.98) were recorded in 5 mg L-1 treatments. The results also suggested that 5 and 10 mg L-1 2,4-D treatments are promising for enhancing plant productivity and fruit quality in wax apple trees under field conditions.
A study was carried out to investigate the effects of different girdling techniques on the growth, development and quality of red wax apple fruits (Syzygium samarangense). Selected horticultural parameters were monitored at one week interval during the growth period from December 2008 to October 2010, using I, C, V shaped, 50%, and 100% girdling. Girdling was applied 2 weeks before flowering. The results showed that the C-shaped girdling technique produced the best results with regard to the fruit setting and chlorophyll content in comparison to the control and the other girdling
techniques employed. Furthermore, C-shaped girdling enhanced faster fruit growth producing the best final fruit length and diameter. In addition to significantly increased yield, juice percentage, leaf dry matter, biomass and TSS content of fruits. It was also observed that 50% girdling decreased fruit dropping. V-shaped girdling also increased the number of bud and reduced bud dropping compared to control. I-shaped girdle fruits produced the highest amount of K+ content in fruit juice compared to other treatments. The color development of the fruit peel in 100% girdling was also the highest among the treatments. From this study, it can be concluded that C-shaped girdling applied two weeks before flowering produced better fruit growth, yield and quality of red wax apple fruits under field conditions.