Yahya Awang

Chemical and Physical Characteristics of Cocopeat-Based Media Mixtures and Their Effects on the Growth and Development of Celosia cristata

Problem statement: Cocopeat is considered as a good growing media comp onent with acceptable pH, electrical conductivity and other ch emical attributes but it has been recognized to hav e high water holding capacity which causes poor air-w ater relationship, leading to low aeration within the medium, thus affecting the oxygen diffusion to the roots. Incorporation of coarser materials into cocopeat could improve the aeration status of the m edia. Approach: Selected chemical and physical characteristics of five types of growing media comp rising of (v/v) 100% cocopeat, 70% cocopeat: 30% burnt rice hull, 70% cocopeat: 30% perlite, 70% coc opeat: 30% kenaf core fiber and 40% cocopeat: 60% kenaf core fiber were determined and their suitabil i y as growing media was tested using Celosia cristata. Data on pH, Electrical Conductivity (EC) and variou s aspects of air-water relationships of the media, as well on growth and flowering of test plant and leaf nutrient contents were collected. Results: Initial pH for 100% cocopeat and 70% cocopeat: 30% kenaf core fiber was higher than the other media but the values were eventually similar by the end of the st udy. The bulk density and EC of media containing burnt rice hull was markedly higher than the other m dia (0.12 g cm and 0.48 mS cm, respectively). Media comprising of 70% cocopeat: 30% burnt rice hu ll and 70% cocopeat: 30% perlite contained higher air content. The former held the highest vol ume of available water. Incorporation of burnt rice hull and perlite into cocopeat increased water abso rption ability of the media which reached saturatio n earlier than the other media. Addition of burnt ric e hull (30%), perlite (30%) and kenaf core fiber (3 0%) to cocopeat elevated the Air-Filled Porosity (AFP) of the media. The growth and flowering of Celosia cristata were the greatest when grown in a mixture of 70% co copeat: 30% burnt rice hull and perhaps linked with a good balance in the aeration and mois ture relationship of the media. Conclusion: Results of this study indicated that certain chemical and p hysical properties of cocopeat can be improved through incorporation of burnt rice hull and its po sitive effect was clearly reflected in the growth a nd development of Celosia cristata.

Effects of selected herbicides on soil microbial populations in oil palm plantation of Malaysia: A microcosm experiment

Herbicides are commonly used in Malaysia to control weeds in oil palm plantation. In addition to their impact on weeds, these herbicides are also affecting soil microorganisms which are responsible for numerous biological processes essential for crop production. In the present study, we assessed the impact of four commonly used herbicides (paraquat, glyphosate, glufosinate-ammonium and metsulfuron-methyl) on soil microbial populations in oil palm plantation. Our study showed that the herbicide treatments significantly inhibited the development of microbial populations in the soil, and the degree of inhibition closely related to the rates of their applications and varied with the types of herbicide. Paraquat caused the highest inhibitory effect to bacteria and actinomycetes, whereas fungi were most affected by glyphosate. Metsulfuron-methyl had least inhibitory effects to all the microbial populations. The highest inhibition (59.3%) for fungal population was observed at 6 DAT (days after treatment), whereas for the bacteria and actinomycetes (82.0 and 70.6%, respectively) were at 4 DAT. Increasing trend of inhibition on growth of microbial populations was observed from the initial effect until 6 DAT, followed by a drastic decrease of the inhibition at 10 DAT. No inhibition was observed at 20 DAT. The study suggests that the herbicide application to soil of oil palm plantation cause transient impacts on microbial population growth, when applied at recommended or even as high as double (2x) of the recommended field application rate.

Phylotype classification of Ralstonia solanacearum biovar 1 strains isolated from banana (Musa spp) in Malaysia

During 2011–2012, 15 bacterial isolates were obtained from wilting banana plants from seven locations in Malaysia. Characterisation of the Malaysian isolates was determined by biovar determination, pathogenicity test, phylotype-specific multiplex PCR (Pmx-PCR) and endoglucanase (egl) gene amplification. Based on the genotype, phenotype and pathogenic characteristics, all isolates were identified as Ralstonia solanacearum. Pmx- and egl-PCRs indicated that all isolates belong to phylotype II of Ralstonia species complex hierarchical classification. The neighbour joining phylogenetic tree of egl sequences also verified the results where the isolates were all clustered into phylotype II, together with the reference sequences strains, UW070 and UW162. Therefore, the results of our study may provide a better understanding on the taxonomy of R. solanacearum species occupying banana plantations in Malaysia. This study is indeed the first report of phylotype II classification of R. solanacearum biovar 1 strains isolated from banana plants in Malaysia.

Mitigation of salt-induced oxidative damage in Chinese kale (Brassica alboglabra L.) using ascorbic acid

Salinity could become a threat to hydroponically grown plants due to the differential ion uptake process by the crop itself and/or using low quality irrigation water containing non-essential ions such as sodium and chloride. This study was conducted to determine the interactive effects of salinity and foliar application of ascorbic acid (AsA) on the survival capacity of Chinese kale plants. Three-week-old plants at the 4-leaf stage were exposed to salinity by application of 0, 50 and 100 mM NaCl for 14 days. The activities of antioxidant enzymes, catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) along with changes in the accumulation of proline, lipid peroxidation and chlorophyll content in leaves were estimated. Salinity induced obvious changes in the activities of antioxidant enzymes, lipid peroxidation, proline accumulation and chlorophyll content in the leaf tissues. Exogenous application of AsA (5 and 10 mM) to stressed plants resulted in a significant increase (P < 0.05) in APX activity and reduction in the activities of antioxidant enzymes (CAT and POX) as well as a decrease in the contents of stress-induced proline and malondialdehyde (MDA). Higher chlorophyll content was also recorded in stressed plants using AsA. The inherent capability of AsA to scavenge free radicals may have assisted the plant using the lower oxidative damages. The results of this study showed that AsA treatment would reduce the deleterious effects of salt-induced oxidative stress and improve plant tolerance to salt stress.

Use Of Absolute Function And Its Associates In Formation And ‘Redevelopment’ Of Mathematical Models In Some Plant‐Related Quantitative Physiology: Salinity Effects On Leaf Development Of Schefflera arboricola And Harvest Index In Rice

The roles of quantitative physiology are becoming more apparent and crucial in the era of ICT recently. As based on the rate‐related variables, most of the mathematical models are in the form of ‘non‐linear’ function in describing the responses or the observed within‐plant processes outcomes versus time. Even though if some responses change in a drastic manner at certain response point within a biological unit or space of a plant system, the response curve ‘should’ be dependent on a continuous independent variable range in a specified period of determination where biologically ‘should not’ functioned by independent variable range having ‘IF’ statement(s). Subjected to nutrient concentration of high salinity (6.0 mS cm−1), the leaf turgidity (measured as leaf surface area) of S. arboricola which initially was described by one form of the logistic growth functions [(y = 1/(a+be⎯cx)] abruptly reduced as explained by a model having terms of Absolute function (ABS) containing tan−1(x) and its parameter of leaf life expectancy as affected by high salinity growing medium at a certain point of days after planting. This yielded an overall function of y = 1/(a+be−cx)−A[tan−1{(x⎯B)/D}+ABS(tan−1{(x⎯B)/D})]E, where a, b, c, A, B, D, and E are constants that most of them can be ‘biologically’ interpreted. The constant B is the point similar to ‘IF statement’ as normally used in other mathematical functions. Plants subjected to lower salinity status (<3.0 mS cm−1) were only having function of y = 1/(a+be−cx). In the harvest index or HI (economic yield/above ground biomass) study of 20 rice varieties grown over two planting seasons, the long flattened tails at both sides of a peak in the middle of function of y = R+B(T+ABS(B⎯x))e⎯k(T+ABS(B⎯x)) had indicated that those varieties maturing at 123 to 133 days after transplanting were having high HI values. In our observation, Absolute (ABS) function coupled with some terms could be used in the formation of some mathematical functions having biological meaningful constants in explaining some quantitative physiological and biological responses vs. independent variables studied.