Ahmad Selamat

Effect of salt stress on germination and early seedling growth of rice (Oryza sativa L.).

The response of twelve rice varieties against six salinity levels (0, 4, 8, 12, 16 and 20 dS m-1) were studied at germination and early seedling stages. Data were analyzed using SAS and means were separated by LSD for final germination percentage (FGP), speed of germination (SG), germination energy percentage (GE%), plumule and radical length and plumule and radical dry weight. Based on dry matter yield reduction, rice varieties were classified as tolerant (T), moderately tolerant (MT), moderately susceptible (MS) or susceptible (S). Germination was completely arrested at 20 dS m-1 salt concentration. Salinity decreased FGP, SG, GE % and led to reduction in shoot and root length and dry weight in all varieties and the magnitude of reduction increased with increasing salinity stress. Rice varieties MR211, IR20, BR40 and MR232 showed greater salt tolerance during germination (germinated at 12 dS m-1 salinity). However, MR211, MR232 and IR20 performed better based on dry matter yield reduction. The result suggested that MR211, MR232 and IR20 might be used for further study of salinity effect on growth processes and physiological consequences at advanced stage of growth, since salt tolerance of a crop at germination and early seedling stage may not correspond to that at advanced stage.

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.

Seeding method and rate influence on weed suppression in aerobic rice

-2 (SR400); and two weed control levels were established as weedy (W) and weed free (F) in a factorial RCBD with four replications. Twenty (20) weed species comprising eleven broadleaved, five grasses and four sedges were identified. Broadleaved weeds contributed more than 50% of the total dry matter. Weed density and dry weight decreased gradually with increased seeding rate, but were independent of methods. REW produced significantly higher grain yield compared with CBS. Among the seeding rates, SR300 produced the highest grain yield followed by SR200 and SR400. Weed free treatment performed better with a yield advantage of 23% over weedy treatment. Weed inflicted relative yield loss did not vary due to seeding methods or rates. Therefore, increasing seeding rate up to 300 seeds m -2 may be

Biochemical and Anatomical Changes and Yield Reduction in Rice (Oryza sativa L.) under Varied Salinity Regimes

Five Malaysian rice (Oryza sativa L.) varieties, MR33, MR52, MR211, MR219, and MR232, were tested in pot culture under different salinity regimes for biochemical response, physiological activity, and grain yield. Three different levels of salt stresses, namely, 4, 8, and 12 dS m−1, were used in a randomized complete block design with four replications under glass house conditions. The results revealed that the chlorophyll content, proline, sugar content, soluble protein, free amino acid, and yield per plant of all the genotypes were influenced by different salinity levels. The chlorophyll content was observed to decrease with salinity level but the proline increased with salinity levels in all varieties. Reducing sugar and total sugar increased up to 8 dS m−1 and decreased up to 12 dS m−1. Nonreducing sugar decreased with increasing the salinity levels in all varieties. Soluble protein and free amino acid also decreased with increasing salinity levels. Cortical cells of MR211 and MR232 did not show cell collapse up to 8 dS m−1 salinity levels compared to susceptible checks (IR20 and BRRI dhan29). Therefore, considering all parameters, MR211 and MR232 showed better salinity tolerance among the tested varieties. Both cluster and principal component analyses depict the similar results.

Seed priming influences weed competitiveness and productivity of aerobic rice

Abstract Growing rice under aerobic soil conditions is a promising water-wise technology under the context of ever-mounting water scarcity, but it is subject to poor stand establishment and high weed pressure. The present study was, therefore, designed to explore the possibility of adopting seed priming as a sustainable tool for weed management in aerobic rice. The trough experiment was established with aerobic rice line Aeron 1 considering four priming techniques: hydropriming, hardening, Zappa® priming and untreated control; and two weeding regimes: weed-free and weedy. Treatments were arranged in a randomized complete block design with four replications. Seed priming significantly improved germination attributes, weed suppressive ability and yield of rice, whilst unprimed control exhibited inconsistent germination, poor stand establishment and less weed competitiveness resulting in poor yield. Seed priming resulted in reduced mean germination time and increased germination percentage, germination index and seedling vigour index. Weed dry matter reduction by primed stand of rice ranged from 22% to 27% compared with control. A positive influence of seed priming was also evident in rice yield with an average increment of 0.4 t ha−1 over control. Weed-inflicted relative yield loss of rice was minimized by 10% as a consequence of seed priming. Zappa® solution emerged as the best priming agent, which demands its incorporation as a viable component in an integrated weed management strategy for aerobic rice.

Demarcation of informative chromosomes in tropical sweet corn inbred lines using microsatellite DNA markers

A study of genetic variation among 10 pairs of chromosomes extracted from 13 tropical sweet corn inbred lines, using 99 microsatellite markers, revealed a wide range of genetic diversity. Allelic richness and the number of effective alleles per chromosome ranged from 2.78 to 4.33 and 1.96 to 3.47, respectively, with respective mean values of 3.62 and 2.73. According to the Shannon’s information index (I) and Nei’s gene diversity coefficient (Nei), Chromosome 10 was the most informative chromosome (I = 1.311 and Nei = 0.703), while Chromosome 2 possessed the least (I = 0.762 and Nei = 0.456). Based on linkage disequilibrium (LD) measurements for loci less than 50 cM apart on the same chromosome, all loci on Chromosomes 1, 6 and 7 were in equilibrium. Even so, there was a high proportion of genetic variation in Chromosomes 4, 5, 8, 9 and 10, thereby revealing their appropriateness for use in the genetic diversity investigations among tropical sweet corn lines. Chromosome 4, with the highest number of loci in linkage disequilibrium, was considered the best for marker-phenotype association and QTL mapping, followed by Chromosomes 5, 8, 9 and 10.

Corn yield response to crowding stress and cropping season

Corn (Zea mays L.) is planted in two seasons per year in northern Iran (mid-April as a main crop and mid-June as a second crop). The main objective of this study was to determine whether corn yield response would differ between these two seasons and different plant populations. Two field experiments were conducted at the Agricultural Research Center of Golestan – Iran in 2007 and 2008 at different planting densities. The results showed that the values of grain yield and most traits were significantly lower in the second season. Maximum grain yield was observed at planting densities of 6.5 plants m−2 in the first season, whereas in the second season grain yield was the same for planting densities between 2.5 and 12.5 plants m−2. Based on the second-year experimental results, the following functions were fitted to show the relationship between yield ha−1 (Y) and planting densities (X) for the first and second seasons, respectively: (Y = −167.6X 2 + 2672.2X + 511.77; R 2 = 0.992) and (Y = 1200.1 ln(X) + 2924.4; R 2 = 0.935). This study found that the optimum plant population was 6.5 plants m−2 under low heat stress, and should be reduced to 2.5–4.5 plants m−2 under heat stress conditions.

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.