M. A. Hakim

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.

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 12u2009dSu2009m−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 8u2009dSu2009m−1 and decreased up to 12u2009dSu2009m−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 8u2009dSu2009m−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.

Contribution of morpho-physiological attributes in determining the yield of mungbean

Field experiments were conducted in 2006 and 2007 under subtropical conditions to investigate the variations in growth and reproductive characters, and yield attributes for selection of important source and sinks characters using correlation and path coefficient analyses in 45 mungbean genotypes. Large genetic variability existed in source characters viz., leaf area index (LAI) (1.22 to 3.80) and sink characters viz., number of racemes plant -1 (6.30 to 22.9), flowers plant -1 (18.1 to 51.9) and pods plant -1 (9.6 to 22.1). Genotypic correlation study revealed that among the traits investigated, LAI was the most important source that determined total dry mass (TDM) yield, and reproductive characters like number of racemes, flowers and pods plant-1 were the most important sinks that determined seed yield. Contrarily, reproductive efficiency (RE, % pod set to opened flowers) did not show significant relationship with pod number and seed yield, indicating that selection of high yield based on RE may be misleading. Path coefficient analysis further revealed that number of flowers, pods and 100-seed weight constituted central important sinks which exerted direct positive influence on seed yield. The results indicated that pod yield could be increased by increased raceme and flower production, while seed yield could be increased by increasing pod production. High yielding genotypes, in general, possessed higher earlier mentioned source (LAI) and sink (flower and pod number) characters which resulted in higher seed yield in mungbean. This information could be exploited in the future plant breeding programmes. Key words : Source-sink, correlation, path analysis, mungbean.

Salinity-induced changes in the morphology and major mineral nutrient composition of purslane (Portulaca oleracea L.) accessions.

This study was undertaken to determine the effects of varied salinity regimes on the morphological traits (plant height, number of leaves, number of flowers, fresh and dry weight) and major mineral composition of 13 selected purslane accessions. Most of the morphological traits measured were reduced at varied salinity levels (0.0, 8, 16, 24 and 32xa0dSxa0m−1), but plant height was found to increase in Ac1 at 16xa0dSxa0m−1 salinity, and Ac13 was the most affected accession. The highest reductions in the number of leaves and number of flowers were recorded in Ac13 at 32xa0dSxa0m−1 salinity compared to the control. The highest fresh and dry weight reductions were noted in Ac8 and Ac6, respectively, at 32xa0dSxa0m−1 salinity, whereas the highest increase in both fresh and dry weight was recorded in Ac9 at 24xa0dSxa0m−1 salinity compared to the control. In contrast, at lower salinity levels, all of the measured mineral levels were found to increase and later decrease with increasing salinity, but the performance of different accessions was different depending on the salinity level. A dendrogram was also constructed by UPGMA based on the morphological traits and mineral compositions, in which the 13 accessions were grouped into 5 clusters, indicating greater diversity among them. A three-dimensional principal component analysis also confirmed the output of grouping from cluster analysis.

Interaction effect of nitrogen and potassium on growth and yield of carrot

The experiment was carried out to study the effects of three mulching practices viz., no mulch, water hyacinth mulch and polythene mulch, three levels of nitrogen viz., 0, 150 and 200 and three levels of potassium viz., 0, 200 and 250 kg/ha on the growth and yield of carrot. The yield and yield contributing characters of carrot were significantly influenced by the application of nitrogen and potassium fertilizers with mulching treated plot. The highest marketable yield (63.47 t/ha) was recorded from the treatment combination of black polythene mulch with 200 kg N/ha and 200 kg K/ha treated plot and the lowest (23.69 t/ha) from the control treatment (M0N0K0). But the benefit-cost ratio (BCR) was found maximum (5.60) in the treatment combination of water hyacinth mulch with 200 kg N/ha and 200 kg K/ha, and the lowest (2.54) in control treatment. Considering the above findings, water hyacinth mulch with the application of 200 kg N/ha and 200 kg K/ha appeared to be recommendable for carrot cultivation for the place where irrigation facility was not available.