| Materials and Methods Preliminary screening was carried out by testing the germination of three wild species Aegilops bicornis (V1), Aegilops ovata (V2), Aegilops tauschii (V3) and Triticum dicoccum (V4) and Triticum monococcum (V5), provided by Plant Genetics Division, AEARC, Tando Jam, Sind. (i) Germination trials: This experiment sought only to determine the best qualified candidate for soil salinity pot studies and further experimentation. Ten healthy seeds of three Aegilops and two Triticum species were sown on whatman filter paper No. 41 placed in petri dishes and uniformly moistened by submerging them in solution containing equal weights of NaCl and Na2SO4 to produce water salinity levels of 0.0, 0.2, 0.4 and 0.6%. The petri dishes were placed in a dark growth room for the purpose of germination at a temperature of 25C in a randomized experimental design with four replicates. The germination counts were taken after 120 hrs. Seeds which produced a combined radicle and hypocotyl length of 2 mm were considered germinated. Germination results in the salinities solution are reported as a percent of germination in the control solution for each species. After counting the number of seeds germinated, the shoot length of seedlings was also measured. (ii) Pot experiment: To study further the growth and elemental composition of three Aegilops and Triticum species four healthy seedlings of unfirm height of each specie used for germination test were transferred carefully to earthen pots containing 3.7 kg of alluvial soil (pH 7.8, N0.075% and O.M. 0.545%) and previously fertilized with 120 kg N/ha, 60 kg P2O5 /ha and having the same level of four salt concentrations as were used for germination test i.e. 0.0, 0.2, 0.4 and 0.6% NaCl and Na2SO4 in equal volume. The pots after transplanting the seedlings were kept in a pot house according to a completely randomized design with four replicates. All the normal cultural practices were followed during the growth of the crops. The mean maximum and minimum temperatures of the pot house were 28C and 20C. After 8 weeks, one plant from each replicate was harvested, washed with distilled water, blotted dry, dried in an oven at 70C and weighed. The dried samples were finely ground into a fine powder and assayed for mineral ions determination after wet-digestion with H2SO4 and H2O2. From the digested sample Na, K, Ca contents were measured by flame photometry. Phosphorus content in the plant was determined by molybdoyellow colour method and total N by modified micro-Kjeldahl method (JACKSON 1958). Iron and Mn were determined colorimetrically using orthophenonthroline and periodate reagents (JACKSON 1958). Results and Discussion Data presented in Table 1 where 3 Aegilops and 2 Triticum species were screened for their germination test indicate that increasing salinity levels (0.2% to 0.6%) had significantly decreasing effect on germination percent. The specie Aegilops bicornis (V1) had the lowest germination percentage (77.9%) differing significantly from the other four cultivars. On the average, germination percentage of the remaining four differed slightly from one another (86 to 81.0%). It is assumed that in addition to the toxic effects of certain ions, higher concentration of salts can cause ionic imbalance as well as contribute to osmotic maladjustment, reducing the water potential in the medium which hinders water absorption by germinating seeds and thus reduces germination (MAAS & HOFFMAN 1977). The toxicity of higher concentrations may also be due to Na or SO4 induced Ca deficiency or to Na or Ca induced K deficiency (BERNSTEIN 1975). Table 2 summarizes the mean shoot length of the five species. Shoot length of all the species variously decreased by increasing salinity levels. Triticum monococcum (V5) seemed to be the most tolerant one (56.2%) and the Aegilops bicornis (V1) the sensitive one (29.3%) at the highest salinity level, while the percentage decrease at the highest salinity level (0.6%) in the remaining species did not differ much and vary from 41.1% to 49.8%. |
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