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Each genotype was exposed to controlled PHS conditions for evaluation of susceptibility or tolerance to sprouting, falling number, kernel color, test weight, and yield. The 24 genotypes were grown in replicated trials at three locations over three years, all data subjected to an analysis of variance. Over three years the genotypes were rated for visual PHS using a 1 to 9 scale, with 1 equivalent to no visual PHS and 9 equivalent to maximum visual PHS. The red genotypes exhibited a higher tolerance to PHS than white genotypes with a mean PHS score of 4.46 compared with 5.16 for white genotypes. Not all the white genotypes were equally susceptible to PHS or more susceptible than the red genotypes, suggesting that not all seed dormancy is linked to the kernel color genes.

Malts prepared from sorghum and cowpeas that was germinated at 25°C for 0, 1, 2 or 3 days and dried at 60°C for either 2.5, 5, 7.5 and 10 hours, were evaluated for α-amylase, β-amylase and endo-(1,3)(1,4)-β-D-glucanase activity. Germination had a highly significant effect on enzyme activity (P < 0.01). However, cowpea endo-(1,3)(1,4)-β-D-glucanase was not significantly affected by the combined action of germination and drying. β-Amylase was not detected in any of the samples of this experiment. Further analysis using Duncan’s Multiple Range Test, indicated that there was no significant difference in α-amylase activity in samples dried between 5 to 10 hours. Compared to α-amylase, sorghum and cowpea samples had low endo-(1,3)(1,4)-β-D-glucanase activity. / Master of Science

Three cotton (Gossypium hirsutum L.) germplasms (DP62, 84027, and 84033) were used to investigate the physiology of salt tolerance. Lines 84027 and 84033 were developed from the parental line DP62 and showed superior vigor under varying NaCl conditions (0.5 to 2.0 M) during germination and emergence. Proline levels increased in the leaves of all germplasms in response to increasing salinity. Varietal differences in proline levels did not reflect their variation in salt tolerance. Several physiological characteristics were also evaluated under non-saline condition in the greenhouse. There were no significant differences among germplasm sources for all parameters measured. However, salinity reduced transpiration rate, increased leaf diffusive resistance and leaf temperature for all lines. Ribosomal-RNA levels in all germplasms were evaluated after seeds were stressed for 24 hrs in various concentrations of NaCl and then germinated under normal conditions for 72 hrs. Ribosomal-RNA levels were inversely related to salt concentrations. Line 84033 followed by line 84027 had highest ribosomal-RNA content than the parental line DP62 when averaged over the four salt concentrations. Sodium content (ppm/g FW) and Cl⁻ content (ppm/g FW) were evaluated in microsomal and cell walls fractions as well as a cytoplasmic fraction which consisted of vacuoles, mitochondria, and plastids. The Cl⁻ ion exhibited a greater consistency in a concentration shift from one fraction to another as a function of time than did the Na⁺ ion. As a result, there may be a correlation between the drop in ribosomal-RNA and the amount of Cl⁻ in the microsomal fraction. Other parameters measured in the germinating seed were soluble protein (globulin), insoluble proteins (prolamin and glutelin) and fiber percentage. Variations within the germplasms were shown to exist. This study shows that even among lines that have been selected for salt tolerance from a single variety, the possibility exists that each of these lines may have a different mechanism to cope with salt stress.

published_or_final_version / Botany / Master / Master of Philosophy

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