School of Botany - Theses
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ItemPollen-wall proteins and breeding systems of plants(University of Melbourne, 1978)Quatitative cytochemical methods have been developed to estimate changes during development in the pollen-wall proteins. Acid phosphatase was used as a marker for intine proteins, and non specific esterase for the exine proteins. In marrow-stem kale, Brassica oleracea and ryegrass, Lolium perenne the intine enzyme showed two peaks of accumulation during development, the first corresponding to its synthesis and incorporation in the intine, and the second to accumulation in the pollen cytoplasm at maturity. In contrast, the exine enzyme showed a single peak at pollen maturation. This was correlated with dissolution of the tapetum and consequent loss of its very high esterase activity, coincident with the accumulation of esterase in the exine cavities. In sunflower, Helianthus annuus acid phosphatase and esterase were detected in both exine and intine sites during pollen development. Acid phosphatase was associated with the nexine at pre-vacuolate period with high levels in the tapetum. At mid-vacuolate period the tapetum became plasmodial and enzyme activity was detected around the exine surface and was transferred to the exine cavities by the end of the vacuolate period. Esterase activity was associated with the exine at pre-vacuolate period; subsequently during the vacuolate period, activity was present in the intine, and in the cytoplasm at maturity. Two peaks of accumulation were detected, closely resembling those for the intine marker enzyme in Brassica and Lolium. The developmental cytochemistry of the stigma of Helianthus, Lolium and Secale has been investigated with a view to understanding the nature of selfincompatibility, the site of tube arrest and the route of pollen tube penetration. The callose rejection response in pollen and stigma that has been established for Cosmos and various Crucifers have been found in Helianthus. The rejection reaction is found to occur in the pollen grain and pollen tubes of grasses. The callose produced in germinating self pollen of the grass, Secale cereale has been isolated by a degredative physicochemical procedure. Partial acid hydrolysis, enzyme hydrolysis, sugar analysis and methylation analysis have shown that the material is a 1,3-?-linked glucan; however some evidence points to the presence of 1,4-?-linkages in addition.