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Title: Cytokinin production in legume cuttings
Author: Griggs, Patricia Jane
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1987
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A radioimmunoassay (RIA) for dihydrozeatin riboside (DHZR), one of the major cytokinins in decapitated bean plants, was developed, based on an antiserum raised in rabbits against a DHZR-bovine serum albumin conjugate. The antiserum which was specific for the dihydrozeatin-type cytokinins had a titre of 1:24000. The RIA had a detection limit of 0.18 pmol for DHZR. Using the RIA and a bioassay, the cytokinins in the roots of decapitated bean plants were identified as zeatin (Z) or dihydrozeatin (DHZ), zeatin riboside (ZR) and the nucleotides of Z, DHZ and N-isopentenyl adenine on the basis of chromatographic properties. Similarly, root nodule cytokinins were identified as O-glucosides of Z or DHZ. The major cytokinins in xylem sap were characterised as DHZR, ZR and DHZ by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Two enzymes thought to be involved in cytokinin interconversions---5'-nucleotidase and nucleosidase---were studied in bean roots. More than one form of each enzyme, differing in affinities for the purine substrates, were detected. One form of nucleosidase appeared to be inhibited by N-isopentenyl adenosine and a crude extract of roots was found to deribosylate DHZR. One of the forms of 5'-nucleotidase appeared similar to enzymes from wheat germ and tomato. The cytokinin economy of the plant was investigated during the period of cytokinin accumulation in the leaves. Between 3 weeks and 5 weeks after decapitation the sap cytokinins, detected by RIA, decreased but increased again after this time. When sap cytokinin content was at a minimum, root nucleotidase activity was also low whereas nucleosidase activity had reached a maximum, leading to decreased levels of the immunoreactive cytokinin ribosides in the sap. Maximum root nucleosidase activity coincided with a large increase in the stem immunoreactive cytokinins in spring-grown plants, possibly due to the uptake of cytokinin bases from the sap.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available