SUMMARYDimorphic fruits of Bidens pilosa were tested separately for differences in germinability and seedling development. The long achenes were found to germinate readily under a wide range of conditions while the short achenes showed fairly exacting germination requirements. Germination of the short achenes was found to be enhanced by red light treatment, scarification, applied hormones, leaching and increased oxygen tensions. Seedlings originating from short achenes showed lower survival rates and initially slower development than those originating from the long achenes. The implications of the morphological differences and differences in germination and development of the two achenes are discussed.

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Decapitation of the primary roots of Pisum sativum L. resulted in a significant increase in the initiation of lateral root primordia within 12 h of the surgical treatment. Although this increase occurred both in the light and in the dark, lateral root initiation and development was much more rapid in the dark. The formation of lateral root primordia was accompanied by increased levels of endogenous cytokinins suggesting that newly formed root primordia start producing cytokinins very soon after being initiated. The significance of the present results in terms of possible sites of synthesis in vegetative tissue is discussed.

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Isolated embryos of Picea abies (L.) Karst. were pulsed with either distilled water, cold benzyladenine (BA) or [8‐14C]‐BA for 3 h under sterile conditions, whereafter they were transferred to cytokinin‐free media for a further 24 h. Embryos of each treatment were then analysed for cytokinin activity. The embryos themselves yielded very little cytokinin activity. Analysis of the [14C]‐BA‐treated material revealed that some residual BA was present even after 27 h of treatment but that the total radioactivity recovered from the embryos at this time was less than 10% of that recovered after the 3 h treatment. Apart from BA, the embryos contained other radioactive peaks, the major ones apparently being of a nucleotide nature. The BA‐containing medium in which the embryos were incubated initially was also analysed and again, apart from residual BA, the major metabolite(s) appeared to be BA‐nucleotide. However, two radioactive peaks were found in the medium which were absent from the embryos themselves and chemical tests indicated that these could be 7‐ and 9‐glucosides of BA. As the major metabolite resulting from the BA‐pulse was of a nucleotide nature and was found to be biologically active, it is postulated that the action of the BA may be mediated via the nucleotide.

Decapitated tomato plants were supplied via the roots with [8-14 C]-kinetin or [8-14 C]-benzyladenine in a nutrient solution for a period of 24h . After this time the root material, the root sap produced during the 24h period and the nutrient solution remaining at the end of the experiments were analysed for cytokinins . HPLC techniques and chemical treatments were used to tentatively identify radioactive metabolites formed . Uptake of kinetin and benzyladenine by the roots was found to be limited but once within the root tissues metabolism was both rapid and extensive .

Abstract. Nodal stem segments of Dioscorea bulbifera were induced to form plantlets in vitro. Rooted plantlets were obtained on Murashige-Skoog [14] revised medium supplemented initially with 5 mg 1-1 kinetin and subsequently with 5 mg 1-1 indolebutyric acid. By increasing the kinetin concentration from 5 mg 1-1 to 10 mg 1 -t , the number of shoots forming per node was increased from five to eight. When kinetin was substituted with 6-benzylaminopurine at only 1 mg 1-1 , nine shoots formed on each node. Each shoot could be excised from the node and induced to form a new crop of multiple shoots. Rooted plantlets could be successfully transferred to in vivo conditions.