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Elsevier, South African Journal of Botany, 2(76), p. 391, 2010

DOI: 10.1016/j.sajb.2010.02.011

Springer Verlag, Plant Growth Regulation, 2(63), p. 105-114

DOI: 10.1007/s10725-010-9558-6

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Changes in endogenous cytokinin profiles in micropropagated Harpagophytum procumbens in relation to shoot-tip necrosis and cytokinin treatments

Journal article published in 2010 by Michael W. Bairu, Ondřej Novák ORCID, Karel Doležal, Johannes Van Staden
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Changes in cytokinin (CK) profiles and their physiological implications in micropropagated Harpagophytum procumbens [(Burch.) DC. ex Meisn.] tissues in relation to shoot-tip necrosis (STN) and CK treatments were studied. Total CK content was quantified in benzyladenine (BA)-treated necrotic and normal plantlets and in plantlets treated with the CKs BA, meta-topolin (mT) and meta-topolin riboside (mTR) with and without the auxin indole-3-acetic acid (IAA). Generally necrotic shoots yielded more total CK compared to normal shoots. Cytokinin accumulation was higher at the basal section (basal > middle > top). Further analysis of the CKs based on structural and functional forms revealed excessive accumulation of 9-glucosides (deactivation products—toxic metabolites) and limited amounts of O-glucosides (storage forms—re-utilizable) in necrotic and BA-treated shoots compared to normal and topolin-treated cultures. The addition of IAA enhanced the formation of 9-glucosides in BA-treated cultures but reduced it in topolin-treated cultures. The symptom of STN could therefore be attributed to conversion of active cytokinins to other forms such as 9-glucosides which are neither active nor reversibly sequestrated to active forms. Literature shows that metabolites like 9-glucosides of BA have a detrimental effect in plant tissue culture.