Are polyamines involved in the potassium nitrate-induced flowering in mango?

Abstract

The hypothesis that potassium nitrate-induced flowering in mango is mediated by polyamines was investigated. High performance liquid chromatography analysis of extracts from maturing mango leaves (5-9 months after flushing) for polyamine content revealed that putrescine content was high initially and declined with the approach of the dry season and time of natural flowering. Hydroxycinnamic acid conjugates of putrescine were not detected in leaf extracts. Putrescine (1-100 mM) and spermidine (5- 50 mM) were sprayed on the shoots, with 2% potassium nitrate as positive, and water as negative control. In trees that responded to potassium nitrate, no flowering was observed in response to polyamine and water application, suggesting that increased polyamine content is not necessary for mango flower initiation. Preliminary evidence suggests that the nitrate is channeled elsewhere with polyamines acting as transient intermediates. Within an hour from spraying potassium nitrate, spermidine level in the leaves increased six times as compared to the control but declined to control levels after 24 hours. Another approach taken to the test the hypothesis was to spray 20 mM cyclohexylamine (an inhibitor of spermidine synthase) simultaneously with potassium nitrate. Preliminary results indicate that cyclohexylamine stimulated flowering when applied together with potassium nitrate but not when applied alone. Since spermidine and ethylene biosynthesis share a common precursor, inhibition of spermidine synthase may have favored ethylene biosynthesis, a compound also known to stimulate flowering in mango. © ISHS.

Source or Periodical Title

Acta Horticulturae

ISSN

5677572

Page

76-83

Document Type

Article

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