Developmental Regulation of Sterol and Pentacyclic Triterpene Biosynthesis and Composition: A Correlation with Sorghum Floral Initiation
Sterol and pentacyclic triterpene (PT) composition have been examined in vegetative1–4 and reproductive tissues3,5 of Sorghum bicolor (L.) Moench in various stages of development. Evidence for the developmental regulation of the amounts and biosynthesis of these polycyclic isopentenoids and its correlation with floral initiation have been obtained in this and our previous studies.1–4 Sterol and PT composition of individual fully mature leaf blades was determined at various stages in the life cycle of S. bicolor (L.) Moench cv. G499 GBR (Figure 1). Free sterol content increased in the leaf blades logarithmically during the vegetative phase of the life cycle (day 7–34); this increase continued during the transition (Figure 2) of the vegetative to floral meristem (day 34–38), and then decreased during panicle development (day 48–104) (Figure 1). The relative ratio of the bulk sterols remained constant throughout the plant’s development not only in the leaf blade but in other tissues, such as the spikelets (data not shown). Early in the plant’s development the leaf blade free PT content was negligible. Following floral induction, free PT content increased to a level greater than the sterols as flowering progressed. The relative ratio for the individual free PT, unlike that of the sterols, did not remain constant.
KeywordsLeaf Blade Floral Meristem Free Sterol Sterol Biosynthesis Floral Induction
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