Physiologia Plantarum

Abstract At the reproductive stage, lily plants bear two morphological types of mature leaves, one at the lower and one at the upper part of the stem. At the vegetative stage, all the leaves are similar to each other and to the reproductive plant's lower leaves. This heterophylly has not yet been explored. In this study, we show that it is not a result of the plant's age but rather an outcome of floral induction. The induction appears as an on-going process, during which the meristem still produces leaves but progressively becomes committed to reproduction. This intermediate period lasts until the ultimate switch to flower primordia occur. The leaves produced during floral induction, termed here as 'inductive', appear at the upper part of the stem. Besides their typical higher stomata density, these leaves have a poly-layered palisade mesophyll, whose cells exhibit a unique morphology and contain more chlorophyll than leaves of vegetative plants. These leaves display higher carbon assimilation, soluble sugars production and chloroplast-lipid accumulation. Accordingly, genes associated with stomata, chloroplast and photosynthesis are upregulated in these leaves. Our results were obtained when floral induction was achieved either by vernalization or photoperiod signals, ruling out a mere environmental effect. We suggest that lily plants prepares themselves for the high energy-demanding bloom by producing leaves with enhanced photosynthetic capacity, leading to an increase in soluble sugars. These novel findings introduce an adjacent affinity between photosynthesis and flowering and provide a non-destructive tool for identifying the plant's developmental stage ? vegetative or reproductive. This article is protected by copyright. All rights reserved