Abstract
Despite numerous studies, the role of hormones in the induction of shoot apical meristem leading to reproductive development, especially regarding thermoperiodic plants, is still not fully understood. The key problem is separating the effects of the low temperature required for vernalization from those responsible for low temperature stress. An earlier experiment demonstrated the correlation between an increase of cytokinin level in the apical parts of winter rapeseed and the transition time into their reproductive phase during vernalization, i.e., low temperature treatment. From data obtained from the presented experiments, this study aims to contribute to the understanding the role of cytokinins in the induction of flowering based on the grafting of vegetative apical parts of winter rapeseed (scion) on the reproductive (stock) winter and spring genotypes. On the basis of analyses carried out using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry in combination with microscopic observation of changes at the apical meristem, it was indicated that the increase in the amount of trans-zeatin and trans- and cis-zeatin-O-glucoside derivatives appeared in the early stages of apex floral differentiation. During further development, the content of all investigated cytokinins passed through the maximum level followed by their decrease. The final level in reproductive apices was found to be higher than that in vegetative ones.
Highlights
Flowering is the crucial developmental phase in the lifecycle of seed-bearing vascular plants and represents their transition from the vegetative to the reproductive stage, i.e., the transformation of the vegetative meristems into inflorescence meristems (IMs) after the plant has passed from the juvenile to the adult phase [1]
Microscopic observations indicated that the initiation of reproductive development in vegetative winter rapeseed apices occurred independently of the genotype of the plants to which they were grafted, Figure 1
The stimulation of apices to reproductive development was faster when they were grafted on the winter rapeseed cultivar
Summary
Flowering is the crucial developmental phase in the lifecycle of seed-bearing vascular plants (angiosperms) and represents their transition from the vegetative to the reproductive stage, i.e., the transformation of the vegetative meristems into inflorescence meristems (IMs) after the plant has passed from the juvenile to the adult phase [1]. The initiation of cell differentiation in the apical meristem associated with achieving the reproductive stage is regulated by a complex of environmental and endogenous inductive cues, such as day length (photoperiodism), temperature (vernalization) and hormones [3,4,5,6]. It has been convincingly demonstrated in Arabidopsis that CKs may induce flowering by activating the Flowering Locus T (FT) paralogue twin sister of FT (TSF). This effect possessed the same kinetics as exposure to inductive long days; CKs should be considered as an obligatory component of floral induction [13,14]
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