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Arabidopsis development in fast-forward or slow-motion: shifts in developmental timing are revealed by the transition from juvenile leaves (round, smooth margins) to adult leaves (elongated, serrated margins).
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How do plants know when to grow up and when to bloom?
The Zhao lab at DePaul University investigates how plants control the timing of growth and developmental transitions. Using Arabidopsis as a model, we study how genetic programs, microRNAs with their targets, and environmental signals coordinate changes in leaf identity and the transition toward reproduction.
Our goal is to understand not only how plants develop, but how they develop at the right time.
Amazed by how trillions of cells across a plant can develop in synchrony?
Ever wonder how plants know when to grow up or bloom?
We explore the Developmental Timing System behind their choices!
How is Plant Developmental Timing Measured?
Leaf Heteroblasty: (Left) 3-week-old Arabidopsis thaliana plant. The number represents the emergence sequence of the rosette leaves generated during vegetative growth. (Right) Leaf 1&2: cotyledon, embryonic leaves. Leaf 3-6, juvenile rosette leaves. Leaf 7-10, adult rosette leaves. Copyright@Jianfei Zhao.
The above figure represents the leaf heteroblasty in Arabidopsis thaliana growing in the long-day condition (16-hour light: 8-hour dark). This plant ongoing growth, regulated by the shoot apical meristem, follows a predictable sequence known as heteroblasty. As a plant ages, it generates different types of above-ground organs in a specific order. First come the cotyledons (embryonic leaves), and Leaf 1&2 as well as other juvenile leaves (Leaf 3-5), then adult leaves (Leaf 7-10), and eventually bracts and floral organs like sepals and petals. Even stamens and carpels, which don’t look like leaves, are thought to be highly modified versions of them, tracing back to a shared developmental origin.
The timing and rate of new organ formation in plants—measured by parameters like the plastochron (the interval between successive leaf initiations) or the number of organs produced over time—are regulated by genetic programs responsive to both internal and environmental cues. Because these structures are easily counted and observed, plants serve as excellent models for unraveling how organisms control not only their form but also the timing of developmental transitions.
Developmental timing can move faster or slower depending on various factors and is regulated by internal genetic programs that respond to both internal signals and environmental cues. In plants, one way to measure this is by looking at the plastochron, which is the interval between the formation of two successive leaves. Another is to track the developmental rate, or the number of new organs (like leaves or flowers) produced over a given period.
A major component within the plant’s developmental timing system is a tiny molecular “switch” called microRNAs. These are very small pieces of RNA that help control when and where certain genes are turned on or off. In plants, specific microRNAs—like miR156 and miR172—act a bit like timers, guiding the plant through different stages of life. They help decide when a plant should grow new leaves, change from its juvenile to adult form, or begin to bloom. By adjusting gene activity in response to both internal signals and the environment, microRNAs serve as master regulators, helping plants grow and flower at just the right time. Please check the Research webpage for details.
Benefits from Studying Developmental Timing in Plants
Understanding the mechanisms of vegetative phase change offers farmers powerful insights to improve crop management and productivity. This developmental transition—from juvenile to adult growth stages—affects traits such as leaf shape, plant architecture, and the timing of flowering. By learning how phase change is regulated, farmers can better control when crops mature, enhance stress resilience, and increase yield quality and consistency. For example, delaying or accelerating phase transitions can help crops better match local growing seasons or environmental conditions. Knowledge of these mechanisms also supports more targeted breeding strategies, enabling the development of crop varieties with improved performance, adaptability, and market value.
By deciphering these timing mechanisms in plants—using easily measurable traits like plastochron or organ formation rates—scientists gain insight into universal principles of developmental biology, applicable to both plant and animal systems. This connects plant developmental timing research directly to broader fields such as evolutionary biology, genetics, and systems biology, as similar regulatory networks often control growth and differentiation across life forms.
Furthermore, there are clear links to ecology and environmental science, as understanding how plants adjust their developmental timing in response to climate or stress helps predict ecosystem responses to environmental change.
Biotechnological applications also stand to benefit: manipulating developmental timing could accelerate breeding programs, optimize crop yield, enhance stress resilience, or enable precision agriculture using gene-editing technologies. Thus, plant developmental timing research not only addresses foundational scientific questions but also fuels innovation across agriculture, ecology, and biotechnology.
Our lab is in the beautiful Lincoln Park Campus of DePaul University in Chicago.
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