PAR & DLI Requirements for Nicotiana (Flowering Tobacco) at Different Growth Stages

Nicotiana, often called flowering tobacco, is a decorative plant prized for its tall stalks and star-shaped, fragrant flowers. While not as light-demanding as fruiting crops, Nicotiana still depends on proper PAR (Photosynthetically Active Radiation) and DLI (Daily Light Integral) to ensure strong stem growth, rich leaf color, and abundant flowering.

Below is a guide to optimal PAR and DLI levels across its main growth stages.

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1. Germination / Seedling Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	100–150	Gentle light encourages germination and prevents leggy growth.
DLI (mol·m⁻²·day⁻¹)	6–10	Enough to stimulate chlorophyll production without drying young seedlings.

Tips:

• Use cool white LEDs or filtered sunlight for uniform illumination.
• Maintain warm temperatures (22–25 °C) and consistent humidity.
• Avoid strong directional light to prevent seedling stretch.

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2. Vegetative / Leaf Growth Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	250–400	Supports lush leaf growth and sturdy stems.
DLI (mol·m⁻²·day⁻¹)	12–20	Promotes balanced growth and prepares the plant for flowering.

Tips:

• Provide a full-spectrum light with slightly higher blue content for compact leaves.
• Ensure uniform canopy lighting to reduce shading and promote even development.
• Gradually increase PAR intensity as plants mature.

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3. Flowering / Maturation Stage

Metric	Typical Range	Notes
PAR (µmol·m⁻²·s⁻¹)	400–600	Enhances pigment production and flower count.
DLI (mol·m⁻²·day⁻¹)	18–28	Encourages vibrant color and longer flowering duration.

Tips:

• Supplement with red and far-red light to stimulate flowering and fragrance production.
• Maintain airflow to prevent heat stress under high light.
• Avoid excessive DLI (>30), which can shorten flower longevity.

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Quick Reference Table

Growth Stage	PAR Target	DLI Target	Key Focus
Seedling	100–150 µmol·m⁻²·s⁻¹	6–10 mol·m⁻²·day⁻¹	Early germination and leaf initiation
Vegetative	250–400 µmol·m⁻²·s⁻¹	12–20 mol·m⁻²·day⁻¹	Leaf density and stem strength
Flowering	400–600 µmol·m⁻²·s⁻¹	18–28 mol·m⁻²·day⁻¹	Flower color, fragrance, longevity

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Why Light Control Matters for Nicotiana

Nicotiana plants are day-length sensitive, meaning their bloom timing depends on both light intensity and duration. Under ideal PAR and DLI levels:
✅ Plants stay compact and strong.
✅ Flower spikes form earlier and more uniformly.
✅ Flower color saturation increases under balanced light spectra.

For growers, using a Bluetooth PAR/DLI logger like AH-PARDLI allows precise measurement and tracking of these variables — even outdoors. The device automatically logs up to 180 days of light data and exports via Bluetooth, helping you match your lighting setup to the needs of each growth phase.