High-Wire Strawberry Greenhouse Microclimate: Flower Bud Differentiation & Diurnal Temperature Integration

1. The Physiology of High-Yield Strawberry Production: Flower Bud Differentiation

Commercial greenhouse strawberry cultivation (e.g., Fragaria × ananassa cv. 'Seolhyang', 'Albion', 'Elsanta') demands rigorous control of flower bud differentiation. Successful floral induction transitions the vegetative apical meristem into reproductive floral primordia, establishing cluster numbers and primary fruit size. Inadequate environmental cues cause vegetative proliferation with excessive runner production and delayed harvest flushes.

2. Triad of Environmental Drivers: Photoperiod, Temperature, and Nitrogen Starvation

• Short-Day Photoperiod: Short-day cultivars require day lengths under 10–12 hours to trigger floral induction proteins.
• Chilling Accumulation & Low Temperatures: Optimal night temperatures between 10–15°C stimulate floral transitions, whereas temperatures above 25°C suppress differentiation and induce runner growth.
• Nitrogen Restriction (Starvation Protocol): Restricting rootzone nitrogen supply (\(NO_3^-\) reduced to < 3 meq/L) 2–3 weeks prior to floral induction prevents excessive gibberellin synthesis, triggering strong reproductive floral differentiation.

3. Phenological Climate Management: DIF Optimization & Humidity Regulation

Managing the diurnal temperature differential (\( ext{DIF} = T_{day} - T_{night}\)) is paramount across successive crop stages:

• Flowering Stage: Maintain daytime temperatures at 22–24°C and night temperatures at 8–10°C (\( ext{DIF} pprox +12 ext{--}14 ext{°C}\)) with relative humidity at 60–70% to promote pollen anthesis and bumblebee foraging.
• Fruit Swelling: Moderately reduce daytime temperatures to 20–22°C to extend the maturation window, maximizing brix sugar synthesis and fruit firmness.
• Crown Moisture Control: High nighttime humidity (VPD < 0.3 kPa) on strawberry crowns must be avoided via early morning tube heating, eliminating gray mold (Botrytis cinerea) and powdery mildew outbreaks.