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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Research Project #435019

Research Project: Interactive Effects of Temperature and Photoperiod on Flower Initiation and Development

Location: Application Technology Research

Project Number: 5082-21000-018-10-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2018
End Date: Aug 31, 2019

The objective of this project is to evaluate the impact of temperature and photoperiod interactions that affect the plant’s perception of night length, and subsequent flower initiation and development.

Expected critical night length and in 20-minute intervals, e.g., 10:00, 10:20, 10:40, 11:00, 11:20, 11:40, 12:00, 12:20, 12:40, 13:00 HR:MIN. The experiment will be conducted at three temperatures (18, 24 and 30C). Temperature-sensitive and heat tolerant varieties will be compared. Varieties with different photoperiod responses will also be tested, e.g. early, mid and late season varieties). All plants will be grown in greenhouses containing a blackout curtain that will allow for 9 h of sunlight, then day length extension lighting with white LEDs will be used to create the range of night lengths required for this study. Time to visible bud, first color and anthesis will be recorded. Critical night length (defined as the night length at which flower initiation begins, i.e., shorter nights result in vegetative plants) and optimal night length (defined as the night length at which flower development occurs at the optimal rate, i.e, longer nights do not result in any change in flower development rates) will be identified. A model will be created to predict flower development rates under natural night length conditions and typical production temperatures. The model will be tested in under natural day length condictions in commercial greenhouses located at a range of latitudes in the U.S. Garden mums (Facultative short day plant): Fall garden mum flowering can be difficult to predict due the interaction of temperature and photoperiod. Garden mums flower sooner during cool summers, while warm summers delay flower initiation and development. Premature flowering is often a problem because the temperature x photoperiod conditions may initially be conducive for flower initiation and then warmer mid-summer temperatures do not allow for flower bud development resulting in crown bud formation. Florel (ethephon) can be used to inhibit premature flower development if temperatures are cool after May, June and July plantings. Plants (very early, early, mid and late season varieties) will be placed at various night lengths (12, 13.5, 15, 16.5 h) at three temperatures (18, 24, 30C). Plants in each temperature x photoperiod treatment will be treated with weekly applications of 0, 500 or 1000 ppm Florel for the first three weeks to determine the rate required to prevent premature flowering at each temperature x photoperiod treatment. Time to visible bud, first color and anthesis will be recorded.