Light deprivation, also known as "light dep," is a technique that controls how often plants receive light, and how much light is received. Through the use of blackout materials such as greenhouse covers, growers utilizing light deprivation can simulate various parts of a season. Each part of a season has a particular correlation to the growth phase of plants. For example, since the fall season has fewer daylight hours, using a light deprivation greenhouse year-round will trick plants into producing flowers and fruits by increasing the concentrations of certain hormones within the plants due to having more hours of darkness. This can allow for plants within a light deprivation greenhouse to go into production several times during a year, instead of just at the end of the season with traditional agriculture and a photoperiod determined by the sun. This can also allow for production in non-peak times during the year, meaning less competition and consequently a higher selling price.
Photoperiodism is a plant's specific response to photoperiods. A photoperiod is the amount of time in a 24-hour day a plant receives light. Shorter days force crops within the light dep to bloom as a response to the increase in darkness hours and the production of flowering hormones.
The gene responsible for plants knowing when to produce flowers is called Apetala1. The photoperiod manipulation, or shortening of days, activates this gene, which stimulates protein production and thus activates more than 1,000 other genes involved in flowering. Researchers at the Plant Developmental Genetics lab located in Dublin, Ireland at Trinity College Dublin isolated this gene in connection with flowering. The Apetala1 gene is known as the master control gene for the flowering process. Once this gene is turned on it sends out a stop signal to the plant's meristems which puts a stop to leaf production. The meristems are where new growth in a plant takes place. These meristems are then signaled to begin flower production. Due to plants flowering earlier and showing sexing characteristics as well as phenotypic characteristics earlier on in the season, the implications for light dep greenhouses for use in plant breeding are very exciting. Instead of having to wait until the end of the year for a plant to sex and create fruit, cultivators can create fruit or new varieties several times within a given year.
The ability to force a plant into its flowering phase, assess its phenotype, and see what type, quality, size, and flavor profile can be attributed to the fruit from that specific plant allows a master gardener to select for those attributes either in a group or singled out. They can also then choose to let the offspring of any given greenhouse inherit those desirable attributes, thus lending further advances in quality and specificity to the crops to be had. Genetics are important to proper crop production, with phenotypic expression taking the highest priority, as this will provide for a better quality attributed to the end product.