Description of the Research

Snapdragon (Antirrhinum majus. L.) is a highly profitable perennial cut flower. It was once ranked as the seventh most valuable cut flower crop and Maryland is one of the most important States in the North-East US involved in the production of snapdragons.

Stem thickness and internode elongation has long been a problem in producing quality Snapdragons for market. Excessive elongation of the stem or an unbalanced development between vegetative and reproductive growth dramatically decreases the economic value of snapdragons and increases production losses. Since DIF (Difference between day and night temperature) was introduced in the late 1980^-s as a technique to reduce plant height, considerable research has been carried out, primarily with bedding plants. Results have shown that DIF is an effective method that significantly reduces internode length and increases plant quality in a wide range of plants. Manipulating day temperature/night temperature to control stem elongation is now used quite extensively in the European and US greenhouse industry as a non-chemical means of reducing plant height. However, because the different studies generally investigate a single aspect in a given species, the mechanism of this phenomenon is still poorly understood.

We are using snapdragon as a model species to investigate how DIF effects plant development. The objective is to develop an integrated model describing the effect of DIF on plant growth and development. We are initially examining the morphological responses of various snapdragon cultivars to a range of DIF treatments. By measuring increase in stem length, stem diameter, leaf initiation, floral number, length and quality, together with total biomass, we want to examine growth effects among the 4 groups of snapdragon cultivars. The objective is to screen for cultivars that are sensitive or insensitive to DIF and build up a quantitative description of DIF on snapdragon. We then hope to investigate more physiological parameters that may be involved in the control of the DIF mechanism. Finally, molecular tools may provide us with a more precise insight about what is occurring in the plant. By observing the response of snapdragon development and flowering to a combination of GA, and ABA treatments, we may then be able to develop a comprehensive model to program snapdragon production in greenhouse production.

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