Light has been shown to be the most important environmental factor influencing the anthocyanin biosynthesis in plants. Phytochromes which are photoreceptors that sense light are involved in the anthocyanin biosynthesis. They respond to light by switching from one form to another and directing so the plant gene expression. This means that some of the enzymes in the biosynthesis of anthocyanins are expressed and regulated through light (with the help of the photoreceptors).
Although the biosynthesis of anthocyanins in response to light is not really understood researchers have found that cranberries that were exposed to one 24-hour day-light circle had for example a 75% higher anthocyanin content.
Slight changes in pH have a significant effect on the color of anthocynin since the acidity affects the ration between the various forms of the pigment and are responsible for the color the fruit has. Acidic ph gives a red color, more basic pH a blue and very basic pH makes it colorless. The molecule that changes with the pH is called cyanidin. Remember: A cyanidin with attached sugars is called an anthocyanin.
The presence of sugar is important in the anthcyanin biosynthesis since all anthcyanins have a sugar molecule bound to their structure. The sugar groups are usually glucose, galactose, or arabinose. The sugar rings have many OH groups, which can hydrogen-bond to water. They help with the pigment's solubility in water.
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