Why is Lettuce a Long Day Plant?

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why is lettuce a long day plant

Wondering if lettuce is a long day plant? In this article, we answer that question. Additionally, we discuss the key differences between long-day and short-day plants. Then, we also provide some examples. 

Why is Lettuce a Long Day Plant?

Lettuce is a long day plant because it bolts during summer when the days are longer. This is because, during this season, the amount of light that lettuce is exposed to is significantly higher. This creates an ideal environment for lettuce as it needs immense amounts of light in order to grow.

What Does a Long Day Plant Need to Flower?

LONG DAY PLANTS Need a night period that is less than a critical length

In order for a long day plant to flower or bolt, it needs a night period that is less than a critical length. It needs more than twelve hours of light. Scientifically, what activates the flowering or bolting of these plants is the active form of phytochrome (Pfr). But its action differs depending on the type of plants. For long-day plants, high levels of Pfr is required, which results from short nights, so consequently, they need longer exposure to light in order to flower or bolt.

What Are Short Day and Long Day Plants?

To understand the differences between short and long day plants, it is important to know Phytochromes (Pfr). These are leaf pigments that plants use to detect periods of light and darkness.

In short-day plants, Pfr inhibits flowering, hence, low levels of it is required for the plants to flower and bolt. The day period required by these plants is less than 12 hours.

Conversely, in long-day plants, Pfr activates flowering, which means more of it is needed, translating to short nights and longer days.

There is a third classification, collectively called Day-neutral plants. These plants’ flowering process is unaffected by the length of day or night. These plants flowers or bolt when they are already mature enough to do so. They are called day-neutral plants.

What is an Example of Long Day Plants?

Besides lettuce, there are other examples of long-day plants. Dill and spinach are common examples that fall under this category too. Dills require more than 11 hours of day length, while spinach requires 13 hours. Other common examples of long-day plants are Pea (Pisum sativum), Sugar beet (Beta vulgaris), Cabbage (Brassica), Wheat (Triticum aestivaticum), Radish (Raphanus sativus), and Henbane (Hyoscyamus niger). 

OTHER LONG DAY PLANTS INCLUDE SPINACH AND Dill

Wrap Up

As a summary, long-day plants are different from short day plants in that they require shorter nights and longer days for them to flower or bolt. In a natural process called photoperiodism, Phytochromes (Pfr), leaf pigments present in plants, detect periods of light and darkness. They activate flowering in long-day plants, while they inhibit it in short-day plants. Plants that are not affected by the length of days and nights and flower instead once mature, are called day-neutral plants. Lettuce is a clear example of long-day plants. Other examples are dill and spinach. 

If you want to know more about photoperiodism, here’s a short video explaining this process.

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