Im learning about plants and I know that light has discrete

I\'m learning about plants and I know that light has discrete particles called photons that each carry a \"quantum\" of energy. A photon of red light for example has a long wavelength and carries a small quantum of energy. According to me Cell Bio book, plant pigments have different configurations of electrons and atoms, which are responsible for the different particular wavelengths of light they are able to absorb.

My question is, can certain wavelengths be dangerous to a pigment? For example, phycoerythrin is capable of absorbing wavelengths between 500-600 nm. Would light at 400 nm therefore be dangerous to it since a photon of ultraviolet or blue light carries a larger quantum energy than the photons the pigment usually absorbs?

Solution

Answer : Plant pigment molecules absorb light only in the wavelength range of 700 nm to 400 nm; this range is referred to as photosynthetically-active radiation. Violet and blue have the shortest wavelengths and the most energy, whereas red has the longest wavelengths and carries the least amount of energy.

Organic pigments have a narrow range of energy levels that they can absorb. Energy levels lower than those represented by red light are insufficient to raise an orbital electron to an excited, or quantum, state. Energy levels higher than those in blue light will physically tear the molecules apart, a process called bleaching. Therefore , light in range between 400-700 nm are neither harmful for the process of photosynthesis but light like UV whose wavelenth less than than is really very harmful for the metabolic process of plant.