The light awakens! Sensing light and darkness

Abstract

In the late nineteenth century, Charles Darwin observed that 'light exerts a powerful influence on most vegetable tissues, and there can be no doubt that it generally tends to check their growth' (The Power of Movement in Plants, 1880). Subsequent to this seminal work, light has been recognised as an important regulator of plant growth. Over the next 150 years, research on light regulation of plant growth and development by immensely imaginative and talented researchers in various laboratories across the globe has given us tremendous insights into how light governs plant growth both at the organismal and molecular levels. The discovery of light-responsive photoreceptor proteins that are activated by red, far-red, blue/UV-A and UV-B light has helped further our understanding of how plants respond to the light that falls on the surface of the earth. This chapter brings together the recent developments in our understanding of how plants sense light by using photoreceptors and the various molecular mechanisms involved in light perception and transmission of the light signal within the plant. Furthermore, the chapter discusses recently ascribed functions of photoreceptors such as the ability of plants to distinguish their kin from non-kin through the action of phytochrome, the role(s) of cryptochrome as a magnetoreceptor and the role of phytochrome and phototropin as temperature sensors. The chapter also rekindles the debate about whether plants can have vision despite the lack of optical or light-sensitive organs such as eyes.