Question

How light can cause variations in different plants and animals?

Answer 1

In the absence of light the plants remain etiolated. Shade produces elongated internodes and thinner and broader leaves. It increases the succulence of many vegetables. Strong light, in the contrary, helps in the production of more mechanical tissue and thicker leaves. Palisade parenchyma becomes multilayered under strong light but remains single layered under moderate initensities of light (e.g., Peach). The effect of light has also been observed by Cunningham in flat fish Solea. The fish habitually rests on left side. It develops pigmentation and eyes on right side, the side exposed to sun. If left side is exposed to sunlight in the young fish, both eyes and pigmentation develop on that side.