13.2.1. Intensity of light on growth of plants

♤ Extremely high intensity favours root growth than shoot growth which results in increased transpiration, short stem, smaller thicker leaves. On the other hand low intensity of light retards growth, flowering and fruiting.

♤ When the Intensity of light is less than the minimum, the plants ceases to grow due to accumulation of CO2 and finally dies.

♤ Out of 7 colours in the visible part of spectrum, only red and blue are effective in photosynthesis.

♤ Plant grown in blue light are small, red light results in elongation of cells results in etiolated plants. Plants grown in ultraviolet and violet light are dwarf.