OBJECTIVE FORESTRY

Detailed explanation-1: -However, as light intensity increases further, photosynthesis rates are inevitably restricted by some other element.-For example, in the presence of a green leaf and optimum light and $CO 2$ levels, if the temperature is very low the plant cannot photosynthesize. Thus, the correct answer is light duration.

Detailed explanation-2: -Increased light duration allows the plant to make sufficient food to survive and grow. However, plants require some period of darkness to properly develop and should be exposed to light for no more than 16 hours per day. Excessive light is as harmful as too little..

Detailed explanation-3: -The photosynthetic activity of light is wavelength dependent. Based on McCree’s work (McCree, 1971, 1972), photosynthetically active radiation is typically defined as light with a wavelength range from 400 to 700 nm.