80 CONTENTS 13.1 Introduction 13.2 Eucalyptus diseases (gum) 13.3 Acacia diseases (wattle) 13.4 Pinus diseases (pine) 13.1 Introduction This chapter deals only with the major diseases of commercial forestry trees in South Africa.0 CONTENTS 13.1 Introduction 13.2 Eucalyptus diseases (gum) 13.3 Acacia diseases (wattle) 13.4 Pinus diseases (pine) 13.1 Introduction This chapter deals only with the major diseases of commercial forestry trees in South Africa.
The pigment responsible for most light-harvesting by plants is chlorophyll, a green pigment. The green color indicates that it is absorbing all the non-green light-- the blues (~425-450 nm), the reds and yellows (600-700 nm).
Plants absorb energy only from the red and blue ends of the visible electromagnetic spectrum. They reflect the unused green light to our eyes. Plants use visible light (400 nm to 700 nm) for growth and photosynthesis. The wavelength of red light is about 650 nm. Green light has a wavelength of about 510 nm, and the wavelength of blue light is about 475 nm. Photosynthesis depends on on the absorption of light by pigments in the leaves of plants.