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).
Green: The green color of leaves throughout spring and summer comes from chlorophyll, a pigment vital to photosynthesis. Yellow and Orange: Along with chlorophyll, there are yellow and orange pigments, carotene and xanthophyll, inside some trees' leaves. For most of the year, these pigments are masked by chlorophyll, but as the chlorophyll breaks down and the green color dissipates, the yellow to orange colors become visible.