Secondary plant growth substances

Figure 1. Biosynthetic pathways for secondary plant growth substances...

Tannins and lignins are also derived from these pathways but are not included in Table 1. To make the list as simple as possible, all compounds of aromatic nature, viz., simple phenols, benzoic and cinnamic acid derivates, coumarins, flavonoids and quinones are condensed into one group - aromatic compounds. Thus I will attempt to cover systematically the secondary plant growth substances that fall into 11 major groups as shown in Table 1. 

This review also includes some work on plant growth substances from the United States Department of Agriculture. A section on the mode of action of the secondary plant growth substances is included. A closely related subject which is now receiving considerable attention is the biochemical interactions of natural compounds from plants with other plants in the natural habitat (allelopathy) and this topic is included in this review. 

Plants possessing Ik show significant elongation and increased sensitivity to applied GAj after treatment with the ethylene synthesis inhibitor AVG. The Ik plants also produced more ethylene than comparable Lk plants under the conditions used [21]. However, whether the involvement of ethylene is a primary action of this gene, or merely a secondary consequence, is not clear. However, it does highlight the need to look at more than one group of growth substances. 

The information obtained at Los Tuxtlas shows that the studied species from the secondary vegetation produce one or more allelopathic substances, mainly in leaves or through the decomposition of their organic matter, that can inhibit growth or have deleterious effects on plants and may cause parallel effects that are related to the role of auxins and to tropisms and other metabolic processes. 

Are the secondary substances that exhibit growthregulating properties actually involved in controlling the growth and developmental processes of the host plants ... 

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