Allelopathic Effect of S. Macrophylla on the Growth of V. Radiata Seedlings

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Allelopathic effect of S. macrophylla on the growth of V. radiata seedlings

Thea Philea I. Mostralesa, Greeny Joy A. Perucho, Rhoshela Vi C. Rendon, John Gregor A. Rono, Emmerson P. Rullog, Riffcord R-Denz M. Tabula Institute of Biology, College of Science, University of the Philippines, Diliman, Quezon City (a Thea Philea I. Mostrales, e-mail: theaphilea.mostrales@gmail.com)

ABSTRACT
Swietenia macrophylla, or commonly known as the mahogany tree in the Philippines, is an introduced species of the family Meliaceae that is commonly used for lumber and reforestation projects. However, based on studies, it is shown that the mahogany tree has inhibitory effects that affect adjacent growing plants. This is made possible chemically and is referred to generally as allelopathy. This study aimed to determine is S. macrophylla had any adverse effects to the growth of plants in close proximity to it. The researchers selected three mahogany trees and planted six plots of differeing distances with each plot containing ten monggo seedlings. The results obtained indicate that there is no significant difference between the growth of monggo seedlings growing near the mahogany tree to that of monggo seedling growing near the control tree based on the analysis done on the seedlings’ height, weight and survival rate. Results also indicate that distance of the seedlings from the S. macrophylla has no effect on the intensity of inhibition of the growth of the V. radiata. The results obtained can be attributed to factors that include the texture of soil, fine-textures soil having been proven to have a greater retention capacity of allelochemicals than coarse-textures soils. Also, allelopathic interactions include both promontory and inhibitory activities of phenolic allelochemicals and thus using seed germination as a bioassay parameter may be of little value.

KEY WORDS: Swietenia macrophylla, allelopathy, growth of monggo seedlings, inhibitory effect of mahogany, introduced species

INTRODUCTION

BACKGROUND AND SIGNIFICANCE OF THE STUDY
Swietenia macrophylla, commonly known in the Philippines as mahogany, is a member of the order Sapindales, under family Meliaceae. It is a large, fast-growing, semi-evergreen tree, popular for landscaping, especially in North American and Carribean countries, where it has a vulnerable status as provided by CITES (Oldfield 1995), and for its strong wood for lumber. This tree was first introduced in the Philippines as early as 1907, and 1913 as part of the Mt. Makiling forest. It is currently used in the Philippines as a lumber tree and utilized in many reforestation projects. However, studies have shown that however beneficial S. macrophylla may be to the Philippine economy and to its environment, it also displays adverse effects to the Philippine wildlife. As a recently introduced species, the said tree has been unable to produce a natural web of life around it; there are no natural consumers of mahogany in the country, and as such, the area around the tree will not be populated by native fauna immediately.

It is also suspected that mahogany leaves contain allelopathic compounds. In a study conducted by P. Thinley in 2002, it was shown that S. macrophylla leaves inhibited the growth of Pterocarpus indicus. Allelopathic compounds inhibit growth and development of other plants when introduced to them. Allelopathy is the production of a certain plant of such compounds and should not to be confused with competition, which may or may not involve allelopathy. Allelopathy is common in the plant kingdom, spread out in random fashion across orders. Some plants are deemed invasive due to their allelopathic nature and mahogany trees are not exempt. STATEMENT OF THE PROBLEM

The study aimed to determine if S. macrophylla can adversely affect the growth of plants in close proximity to it and specifically sought to answer the following questions: 1) Does mahogany affect the growth of newly planted...
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