# Allelopathic Activity of Leaf Wastes of _Lriodendron tulipifera_ for Sustainable Management
## 4 Discussion  
### Alleleptathic Activity of the Fresh and Fallen Leaves of \(L\). tulipifera  
\(L\). _tulipifera_ is a popular timber species, and logging operations of the trees produce a large amount of leaf waste [1; 2; 3; 6; 7; 8; 9]. \(L\). _tulipifera_ is also grown in residential areas as shade and ornamental trees, and the fallen leaves accumulate on the streets and ground in the autumn. These fallen leaves need to be organized at a large expense [20]. However, there is no information available on the allelopathic activity and allelochemicals in the leaves of \(L\). _tulipifera_ on the literature. Therefore, we have examined the allelopathic activity of \(L\). _tulipifera_ fresh and fallen leaves under laboratory and greenhouse conditions. The fresh leaves were used as substitutes for leaf waste from the logging operations of \(L\). _tulipifera_. The fresh leaf extracts showed significant growth inhibition on the roots and coleophiles of weed plant species--_V. myuros_, \(E\). _crus-galli_, and \(L\). _multiformum_--under laboratory conditions (Figure 3). The fallen leaf extracts also showed significant growth inhibition on these weed species (Figure 4). However, the sensitivity of these weed species differed to the fresh and fallen leaf extracts, and differed in the organs of test plant species (coleophiles and roots). Comparing their \(IC_{50}\) values, the sensitivity of the \(E\). _crus-galli_ roots to the fresh leaf extracts was the highest among the roots and coleophiles of these weed species, and that of the \(L\). _multiformu_ coloeptiles to the fallen leaf extracts was the lowest (Table 1). The \(IC_{50}\) values of the fallen leaf extracts were 2- and 2.8-fold, 4.3- and 7.2-fold, and 6.5- and 6.6-fold greater than those of the fresh leaf extracts for the coleophiles and roots of \(V\). _myuros_, \(E\). _crus-galli_, and \(L\). _multiformu_, respectively, which indicates that the allelopathic activity of the fresh leaves is greater than that of the fallen leaves. These results suggest that the \(L\). _tulipifera_ fresh and fallen leaves may contain extractable allelochemicals, and the fresh leaves may contain more allelochemicals than the fallen leaves. The fresh and fallen leaf powder of \(L\). _tulipifera_ significantly suppressed the germination of \(E\). _crus-galli_ under greenhouse conditions (Figure 6). The \(IC_{50}\) value of the fallen leaf powder was 3.1-fold greater than that of the fresh leaf powder, which consists of the \(IC_{50}\) values of the fresh and fallen leaf extracts (Table 1). As described in Materials and Methods (Section 2.3), \(E\). _crus-galli_ seeds were some 9 days after the leaf powder was applied onto  
Figure 8: Effects of lipiferolide on the \(L\). _sativum_ hypocotyl and root growth, as well as on the \(L\). _multiformu_ coloeptile and root growth. The means \(\pm\) SE were calculated from four independent experiments with 10 seeds (\(L\). _sativum_) and 10 germinated seeds (\(L\). _multiformu_) for each determination. Different letters on the bars in the same panels indicate significant differences at a \(p<0.05\) level. the soil. Therefore, allelochemicals in the \(L\). _tulipifera_ leaf powder may be released into soils within 9 days, and may cause the suppression of the germination (Figure 6). In addition, the amount of released allelochemicals from the fresh leaves may be greater than that from the fallen leaves. As described in the Introduction, when certain plant parts of some allelopathic plant species were incorporated into soil, these plant parts suppressed the germination and growth of several weed species in greenhouse and field conditions due to their allelochemicals [40; 41; 42; 43; 44]. When the soaking water and extracts of some allelopathic plant leaves were applied to several weed species as a foliar spray and/or irrigation water, the germination and growth of several weed species were restricted [40; 41; 42; 43; 44; 45; 51; 52; 53; 54; 55; 56; 57]. The fresh and fallen leaves of \(L\).