Encyclopedia
Lantana camara L. (Verbenaceae) is native to tropical America and has been introduced into many other countries as an ornamental and hedge plant.
- allelochemical
- decomposition
- indigenous plant
- monospecies stand
- phytotoxicity
1. Introduction
Lantana camara L., which belongs to the family of Verbenaceae, is known as wild sage and red sage (Figure 1). It is a perennial shrub 1–4 m tall and forms dense stands. The leaves are opposite with long petioles, oval blades, hairy, and serrate. The species flowers all year round if the condition is adequate. A pair of inflorescences occurs at leaf axils. The flowers are small, multi-colored, and dense in flat-topped clusters. Each inflorescence bears 10–30 fruits, which are small, round drupes containing 1–2 seeds [1][2][3][4][1,2,3,4].
Figure 1. Lantana camara. Photos were taken by Kato-Noguchi.
The species is native to tropical America and has been introduced into other countries as an ornamental and hedge plant. It adapts to varied habitats ranging from open, unshaded areas, such as pastures and crop fields, to disturbed areas, such as roadsides, railway tracks, and fired forests [3][4][5][3,4,5]. The plant has naturalized more than 60 countries as an invasive noxious weed and is considered to be one of the world’s 100 worst invasive alien species [6]. For example, L. camara was introduced in India at the beginning of the 19th century and has been growing densely, occupying 13.2 million ha [7]. The plant was first reported in 1841 in Australia and has spread and formed a pure stand over 4 million ha across Australia [8]. The first introduction of the plant in South Africa was in 1858. The species occupied 2 million ha with condensed area of 70,000 ha in 1998 [9]. The species has globally invaded millions of hectares of pastureland and infested major crop plantations, such as tea, coffee, sugarcane, and cotton plantations [3][4][3,4]. The invasion of the species also causes the severe reduction of biodiversity in the invaded ecosystems. The species threatened the habitat of 83 indigenous plant species in New South Wales in Australia [10].
L. camara displays high morphological variation because of extensive breeding [11]. The genetic diversity of L. camara population is high [3][12][3,12]. The species has diploid (n = 22), triploid (n = 33), tetraploid (n = 44), and pentaploid (n = 55) varieties [13]. Different ploidy levels are of ecological significance in the invasive potential of the species. L. camara in the native range of tropical America generally grows as a small clump less than 1 m in diameter. However, it often forms dense monospecies stands in diameter of 1–4 m in the invaded range [2][14][2,14]. The requirement conditions for L. camara growth and survival are 4.5–8.5 soil pH, 1000–4000 mm annual rainfall, unshaded conditions (however, it is tolerant to shade), and tropical to temperate regions (it is intolerant to frequent freezing) [4]. Thus, the potential of ecological adaptation is very high. Morphological characteristics of the species may contribute to the invasion and naturalization into the nonnative range [15][16][17][15,16,17].
The plants usually flower at the first growing season after establishment in most places [3][18][3,18], and there is a range of pollinators, such as insects and birds [19]. It was recorded that one plant produced up to 12,000 fruits each year [20]. Frugivorous birds and other animals contribute to the distribution of the seeds with animal feces, which adds additional nutrients for seed development [19]. L. camara also reproduces asexually. Vegetative reproduction occurs by layering horizontal stems and generating root systems [2][21][2,21]. The characteristics of L. camara for high reproduction may also contribute to the success of its invasion.
2. Allelopathy of L. camara
Allelopathy is the interaction of one plant with another plant in its vicinity through releasing certain secondary metabolites, which are defined as allelochemicals [22][28]. The allelochemicals are released into the neighboring environments and rhizosphere soil of the plants by rainfall leachates, decomposition of plant residues, root exudation, and volatilization from living plant parts [22][23][24][25][28,29,30,31]. Therefore, the allelopathic potential of the extracts, leachates, residues, and rhizosphere soil of L. camara was evaluated by many researchers. In this chapter, the allelopathic potential of the extracts, leachates, residues, and rhizosphere soil of L. camara is summarized (Table 1).
2.1. Extract
Aqueous leaf extracts of L. camara inhibited the germination of Lactuca sativa L. due to the suppression of cellular membrane developments and increase in the production of reactive oxygen forms [26][32]. Aqueous leaf extracts of L. camara suppressed the development of leaf buds of Eichhornia crassipes Mart., increased the decay, and caused necrosis of E. crassipes leaves. The extracts also increased SOD activity in the leaves of E. crassipes concomitant with H2O2 accumulation and increased the membrane peroxidation level. The activity of catalase was decreased by the extract treatments. These observations indicate that leaf necrosis of E. crassipes may occur due to the oxidative stress caused by leaf extracts of L. camara [27][33].
Aqueous leaf extracts of L. camara inhibited the germination and growth of Brassica juncea (L.) Czern, Cucumis sativus L., Phaseolus mungo L., Raphanus sativus L., Vigna unguiculata (L.) Walp, Cicer arietinum L. [28][34], Centroma pubescens Benth. [29][35], and Vigna radiata (L.) R. Wilczek [30][36]. Aqueous extracts of L. camara leaves, stems, and roots also suppressed the germination and growth of Cicer arietinum L. [31][37], Phaseolus mungo (L.) Hepper [32][38], and Lens esculenta Moench [33][39]. In addition, the aqueous leaf extracts suppressed the regeneration of the moss species Funaria hygrometrica Hedw. [34][40].
Aqueous extracts of L. camara flowers suppressed the germination and seedling growth of Eruca sativa (L.) Cav. [35][41]. Aqueous extracts of flowers, fruits, and leaves inhibited the germination and seedling growth of Raphanus sativus L. and Lactuca sativa L. The inhibitory effect was more significant with flower and fruit extracts than leaf extracts [36][42]. Methanol extracts of stem and leaves of L. camara also inhibited the germination and growth of Lolium multiflorum Lam. [37][43]. The observations described in this section indicate that the extracts of L. camara possess inhibitory activity on the germination and growth of several other plant species and probably contain some extractable allelochemicals.
2.2. Leachate
Shoots and flowers of L. camara were cut into small pieces and soaked in water for 48 h. Filtered water was used as the leachates of L. camara. The leachates inhibited the growth of Eichhornia crassipes Mart. and finally killed E. crassipes 21 days after the treatment due to its high toxicity [38][39][44,45]. Leachates from L. camara leaves suppressed the germination and seedling growth of Mimosa pudica L. The concentrations of insoluble carbohydrate, proteins, and nucleic acids and the activities of dehydrogenase, catalase, and peroxidase in the seedlings were reduced by the leachates. However, the concentrations of amino acids and soluble carbohydrates were increased by the treatment [40][41][46,47]. Root leachates of L. camara inhibited the radical growth of Cucurbita pepo Linnaeus, Phaseolus vulgaris L., and Lycopersicon esculentum Mill. and altered the cytoplasmic protein synthesis in those radicals [42][48]. Leachates from L. camara roots also suppressed the germination and seedling vigor of Triticum aestivum L. [43][49]. Leachates from fruits and leaves of L. camara significantly inhibited the growth of Pennisetum americanum (L.) Tzvelev, Setaria italica (L.) P. Beauvois, and Lactuca sativa L. [44][50]. These observations suggest that some allelochemicals may be released into the soil under the trees from the leaves, shoots, flowers, fruits, and roots of L. camara by rain and irrigation water as leachates.
2.3. Residue
L. camara shoots were cut into small pieces and mixed with sand, and the seeds of Triticum aestivum L., Zea mays L., Glycine max (L.) Merr., Lepidium virginicum L., and Abutilon theophrasti Medik. were sown into the mixture. The growth of those seedlings was significantly suppressed by the residues of L. camara [45][51]. L. camara root and shoot residues and those decomposed residues also suppressed the growth of Morrenia odorata (Hook. & Arm.) Lindi. [46][52]. Decomposed leaf litter of L. camara inhibited the seedling growth of Raphanus sativus L., Lactuca sativa, L. Bidens pilosa L., Bidens bipinnata L., and Urena lobata L. [47][53]. These findings indicate that some allelochemicals were released into the soil during the decomposition process of L. camara residues.
2.4. Rhizosphere Soil
Rhizosphere soil of L. camara suppressed the growth of Achyranthes aspera L. and Albizia lebbeck [48][54]. Rhizosphere soil of L. camara also reduced the germination and seedling growth of Avena sativa L., Cicer arietinum L., Hordeum vulgare L., and Triticum aestivum L. [49][55]. These observations suggest that the rhizosphere soil of L. camara may contain some allelochemicals. The allelochemicals may occur during the decomposition process of plant residues in the soil and/or as leachates from living plant parts and root exudation.
Table 1.
Allelopathic activities of the extracts, leachates, residues, and rhizosphere soil of
Lantana camara
.
| Source | Inhibition | Target Plant Species | Stimulation | Inhibition | Reference | Stimulation | Reference |
|---|---|---|---|---|---|---|---|
| Extract | |||||||
| Leaf | Germination, cellular membrane development | Lactuca sativa | Reactive oxygen form | Germination, cellular membrane development | [26] | Reactive oxygen form | [32] |
| Development of leaf buds, catalase, leaf necrosis | Eichhornia crassipes | SOD activity, H2O2 accumulation, membrane peroxidation | Development of leaf buds, catalase, leaf necrosis | [27] | SOD activity, H2O2 accumulation, membrane peroxidation | [33] | |
| Germination and growth | Brassica juncea, Cucumis sativus, Phaseolus mungo, Raphanus sativus, Vigna unguiculata, Cicer arietinum | Germination and growth | [28] | [34] | |||
| Germination and growth | Centroma pubescens | Germination and growth | [29] | [35] | |||
| Germination and growth | Vigna radiata | Germination and growth | [30] | [36] | |||
| Regeneration | Funaria hygrometrica | Regeneration | [34] | [40] | |||
| Leaf, stem | Germination and growth | Lolium multiflorum | Germination and growth | [37] | [43] | ||
| Leaf, stem, root | Germination and growth | Cicer arietinum, | Germination and growth | [31] | [37] | ||
| Germination and growth | Phaseolus mungo | Germination and growth | [32] | [38] | |||
| Germination and growth | Lens esculenta | Germination and growth | [33] | [39] | |||
| Flower | Germination and growth | Eruca sativa | Germination and growth | [35] | [41] | ||
| Flower, fruit, leaf | Germination and growth | Raphanus sativus, Lactuca sativa | Germination and growth | [36] | [42] | ||
| Leachate | |||||||
| Shoot, flower | Growth | Eichhornia crassipes | Growth | [38][39] | [44,45] | ||
| Leaf | Concentrations of insoluble carbohydrate, protein and nucleic acid. Activities of dehydrogenase, catalase and peroxidase | Mimosa pudica | Concentrations of amino acid and soluble carbohydrate | Concentrations of insoluble carbohydrate, protein and nucleic acid. Activities of dehydrogenase, catalase and peroxidase | [40][41] | Concentrations of amino acid and soluble carbohydrate | [46,47] |
| Root | Growth, protein synthesis | Growth, protein synthesis | [42] | [48] | |||
| Germination and growth | Triticum aestivum, | Germination and growth | [43] | [49] | |||
| Fruit, leaf | Growth | Pennisetum americanum, Setaria italica, Lactuca sativa | Growth | [44] | [50] | ||
| Residue | |||||||
| Shoot | Growth | Triticum aestivum, Zea mays, Glycine max, Lepidium virginicum, Abutilon theophrasti | Growth | [45] | [51] | ||
| Root, shoot, decomposed | Growth | Morrenia odorata | Growth | [46] | [52] | ||
| Decomposed leaf litter | Growth | Raphanus sativus, Lactuca sativa, Bidens pilosa, Bidens bipinnata, Urena lobata | Growth | [47] | [53] | ||
| Rhizosphere soil | Growth | Achyranthes aspera, Albizia lebbeck | Growth | [48] | [54] | ||
| Germination and growth | Avena sativa, Cicer arietinum., Hordeum vulgare, Triticum aestivum | Germination and growth | [49] | [55] |
