'Variables such as PH, temperature, humidity and light intensity coupled with effects of biota and soil's physicochemical structure can affect both the chemical structure, production of metabolites and the level of activity of substances which are in the environment.'
Allelopathy can be defined as the ability of an organism, having a biochemical phenomenon where there is a production of one or more biochemical by the organism, to have germination, growth and survival influence and controlled reproduction of other organisms. According to Bais (2003), this is an ecological factor that attempts to explain the distribution of species and abundance within plant communities. Allelopathy is a common characteristic in some algae, plants, fungi, coral and bacteria.
Various kind of literature has attempted to study the phenomenon of allelopathy in plants and how they impact the ecology in which they grow. (Bais, 2003), have deduced that all plants produce secondary metabolites at different degrees of concentration, composition, and diversity of plant tissues. Such metabolites can belong to various categories of phenolic compounds, specific terpenes, and alkaloids. He then suggests that production of metabolites is dependent on the species genetic characteristics and the environmental conditions in which the plant is growing. Variables such as PH, temperature, humidity and light intensity coupled with effects of biota and soil's physicochemical structure can affect both the chemical structure, production of metabolites and the level of activity of substances which are in the environment.
A study by Grove et al. (2012) on allelopathy in plants would involve the conducting of studies on the chemical substances which have been extracted from various case study plants. This is done by using natural methods of extraction from the plant tissues such as exudation, leaching, and vaporization. Laboratory extraction can involve the extraction of allelochemicals which are extracted using laboratory experiments which can replicate the natural conditions of the plant life. According to them, it is worth noting that the substances which are released from plants can be of different mixtures of substances which can then be used in conducting research to determine the validity of a certain hypothesis. These mixtures of substances can have antagonistic or synergistic effects which can be modified by the biotic, physical and chemical soil properties. The degree of interaction and the level of toxicity can be dependent on the stage of growth of recipient and the donor of the species alike.
Many of studies done on allelopathy are usually carried out to determine the effect of one donor species, and on the growth of the target plant, however, most of the findings are conclusions in that the allelochemicals have no effect on the organism. An example is a conclusion done by Grove et al. (2012), was that ectomycorrhizal fungi abundance is lower In regions which the seedlings of Douglas- fir grown in the soils of forests which had been invaded by Cytisus scoparius, than those grown in forest soils which have not been invaded. This is because the roots of mycorrhizae assist in the absorption of nutrients more efficiently. Therefore the authors drew the conclusion that the production of allelochemicals by C. scoparius inhibits the growth of conifer by reduction of the ectomycorrhizae in quantity by the roots.
However, the effects of allelopathy in plants have not been widely demonstrated in the various literature on the allelopathy of organisms. Nonetheless, Rawat et al., (2016) have given the evidence of secondary metabolites in that it is essential to the producer plant as it assists in avoiding of insects, herbivore and fungi invasion. This makes them useful and paramount as natural herbicides and medicines. In regions where there are technological challenges such as the mountains of Himalayas, studies showed that people in these regions adopted in the cultivation of plants which were known to have medicinal capabilities. Their study found out that when these medicinal plants such as the Picrorhiza kurroa and Ocimum sanctum were grown together with other crops, there was inhibition of ion and nutrient absorption, which was by affecting the permeability of the plasma membrane. This was a confirmation that most of the plant species and especially the medicinal ones usually have allelochemicals which are responsible for determining the functionality of the enzyme used for hormone synthesis of the plant.
On the effect of the study on the medicinal plant's allelochemicals effect on other crops, Rawat et al., (2016) found out that the effects of plant metabolites or compound were either stimulatory or inhibitory depending on the surrounding medium concentration. This has been the study done in controlled environments such as greenhouses, or in fields, laboratory experiments done with extracts, residues and purified allelochemicals. The suggestion here is that extracts from medicinal plants can inhibit the growth characteristics of plants and the efficiency of germination of seedlings.
Rationale
The rationale of this understanding is that different concentration of phenolic compounds exposed in low concentration can have a stimulatory effect on germination of seeds and when higher concentration is exposed to seedlings, it can have an inhibitory tendency in germination or reduction in the rate of seed germination.
Experimental Hypothesis.
The purpose of the experiment will be to test the hypotheses that whether herbs or medicinal plants are highly allelopathic and which section of the plant has Allelopathic effects. Therefore, if seeds were exposed with varying concentrations of extracts from cannabis sativa l, on levels ranging from 25%, 50%, 75 % and 100% of aqueous extracts from the shoots and a different one with extract from the roots versus seeds of lettuce exposed to distilled water.
Null Hypothesis.
The purpose of this experiment is to test the hypothesis that the all levels of concentrated extracts from the shoots and roots of cannabis sativa l. has no effect on the germination of treated l lettuce seeds. Therefore, if lettuce seeds are treated with different levels of concentration of extracts from the roots and shoots of cannabis sativa, then there will be no change in the germination of lettuce seeds versus lettuce seeds treated with distilled water.
References.
Bais, H. (2003). Allelopathy and Exotic Plant Invasion: From Molecules and Genes to Species Interactions. Science, 301(5638), 1377-1380. http://dx.doi.org/10.1126/science.1083245
Grove, S.; Haubensak, K.A. & Parker, I.M. 2012. Direct and indirect effects of allelopathy in the soil legacy of an exotic plant invasion. Plant Ecology 213(12): 1869-1882.
Rawat, L., Maikhuri, R., Negi, V., Bahuguna, Y., Pharswan, D., & Maletha, A. (2016). Allelopathic Performance of Medicinal Plants on Traditional Oilseed and Pulse Crop of Central Himalaya, India. National Academy Science Letters, 39(3), 141-144. http://dx.doi.org/10.1007/s40009-016-0435-3
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