The Photochemical Survey and Allelopathic Ability of the Leaf Essence in Vitex pseudo-negundo and its Effect on the Germination and the Growth of Malva neglecta and Secale montanum

The role of allelopathy in weed management is useful and has attracted a lot of attention in the last two decades. The main goal of the allelopathic research is to find a reason for the interference of chemicals in natural circumstances and to introduce allelochemicals that affect the growth of other plant’s in farm or natural ecosystems. The other aim of this science is to identify and separate the plants allelochemicals. The prevention of weed growth by the crop allelopathy in the primary stages of establishment can reduce the need for commercial herbicides used at the beginning of the planting season. After that by increasing the competition, the crop can control the weed. The aim of this research is to identify the constituents of the leaf essence of Vitex pseudo-negundo and also to survey the allelopathic potential of different concentrations of the essence of Vitex pseudo-negundo in the prevention of the germination and the growth of Malva neglecta and Secale montanum weed bushes in the laboratory.
Material and The leaf samples of Vitex pseudo-negundo were collected from wild in Fasa, Fars province in 2016. To extract the essence, the leaves were collected and dried in the shade and then the essence was extracted. The extraction of the essence was done in the laboratory of the agricultural research and natural resources center of Shiraz. To analyze and survey the constituents of the essence, the gas chromatograph device with Flame Ionization detector and coupled chromatograph with mass spectrometer were used. In another part of this research, the potential of the allelopathy of the essence of the leaf of Vitex pseudo-negundo on the seed germination and the growth of Malva neglecta and Secale montanum were surveyed. This research was done in the form of factorial in the randomized complete block design with 4 repetitions in 2015. The first factorial included Malva neglecta and Secale montanum weeds and the second factorial included the essence of Vitex pseudo-negundo with the concentrations of 0, 250, 500, 1000, 200 ml. To analyze the data the statistical analysis software was used. To compare the means the Duncan test with 5 percent probability was used.
In this research, the analysis of the leaf essence of Vitex pseudo-negundo which was gained by distillation using gas chromatography and also gas chromatography attached to mass spectrometer made it possible to identify 53 compounds which constituted 98.91 percent of the essence. In this research, the essence of Vitex pseudo-negundo consisted of 37.743 percent Hydro carbonic monoterpenes, 28.865 percent Oxygen monoterpenes, 25.858 percent Sesquiterpene of Hydrocarbons, 6.32 percent Sesquiterpene Oxygen and 0.397 of other compounds. The most important constituents were α-Terpinyl acetate (22.007 percent) ¡ α-Pinene (16.378 percent))¡ E)-Caryophyllene (11.724 percent) and Limonene (8.68 percent). The highest percentage and rate of germination of Malva neglecta and Secale montanum were obtained in no essence condition of Vitex pseudo-negundo (control) with the increase of the essence concentration of Vitex pseudo-negundo, the percentage and rate of germination were decreased in Malva neglecta and Secale montanum so that lowest germination which was obtained in the treatment was 2000 ml. The length of the radical in Malva neglecta in the treatment was 1000 ml and the concentration of Vitex pseudo-negundo essence was 4.4 ml which showed a significant difference with 2000 ml treatment (2.2 ml). The length of the radical in Secale montanum in no essence condition of Vitex pseudo-negundo (control) showed a significant difference with 250 mg/l of the treatment Vitex pseudo-negundo. The shortest length of the radical of Secale montanum was 26.6 mm in average in the 2000 ml evidence of the essence of Vitex pseudo-negundo. The increase of the essence of Vitex pseudo-negundo caused the decrease of the wet weight average of Malva neglecta and Secale montanum. The other obtained results show that the wet weight of Malva neglecta with Secale montanum in different levels does not show any significant difference with Vitex pseudo-negundo when the concentrations are equal. The seed vigor index of Malva neglecta and Secale montanum were decreased with the increase of the essence concentration. The lowest seed vigor index was obtained in the essence concentration of 2000 mg/l. The highest seed vigor index in the no essence treatment of Vitex pseudo-negundo (control) in Malva neglecta and Secale montanum were 23.1 and 77.8 consecutively.
The results of this research showed that the essential oil of Vitex pseudo-negundo has a high allelopathic ability on Malva neglecta and Secale montanum weeds. The Malva neglecta weed had a higher sensitivity to the concentration of the essential oil. There has been a widespread effort to the degree of inhibition increased with an increase in the concentration of the essential oil so that in all the measured characteristics, the highest prevention was observed at 2000 ml. In the present situation that there has been a widespread effort to improve the performance of the crops, knowing the allelopathic effects of the plants can be a great help in the suitable management of sustainable agriculture and weed control methods.