Research on reproductive characteristics and multiplication measures of vetiver grass in Thua Thien Hue

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This article introduces some results on reproductive characteristics and methods of asexual propagation by cuttings in Hue Vetiver cuttings under the action of some growth regulating substances.

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Nội dung Text: Research on reproductive characteristics and multiplication measures of vetiver grass in Thua Thien Hue

JOURNAL OF SCIENCE, Hue University, Vol. 67, No. 4A, 2011 RESEARCH ON REPRODUCTIVE CHARACTERISTICS AND MULTIPLICATION MEASURES OF VETIVER GRASS IN THUA THIEN HUE Nguyen Minh Tri1, Nguyen Dac Tao1 1 College of Sciences, Hue University Nguyen Ba Loc2 2 College of Education, Hue University Abstract. Vetiver grass - Vetiveria zizanioides (L.) Nash has been planted on the banks of some main rivers in Thua Thien Hue province (Huong river, Xuoc Du river, Bo river...) to prevent landslide. However, its current range of use seems to be restricted. It may be due to the shortage of materials and the fear that it might possibly develop into a kind of environmental weed. In this circumstance, the study attempted to prove the non-invasive nature of vetiver and develop a suitable protocol for its propagation. The results revealed that its flower is bisexual, unisexual or asexual. It appears from June to November. Vetiver seeds after physiological maturation could not germinate on both artificial conditions suggested by Murashige Skoog (1962) and natural soil. Meanwhile, the seedlings could sprout from the original form of the mother plant. The breeding of vetiver by separating the single bud cuttings and put into PE bags offered a higher ratio of living plant and better ability to form roots compared to traditionally propagating the bare root buds. This makes breeding simpler and easier to be put into practice, but some disadvantages remain such as the requirement of a large shoot source and areas, the high cost of labor and the low uniformity of created seedlings. Faced with this situation, NAA, one of the plant growth regulators, was used to stimulate the roots of the cuttings. At the concentration of 500 ppm, the ratio of forming roots and the average number and length of roots were the highest in the cases of tender and mature cuttings. Therefore, it is possible to use the mature or flower stem as a source of breeding materials for producing a large number of seedlings to meet the current need. 1 Introduction Vetiver grass has been introduced into Vietnam for a long time for oil production. Since 2005, Vetiver has been grown by Managing the Huong River and Dyke Management Department of Thua Thien Hue to combat soil erosion on the banks of major rivers such as Huong River, Xuoc Du River, Bo River... In 2006, the Institute of Geological Mineral 85 with International Networks tested the capacity of Vetiver to treat soil contaminated with dioxins in A So airport of A Luoi district belonging to Thua Thien Hue province. Currently, the area and extent of use of this grass species are still restricted; that is because this species can grow well in ecological areas so people fear that it would develop into a disastrous kind of weed. Furthermore, there is not enough supply of seedlings for combating land erosion in the river, road slopes and other purposes, all of which require a very large number of seedlings. This article introduces some results on reproductive characteristics and methods of asexual propagation by cuttings in Hue Vetiver cuttings under the action of some growth regulating substances. 2 Methods + Subject matter: Vetiver grass - Vetiveria zizanioides (L.) Nash. [7] + Methodology: To explore the possibility of seed germination by choosing Vetiver grass seeds grown during summer. These seeds were sterilized by the method of George (1993), then planted into Murashige and Skoog environment (1962); no growth regulators were added. The ability of seeds to germinate was then monitored. [6] Research was carried out on the measure of Vetiver grass cuttings by means of stem cuttings from mature stems treated with growth regulators at different concentrations. [4] Statistics and data were analyzed and processed using Microsoft Excel 2003. 3 Results and discussion 3.1 Reproductive characteristics of Vetiver 3.1.1 The ability of Vetiver seeds to germinate The results observed on morphological characteristics showed that Vetiver seed had no endosperm. However, in some cases, seeds which did not have endosperm but had embryo were still able to germinate in Murashige and Skoog (MS) nutrient environment, as in the case of Orchid seeds. To confirm whether the seeds of this plant could grow into a tree or not, we inquired into the ability of Vetiver seeds to germinate in the soil environment and Murashige and Skoog environment completely disinfected. After having riped, Vetiver grass seed was planted in MS environment and soil environment. As we observed the process of seed germination, the results showed that no seed germinated in both environments. On the other hand, for the immature seeds (approximately 16 days after bloom), we observed that 15 days after the seeds were sowed into the MS environment, the anther was still blue-yellow in color but did not open to pollinate, so it was difficult for these seeds to germinate. 86 According to Pham Hong Duc Phuoc, the grass Vetiveria zizanioides are low quality seeds which cannot germinate [2]. As Chomchalow [3] and Hanping [5] pointed out, most of Vetiver seeds easily lost the ability to germinate only a short time after falling because they are sensitive to environmental factors such as drought, wind, sunlight. 3.1.2 Reproduction by budding form We observed the time of bloom and seed-making of Vetiver from June to November for many years. During the period from December to July of the following year, we conducted an investigation and observed that no Vetiver seeds which fell from the mother plant onto the ground within a radius of 150-200m germinated into saplings. However, the seedlings were formed by budding from the stump of the mother plant or from the internode of the tree-trunk which was blossoming. Fig. 1. Vetiver reproduced by sprouting from flowered tree-trunk Fig. 2. Vetiver reproduced by budding from the root of the mother plant The results from our study are relatively close to that of Thai Phien; it shows that Vetiver seeds do not germinate in natural conditions because embryos are smaller; the seeds have fewer chances of survival so they would not develop into a kind of disastrous weed. The main method of reproduction of this species is by budding formed in stump nodules from the mother plant [1]. 3.2 Propagation method by separating bud We separated buds from the mature shoot, the buds being cut at about 20cm and the root length was about 1-2 cm. Each bud was kept in a plastic bag containing polyethylen (PE), usually a mixture of rice husk ash, manure and a little rich soil. The size of PE plastic bags used was 15x5cm, 7 cm in diameter with paddle environment. The results in figure 3 show that after the buds have been kept in a PE plastic 87 bag and taken care of for 14 days, the new roots began to emerge on the new shoots; the root percentage increased in the next day. The highest rate was 60% on 21th date, after that the remaining buds no longer develop into roots. The method of asexual propagation by separating grass into single bud cuttings in plastic bags containing PE gave a higher proportion of living plant and a higher possibility of roots growing faster compared to the traditional method which used bare root buds. This method is simple and easy to apply widely in actual production. However, this method has many shortcomings, namely a large number of shoots required occupying large areas and high cost of labor, so the production cost will be high. Moreover, seedlings have low uniformity and the propagation coefficient is not high. (%) 70 60 50 40 30 20 10 0 (date) 0 14 15 16 17 18 19 20 21 22 23 24 25 Fig. 3. The rate of the roots of Vetiver grass cuttings by bud 3.3 Fig. 4. Vetiver grass is propagated from shoots The impact of agent growth regulators on the possibility of their rooting Vetiver belongs to Poaceae set including many root germs which exist in tissue and produce internodes. Thus, the ability of plant roots is easier than those of dicot species. Furthermore, this species has a well developed root system so creating the root is not difficult. On that basis we have used growth regulators such as IAA, IBA and NAA on the cuttings to shorten the time of the root formation and increase the percentage of cuttings. Results from the research on the effect of IBA, IAA, NAA at the concentrations: 250, 500, 750, 1000ppm on the growth of Vetiver cuttings are presented in table 1. Results showed that for this kind of cuttings, the time of root formation is shorter than that of young cuttings when using substances with growth regulators at the same concentration to stimulate the cutting to develop roots. Table 1 shows that each growth regulator needs a different amount of time for the root formation and development. NAA needs 15 days, whereas IAA needs 16 days and IBA 17 days. After 18 days, there 88 are no changes in the rate of the root development from the cuttings in the laboratory formula. Table 1. The time and the rate of the root cuttings of processing substances growth regulators Growth regulators IBA IAA NAA Confronting Time out roots (date) The root ratio 15 16 17 n (%) 30 - - + 5 16,67 5 500 30 - - + 11 36,67 11 750 30 - - + 7 23,33 7 1000 30 - - + 14 46,67 14 250 30 - + + 7 23,33 7 500 30 - + + 16 53,33 16 750 30 - + + 11 36,67 11 1000 30 - + + 19 63,33 19 250 30 + + + 10 33,33 10 500 30 + + + 20 66,67 20 750 30 + + + 13 43,33 13 1000 30 + + + 16 53,33 16 0 30 - - + 4 13,33 4 Concentrations (ppm) number of cuttings 250 Plant cuttings When we treated mature cuttings by NAA, we observed that the roots grow at a higher rate compared with the control (13,33%). In terms of percentage, the roots at a concentration of 500ppm NAA rooting give the highest percentage (66,67%). In terms of average length, the roots at a concentration of 750ppm NAA have the longest root length (7,15 cm) but the rate of the roots is only 43.33%. In overall, our preliminary conclusion is that the concentration of 1000ppm NAA is optimal for the growth of the roots of vetiver cuttings because the roots are the targets of average/highest (4,56) and average length of roots (6,25 cm) high. Table 2. Quality of recipe the root cuttings Growth regulators IBA Concentrations (ppm) average root/ cutting average root (cm) the root index 250 1,56 ± 0,03 2,50 ± 0,04 3,90 500 2,67 ± 0,05 5,90 ± 0,10 15,75 750 2,50 ± 0,04 3,17 ± 0,06 7,93 1000 3,75 ± 0,07 5,51 ± 0,10 20,66 250 1,0 ± 0,02 1,85 ± 0,03 1,85 89