GB2613253A

GB2613253A - Preparation for improving survival rate of colored-leaf poplar and application thereof

Info

Publication number: GB2613253A
Application number: GB2216337.2A
Authority: GB
Inventors: Zhuang Weibing; Shu Xiaochun; Wang Tao; Li Yuhang; Wang Zhong; Wang Ning; Zhang Fengjiao
Original assignee: Institute of Botany of CAS
Current assignee: Institute of Botany of CAS
Priority date: 2021-11-03
Filing date: 2022-11-03
Publication date: 2023-05-31
Anticipated expiration: 2042-11-03
Also published as: CN114009438B; GB2613253B; GB202216337D0; CN114009438A

Abstract

Preparation for improving a survival rate of colour-leaf poplar, wherein the active ingredients of the preparation comprise melatonin and indole butyric acid. Preferably, the concentration of IBA is 350-450 mg.L-1 and the concentration of N-[2-(5-methoxy-1H-indol-3-yl)ethyl]acetamide is 100 – 200 micromolar. Also claimed is a method for improving the survival rate of color-leaf poplar wherein the method comprises dipping a leafy stem cutting into the preparation described herein, and conducting cuttage. The leafy stem may be dipped for 4 seconds to 8 s. The leafy steam cutting may have 1-2 leaves and the leaves are cut off by one-third to a half. The leafy stem cutting may be obtained via cutting at 3-4 mm from a leaf base; such a cut may be horizontal if the upper end is cut and oblique if the lower end is cut.

Description

PREPARATION FOR IMPROVING SURVIVAL RATE OF COLOR-LEAF POPLAR

AND APPLICATION THEREOF

TECHNICAL FIELD

[0001] The present disclosure relates to the field of horticultural gardening, in particular to a preparation for improving a survival rate of color-leaf poplar and application thereof.

BACKGROUND

[0002] Populus cv. Thongshan Caiyun is the latest generation of new color-leaf poplar cultivar. The poplar cultivar has the advantages of bright color, stable performance, and excellent ornamental effect. It has obtained the National Forestry New Variety Protection Certificate at the end of December, 2020. The leaf colors of Populus cv. Zhongshan Caiyun show bright red, light yellow, orange, and yellow green from top to bottom in the growth period all year round, and it is a male plant, which will not cause ecological environment pollution due to floating flocs. Meanwhile, because of the strong adaptability of the cultivar. Populus cv. Zhongshan Caiyun can be planted in vast swathes of areas suitable for common poplar growth, and can be widely used in new rural construction, road aesthetics, and garden landscape configuration, with high economic, social and ecological value. Due to the large demand and slow breeding speed of Populus deltoides cv. Zhongshan Caiyun, it can no longer meet the needs of urban landscape and landscaping.

[0003] The breeding methods in plants mainly include hardwood cuttage, grafting, and softwood cuttage. However, when the color-leaf poplar is propagated by the above method, the survival rate of the color-leaf poplar can not be effectively improved. Therefore, in order to better propagate the color-leaf poplar, it is necessary to seek for an effective method for improving the survival rate of the color-leaf poplar.

SUMMARY

[0004] To solve the above problems, the present disclosure provides a preparation for improving a survival rate of color-leaf poplar and application thereof. The survival rate of the color-leaf poplar can be effectively increased by using the preparation provided by the present disclosure. [0005] To achieve the above objective, the present disclosure provides the following technical solutions: [0006] The present disclosure provides a preparation for improving a survival rate of color-leaf poplar. and active ingredients of the preparation include melatonin and indole butyric acid (IBA). [0007] Preferably, a concentration of the melatonin in the preparation may be 100-200 RM, and 1 a concentration of the IBA may be 350-450 mg/L.

[0008] The present disclosure provides an application of the foregoing preparation in improving the survival rate of the color-leaf poplar.

[0009] The present disclosure provides a method for improving a survival rate of color-leaf poplar, where the method includes the following steps: [0010] dipping a leafy stem cutting into the foregoing preparation, and conducting cuttage. [0011] Preferably, each leafy stem cutting may be dipped for 4-8s.

[0012] Preferably, in the cuttage, a plant spacing may be 40-60 cm, and a row spacing may be 60-80 cm.

[0013] Preferably, the leafy stem cutting may have 1-2 leaves; and the leaves may be cut off by 1/3 to 1/2.

[0014] Preferably, a method for obtaining the leafy stem cutting may be implemented as follows: cutting off at 3-4 mm from a leaf base of a cutting to obtain the leafy stem cutting.

[0015] Preferably, if the upper end of the cutting is cut off, a horizontal cutting method may be adopted; and if the lower end of the cutting is cut off, an oblique cutting method may be adopted. [0016] Preferably, the cutting may be 10-15 cm in length; and the cutting may be 0.4-0.7 cm in diameter.

[0017] The present disclosure has the following beneficial effects: The present disclosure provides a preparation for improving a survival rate of color-leaf poplar, and active ingredients thereof include melatonin and IBA. In the preparation provided by the present disclosure, the melatonin is a new hormone-like substance having a similar action to auxin, which has a promoting effect on the induction, generation and elongation of plant roots, and can induce the generation of adventitious roots of plants. IBA is a one of the auxins that are easy to synthesise artificially, and physiological effects thereof are mainly intended to cause cell elongation and bending, promote cell sorting, inhibit the growth of lateral buds and the formation of abscission layers, and are often used as exogenous auxin to promote rooting of cuttings. The present disclosure can effectively improve the survival rate of the color-leaf poplar after mixing the two active ingredients, so that the survival rate of the color-leaf poplar is increased from 30% to 94% and the efficient breeding of the color-leaf poplar is realised.

[0018] In addition, in order to solve the core problems of efficient breeding and high survival rate of the color-leaf poplar in the growth period, the present disclosure applies a preparation containing the melatonin and the IBA in the softwood cuttage of the color-leaf poplar, and finds out a set of mature softwood cuttage and breeding technology system of the color-leaf poplar, providing technical support for the scale development of the color-leaf poplar.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present disclosure provides a preparation for improving a survival rate of color-leaf poplar, and active ingredients of the preparation include melatonin and IBA. In the present disclosure, a concentration of the melatonin in the preparation may preferably be 100-200 pM, further preferably 120-180 pM, more preferably 140-160 pM, and most preferably 150 pNI; a concentration of the IBA in the preparation may preferably be 350-450 mg/L, further preferably 370-430 mg/L, more preferably 390-410 rng/L, and most preferably 400 mg/L. Different concentrations of the melatonin have different effects on the development of plant adventitious roots. For example, the rooting of pomegranate softwood cuttings can be promoted by using 1.16 mg/L melatonin, while 10 JIM melatonin can inhibit the generation of adventitious roots in cherry rootstocks and affect the root quality. In the present disclosure, by limiting the concentrations of the melatonin and the IBA, the two ingredients can better achieve the effect of improving the survival rate of the color-leaf poplar.

[0020] In the present disclosure, the melatonin and the IBA are used in the cuttage of the color-leaf poplar, which can effectively improve the survival rate of color-leaf poplar; in particular, the concentrations of the melatonin and the IBA in the preparation are formulated to enable reasonable collocation of efficacy thereof, which is particularly suitable for the growth requirements of the color-leaf poplar, so that the survival rate of the color-leaf poplar is increased from 30% to 94%, and the efficient breeding of the color-leaf poplar is realised. It can be seen that the preparation provided by the present disclosure can be used to improve the survival rate of color-leaf poplar.

[0021] The present disclosure provides an application of the foregoing preparation in improving the survival ratc of the color-leaf poplar. In the preparation provided by the present disclosure, the IBA is used as an exogenous auxin to promote the rooting of cuttings. However, this study finds that the survival rate is still lower than 50% although the survival rate of softwood cuttage of the color-leaf poplar can be significantly improved after treatment with IBA alone. The melatonin can promote the generation of adventitious roots, while having antioxidant activity; further, the melatonin and the IBA are used in combination in the present disclosure and concentrations are set, so that the generation of adventitious roots can be better facilitated and the survival rate of softwood cuttage is improved. The results of the specific examples of the present disclosure show that adopting the method provided by the present disclosure can increase the survival rate of the color-leaf poplar from 30% to 94%.

[0022] The present disclosure provides a method for improving a survival rate of color-leaf poplar. where the method includes the following steps: [0023] dipping a leafy stem cutting into the foregoing preparation, and conducting cuttage.

[0024] In the present disclosure, each leafy stem cutting may preferably be dipped for 4-8 s, and more preferably 5 s; the leafy stem cutting may preferably have 1-2 leaves, and more preferably 2 leaves, which can normally perform photosynthesis and provide nutrients for the leafy stem cutting; the leaves may preferably be cut off by 1/3 to 1/2, and more preferably 1/2, so as to reduce the loss of more water from the leafy stem cutting due to transpiration, causing plants to wither and die due to water loss and reducing the survival rate thereof.

[0025] In the present disclosure, a method for obtaining the leafy stem cutting may preferably be implemented as follows: cutting off at 3-4 mm from a leaf base of a cutting to obtain the leafy stem cutting. In the present disclosure, the cutting may preferably be a stem segment of the color-leaf poplar, more preferably a semi-lignified stem segment of the color-leaf poplar, and most preferably an annual stem segment of the color-leaf poplar; in terms of physiological properties, semi-lignified branches can transmit water throughout the branches, and the vitality of the semi-lignified branches is stronger than that of lignified branches; in terms of physical properties, the semi-lignified branches are softer and have certain toughness and hardness. In the present disclosure, the cutting may preferably be 10-15 cm in length; and the cutting may preferably be 0.4-0.7 cm in diameter. The use of the cutting provided by the present disclosure can avoid the situation that the cutting is too short to survive and too long to keep a branch. A longer diameter easily leads to lignification, while a shorter diameter leads to lignification not easily. Thus, the cutting provided by the present disclosure can further achieve an effect of reducing material costs and subsequent labor costs.

[0026] In the present disclosure, the leaf base may preferably be a position where a leaf bud is located before a leaf germinates. In the present disclosure, if the upper end of the cutting is cut off, a horizontal cutting method may preferably be adopted, which can reduce a contact surface with air, avoid excessive water loss, and reduce energy consumption; and if the lower end of the cutting is cut off, an oblique cutting method may preferably be adopted, which can increase the contact surface with soil and make rooting easier. The present disclosure can further ensure the survival rate of the color-leaf poplar in a manner of "horizontal cutting at the upper end and oblique cutting at the lower end". In the present disclosure, the upper end of the cutting may preferably be above the stem segment of the color-leaf poplar; the lower end of the cutting may preferably be below the stein segment of the color-leaf poplar; in the present disclosure, both the upper end of the cutting and the lower end of the cutting may preferably be morphologically named.

[0027] After the horizontal cutting, in the present disclosure, a cut obtained after the horizontal cutting may preferably be applied with vaseline or tied with a plastic film.

[0028] After the oblique cutting, in the present disclosure, a cut obtained after the oblique cutting may preferably be applied with the vaseline or tied with the plastic film.

[0029] In the present disclosure, applying the cut with vaseline or tying the cut with the plastic film after the horizontal or oblique cutting can better reduce a contact surface between the cut and the air, avoid excessive water loss, and further reduce energy consumption.

[0030] After obtaining the leafy stern cutting, the present disclosure may preferably further include performing moisturising treatment and bundling treatment on the leafy stem cutting. In the present disclosure, the moisturising treatment may preferably adopt water spraying on a newspaper for moisturising, namely, water spraying after laying the newspaper on the leafy stem cutting; the moisturising treatment may preferably be conducted at a humidity of 70wt.%-90wt.%, and more preferably 75wt.%-85wt.%; in the bundling treatment, 50 leafy stem cuttings may preferably be bundled into a bundle for use.

[0031] In the present disclosure, a method for the cuttage may preferably be softwood cuttage, which can be conducted in summer, make up for the shortcoming that hardwood cuttage can only be conducted in spring or autumn after leaves have fallen, and improve the number of outplanted color-leaf poplar seedlings. It can be seen that the softwood cuttage can effectively improve the breeding efficiency of the color-leaf poplar. In the present disclosure, in the cuttage, a plant spacing may preferably be 40-60 cm, more preferably 40-55 cm, and most preferably 40 cm; and row spacing may preferably be 60-80 cm, more preferably 60-75 cm, and most preferably 60 cm. In the present disclosure, the cuttage may preferably be conducted in a greenhouse, and more preferably on a seedbed in the greenhouse.

[0032] In the present disclosure, before the leafy stem cutting takes root, the greenhouse may preferably be covered with a sunshade net that can prevent the leaves of the leafy stem cutting from losing water and wilting.

[0033] In the present disclosure, before the cuttage, substrate blocks used for the cuttage may preferably be placed evenly on the seedbed; in the present disclosure, the substrate used for the cuttage may preferably be a commercialised Norwegian imported Jiffy Growblock. in the present disclosure, before use, it may be preferable to conduct soaking treatment and water control treatment on the Norwegian imported Jiffy Growblock; a specific step of the soaking treatment may preferably be to soak the Norwegian imported Jiffy Growblock in water; a specific step of the water control treatment may preferably be to take out after the Norwegian imported Jiffy Growblock is completely swollen by the water and to drain off the moisture in the Norwegian imported Jiffy Growblock; draining-off treatment is conducted until the Norwegian imported Jiffy Growblock no longer drips. The method provided by the present disclosure adopts the Norwegian imported Jiffy Growblock. The substrate block is characterised by air permeability, water retention and moisture retention, and can provide plants with nutrient elements, and the substrate block has been disinfected and can be used directly, omitting a process of preparing the substrate in common cuttage.

[0034] In the present disclosure, after the cuttage, an automatic sprinkler irrigation system may preferably be started to water the seedbed thoroughly; and an automatic sprayer in the automatic sprinkler irrigation system may preferably spray for 1 min every 2 h, so that relative humidity is controlled at around 85wt.%.

[0035] In the present disclosure, after the cuttagc, the leafy stern cuttings may preferably be disinfected once every 15 days, and dead leafy stem cuttings are sorted out in time to avoid infection of other leafy stem cuttings. In the present disclosure, disinfection is conducted in the early morning or evening; during the disinfection, a disinfectant used may preferably include carbendazim or thiophanatc-methyl; a concentration of the carbendazim or thiophanate-tnethyl may preferably be 0.1wt.%-0.5wt.%, further preferably 0.15wt.%-0.45wt.%, and more preferably 0.2wt.%-0.4wt.%; the disinfection may preferably be conducted in the form of spraying; and a dosage of the disinfectant may preferably be 50 glint'.

[0036] In the present disclosure, a foliar fertiliser may preferably be applied every 30 days after the leafy stem cutting takes root. In the present disclosure, the foliar fertiliser may preferably be applied by spraying; the foliar fertiliser may preferably be a urea solution; and a concentration of the urea solution may preferably be 0.5wt.%, which can supplement nutrient elements for the leafy stem cutting for seedling growth.

[0037] In the present disclosure, after the leaves of the leafy stem cutting fall off, new leaves emerge from axillary buds, and a root system becomes relatively developed, a fertiliser may preferably be applied to the seedbed; the fertiliser includes a mixed solution of ammonium nitrate and potassium dihydrogen phosphate; a concentration of the ammonium nitrate in the mixed solution may preferably be 3wt.%, and a concentration of the potassium dihydrogen phosphate may preferably be 3wt.%, so as to provide nutrients for the leafy stem cutting and promote the growth of the leafy stem cutting.

[0038] To further illustrate the present disclosure, the preparation for improving a survival rate of color-leaf poplar and application thereof provided by the present disclosure will be described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present disclosure.

[0039] Example 1

[0040] (1) Selection of cutting materials [0041] Semi-ligni lied stem segments of the color-leaf poplar in the current year were selected as cuttings. The cuttings were around 0.5 cm in diameter, and the cuttings were cut into cuttings with a length of around 10 cm.

[0042] (2) Selection of cutting substrate blocks [0043] The commercialised Norwegian imported Jiffy Growblocks were used. The Norwegian imported Jiffy Growblocks were soaked in water. After the substrate blocks were completely swollen by water absorption, they were taken out, and the moisture in the substrate blocks was drained off until substrate blocks no longer dripped, so that cutting substrate blocks were obtained for later use.

[0044] (3) Treatment of cutting materials [0045] Two leaves were reserved from each cutting prepared in step (1), and each leaf was cut off by 1/2; a cut was made at 3-4 mm close to the leaf base of the cutting, the upper end was cut horizontally, and the lower end was cut obliquely to obtain a leafy stem cutting; the leafy stem cutting was moisturised by water spraying on the newspaper, namely, water spraying after laying the newspaper on the leafy stem cutting. The humidity was held at 70wt.%-90wt.%, and every 50 leafy stem cuttings were bundled into a bundle for later use.

[0046] (4) Cuttage of leafy stem cuttings [0047] The greenhouse was covered with a sunshade net, the cutting substrate blocks were evenly placed on the seedbed in the cuttage greenhouse, and the leafy stern cuttings were quickly dipped in the preparation (each bundle was dipped for 5 s) and inserted into substrate blocks. After cuttage, an automatic sprinkler irrigation system was started to water the seedbed thoroughly. Herein, the preparation included melatonin and IBA, where the concentration of melatonin in the preparation was 150 pM, and the concentration of IBA was 400 mg/L.

[0048] (5) Post-cuttage management of leafy stem cuttings and statistics on the survival rate [0049] After the cuttage, the agricultural film of small arched shed was scaled to keep moist, and the automatic sprayer sprayed for 1 min every 2 h, so that the relative humidity was controlled at around 85wt.%, and it was advisable to attach a water film on the leaves.

[0050] One week after cuttage, the leafy stem cuttings began to take root. After cuttage, every 15 days in the early morning or evening, leaves were sprayed with 0.5wt.% carbendazim to disinfect once. The spraying dosage was 50 gltnu. Dead branches were sorted out in time to avoid infection of other branches.

[0051] After the leafy stem cuttings took root, normal seedling management was resumed, namely, the sunshade net was uncovered, and a 0.5wt.% urea solution was sprayed on the foliage every 30 days to supplement nutrient elements for seedling growth.

[0052] After the leaves of the leafy stem cuttings fallen off, new leaves emerged from axillary buds, and a root system became relatively developed, a mixed solution of 3wt.% ammonium nitrate and 3wt.% potassium dihydrogen phosphate was evenly sprayed on the seedbed to promote the seedling growth.

[0053] Example 2

[0054] In the same manner as in Example 1, the only difference was that the preparation for dipping leafy stem cuttings in this example included melatonin and IBA, where the concentration of melatonin in the preparation was 150 RM, and the concentration of IBA was 350 mg/L. [0055] Example 3 [0056] In the same manner as in Example 1, the only difference was that the preparation for dipping leafy stem cuttings in this example included melatonin and IBA, where the concentration of melatonin in the preparation was 150 RM, and the concentration of IBA was 450 mg/L. [0057] Example 4 [0058] In the same manner as in Example I, the only difference was that the preparation for dipping leafy stem cuttings in this example included melatonin and IBA, where the concentration of melatonin in the preparation was 100 RM, and the concentration of IBA was 400 mg/L. [0059] Example 5 [0060] In the same manner as in Example 1, the only difference was that the preparation for dipping leafy stem cuttings in this example included melatonin and IBA, where the concentration of melatonin in the preparation was 200 RM, and the concentration of IBA was 400 mg/L. [0061] Comparative Example 1 [0062] In the same manner as in Example I. the only difference was that leafy stem cuttings in this comparative example were not dipped in the preparation.

[0063] Comparative Example 2 [0064] In the same manner as in Example 1, the only difference was that leafy stem cuttings in this comparative example were dipped in IBA, where the concentration of IBA was 400 mg/L. [0065] Comparative Example 3 [0066] In the same manner as in Example 1, the only difference was that leafy stem cuttings in this comparative example were dipped in IBA, where the concentration of IBA was 350 mg/L. [0067] Comparative Example 4 [0068] In the same manner as in Example I. the only difference was that leafy stem cuttings in this comparative example were dipped in IBA, where the concentration of IBA was 450 mg/L. [0069] Comparative Example 5 [0070] In the same manner as in Example I, the only difference was that leafy stem cuttings in this comparative example were dipped in melatonin, where the concentration of melatonin was 100 RM.

[0071] Comparative Example 6 [0072] In the same manner as in Example 1, the only difference was that leafy stem cuttings in this comparative example were dipped in melatonin, where the concentration of melatonin was RM.

[0073] Comparative Example 7 [0074] In the same manner as in Example I. the only difference was that leafy stem cuttings in this comparative example were dipped in melatonin, where the concentration of melatonin was 200 RM.

[0075] Comparative Example 8 [0076] In the same manner as in Example I. the only difference was that leafy stem cuttings in this comparative example were dipped in melatonin and IBA, where the concentration of melatonin in the preparation was 150 04, and the concentration of IBA was 500 mg/L.

[0077] Comparative Example 9 [0078] In the same manner as in Example I. the only difference was that leafy stem cuttings in this comparative example were dipped in melatonin and IBA, where the concentration of melatonin in the preparation was 250 04, and the concentration of IBA was 400 mg/L.

[0079] Statistics were made on the survival rate of cuttage of leafy stem cuttings of Examples 1 to 5 and Comparative Examples 1 to 9 30 days after cuttage. The results are shown in Table I. [0080] Table 1 The survival rate of cuttage of leafy stem cuttings of Examples 1 to 5 and Com arative Exam les 1 to 9 Different treatments Number of cutting slips (slip) Survival rate of softwood cuttage (%) Comparative Example 1 No dipping preparation 100 30 used Comparative Example 2 400 mg/L IBA 100 46 Comparative Example 3 350 mg/L IBA 100 38 Comparative Example 4 450 mg/L IBA 100 35 Comparative Example 5 100 04 Melatonin 100 53 Comparative Example 6 150 pM Melatonin 100 62 Comparative Example 7 200 04 Melatonin 100 52 Comparative Example 8 500 mg/L IBA + 150 RM 100 50 melatonin Comparative Example 9 400 mg/L IBA + 250 RM 100 48 melatonin Example 1 400 mg/L IBA + 150 RM 100 94 melatonin Example 2 350 mg/L IBA + 150 RM 100 86 melatonin Example 3 450 mg/L IBA + 150 RIVI 100 84 melatonin Example 4 400 mg/L IBA + 100 RM 100 74 melatonin Example 5 400 mg/L IBA + 200 RM 100 70 melatonin [0081] As can be seen from the data recorded in Table 1, the survival rate of the leafy stem cuttings after respective treatment with MA (Comparative Example 2) and melatonin (Comparative Examples 3 to 7) was significantly higher than that after treatment in Comparative Example 1, but after a mixture of IBA and melatonin was used, the survival rate of the leafy stem cuttings was significantly higher than that after treatment with either of them alone, and in the presence of 400 mg/L IBA + 150 RM melatonin (Example 1), the survival rate of the leafy stem cuttings reached 94%. It can be seen that the present disclosure can effectively improve the survival rate of the color-leaf poplar after mixing both active ingredients, so that the survival rate of the color-leaf poplar is increased from 30% to 94% and the efficient breeding of the color-leaf poplar is realised.

[0082] It can be seen from records in the foregoing examples and comparative examples that the preparation provided by the present disclosure can effectively improve the survival rate of the color-leaf poplar, so that the survival rate is increased from 30% to 94% and the efficient breeding of color-leaf poplar is realised.

[0083] Although the present disclosure has been disclosed above with preferred examples, they are not intended to limit the present disclosure. Those skilled in the art can make various alterations and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope defined by the claims.

Claims

CLAIMSI. A preparation for improving a survival rate of color-leaf poplar, wherein active ingredients of the preparation comprise melatonin and indole butyric acid (IBA).
2. The preparation according to claim 1, wherein a concentration of the melatonin in the preparation is 100-200 uM, and a concentration of the IBA is 350-450 mg/L.
3. An application of the preparation according to claim 1 or 2 in improving a survival rate of color-leaf poplar.
4. A method for improving a survival rate of color-leaf poplar, wherein the method comprises the following steps: dipping a leafy stem cutting into the preparation according to claim 1 or 2, and conducting cuttage.
5. The method according to claim 4, wherein each leafy stem cutting is dipped for 4-8 s.
6. The method according to claim 4, wherein in the cuttage, a plant spacing is 40-60 cm, and a row spacing is 60-80 cm.
7. The method according to claim 4, wherein the leafy stem cutting has 1-2 leaves; and the leaves are cut off by 1/3 to 1/2.
8. The method according to claim 4, wherein a method for obtaining the leafy stem cutting is implemented as follows: cutting off at 3-4 mm from a leaf base of a cutting to obtain the leafy stem cutting.
9. The method according to claim 8, wherein if the upper end of the cutting is cut off, a horizontal cutting method is adopted; and if the lower end of the cutting is cut off, an oblique cutting method is adopted.
10. The method according to claim 8, wherein the cutting is 10-15 cm in length and the cutting is 0.4-0.7 cm in diameter.