The Effects on the Cutting Propagation of Cinnamomum micranthum in Different Seasons

Bihua CHEN，Shaohua HUANG，M eifang XIE，Juan ZHANG ，Liuying CHEN，Xiaohan SHE，Huihua FAN，Qianzhen LI

1.Fujian Academy of Forestry Sciences，F(xiàn)uzhou 350012，China；2.Jian'ou Forestry Technology Extension Center，Jian'ou 353100，China

1 Introduction

Cinnamomum micranthum（Hayata）Hayata is a rare buteconomically important tree species native to Taiwan province，Guangxi province，Guangdong province，Hunan province and Fujian province，China.C.micranthum produces an excellent quality timber for ship-and furniture-making as it possesses the qualities of a pleasing fragrance，straight wood texture，and a uniform and exquisite structure.The camphor oil extracted from C.micranthum is heavier than water and expensive.It grew at low altitude and was heavily destroyed.The fruits are subjected to the pest's damage，and most of the seeds are hollow，therefore the trees are dying out.This species was listed on one of China Third-class Endangered Tree Species in 1982.The seeds and seedlings are very difficult to obtain.It is important to study the cutting propagation of C.micranthum in different seasons to improve the rooting rate，so as to provide seedling propagation technique for the afforestation industry.The cutting propagation of C.micranthum was studied by Zhang（2000），Geng（2006），F(xiàn)eng et al.（2007）and Chen et al（2014），and the highest rooting rate was 51.7% （Zhang，2000），50% （Feng et al.，2007）or 70.6% （Chen et al，2014）and yet these approaches have been unable to provide sufficient clonal material for afforestation.Therefore，we revisit cutting propagation for this species with the aim of further optimizing propagation parameters in seasons to support afforestation of this important economic tree species.

2 Material and methods

2.1 The site conditionsThe experimental site is located at the nursery of Fujian Academy of Forestry Sciences，China（longitude 119°17′05.79″East，latitude 26°09′02.87″North）.It belongs to the subtropical maritime monsoon climate zone with mild climate and plentiful rainfall.The frost free period lasts for 326 days per year.Annual average temperature is 19.6℃.The average temperature during the coldest January is 10.5℃，and the average temperature during the hottest July is28.6℃.The average relative humidity is77%，and annual rainfall is1342.5mm.

2.2 Media preparationThe local new red-core soil was pulverized to form the media for cutting propagation.Plastic basins with drain holes，length 40cm×width 30 cm×height 30 cm were filled with the soil then placed in a greenhouse with 70%shade level.The media was then sterilized by0.1‰ KMnO4and covered by the plastic film for 3 days prior to use.

2.3 The source of the scionsIn September 2013 scions were taken from 10-to 11-year-old stock trees of C.micranthum in Jian'ou City.The stock trees were cut at the height of 1 meter 1 year earlier to induce juvenile shoots for tested scions.Pests and diseases free，vigorously growing branches were selected for scion material.

2.4 Experimental designAccording to previous study，the optimal plant growth regulator for the cutting propagation of C.micranthum was500 ppm IBA（Chen et al，2014）.500 ppm IBA was adopted in all tests in this study.The scions were taken from Jian'ou Fujian to Fuzhou Fujian.A randomized block design was used in this experiment，with 300 scions for each treatment and 3 replicates.The root system was rinsed and the cleaned roots were assessed for obtaining rooting rate，root number per individual cutting，and root length parameters.

2.5 Scion treatmentThe8－15 cm length branches with 3－5 leaves were trimmed as the scions.The top leaves were kept but lower leaves were cut half（See Fig.1）as previous study（Chen et al，2014）.The scions were cut and immersed immediately into the water in a large basin to prevent dehydration.Then all the scions were taken out and immersed into 1／1000 dilution of carben-dazim（effective constituent50%）for10－15minutes.The bases of scions were dipped with 500 ppm IBA for 5 minutes，then inserted into the soil to a depth of2／5－1／2 scion length by using a bamboo stick digging a hole prior to do it.30 scions were put in each plastic basin.The soil was pressed tightly after the scions were inserted then the soil was fully watered.

2.6 Scion managementTo maintain high humidity the tent containing the scions were enclosed in a transparent plastic paper.The soil and atmosphere was kept moist with an automated misting system by a supplemented with hand-watering with the frequency of once a day on sunny day or once per 2－3 days on cloudy or rainy day.The plastic tent was removed after watering and covered again immediately.The scions were sprayed by 1／800 dilution of carbendazim（effective constituent 50%），mancozeb（effective constituent80%）and difenoconazole（effective constituent10%）once a week.After 6 months（i.e.March of the following year）most of the new buds emerged，and the film was gradually taken off.The mist frequency was increased and the soil was kept wet.Two weeks after the film was taken off，the survival rate，rooting number per individual and root length were determined.

2.7 Statistics analysis methodThe data were analyzed by using SPSS Statistics 17.0 analysis of variance（ANOVA）and a post-hoc Tukey's test if the ANOVA was significant.Means were provided with standard errors，and means considered significantly different at P＜0.05.

3 Results

The experiment of cutting propagation was performed from September 2012 to April 2015.The results were shown on Table 1.The data were analyzed by the software SPSS 17.0.The cutting scions were treated by using 500 ppm IBA.The results indicated there were significant different among the different treatments，i.e.four different seasons.Firstly，the rooting rate of test No.2，Summer（may），was the highest of all，providing 80.6% （a）rooting rate；Secondly，the rooting rate of test No.3，Autumn（September），was 70.6% （b）；Thirdly，the rooting rate of test No.4，Winter（December），was65.4% （c）；the rooting rate of No.1，Spring（Mar），was the lowest of all，providing 47.2% （d）rooting rate.There were significant different among the average root number per individual in different seasons，among of which Test No.2，3 and 4 i.e.Summer，Autumn and Winter，were the best of all（a），but the worst was the No.1，Spring，4.3（b）only.There were significant different among the average root length in different seasons，among of which Test No.2，3 and 4 i.e.Summer，Autumn and Winter，were the best of all（a），but the worst was the No.1，Spring，2.3 cm（b）only.Therefore，Summer（May）was the best season for cutting propagation（Fig.1）.

Table 1 The analysis data of the cutting propagation of C.micranthum in different seasons

4 Discussions

（i）In conclusion，firstly，the optimal season for the cutting propagation of C.micranthum was Summer（May），providing highest rooting rate 80.6%.Secondly，the rooting rate of test No.3，Autumn（September），was70.6% （b）；Thirdly，the rooting rate of test No.4，Winter（December），was 65.4% （c）；the rooting rate of No.1，Spring（Mar），was the lowest of all，providing 47.2% （d）rooting rate.In this study the average rooting rate obtained was 80.6%by cutting，which was higher than that of Zhang（2000），F(xiàn)eng et al（2007），in the same species C.micranthum.（ii）Chinese researchers studied the cutting propagation of Cinnamomum camphor a which is the same family and same genus to C.micranthum.Liu et al（2003）used 400 ppm ABT1（Produced by Chinese Academy of Forestry）with which the rooting rate achieved 79.3% －94.3%；Huang et al（2008）used 100 ppm ABT treating for 720 minutes or 500 ppm ABT treating for 10 minutes with which the rooting rate achieved was 85%.Zhang et al（2006）used 300－500 ppm ABTwith which the rooting rate achieved was 90－100%.Long et al（1990）used 50 ppm IBA or NAA treating for 23 hours with which the rooting rate achieved 76－84%.The former，Liu et al（2003），Huang et al（2008），and Zhang et al（2006），adopted ABT but the latter，Long et al（1990），used IBA，which was the same plant growth regulator as that used in this experiment，but all the cutting rooting rates reported for C.camphora were higher than that of C.micranthum in the current experiment.The higher rates of rooting obtained for C.camphora is believed to be due to the fact that the branch of C.micranthum has medulla which is easily infected by fungus or bacteria from the soil，hence more cuttings are lost due to disease.（iii）The cutting propagation rate 80.6%in this study was 10%more than that of previous study（Chen et al，2014）.The rooting rate in Summer was33.4%higher than that of Spring.In Summer more lignified and semi-lignified branched were harvested than that in Spring，and the sap flowed quickly in the tree leading rooting quickly.In Fujian China it was cloudy ad rainy during the Spring leading the branches un-lignified，also the cold temperature caused the sap flowing slowly，therefore the cutting scions decayed quickly.That is reason why the cutting propagation rate in Summer was higher than that of Spring.（iv）The juvenile seedlings and cutting scions are easily subjected to the damage of termites.The nursery for cutting propagation of C.micranthum should be free of termites.（v）No literature reports the cutting propagation of C.micranthum affected by seasons.

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