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Abstract Idesia polycarpa Maxim. var. vestita Diels is an important oil plant with high economic value. In order to improve seed germination and to cultivate high quality seedlings， we set out to identify an optimal medium for its seedling growth in a plastic cave tray （plug seedling）. In this study， four different media including M1 （soil）， M2 （peat∶perlite=2∶1）， M3 （peat）， and M4 （peat∶perlite∶vermiculite=2∶1∶1） were tested in industrialized plug seedlings. The seedling growth of Idesia polycarpa var. vestita including plant height， crown diameter， leaf number， ground diameter， the relative chlorophyll contents of leaves， etc. was measured. The results indicated that the medium M2 was the best for increasing seedling height， crown diameter， leaf counts， ground diameter， and the relative chlorophyll contents of leaves. Therefore， medium M2 is recommended in the industrialized nursery process for the seedling growth of Idesia polycarpa var. vestita.
Key words Idesia polycarpa var. vestita; Medium formulation; Plug seedling; Seedling growth
Received： May5， 2021 Accepted： July 7， 2021
Supported by the grant from forestry science and technology innovation research project of Anhui province， China （AHLYCX-2021-07）.
Jingbo ZHOU （1967-）， Female， P. R. China， professor， senior engineer， devoted to research about garden plants and ornamental horticulture.
Zirui ZHAO （1991-）， Male， P. R. China， engineer， devoted to research about bioengineering.
# These authors contributed equally to this work.
*Corresponding author. E-mail： [email protected].
Idesia polycarpa Maxim. var. vestita Diels， a member of the Flacourtiaceae family， is a deciduous arbor， distributed in the Dabie mountain area of Anhui Province and other provinces in China and Japan. This species has a straight trunk， beautiful canopy， and abundant flowers （inflorescences）. In the fall， its red dangling fruits are especially eye-catching. Idesia tree is a fast-growing heliophile species， and is adaptable to most harsh climates. As a result， it is an ideal tree species for converting farmland to forest and for urban greening and decoration. In addition， it is also a species of woody oil tree widely distributed in China[1-3].
Because of the inherent dormancy characteristics of Idesia polycarpa var. vestita seeds and the natural environmental inhibitory factors， its seed germination rate is quite low， which negatively impacts the utilization of I. polycarpa var. vestita. We have conducted research to identify ways to accelerate its seed germination， and to evaluate the health status and the ecological community characters of I. polycapa var. vestita in the Dabie mountain area of Anhui. In order to improve the seed germination rate and cultivate high quality seedlings， we searched for an optimal cultivation medium for seedling growth of I. polycarpa var. vestita in a plastic cave tray （plug seedling）. In this study， we used the method of hole tray nursery to screen different cultivation media to find the most appropriate soilless substrate formula and conditions for Idesia tree seed germination and seedling growth. The objective of this research is to provide techniques to produce healthy I. polycarpa var. vestita seedlings for industrial application. Materials and Methods
Materials
Mature I. polycarpa var. vestita fruit was collected from Yaoluoping area， Anqing， Anhui Province.
Methods
On February 8， 2020， we stored the mature I. polycarpa var. vestita fruits in trays with alternating layers of wet sand and fruits （sand as the top layer）. They were kept in a refrigerator at 5 ℃ and a relative humidity of 60%. A month later （March 8）， the fruit was returned to room temperature， and the fruit skin was removed. After cleaning and rinsing in distilled water， seeds were laid on gauze to dry.
On March 17， seeds were immersed in 15 g/L KH2PO4 solution for 24 h[4] and then in the 200 mg/L GA3 solution for 15 h[5]. On March 19， the seeds were taken out from the GA3 solution and rinsed with distilled water and dried at room temperature before planting. Four types of media including M1 （soil as a control）， M2 （peat∶perlite=2∶1）， M3 （peat）， and M4 （peat∶perlite∶vermiculite=2∶1∶1） were tested in plug seedling， one hole tray （50 holes per hole tray） for one medium. Each medium was replicated three times. A total of 12 hole trays were used. A completely randomized block design was applied for this test.
Measurement indicators
The germination number was counted at different times， starting at day 22 after planting （April 9， 2020） and ending at day 54 after planting （May 1 2020）. At the same times， the leaf number of the seedlings was counted. The seedling height （cm） and the crown/ground diameters （cm） were measured with a ruler or vernier caliper. The relative chlorophyll contents of leaves （SPAD） were measured with a chlorophyll meter （SPAD-502 plus）. Data were collected at seven different time points， each with 9 seedlings per medium， and the averages were used for comparison.
Results and Analysis
The effect of different media on germination numbers of I. polycarpa var. vestita seeds
The media M M3， and M4 accelerated the germination of the I. polycarpa var. vestita seeds in comparison to the control M1 （Fig. 1）. Among them， M2 performed the best and had the highest germination rate with a final value of 12%. Although M3 had a smaller bud number than the control M1 on the 22nd and the 23rd d after planting （April 9 and 10， 2020）， M3 had a higher number than M1 on April 13 and had an increasing trend thereafter， but always less than M2. From the 47th d after planting （May 4， 2020）， the germination number no longer increased anymore using M3; M4 on the 22nd d after planting （April 9， 2020） had smaller sprout number than M1. From the 23rd d after planting （April 10， 2020）， no difference in germination number was observed between M4 and M1. From April 14， M4 had greater germination number than M but much smaller than M2 and M3. As a result， we can conclude that M2 had the best improvement in the seed germination of I. polycarpa var. vestita. The influence of different media on seedling leaf numbers of I. polycarpa var. vestita
As indicated in Fig. M2 had the greatest impact on the increase in the number of seedling leaves of I. polycarpa var. vestita. Although M3 and M4 both increased seedling leaf number in comparison with M1 during the overall experimental period， M3 had a slightly greater effect than the M4. However， it was still much less than M demonstrating that M2 had the largest effect on the increase of the number of leaves of I. polycarpa var. vestita.
The influence of different media on seedling heights of I. polycarpa var. vestita
The media M M3， and M4 significantly increased I. polycarpa seedling heights compared with the control M1 during the overall experimental period， indicating all media were better than soil for the seedling growth in height （Fig. 3）. Among them， the effect of M2 was the greatest， suggesting that M2 was the best medium among the four to promote the I. polycarpa var. vestita seedling growth in height.
The influence of different media on the crown diameters of I. polycarpa var. vestita
The media M M3， and M4 significantly increased I. polycarpa var. vestita seedling crown diameter when compared with the control M indicating all media were better than soil for the seedling growth （Fig. 4）. Among them， the M2 gave rise to the largest crown diameter， suggesting that M2 is the best medium to promote the I. polycarpa var. vestita seedling growth. Seedlings that can quickly form a bigger crown have the advantage of growing to trees with high ornamental value.
The influence of the different media on the ground diameters of I. polycarpa var. vestita
Compared with the control M M2 significantly increased I. polycarpa var. vestita seedling ground diameter， while the increases in seedling ground diameter using M3 and M4 were not significant， indicating that M2 was most helpful for the seedling ground diameter growth of I. polycarpa var. vestita （Fig. 5）.
The influence of different media on the relative chlorophyll contents of leaves of I. polycarpa var. vestita
The chlorophyll content in plant leaves can be a measure of the overall conditions of plants. Generally， the healthier the plant， the higher the chlorophyll content. The SPAD indicates the relative amount of chlorophyll in the leaves. On the 57th d after planting （May 14， 2020）， the relative contents of chlorophyll in the leaves of I. polycarpa var. vestita using M M3， and M4 were greater than that using the control M1. The effects of M2 and M3 were higher than that of M4. On the 58th d after planting （May 15， 2020）， M2 had the largest impact on relative content of chlorophyll， and M3 the second largest. On the 59th d after planting （May 16， 2020）， there was a similar trend with the 15th measurement results， but the M4 was similar to that of M1. On the 60th d after planting （May 17， 2020）， only M2 and M3 had more， but M4 had less effect on the relative content of chlorophyll than M1 did. On the 61st d after planting （May 18， 2020）， only M2 had more positive effect on the relative content of chlorophyll than M1 did， indicating that M2 was good for maintaining the relative high content of chlorophyll in the leaves of I. polycarpa var. vestita. Conclusions and Discussion
Collectively， the results indicated that the medium M2 is the best for increasing seed germination and overall health of the seedlings including plant height， crown diameter， leaf counts， ground diameter， and the relative chlorophyll contents of leaves. Therefore， we recommend to use M2 in the industrialized nursery process for the seed germination and seedling growth of I. polycarpa var. vestita.
The conclusion of this experiment is that medium M2 （peat∶perlite=2∶1） is the optimal cultivation medium for I. polycarpa var. vestita seedling growth. A similar result was found that the medium M2 was the optimum material for soilless cultivation of Begonia semperflorens[6]. Therefore， medium M2 is recommended in the industrialized nursery process for the seedling growth of I. polycarpa var. vestita.
References
[1] DAI GF， XIE SY， WAN T， et al. Outlook and prospect for Idesia polycarpa exploitage[J]. Journal of Chongqing Three Gorges University， 201 27（132）： 105-109.
[2] WU OZ. Review and expectation on development and use of Idesia polycarpa Maxim. var. vestita Diels in China[J]. China Oils and Fats， 201 36（6）： 54-57.
[3] JIANG XB， LI DW， GONG BC， et al. Primary studies on growth regulation of seedling of Idesia polycarpa Maxim. from different populations[J]. Journal of Henan Agricultural Sciences， 201 41（5）： 133-136.
[4] ZHOU JB， JING Y， ZHAO ZR， et al. Improvement of seed germination of Idesia polycarpa var. vestita by dewaxing and low temperature treatment in moist sand[J]. Journal of Anhui Agricultural University， 2015， 42（2）： 159-164.
[5] LIU XM， SUI LY， LI ZQ， et al. Studies on technique of improving seed germination of Idesia polycarpa Maxim[J]. Acta Agriculturae Boreali-occidentalis Sinica， 2009， 18（4）： 324-327.
[6] ZHOU JB， HUANG CL， BU CX， et al. Selection of substrate for cultivation of Begonia semperflorens Link et Otto cv. Cocktail series[J]. Journal of Anhui Agricultural University， 2009， 36 （1）： 81-84.
Key words Idesia polycarpa var. vestita; Medium formulation; Plug seedling; Seedling growth
Received： May5， 2021 Accepted： July 7， 2021
Supported by the grant from forestry science and technology innovation research project of Anhui province， China （AHLYCX-2021-07）.
Jingbo ZHOU （1967-）， Female， P. R. China， professor， senior engineer， devoted to research about garden plants and ornamental horticulture.
Zirui ZHAO （1991-）， Male， P. R. China， engineer， devoted to research about bioengineering.
# These authors contributed equally to this work.
*Corresponding author. E-mail： [email protected].
Idesia polycarpa Maxim. var. vestita Diels， a member of the Flacourtiaceae family， is a deciduous arbor， distributed in the Dabie mountain area of Anhui Province and other provinces in China and Japan. This species has a straight trunk， beautiful canopy， and abundant flowers （inflorescences）. In the fall， its red dangling fruits are especially eye-catching. Idesia tree is a fast-growing heliophile species， and is adaptable to most harsh climates. As a result， it is an ideal tree species for converting farmland to forest and for urban greening and decoration. In addition， it is also a species of woody oil tree widely distributed in China[1-3].
Because of the inherent dormancy characteristics of Idesia polycarpa var. vestita seeds and the natural environmental inhibitory factors， its seed germination rate is quite low， which negatively impacts the utilization of I. polycarpa var. vestita. We have conducted research to identify ways to accelerate its seed germination， and to evaluate the health status and the ecological community characters of I. polycapa var. vestita in the Dabie mountain area of Anhui. In order to improve the seed germination rate and cultivate high quality seedlings， we searched for an optimal cultivation medium for seedling growth of I. polycarpa var. vestita in a plastic cave tray （plug seedling）. In this study， we used the method of hole tray nursery to screen different cultivation media to find the most appropriate soilless substrate formula and conditions for Idesia tree seed germination and seedling growth. The objective of this research is to provide techniques to produce healthy I. polycarpa var. vestita seedlings for industrial application. Materials and Methods
Materials
Mature I. polycarpa var. vestita fruit was collected from Yaoluoping area， Anqing， Anhui Province.
Methods
On February 8， 2020， we stored the mature I. polycarpa var. vestita fruits in trays with alternating layers of wet sand and fruits （sand as the top layer）. They were kept in a refrigerator at 5 ℃ and a relative humidity of 60%. A month later （March 8）， the fruit was returned to room temperature， and the fruit skin was removed. After cleaning and rinsing in distilled water， seeds were laid on gauze to dry.
On March 17， seeds were immersed in 15 g/L KH2PO4 solution for 24 h[4] and then in the 200 mg/L GA3 solution for 15 h[5]. On March 19， the seeds were taken out from the GA3 solution and rinsed with distilled water and dried at room temperature before planting. Four types of media including M1 （soil as a control）， M2 （peat∶perlite=2∶1）， M3 （peat）， and M4 （peat∶perlite∶vermiculite=2∶1∶1） were tested in plug seedling， one hole tray （50 holes per hole tray） for one medium. Each medium was replicated three times. A total of 12 hole trays were used. A completely randomized block design was applied for this test.
Measurement indicators
The germination number was counted at different times， starting at day 22 after planting （April 9， 2020） and ending at day 54 after planting （May 1 2020）. At the same times， the leaf number of the seedlings was counted. The seedling height （cm） and the crown/ground diameters （cm） were measured with a ruler or vernier caliper. The relative chlorophyll contents of leaves （SPAD） were measured with a chlorophyll meter （SPAD-502 plus）. Data were collected at seven different time points， each with 9 seedlings per medium， and the averages were used for comparison.
Results and Analysis
The effect of different media on germination numbers of I. polycarpa var. vestita seeds
The media M M3， and M4 accelerated the germination of the I. polycarpa var. vestita seeds in comparison to the control M1 （Fig. 1）. Among them， M2 performed the best and had the highest germination rate with a final value of 12%. Although M3 had a smaller bud number than the control M1 on the 22nd and the 23rd d after planting （April 9 and 10， 2020）， M3 had a higher number than M1 on April 13 and had an increasing trend thereafter， but always less than M2. From the 47th d after planting （May 4， 2020）， the germination number no longer increased anymore using M3; M4 on the 22nd d after planting （April 9， 2020） had smaller sprout number than M1. From the 23rd d after planting （April 10， 2020）， no difference in germination number was observed between M4 and M1. From April 14， M4 had greater germination number than M but much smaller than M2 and M3. As a result， we can conclude that M2 had the best improvement in the seed germination of I. polycarpa var. vestita. The influence of different media on seedling leaf numbers of I. polycarpa var. vestita
As indicated in Fig. M2 had the greatest impact on the increase in the number of seedling leaves of I. polycarpa var. vestita. Although M3 and M4 both increased seedling leaf number in comparison with M1 during the overall experimental period， M3 had a slightly greater effect than the M4. However， it was still much less than M demonstrating that M2 had the largest effect on the increase of the number of leaves of I. polycarpa var. vestita.
The influence of different media on seedling heights of I. polycarpa var. vestita
The media M M3， and M4 significantly increased I. polycarpa seedling heights compared with the control M1 during the overall experimental period， indicating all media were better than soil for the seedling growth in height （Fig. 3）. Among them， the effect of M2 was the greatest， suggesting that M2 was the best medium among the four to promote the I. polycarpa var. vestita seedling growth in height.
The influence of different media on the crown diameters of I. polycarpa var. vestita
The media M M3， and M4 significantly increased I. polycarpa var. vestita seedling crown diameter when compared with the control M indicating all media were better than soil for the seedling growth （Fig. 4）. Among them， the M2 gave rise to the largest crown diameter， suggesting that M2 is the best medium to promote the I. polycarpa var. vestita seedling growth. Seedlings that can quickly form a bigger crown have the advantage of growing to trees with high ornamental value.
The influence of the different media on the ground diameters of I. polycarpa var. vestita
Compared with the control M M2 significantly increased I. polycarpa var. vestita seedling ground diameter， while the increases in seedling ground diameter using M3 and M4 were not significant， indicating that M2 was most helpful for the seedling ground diameter growth of I. polycarpa var. vestita （Fig. 5）.
The influence of different media on the relative chlorophyll contents of leaves of I. polycarpa var. vestita
The chlorophyll content in plant leaves can be a measure of the overall conditions of plants. Generally， the healthier the plant， the higher the chlorophyll content. The SPAD indicates the relative amount of chlorophyll in the leaves. On the 57th d after planting （May 14， 2020）， the relative contents of chlorophyll in the leaves of I. polycarpa var. vestita using M M3， and M4 were greater than that using the control M1. The effects of M2 and M3 were higher than that of M4. On the 58th d after planting （May 15， 2020）， M2 had the largest impact on relative content of chlorophyll， and M3 the second largest. On the 59th d after planting （May 16， 2020）， there was a similar trend with the 15th measurement results， but the M4 was similar to that of M1. On the 60th d after planting （May 17， 2020）， only M2 and M3 had more， but M4 had less effect on the relative content of chlorophyll than M1 did. On the 61st d after planting （May 18， 2020）， only M2 had more positive effect on the relative content of chlorophyll than M1 did， indicating that M2 was good for maintaining the relative high content of chlorophyll in the leaves of I. polycarpa var. vestita. Conclusions and Discussion
Collectively， the results indicated that the medium M2 is the best for increasing seed germination and overall health of the seedlings including plant height， crown diameter， leaf counts， ground diameter， and the relative chlorophyll contents of leaves. Therefore， we recommend to use M2 in the industrialized nursery process for the seed germination and seedling growth of I. polycarpa var. vestita.
The conclusion of this experiment is that medium M2 （peat∶perlite=2∶1） is the optimal cultivation medium for I. polycarpa var. vestita seedling growth. A similar result was found that the medium M2 was the optimum material for soilless cultivation of Begonia semperflorens[6]. Therefore， medium M2 is recommended in the industrialized nursery process for the seedling growth of I. polycarpa var. vestita.
References
[1] DAI GF， XIE SY， WAN T， et al. Outlook and prospect for Idesia polycarpa exploitage[J]. Journal of Chongqing Three Gorges University， 201 27（132）： 105-109.
[2] WU OZ. Review and expectation on development and use of Idesia polycarpa Maxim. var. vestita Diels in China[J]. China Oils and Fats， 201 36（6）： 54-57.
[3] JIANG XB， LI DW， GONG BC， et al. Primary studies on growth regulation of seedling of Idesia polycarpa Maxim. from different populations[J]. Journal of Henan Agricultural Sciences， 201 41（5）： 133-136.
[4] ZHOU JB， JING Y， ZHAO ZR， et al. Improvement of seed germination of Idesia polycarpa var. vestita by dewaxing and low temperature treatment in moist sand[J]. Journal of Anhui Agricultural University， 2015， 42（2）： 159-164.
[5] LIU XM， SUI LY， LI ZQ， et al. Studies on technique of improving seed germination of Idesia polycarpa Maxim[J]. Acta Agriculturae Boreali-occidentalis Sinica， 2009， 18（4）： 324-327.
[6] ZHOU JB， HUANG CL， BU CX， et al. Selection of substrate for cultivation of Begonia semperflorens Link et Otto cv. Cocktail series[J]. Journal of Anhui Agricultural University， 2009， 36 （1）： 81-84.