Growth responses of five camellia species to air pollution from sulfur dioxide and fluoride

HU Xian-cong*  YIN Aihua
Foshan institute of Forestry, Foshan, Guangdong,China

Introduction

Environmental pollution is a severe issue for all the nations around the world. As modern industry develops and pollutant discharged into the air increases daily, the ecosystem has been destroyed. Air pollution and acid rain, which sabotage the ecosystem in one way or another [1-3],are among the grave environmental problems. Plants can purify the air through absorption, transition of the pollutant, as a result it can be treated as a feasible tool to avert air pollution and more emphasis has been deployed to it during these years. When selecting a series of forestation trees, one must put into consideration the resistance, absorption and purification ability, restoration function, etc, in addition to its landscape effect.

There is plenty source of Theaceae plants, which is rich in diversity. China has the longest history in Theaceae cultivation. However, only a few kinds of Theaceae plants have been cultivated and used for garden nowadays. Most of the Theaceae plants are still wild type or semi-wild type.

Therefore, it is necessary to carry out studies on wild-type Theaceae plants with high ornamental value. C.nitidissima belongs to the Theaceae family, which is sibling species with tea, C.japonica, C.reticulata, C.oleifera, C.sasanqua.

The C.nitidissima is usually evergreen and small trees up to 5 meters tall. Their leaves are dark green, thick, glossy, and serrated. Their flowers are truly yellow (golden yellow) and shining as there is a layer of wax on it. Its flowering period is from Nov to the next Mar. The discovery of the C.nitidissima shocked the cultivar world and got high-level attention from horticultures, and it was regarded as great material for the cultivation.

Through studying 5 species of Camellia plants including C.nitidissima growing in highly contaminated atmosphere filled with heavy SO₂ and fluoride, in this article the sample trees are rated into 2 degrees in terms of pollution resistance ability by synthesized growth index evaluation. On one hand, this will provide some proves for comprehending the anti-pollution ability of C.nitidissima, on the other hand, theoretical reference can be hoarded for introducing C.nitidissima into urban landscaping forestation. It is suggested that Camellia plants with robust resistance be spread into pollution-hit forestation projects, in a bid to pragmatically improve the local people’s production and living condition, at the same time rendering options and choices for urban garden. Applying these plants possessing aesthetic functions into modern urban garden forestation in a large amount can not only beauties the environment and enhances ecological benefit, but also cleanses the surroundings.

1  Materials and methods

1.1 Experiment area

The plants were grown at a polluted site of the reservoir of Tianzi near ceramic factories and a relative clean site of Yun Yong Forest Farm as control. Air monitoring date showed that the polluted area received remarkably higher sulfation rate and fluoride concentration than the clean site, which significantly exceeds emission limit of National standard.

1.2 Plant materials    

One-year-old nursery-grown plants of five Camellia species were collected and transplanted to plastic pots filled with homogenized soil in May. All the pots were marked and fertilized at the same time. The plants are grown at the same environment in the Foshan Institute of Forestry for about two months. After measurement of some growth parameters including plant height, basal diameter, crown area, they were transplanted to experiment sites in July. There are ten pots for each species. During the experimental period, every plant was treated by same measures. One year later we took the second measure.

Table 1: Five Camellia species

2 Results and analysis

2.1 Effects on increase rate of plant height

Plant height of the five species rate of increase all exceeded 0.8. And the rate of  C.nitidissima，C.oleifera and C.hongkongensis exceeded 1.0 which indicated these three species didn’t receive significant influence. While the rate of C.changii and C.caudata were between 0.8 and 1.0, which exhibited that the height growth of these two species has less tolerance.

Table 2  Increments of plant height, basal diameter and crown area

2.2 Effect on the increase rate of basal diameter

Sorting by the increase rate of basal diameter in a descending manner is that C.changii, C.nitidissima, C.hongkongensis, C.oleifera, C.caudata. Only the rate of C.changii exceeded 1.0. While the rate of C.oleifera and C.caudata was between 0.60 to 0.80.

2.3 Effects on increase rate of crown area

Sorting by the increase rate of crown area in a descending manner is that C.changii, C.nitidissima, C.hongkongensis, C.oleifera, C.caudata. And that the rate of forward four species all exceeded 1.0. While the rate of C.caudata was only 0.627.

2.4 Comprehensive growth index evaluation of plant resistance

Very complex response of plants to air pollution, a single growth indicators are difficult to accurately evaluate the extent of affected plants. The tested plants were sorted in terms of pollution resistance ability by synthesized growth index evaluation. Basal diameter, plant height, crown area respectively assigned to 0.25, 0.30, 0.45 weighting coefficients to calculate the ratio of the tested plants growth. Integrated higher the ratio, indicates that the plant is subject to atmospheric pollution affect the smaller, in turn, influenced by atmospheric pollution growth by more serious suppression.

View of the Theaceae plants generally have good resistance to atmospheric pollution, therefore, the ratio is greater than 0.80, defined as a strong resistance to sulfur fluoride plant. A high concentration of sulfur fluoride environment will not or is a slight degree of impact to these plants growth. The plants whose ratio ranges from 0.60 to 0.80 were defined as middling tolerant species. Ratio of less than 0.40-0.60 as weak resistance to sulfur the fluorine plant, these plants grow in high concentrations of sulfur fluoride environment will be subject to greater impact. The ratio is less than 0.40 of the plant taken as the sensitive plants, these plants are grown in a high concentration of sulfur fluoride environment will be seriously affected.

Table 3:  Complex growth rate of plants

Which can be seen in Table 3, tested 5 kinds of Camellia plants from high to low order C.changii, C.nitidissima, C.oleifera, C.hongkongensis, C.caudata, of which the first 4 kinds of Camellia plants of the integrated growth ratio was greater than 0.80, these plants affected by pollution smaller, are resistant plants; And C.caudata comprehensive growth ratio of 0.74, this shows it is middling tolerant species.

3 Discussions

The resistant ability to fluoride and sulfur dioxide in 5 species of Camellia plants was tested by growth index evaluation. The results of resistance research in C.oleifera of our study were consistent with what the previous researches, which agree that C.oleifera is a strong resistance to sulfur fluoride and sulfur dioxide plant. Nevertheless, C.changii and C.nitidissima have stronger resistance than C.oleifera in our research. Except the C.caudata, the other four kinds of camellia plants of the comprehensive growth ratio were greater than 0.80, all belong to resistant plants. And C.caudata defined as a middle resistance to sulfur fluoride plant. The survival rate of the 4 species of Camellia plants tested in clean area and pollution area were all 100%, which show the same growth in period of different area. That may be due to the plants had adapted to the new environment in a year of testing. And the mechanism of the changes will be studied in the next step.

In addition to being used for garden and business, camellia plants also have strong resistant ability to atmospheric fluorine sulfur pollution. They are valuable plant resources, with the prospect of development and utilization. At present, levels of development and utilization in many kinds of Camellia plants are low, besides C.oleifera is planted a large and the health care efficacy of C.nitidissima is bug up by many people. In our study, C.changii, C.hongkongensis and C.caudata are strong resistance to sulfur fluoride plants, which can be exploited greatly.

 * This project was supported by Foshan Sci.& Tech. Development Programme (200602005)