三种暖季型草坪草对二氧化硫抗性的比较

二氧化硫(SO_2)是城市大气污染的重要污染物之一,这已经越来越成为国家迫在眉睫须彻底解决的环境问题,解决SO_2污染问题仍是一个重要的生态与环保课题。草坪植物现已成为城市绿化的主要造景材料,依据植物对大气污染的反应特性来选择城市草坪草种,使之在发挥景观效果的同时,发挥其更好的生态效果。采用人工模拟熏气法,以CK(自然状态)、S1(4.29mg/m~3)、S2(6.44mg/m~3)、S3(8.58mg/m~3)、S4(10.73mg/m~3)5个SO_2浓度水平,对城市常用的3种暖季型草坪草:结缕草(Zoysiajaponica)、百喜草(Paspalum notatum)、狗牙根(Cynodon dactylon)进行SO_2胁迫处理,并测定3种草坪草生理生化指标,最终比较3种草坪草对SO_2的抗性。结果表明:随SO_2浓度增加,3种草坪草的可溶性糖含量(SS)、脯氨酸含量(Pro)、丙二醛(MDA)含量呈增加趋势;结缕草可溶性蛋白(SP)呈先降后升趋势,百喜草则呈先升后降趋势,狗牙根各胁迫处理下其SP含量均低于CK;结缕草和狗牙根过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性呈增加趋势,百喜草SOD和CAT活性呈先升后降趋势,同时其POD活性在各SO_2胁迫处理下均低于CK。将所有测定指标采用模糊数学隶属度公式进行综合相关分析,得出3种草坪草对SO_2的抗性由强到弱的排序为:结缕草狗牙根百喜草。结缕草在SO_2胁迫下与其它两种草坪草相比,表现出了更好的抗性能力,因此,在城市空气不断遭受污染的今天,结缕草可以作为热带和亚热带城市绿化草坪植物的优选草种之一。

Comparison study of sulfur dioxide resistance of three warm-season turf grasses

Sulfur dioxide (SO₂) is a major air pollutant and has a significant impact on the environment. Because of its widespread presence in air-pollution gases, SO₂ is one of the most important air pollutants in urban areas. Turf grasses are essential landscape plant species among the current urban greening, and understanding the physiological mechanism of turf grass resistance to SO₂ can help us choose suitable turf grass species for various types of lawn. In this study, three warm-season turf grasses-Zoysia (Zoysia japonica), Bahia (Paspalum notatum) and Bermuda (Cynodon dactylon)-growing under greenhouse conditions were selected and screened for tolerance to acute SO₂ injury. Five treatments including CK (0 mg/m³), S1 (4.29mg/m³), S2 (6.44mg/m³), S3 (8.58mg/m³) and S4 (10.73mg/m³) were used in this study, and release of SO₂ was achieved using the artificial simulated fumigation method. The plants screened for SO₂ injury were growing in a pair of sealed glass chambers in the greenhouse. Differential response to SO₂ injury among these three species was manifested by soluble sugar and protein content, and by the activities of peroxidase (POD), catalase (CAT) and the superoxide dismutase (SOD). Our results showed that the leaf content of soluble sugar, proline and malonaldehyde rose gradually as SO₂ concentration in the three grass species increased, each reaching its maximum at the level of 10.73mg/m³ SO₂. The relative increase of these three substances in Bahia was the largest among the three turf grass species, which suggested that Bahia was more susceptible than Zoysia and Bermuda to SO₂ injury. The accumulation of soluble protein in Zoysia showed a decline at 4.29mg/m³ SO₂ compared with the control, and reached its highest level at 10.73mg/m³ SO₂, whereas Bahia had the highest levels at 4.29mg/m³ SO₂. However, the accumulation of soluble protein in Bermuda decreased in all four SO₂ treatments compared with the control. These results implied that Zoysia is much more tolerant of SO₂ injury at higher concentrations than are Bahia and Bermuda. The activities of POD, SOD and CAT in Zoysia gradually increased with increments in SO₂ concentration compared with those in the control and reached the greatest level at the highest SO₂ treatment, achieving the highest levels of SO₂ at 10.73mg/m³. The activities of these three enzymes in Bermuda showed a similar trend to those in Zoysia, except that the relative increase was smaller. The activities of SOD and CAT in Bahia were higher at all four concentrations of SO₂ compared with those in the control, and the activities of SOD and CAT reached their highest levels at 6.44mg/m³ and 4.29mg/m³ SO₂, respectively. However, the activities of POD showed a reverse trend in Bahia compared with those in Zoysia and Bermuda; they gradually decreased, starting from the control through the four SO₂ treatments in ascending order. These results indicated that Zoysia and Bermuda had the stronger protective enzyme system under abiotic stress than Bahia. Combining all the results, we concluded that the resistance of the three turf grasses to SO₂ could be ordered in sequence from strong to weak as Zoysia > Bermuda > Bahia. This conclusion can guide us in respect of the large-scale use of Zoysia in heavily SO₂-polluted areas in tropical and subtropical regions.