黄果龙葵幼苗对镉胁迫的生理生长响应

Physiological and growth responses of Solanum diphyllum seedlings to Cd stress

关键词:  黄果龙葵, 镉, 生理生长, 渗透调节, 光合色素

Key words:  Solanum diphyllum, Cd, physiological growth, osmoregulation, photosynthetic pigment

摘要:

黄果龙葵(Solanum diphyllum)是茄科的小灌木,已有的研究对黄果龙葵的镉(Cd)响应知之甚少。该研究采用水培控制试验,在160 μmol·L^-1 Cd胁迫下,测定了黄果龙葵幼苗在不同胁迫时间点(0、0.5、1、3、7、19 d)的生长、耐性系数(TI)、Cd富集特性、超氧化物歧化酶(SOD)活性、渗透调节物质和光合色素等指标。结果表明:(1)在胁迫0～3 d时Cd对黄果龙葵幼苗的生长无显著影响。胁迫3～19 d时表现为明显抑制,且毒害随胁迫时间延长而加重。与对照组相比,Cd胁迫使黄果龙葵幼苗的生物量降低13.28%～62.40%。(2)黄果龙葵幼苗的最大Cd积累量为60.14 μg·plant^-1,其地上部份的Cd积累量占植株的15.46%～35.24%。(3)丙二醛(MDA)含量呈上升趋势,根的MDA含量最大增幅为对照组的5.25倍。SOD活性、游离脯氨酸、可溶性糖、叶绿素a、叶绿素b和类胡萝卜素的含量均呈先升后降的趋势。(4)黄果龙葵幼苗的耐性系数TI随胁迫时间延长而降低,最小值为0.64。综上结果认为,黄果龙葵是一种潜在的Cd忍耐植物,其幼苗对高浓度的Cd胁迫在短时间内具有一定程度的耐性,并且黄果龙葵可能通过渗透调节和根系固持来缓解Cd毒害。该研究结果为寻找合适的植物修复材料提供了理论依据。

Abstract:

Solanum diphyllum is a kind of small shrub of Solanaceae, and little has been known about its Cd tolerance ability in the existed researches so far. In order to investigate the physiological responses, growth responses and Cd tolerance characteristics of S. diphyllum seedlings, we conducted a hydroponic experiment with 160 μmol·L^-1 Cd stress to determine the indexes of growth(taproot, height, stem diameter, leaf number, biomass, and root to shoot ratio), tolerance index(TI), Cd content, Cd accumulation characteristics, SOD activity, osmotic adjustment substances(MDA, free proline and soluble sugar), and photosynthetic pigment(Chlorophyll a, Chlorophyll b and carotenoid)in different stress time(0, 0.5, 1, 3, 7, 19 d). The results were as follows:(1)Compared with controls, Cd had no significant effects on the growth of S. diphyllum seedlings when stress time was 0-3 d; Obvious Cd toxicity was aggravated with the prolonging of Cd stress time(3-19 d); During the period of experiment, Cd stress reduced the total biomass of S. diphyllum seedlings by 13.28%-62.40%, root suffered the most serious biomass damage among different plant tissues.(2)The maximum Cd accumulation of the whole plant was 60.14 μg·plant^-1, for root and shoot the maximum Cd accumulation were 43.49 μg·plant^-1 and 16.65 μg·plant^-1 respectively, Cd accumulation of shoots accounted for 15.46%-35.24% of the whole plant.(3)MDA content of S. diphyllum seedlings increased with the increase of stress time, the maximum increase of MDA content in roots was 5.25 times that of control; SOD activity, contents of free proline and soluble sugar, as well as photosynthetic pigment contents increased at the beginning and then decreased.(4)Tolerance index(TI)showed a different tendency, it decreased with the increase of stress time, and the minimum value of S. diphyllum seedlings during the whole period of experiment was 0.64. The above results indicate that S. diphyllum seedlings have a certain degree of tolerance to high concentration of Cd stress(160 μmol·L^-1), which suggests that it is a potential Cd tolerance plant. The osmotic adjustment and root retention might be the main methods of S. diphyllum seedlings to alleviated toxicity to plant growth caused by Cd. This research provides a theoretical basis for finding suitable phytoremediation materials.