Effects of Copper on the Photosynthesis and Oxidative Metabolism of Amaranthus tricolor Seedlings

The objective of the present study was to gain better insight into the physiological mechanisms on the effects of copper (Cu) on photosynthesis and active oxygen metabolism in three-colored amaranth plant (Amaranthus tricolor). Three-colored amaranth seedlings were subjected to different Cu levels in soils during the entire experimental period. The parameters of growth, photosynthesis, mineral elements contents, and active oxygen metabolism were investigated using plant physiological methods. The results showed that 2.0 and 4.0 mmol Cu kg⁻¹ treatments decreased the whole plant biomass to 91 and 73% of the control, respectively. The net photosynthetic rate (P_n) and the stomatal conductance (g_s) were similarly reduced in the third leaves of three-colored amaranth seedlings treated with 2.0 and 4.0 mmol Cu kg-¹ soil, respectively. None of the investigated Cu levels decreased the internal CO₂ concentration (C_i). The effect of Cu on the potential efficiency of photosystem II (F_vIF_m) was negligible, whereas the effect of Cu on the PS II quantum efficiency (Φ_PS II) after plant adaptation in actinic irradiation was more noticeable. On the other hand, decreases in water percentage, contents of photosynthetic pigments and mineral elements including Fe, K, and Mg, and significant increase in the Cu content were observed in the third leaves of Cu-treated plants. Superoxide dismutase (SOD) and peroxidase (POD) activities as well as the proline (Pro) content significantly increased in the third leaves of the three-colored amaranth seedlings treated with 2.0 and 4.0 mmol Cu kg⁻¹ soil, while catalase (CAT) and ascorbate peroxidase (APX) activities as well as the contents of carotenoid (Car), glutathione (GSH), and ascorbic acid (AsA) decreased, and accompanied by the increases in the contents of hydrogen peroxide (H₂O₂), superoxide anion (O₂.-), and malondialdehyde (MDA), and electrolyte leakage. As a result of the imbalance of active oxygen metabolism, P_n and Φ_{PS II} decreased, and peroxidization enhanced under levels of 2.0 and 4.0 mmol Cu kg⁻¹ soil. Finally, the growth of three-colored amaranth plant was significantly inhibited.     

三色苋叶片色素分析

该文以三色苋的叶片为材料,用比色法对光合色素测定,用纸层析和薄层层析的方法对叶片进行色素定性分析。结果表明,三色苋由光合色素和花色素共同作用显示彩叶特征,不同部位所含色素种类及含量不同而表现出不同的色彩。由于叶端的叶绿素含量要远远高于叶基部的,且叶端和叶基部分的叶绿素与类胡萝卜素的比值差异较大,因而使叶端的颜色偏绿。     

盐胁迫对三色苋叶片气孔分化及开闭的影响

以三色苋（Amaranthus tricolor L.）为材料,研究了不同浓度（0、50、150、300、500 mmol · L^-1）NaCl 处理后气孔的应答反应和300 mmol · L^-1 NaCl 长时间处理后对不同叶序叶片气孔开闭和分化的影响。结果表明,盐处理后三色苋的气孔不同程度地迅速关闭,气孔开放率在处理3 h 后达到最低,之后小幅回升。24 h 后除50 mmol · L^-1 NaCl 处理外,仍有多数气孔处于关闭状态。长时间盐胁迫使基层的叶片气孔密度略有增加;上层新叶的气孔密度显著降低。长时间盐胁迫使气孔的开放率也降低,越是新分化的叶片盐胁迫对其气孔影响也越大。