镉胁迫对南瓜植株镉吸收积累及光合特性的影响

Effects of Cadmium Stress on Cadmium Uptake Accumulation and Photosynthetic Characteristics of Pumpkin

【目的】研究镉在南瓜植株中的吸收积累特性及镉胁迫对南瓜叶片光合特性的影响。【方法】采用微波消解-ICP-AES技术,以中国南瓜‘盐砧一号’为试验材料,设置0、2、4、6 mg/L共4个镉胁迫质量浓度的基质栽培试验,测定Cd在南瓜不同器官的分布、Cd的亚细胞分布以及镉胁迫下南瓜叶片的光合作用参数。【结果】Cd在南瓜植株根中量远大于茎和叶,随着镉胁迫质量浓度增大,根中富集系数(BCF)呈上升趋势,转运系数TF值逐渐降低。Cd在不同器官亚细胞组分中呈不均匀分布,其中根系中以细胞壁的分配率最高达到47.63%~57.69%;其次为细胞质;细胞器中含Cd量仅占1.93%~4.59%。镉胁迫对南瓜植株净光合速率(Pn)和胞间CO2量(Ci)影响不明显,但镉胁迫显著抑制了气孔导度(Gs)和蒸腾速率(Tr)。【结论】在镉胁迫下,中国南瓜‘盐砧一号’能将Cd富集在根系的细胞壁中,从根部转移到茎和叶的能力减弱,对光合作用没有造成显著抑制作用。

Heavy metal cadmium(Cd)pollution has become one of the hot issues,when Cd enters the tissues and cells of the plant,it interferes with the normal physiological metabolism of the cell,destroys the chlorophyll and transpiration effects of the plant,and causes growth disorder or even death.Pumpkin is one of the cadmium-resistant rootstocks commonly used for cucurbitacae vegetables.【Objective】We aimed to study the absorption and accumulation characteristics of cadmium in pumpkin plants and the effect of cadmium stress on photosynthetic characteristics of pumpkin leaves,further revealing the accumulation characteristics and toxicity mechanism of pumpkin on heavy metal cadmium,provide a scientific basis for the screening of cucumber cadmium-resistant rootstocks in greenhouses.【Method】Using microwave digestion-ICP-AES technology and the Chinese pumpkin"Yanzhen 1"as experimental material,we set up 4 treatments,and added different amounts of Cd(added in the form of CdSO4):0,2,4,6 mg/L,each treatment repeated 4 times,and each plastic small black square pot(7 cm caliber)was assembled with 0.00027 m3 substrate.The sprouted pumpkin seeds are sown in the substrate,and the film is kept warm and moisturized.When the two cotyledons of the seed emerged and the true leaves were exposed,we added different concentrations of Cd into the pots and used a pipette to pour 10 m L Cd solution near the root of the plant every 5 days for a total of 4 times.Pumpkin plants were divided into roots,stems and leaves,washed and dried separately.In order to remove the Cd adsorbed on the surface of the pumpkin root,the pumpkin root was first rinsed with deionized water,and then treated with 20 mmol/L Na2-EDTA exchange for 20 min,then washed with deionized water,and absorbed the surface moisture.Fresh plant samples were kept in the-20℃refrigerator for future use.The photosynthetic parameters of leaves,the sub-cellular distribution of Cd and the distribution of organs(roots,stems and leaves)were determined.【Result】The content of Cd in pumpkin root increased much more than that of stem and leaf.With the increase of Cd concentration,the BCF of root increased and the TF decreased gradually.Cd was unevenly distributed among the subcellular components of different organs.The distribution rate of cell wall in roots was up to 47.63%~57.69%,followed by cytoplasm;and the Cd content in organelles only accounted for1.93%~4.59%.Cd treatment did not significantly inhibit the net photosynthetic rate(Pn)of pumpkin,while Cd treatment significantly inhibited stomatal conductance(Gs)and transpiration rate(Tr),but there was no significant difference in intercellular CO2 concentration(Ci)between Cd treatments.【Conclusion】The cell wall in the root system of"Yanzhen 1"pumpkin plant has a strong ability to accumulate Cd,while the accumulation of the remaining components is relatively reduced,which restricts the transportation and accumulation of Cd to the above ground.With the increase of Cd concentration,Cd transfers from the root to stem and leaves gradually decreased,but Cd stress did not cause significant inhibition on photosynthesis.