Effects of Cadmium and Arsenic on Physiological Responses and Copper and Zinc Homeostasis of Rice

Abstract

Heavy metals reduce the photosynthetic efficiency and disrupt metabolic reactions in a concentrationdependent manner. Moreover, by replacing the metal ions in metalloproteins that use essential metal ions, such as Cu, Zn, Mn, and Fe, as co-factors, heavy metals ultimately lead to the formation of reactive oxygen species (ROS). These, in turn, cause destruction of the cell membrane through lipid peroxidation, and eventually cause the plant to necrosis. Given the aforementioned factors, this study was aimed to understand the physiological responses of rice to cadmium (Cd) and arsenic (As) toxicity and the effect of essential metal ions on homeostasis. In order to confirm the level of physiological inhibition caused by heavy metal toxicity, hydroponically grown rice (Oryza sativa L. cv. Dongjin) plants were exposed with 0-50 µM cadmium (Cd, CdCl 2 ) and arsenic (As, NaAsO 2 ) at 3-leaf stage, and then investigated malondialdehyde (MDA) contents after 7 days of the treatment. With increasing concentrations of Cd and As, the MDA content in leaf blade and root increased with a consistent trend. At 14 days after treatment with 30 µM Cd and As, plant height showed no significant difference between Cd and As, with an identical reduction. However, As caused a greater decline than Cd for shoot fresh weight, dry weight, and water content. The largest amounts of Cd and As were found in the roots and also observed a large amount of transport to the leaf sheath. Interestingly, in terms of Cd transfer to the shoot parts of the plant, it was only transported to upper leaf blades, and we did not detect any Cd in lower leaf blades. However, As was transferred to a greater level in lower leaf blades than in upper leaf blades. In the roots, Cd inhibited Zn absorption, while As inhibited Cu uptake. Furthermore, in the leaf sheath, while Cd and As treatments caused no change in Cu homeostasis, they had an antagonist effect on the absorption of Zn. Finally, in both upper and lower leaf blades, Cd and As toxicity was found to inhibit absorption of both Cu and Zn. Based on these results, it would be considered that heavy metal toxicity causes an increase in lipid peroxidation. This, in turn, leads to damage to the conductive tissue connecting the roots, leaf sheath, and leaf blades, which results in a reduction in water content and causes several physiological alterations. Furthermore, by disrupting homeostasis of the essential metal ions, Cu and Zn, this causes complete heavy metal toxicity.

Effect of Phosphorus on the Cadmium Transfer and ROS-scavenging Capacity of Rice Seedlings

“…이는 Cd 스트레스에 노출된 여러 식물종들의 경우에서도 P시 용에 따라 건물중의 증가를 나타내는 보고와 유사한 결과를 보여주고 있다 (Jiang et al, 2007;Sajwan et al, 2002). (Fergusson, 1990;Park et al, 2009;Jung et al, 2015Jung et al, , 2016.…”

“…활성산소종 (reactive oxygen species, ROS)을 발생시켜 세포 내에서 지질과산화작용을 야기함으로써 세포막을 파괴 하고 최종적으로 세포를 사멸시킨다 (Barceló et al, 1988;Jung et al, 2015Jung et al, , 2016Lagriffoul et al, 1998;. 특히 카드뮴에 의해 발생된 산화적 스트레스는 활성산소종의 세포 내 축 적으로 인하여 탄수화물, 단백질, 지질 및 핵산의 생합성에 부정적인 영향을 미치고 산화 ․ 환원 항상성을 교란하여 정 상적인 생체 기능을 저해한다 (Gayomba et al, 2013;Singh and Agrawal, 2010;Singh et al, 2006, Xu et al, 2014.…”

“…비료의 3요소 중의 하나인 인과 중금속인 비소의 길항작용에 관한 연관성 연구는 여러 연구보고들을 통하여 확실한 정설로 자리매김을 하고 있는 실 정임에도 불구하고 (Brachhage et al, 2014;Gomes et al, 2014), 카드뮴과 인의 상호연관성 연구는 일부 식물에서의 연구를 제외하고 아직도 미진한 상태이므로 깊이있는 연구가 필요할 것으로 판단된다 (Arshad et al, 2016). 인은 식 물의 주된 에너지원인 아데노신 삼인산 (adenosine triphosphate, ATP) 생성과 여러 효소반응을 촉진하여 Cd의 독성 에 의해 발생되는 활성산소종 소거에 관여할 뿐만 아니라 식물의 생장촉진에도 효과를 나타낸다 (Jalil et al, 1994;Mishra et al, 2014 (Jung et al, 2015;Kamachi et al, 1991). Jung et al (2015) …”

“…인은 식 물의 주된 에너지원인 아데노신 삼인산 (adenosine triphosphate, ATP) 생성과 여러 효소반응을 촉진하여 Cd의 독성 에 의해 발생되는 활성산소종 소거에 관여할 뿐만 아니라 식물의 생장촉진에도 효과를 나타낸다 (Jalil et al, 1994;Mishra et al, 2014 (Jung et al, 2015;Kamachi et al, 1991). Jung et al (2015) …”

Effect of Rice Straw Compost on Cadmium Transfer and Metal-ions Distribution at Different Growth Stages of Soybean

“…특히 식물에 있어 카드뮴 독성은 광합성 및 호흡작용의 저해, 식물체 내 이온 상호작용의 교란 등 대사 장애를 유발함으로 써 전체적인 생육에 심각한 악영향을 초래한다 (Gayomba et al, 2013;Jung et al, 2015). 또한 카드뮴은 자연생태계에 서 생물적 및 비생물적으로 분해되어 무독화 또는 안정화된 화합물의 형태로 변환되지 않고 자연생태계 내에 오랜 기간 존재하기 때문에 농경지와 농업용수를 오염시킬 뿐만 아니 라 먹이사슬을 통해 생물체 내에 고농도로 축적됨으로써 식 물 및 인체독성 피해를 야기하고 있다 (Galiulin et al, 2001;Jung et al, 2015;Nagajyoti et al, 2010 (Adriano, 1986;Han et al, 1997;Stevenson, 1994 (Fergusson, 1990;Jung et al, 2015;Lee et al, 2012;Park et al, 2009 (Adriano, 1986;Han et al, 1997;Stevenson, 1994).…”