Abstract
Soil acidification is the main problem in the current rice production. Here, the effects of low pH on the root growth, reactive oxygen species metabolism, plasma membrane functions, and the transcript levels of the related genes were investigated in rice seedlings (Oryza sativa L.) in a hydroponic system at pH 3.5, 4.5, and 5.5. There were two hybrid rice cultivars in this trial, including Yongyou 12 (YY12, a japonica hybrid) and Zhongzheyou 1 (ZZY1, an indica hybrid). Higher H+ activity markedly decreased root length, the proportion of fine roots, and dry matter production, but induced a significant accumulation of hydrogen peroxide (H2O2), and led to serious lipid peroxidation in the roots of the two varieties. The transcript levels of copper/zinc superoxide dismutase 1 (Cu/Zn SOD1), copper/zinc superoxide dismutase 2 (Cu/Zn SOD2), catalase A (CATA) and catalase B (CATB) genes in YY12 and ZZY1 roots were significantly down-regulated after low pH exposure for two weeks. Meanwhile, a significant decrease was observed in the expression of the P-type Ca2+-ATPases in roots at pH 3.5. The activities of antioxidant enzymes (SOD, CAT) and plasma membrane (PM) Ca2+-ATPase in the two varieties were dramatically inhibited by strong rhizosphere acidification. However, the expression levels of ascorbate peroxidase 1 (APX1) and PM H+-ATPase isoform 7 were up-regulated under H+ stress compared with the control. Significantly higher activities of APX and PM H+-ATPase could contribute to the adaptation of rice roots to low pH.
Highlights
Soil acidification is one of the most serious environmental problems in intensive agricultural systems, mainly because of the excessive use of acidic and physiologically acidic nitrogen fertilizers and the acid rain caused by environmental pollution [1,2,3]
The results revealed that the transcript levels of OsCu/Zn SOD1, OsCu/Zn SOD2, OsCATA and OsCATB in YY12 and ZZY1 roots decreased under the low pH treatment
In the present study, when treated with a low pH solution, pronounced symptoms were observed in the root system, and the root growth of rice was markedly depressed (Table 1)
Summary
Soil acidification is one of the most serious environmental problems in intensive agricultural systems, mainly because of the excessive use of acidic and physiologically acidic nitrogen fertilizers and the acid rain caused by environmental pollution [1,2,3]. The pH value of most acidic soil significantly declined from the 1980s to the 2000s in the South China, and the pH is under 4.0 in some highly acidic soils [3]. Along with decreased crop productivity caused by low pH levels, the common causes of reduced yields include aluminum, manganese and hydrogen (H+) ions toxicities, and deficiencies in nutrients such as phosphorus, molybdenum, calcium, and PLOS ONE | DOI:10.1371/journal.pone.0116971. Antioxidant Enzyme and ATPase Activities in the Rice Along with decreased crop productivity caused by low pH levels, the common causes of reduced yields include aluminum, manganese and hydrogen (H+) ions toxicities, and deficiencies in nutrients such as phosphorus, molybdenum, calcium, and PLOS ONE | DOI:10.1371/journal.pone.0116971 February 26, 2015
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