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Soil organic carbon (SOC) is the dynamic medium of carbon transfer and the main way of carbon circulation in karst ecosystem, SOC and soil labile organic carbon (LOC) is essential for karst soil C cycling. There has been very little research about the differentiation of SOC and LOC in karst ecosystem. In this study, six typical restoration measures were investigated in the karst rocky desertification ecosystem, southwest China, including: restoration with Zanthoxylum bungeanums (HJ), restoration with Hylocereus undulates (HL), restoration with Pennisetum sinese (HZ), restoration with Medicago sativa (MX), restoration with Sabina chinensis (YB), and abandoned and natural recovery (LH). The SOC contents, SOC stocks, LOC contents (water soluble organic carbon (WSOC), easily oxidizable organic carbon (EOC), particulate organic carbon (POC), light fraction organic carbon (LFOC)), and the carbon pool management index (CPMI) were investigated. The results indicated that the SOC contents, SOCS and LOC contents of the six measures were the highest in YB, followed by the LH, and the two were significantly higher than the other four measures. The soil CPMI contents of 0-20 cm layer under the different restoration measures decreased in the following order: YB > HJ > MX > HL > HZ. Correlation analysis showed that SOC was positively correlated with soil LOC (P<0.01), and LOC was positively correlated with each other (P<0.01). These findings suggest that restoration with Sabina chinensis, abandoned and natural recovery are more conducive to the management and protection of karst ecological environment. Restoration with Zanthoxylum bungeanums can be used as a priority economic species for karst rocky desertification and mountain agricultural development in southwest China. Soil WSOC, EOC, POC, and LFOC can be used as effective indicators to reflect SOC pools, and soil CPMI can also be used as a sensitive indicator to reflect soil management. [ABSTRACT FROM AUTHOR]

The present study was conducted to screen different growth inhibitors i.e. ethephon (125 mM), methyl jasmonate (1 mM MeJA) and their combinations (125mM ethephon + 1mM MeJA) for minimizing the harmful effects of pre-harvest sprouting during hybrid rice seed production. The combination of both growth inhibitors significantly reduced germination and growth attributes with a more prominent decrease in cultivar Zhu Liang You 06 (ZY) as compared to cultivar Qian You No.1 (QY). Moreover, the activities of a-amylase, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and malonaldahyde (MDA) contents were significantly increased with the combination of both growth inhibitors as compared to the control. CAT activity was significantly increased with 1mM of MeJA as compared to the control. The combination of both growth inhibitors resulted in the increase of abscisic acid (ABA) contents and the decrease of gibberellins (GA) contents as compared with the control. Gene expression analysis showed that the transcription levels of ABA genes (OsNCED1, OsNCED3 and OsABA80x1) were up-regulated with the combination of both growth inhibitors. While, GA genes (OsGA3ox1, OsGA20ox1 and OsGA2oox2) were down-regulated by seed soaking with both growth inhibitors and their combination. [ABSTRACT FROM AUTHOR]

Background: The low seed vigor and poor field emergence are main factors that restricting the extension of sweet corn in China. Spermidine (Spd) plays an important role in plant growth and development, but little is known about the effect of Spd on sweet corn seed germination. Therefore the effect of exogenous Spd on seed germination and physiological and biochemical changes during seed imbibition of Xiantian No.5 were investigated in this study. Results: Spd soaking treatment not only improved seed germination percentage but also significantly enhanced seed vigor which was indicated by higher germination index, vigor index, shoot heights and dry weights of shoot and root compared with the control; while exogenous CHA, the biosynthesis inhibitor of Spd, significantly inhibited seed germination and declined seed vigor. Spd application significantly increased endogenous Spd, gibberellins and ethylene contents and simultaneously reduced ABA concentration in embryos during seed imbibition. In addition, the effects of exogenous Spd on H2O2 and MDA productions were also analyzed. Enhanced H2O2 concentration was observed in Spd-treated seed embryo, while no significant difference of MDA level in seed embryo was observed between Spd treatment and control. However, the lower H2O2 and significantly higher MDA contents than control were detected in CHA-treated seed embryos. Conclusions: The results suggested that Spd contributing to fast seed germination and high seed vigor of sweet corn might be closely related with the metabolism of hormones including gibberellins, ABA and ethylene, and with the increase of H2O2 in the radical produced partly from Spd oxidation. In addition, Spd might play an important role in cell membrane integrity maintaining. [ABSTRACT FROM AUTHOR]

The present study was designed to highlight the impact of seed priming with polyethylene glycol on physiological and molecular mechanism of two cultivars of Oryza sativa L. under different levels of zinc oxide nanorods (0, 250, 500 and 750 mg L−1). Plant growth parameters were significantly increased in seed priming with 30% PEG under nano-ZnO stress in both cultivars. Whereas, this increase was more prominent in cultivar Qian You No. 1 as compared to cultivar Zhu Liang You 06. Significant increase in photosynthetic pigment with PEG priming under stress. Antioxidant enzymes activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) as well as malondialdehyde (MDA) contents were significantly reduced with PEG priming under nano-ZnO stress. Gene expression analysis also suggested that expression of APXa, APXb, CATa, CATb, CATc, SOD1, SOD2 and SOD3 genes were down regulated with PEG priming as compared to non-primed seeds under stress. The ultrastructural analysis showed that leaf mesophyll and root cells were significantly damaged under nano-ZnO stress in both cultivars but the damage was prominent in Zhu Liang You 06. However, seed priming with PEG significantly alleviate the toxic effects of nano-ZnO stress and improved the cell structures of leaf and roots in both cultivars. [ABSTRACT FROM AUTHOR]