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Michelle DaCosta and Bingru Huang

antioxidant enzyme activities, providing indirect evidence for the extent of generation of AOS and the importance of these enzymes in scavenging free radicals ( Smirnoff, 1993 ). Drought stress resistance has been associated with either maintenance or

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Ramón A. Arancibia and Carl E. Motsenbocker

Red-mature Tabasco (Capsicum frutescens) fruit (`McIlhenny Select') normally separate easily at the junction of the fruit and receptacle or calyx. Differences in fruit detachment force (FDF) between two lines, one that separates readily (`McIlhenny Select') and one that does not (`Hard Pick'), have been reported previously (Motsenbocker et al., 1995). In this study, enzyme activity from the detachment area was analyzed by viscosity reduction. The reaction mixture was 0.3% pectin in 20 mm NaAc, pH 5.5, for polygalacturonase (PG) and 0.6% carboxymethyl cellulose (CMC) in 20 mm NaPO4, pH 6.0, for cellulase. Preliminary data indicated that PG and cellulase enzyme activity increased during fruit ripening in both lines. Only cellulase activity, however, correlated with FDF. In addition, the activity of both enzymes was higher in the `McIlhenny Select' line than the `Hard Pick' line at the orange and red-mature stages.

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Lantian Du, Baojian Huang, Nanshan Du, Shirong Guo, Sheng Shu, and Jin Sun

(cv. Yusuan No. 1) to assess the effects of relay intercropping on cucumber plant growth, soil enzyme activities and microbial diversity, and biomass and community diversity. Materials and Methods Experimental materials and treatments. The experiments

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Guangxin Liu, Xiaoqian Su, Lingling Guan, and Fengrong Hu

these harmful products, some enzymes function to clear free radicals and reactive oxygen. When plants are infected by pathogens, some enzyme activities are enhanced and others are reduced. These changes in enzyme activity affect various physiological and

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Xiangdong Huang, Dong Xue, and Lian Xue

as integral components of soil quality. Microbial biomass C (C mic ), basal respiration (R mic ), and enzyme activities have been widely used in soil investigations as a result of their great sensitivity to anthropogenic disturbance and environmental

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Lixin Xu, Liebao Han, and Bingru Huang

damage ( Sharma and Dubey, 2005 ; Turkan et al., 2005 ). However, alterations in antioxidant enzyme activities under drought stress are dependent on plant species, cultivar, and stress intensity and duration ( DaCosta and Huang, 2007 ; Rensburg and

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Lucia E. Villavicencio, Sylvia M. Blankenship, G. Craig Yencho, Judith F. Thomas, and C. David Raper

radial walls of the phellogen, determined by their lability and proneness to fracture, that determines the resistance to skinning ( Lulai, 2002 ). There is no information on how cell wall enzyme activity varies in sweetpotato. Pectinases are

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Carl E. Motsenbocker and Ramon A. Arancibia

Two tabasco pepper (Capsicum frutescens L.) lines were previously identified that differ in fruit detachment characteristics. Ethephon treatment (1000 μl/L) to intact tabasco fruit 29 days after anthesis (green-mature) enhanced ripening as indicated by fruit coloration in both lines. `McIlhenny Select' fruit, which normally separate readily at the red-mature stage, however, had a quicker ripening response compared to `Hard Pick' fruit. Ethephon increased cellulase activity in the fruit tissue of both tabasco lines compared to the untreated control, and there was a trend of higher cellulase activity in `McIlhenny Select' compared to `Hard Pick'. Differences in ripening and enzyme activity in response to ethylene generators indicate that the two tabasco lines are suitable material to investigate the physiological processes involved in pepper fruit ripening.

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Huiying Li, Hongji Luo, Deying Li, Tao Hu, and Jinmin Fu

, respectively ( Table 4 ). Table 4. Antioxidant enzyme activities of perennial ryegrass subjected to 0.5 and 3.2 m m Pb in a hydroponic system using half-strength Hoagland's solution for 7 d. Gene expression of antioxidant enzymes. The expressions of MnSOD

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Zohar Shaham, Amnon Lers, and Susan Lurie

`Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] were harvested in two seasons and stored at 0 °C air storage with no pretreatment (control), after heating for 4 d at 38 °C, or after treating for 16 hours at 20 °C with 1 μL·L-1 1-methylcyclopropene (1-MCP). The effects of the two treatments on superficial scald development were consistent over both seasons. Scald began to appear after 8 weeks in control fruit, after 16 weeks in heated fruit but not on 1-MCP treated fruit. α-Farnesene accumulation and oxidation were slower in the skin of heated than in control fruit, and almost entirely absent in 1-MCP treated fruit. The activities of five antioxidant enzymes, ascorbate peroxidase, catalase, glutathione reductase, peroxidase and superoxide dismutate, were measured at two-week intervals in the apple peel, quantitatively as total activity and qualitatively by isozyme analysis. Enzyme activities either increased or remained stable during 16 weeks of storage, except for superoxide dismutase activity, which decreased. Ascorbate oxidase activity was higher in heated than control apples and there was an additional peroxidase isozyme present in activity gels. The activities of antioxidant enzymes were lower in 1-MCP treated fruit except for catalase during the first month of storage. Lipid soluble antioxidant activity was higher in 1-MCP treated fruit than the fruit of the other treatments, and water soluble antioxidant activity was higher in both treatments than in control fruit during the time that scald was developing in control apples. Both free and total phenol contents in the peel fluctuated during storage but no consistent trend was detected. The differences in enzyme activity and antioxidant content of the peel of 1-MCP and heated apples may play a role in preventing or delaying the appearance of superficial scald.