Induced resistance in cotton seedlings against fusarium wilt by dried biomass of<Emphasis Type="Italic">Penicillium chrysogenum</Emphasis> and its water extract

Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants. Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested.     

泡桐丛枝病与过氧化物酶含量关系的研究初报

分别采用分光光度法和不连续聚丙烯酰胺凝胶盘状电泳法，比较分析了感病与未感病泡桐树木的过氧化物酶总活性与同工酶的变化。结果表明，泡酮感病后，叶片的ＰＯＤ总活性没有显著变化，枝，根韧皮部的ＰＯＤ总活性，病株高于健株。健株枝部和根部的ＰＯＤ同工酶谱带多于病株，活性也高于后者。可以用ＰＯＤ总活性与同工酶变化两个指标作为判别泡桐感病与束的依据。     

Effects of Zinc on Root Morphology and Antioxidant Adaptations of Cadmium-Treated Sedum alfredii H.

ABSTRACT

The study demonstrated S. alfredii is an excellent cadmium (Cd)/zinc (Zn) hyperaccumulator as Cd and Zn concentrations in leaves reached 2,183 and 13,799 mg kg^?1 DW, respectively. There was a significant increase in root morphological parameters induced by 50 and 500 μM Zn supplement; however, a sharp decrease in these parameters occurred when treated with 100 μM Cd +1000 μM Zn. The inhibited root dehydrogenase activity in 100 μM Cd treated plants was restored to control levels when supplemented with 500 μM Zn. Moderate Zn supplement did not produce significant changes in (malondialdehyde) MDA concentrations as compared with those treated with Cd alone. Variations of the antioxidative enzymes proved an ineffective role in coping with metal-stress in S. alfredii. Combined Cd and Zn treatment significantly enhanced ascorbic acid (AsA) and glutathione (GSH) contents in leaves of S. alfredii, as compared with those treated with Cd alone. Thus, Zn may rely on the involvement of GSH in detoxification and tolerance.     

Glutathione and its Related Enzymes in the Nile Fish

Glutathione (GSH) and related enzymes, glutathione transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR) form an important phase 2 biotransformation enzymes system. The objective of this study was to compare this enzymes system in three fish species from the river Nile, Oreochromis niloticus, Claris lazera and Cyprinus carpio in order to establish the main differences and to purify and characterize GST from the liver of O. niloticus.The level of GSH and the activity of GST, GPx and GR in the liver, kidney and gills of the three fish species were examined. A simple reproducible procedure for the purification of GST from the liver of O. niloticus to homogeneity, which includes chromatography on DEAE- cellulose followed by affinity chromatography on GSH-sepharose was established. The molecular mass was found to be 25,460 Da by SDS-PAGE. The Michaelis-Meneten constants (K_m) of the enzyme for GSH and CDNB were 0.35 mM and 0.42 mM, respectively. The affinity purified enzyme exhibited maximum pH at pH 8.0 and increasing pH above 8.0 did not affect the observed maximum. The purified enzyme acts readily on CDNB, less readily on some standard transferase substrates (1,2-dichloro-4-nitrobenzene and p-nitrophenethyl bromide) and not at all on others (bromosulphophthalein and p-nitrobenzyl chloride). Bromosulfophthalein, cibacron blue and hematin inhibited CDNB-conjugating activity of the purified enzyme with IC₅₀ 0.079, 3.98 and 0.126 μM, respectively.     

Glutathione Peroxidase Activity in Porcine Blood

Determination of the seleno-enzyme glutathione peroxidase (GSH-Px) in blood from Danish Landrace pigs was done using a quantitative, spectrophotometric method and a simple “spot test”. A close correlation between the net reaction rate measured spectrophotometrically (Δ A/min.) and time for defluores-cence (minutes) was obtained (r² = 0.72—0.77, P < 0.0005). From these results the factors used for a conversion of defluorescence time to u/g hemoglobin were evaluated. The results further showed that the “spot test” can be used as a screening method for detection of subnormal GSH-Px levels in pigs.While red cell GSH-Px seems independent of the sex, an elevation of both plasma and red cell GSH-Px was found with increasing age of pigs. The normal range of red cell GSH-Px activity was wide, contrasting the small variations observed in the individual pig. Some evidence that porcine red cell GSH-Px is under genetical control was found and discussed in relation to the possible use of GSH-Px as an indicator of the pig''s selenium status.