热处理对黄皮果实贮藏效果和活性氧代谢的影响

以海南本地黄皮果实为试验材料,采用45℃、50℃、55℃和60℃热水对果实进行热处理,以不作热处理为对照,研究热处理对黄皮果实贮藏效果和活性氧代谢的影响。结果表明,50℃以上热处理能将果实贮藏期延长至21d,好果率在90%以上,且能明显抑制果实重量损失;热处理能使果实维持较高的可溶性固形物和总酸含量,55℃以下热处理能维持较高的固酸比;热处理果肉和果皮的MDA含量和PPO活性表现低于对照的趋势,SOD、POD和CAT活性表现高于对照的趋势,表明热处理能减轻果实活性氧自由基损伤和增强果实清除活性氧自由基的能力。热处理中以55℃热水最宜。     

茉莉酸甲酯诱导辣椒抗青枯病与活性氧代谢的关系

为探究茉莉酸甲酯(Methyl Jasmonate,Me JA)诱导辣椒抗青枯病效应与活性氧代谢相关酶的关系,以辣椒易感青枯病品种‘粤红1号’和抗青枯病品种‘辛香8号’幼苗为试验材料,在0.1mmol·L-1 Me JA喷雾处理后12、24、48、72和96 h接种青枯劳尔氏菌(Ralstonia solanacearum),对其进行青枯病病情指数与活性氧代谢相关酶——超氧化酶歧化酶(Superoxide Dismutase,SOD)、过氧化氢酶(Catalase,CAT)、过氧化物酶(Peroxidase,POD)和抗坏血酸过氧化物酶(Ascorbate Peroxidase,APX)活性以及丙二醛(Malondialdehyde,MDA)含量测定及相互关系的分析。结果表明:‘粤红1号’和‘辛香8号’的病情指数随喷Me JA处理时间的推移表现为先降后升,但都低于对照;而诱导效果则相反,Me JA处理对两个辣椒品种幼苗抗性的最适诱导时间均为接种前48 h。接种后0~96 h,Me JA喷雾处理的辣椒幼苗叶片SOD、CAT、POD和APX酶活性均显示先升后降的趋势,且明显高于对照,接种后24~48 h达到最高,而MDA含量则明显低于对照。因此,Me JA可诱导辣椒幼苗抗青枯病,其实现途径可能与提高活性氧代谢相关酶活性和缓解膜脂过氧化有关。     

狭叶茶提取物对小鼠氧化应激性肝损伤的保护作用

研究狭叶茶(Camellia angustifolia Chang)提取物对拘束负荷诱发小鼠应激性肝损伤的保护作用。采用拘束负荷小鼠应激性肝损伤模型,18h拘束负荷诱发小鼠应激性肝损伤,分别用赖氏法测定小鼠血浆和肝组织丙氨酸转移酶(ALT)活性、硫代巴比妥酸法测定丙二醛(MDA)含量、HPLC法测定谷胱甘肽(GSH)水平、比色法测定黄嘌呤氧化酶(XOD)、谷胱甘肽过氧化物酶(GPX)和谷胱甘肽S转移酶(GST)活性,荧光酶标仪测定血浆、肝组织及狭叶茶提取物体外抗氧化能力指数(ORAC)。与拘束模型组相比,狭叶茶提取物可以明显提高拘束负荷小鼠血浆与肝组织匀浆的ALT活性和抗氧化能力指数,提高GSH水平,增强GPX和GST活性,有效降低肝组织中MDA含量和XOD活性,并在体外显示出较强的抗氧化能力。说明狭叶茶提取物对拘束应激引起的小鼠肝损伤具有一定的保护作用,其作用机制可能部分来自于减少拘束负荷小鼠氧化应激水平,清除自由基和抑制脂质过氧化过程。     

水稻根际含氧量对根系生长的影响

以多个水稻品种为材料, 采用营养液培养试验, 通过气泵增加水稻根际的含氧量, 研究水稻根际含氧量与根系生长的关系。结果表明, 在水稻生长过程中, 抽穗期根系吸收氧气的能力最强, 需氧量最大。根际含氧量对水稻根系形态与分布有影响, 增氧显著增加根长, 提高根系自根基到根尖10~20 cm、＞20 cm部分所占的生物量比例, 同时减少根数; 而在缺氧环境下生长的水稻根数增多, 根长缩短。氧溶量对水稻根系活力的影响存在品种间差异, 提高水稻根际的氧溶量, 杂交稻汕优63和国稻1号齐穗期根系的活跃吸收面积和根系活力显著增加; 根系活力较高的常规籼稻湘早籼11和甬粳18在充氧处理中的根系活力也明显提高, 但根际氧含量的增加对根系活力较低的水稻品种湘早籼24和春江06的根系活力并无明显作用; 缺氧环境下生长的水稻根系的活力降低。     

Effects of fuel injection and intake parameters on low temperature combustion

The effects of fuel injection and intake parameters on low temperature combustion are investigated using CFD modeling in the present study. With the increase of injection pressure or decrease of nozzle hole diameter:the maximum in-cylinder pressure and temperature increase. Heat release from premixed combustion increases at the same oxygen concentration and oxygen concentration that obvious premixed combustion appears increases. As to emissions, soot emission decreases because of the improvement of mixing of fuel and air and NOx emission increases because the increase of local temperature in the cylinder. With the increase of intake pressure:the maximum cylinder pressure increases but the maximum cylinder temperature decreases. The ignition timing advances at the same oxygen concentration. The combustion efficiency increases. As to emissions, both soot and NOx emissions decrease.     

Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils

Phosphorus (P) cycles rapidly in lowland tropical forest soils, but the process have been proven difficult to quantify. Recently it was demonstrated that valuable data on soil P transformations can be derived from the natural abundance of stable oxygen isotopes in phosphate (δ¹⁸O_P). Here, we measured the δ¹⁸O_P of soils that had received long-term nutrient additions (P, nitrogen, and potassium) or litter manipulations in lowland tropical forest in Panama and performed controlled incubations of fresh soils amended with a single pulse of P. To detect whether δ¹⁸O_P values measured in the incubations apply also for soils in the field, we examined the δ¹⁸O_P values after rewetting dry soils. In the incubations, resin-P δ¹⁸O_P values converged to ∼3.5‰ above the expected isotopic equilibrium with soil water. This contrasts with extra-tropical soils in which the δ¹⁸O_P of resin-P matches the expected equilibrium with soil water. Identical above-equilibrium resin-P δ¹⁸O_P values were also found in field soils that did not receive P additions or extra litter. We suggest that the 3.5‰ above-equilibrium δ¹⁸O_P values reflect a steady state between microbial uptake of phosphate (which enriches the remaining phosphate with the heavier isotopologues) and the release of isotopically equilibrated cell internal phosphate back to the soil. We also found that soil nutrient status affected the microbial turnover rate because in soils that had received chronic P addition, the original δ¹⁸O_P signature of the fertilizer was preserved for at least eight weeks, indicating that the off-equilibrium δ¹⁸O_P values produced during microbial phosphate turnover was not imprinted in these soils. Overall, our results demonstrate that ongoing microbial turnover of phosphate mediates its biological availability in lowland tropical soils.     

NADPH Oxidases Act as Key Enzyme on Germination and Seedling Growth in Barley (Hordeum vulgare L.)

Reactive oxygen species (ROS) play an important role in seed germination. Although hydrogen peroxide (H₂O₂), a type of ROS, enhances the germination rate of various plant seeds, little is known about the mechanism. NADPH oxidases catalyze the production of superoxide anion (O₂^-) that is one of the ROS and the enzymes regulate plant development. We, therefore, investigated the role of NADPH oxidases in seed germination and seedling growth in barley (Hordeum vulgare L.). The production of O₂^- was observed both in embryo and aleurone layers in barley seeds treated with distilled water (DW). However, it was suppressed in seeds treated with diphenylene iodonium (DPI) chloride, NADPH oxidase inhibitor. Moreover, DPI markedly delayed germination and remarkably suppressed α-amylase activity in barley seeds, indicating the importance of NADPH oxidases in germination of barley seeds. The gene expression and the enzyme activity of NADPH oxidases gradually increased after imbibition, and the enzyme activities were closely correlated with seedling growth after imbibition. Besides, DPI markedly suppressed the seedling growth. These results indicated that NADPH oxidases perform a crucial function in germination and seedling growth in barley. These facts clearly reveal that O₂^- produced by NADPH oxidases after imbibition regulates seed germination and seedling growth in barley.     

不同硒源对刺参呼吸代谢的影响

为了研究不同硒源对刺参Apostichopus japonicus特定生长率和呼吸代谢指标的影响,以刺参幼参和成参为研究对象,分别强化投喂硒添加量为0.6 mg/kg的硒代蛋氨酸、硒酸钠和亚硒酸钠饲料,试验周期为60 d。结果表明:硒添加组成参和幼参的特定生长率均显著大于对照组(P0.05),其中硒代蛋氨酸组最大,且显著大于硒酸钠组和亚硒酸钠组(P0.05),除硒代蛋氨酸组外,其他各试验组成参的特定生长率均大于幼参;硒添加组成参和幼参的耗氧率均显著大于对照组(P0.05),其中硒代蛋氨酸组最小,显著小于硒酸钠组和亚硒酸钠组(P0.05),对应组中,幼参耗氧率大于成参;硒添加组成参和幼参的排氨率均低于对照组,除硒代蛋氨酸组成参显著低于对照组(P0.05)外,其余硒添加组与对照组均无显著性差异(P0.05),硒代蛋氨酸组的排氨率最小,对应组中,幼参排氨率大于成参;硒添加组成参和幼参的O/N值均显著大于对照组(P0.05),其中硒代蛋氨酸组最小,但硒添加组间无显著性差异(P0.05),对应组中,成参的O/N值大于幼参。研究表明,饲料中添加硒能够提高刺参的代谢率,促进刺参生长,其中有机硒(硒代蛋氨酸硒)的促生长效果好于无机硒(硒酸钠和亚硒酸钠),且硒代蛋氨酸对幼参的促生长效果要好于成参。     

5‐Aminolevulinic Acid Activates Antioxidative Defence System and Seedling Growth in Brassica napus L. under Water‐Deficit Stress

The present study assesses the effects of 5‐aminolevulinic acid (ALA, 0, 0.1, 1 and 10 mg l^?1) on the growth of oilseed rape (Brassica napus L. cv. ZS758) seedlings under water‐deficit stress induced by polyethylene glycol (PEG 6000, 0 and ?0.3 MPa). Water‐deficit stress imposed negative effects on seedling growth by reducing shoot biomass, cotyledon water potential, chlorophyll content and non‐enzymatic antioxidants (glutathione and ascorbic acid) levels. On the other hand, water‐deficit stress enhanced the malondialdehyde (MDA) content, reactive oxygen species (ROS) production, enzymatic antioxidants activities, reduced/oxidized glutathione ratio (GSH/GSSG) and reduced/oxidized ascorbic acid (ASA/DHA) ratio in seedlings. Application of ALA at lower dosages (0.1 and 1 mg l^?1) improved shoot weight and chlorophyll contents, and decreased MDA in rape seedlings, whereas moderately higher dosage of ALA (10 mg l^?1) hampered the growth. The study also indicated that 1 mg l^?1 ALA improved chlorophyll content, but reduced MDA content and ROS production significantly under water‐deficit stress. Lower dosages of ALA (0.1 and 1 mg l^?1) also enhanced GSH/GSSG and ASA/DHA as compared to the seedlings under water‐deficit stress. The antioxidant enzymes (ascorbate peroxidase, peroxidase, catalase, glutathione reductase and superoxide dismutase) enhanced their activities remarkably with 1 mg l^?1 ALA treatment under water‐deficit stress. It was also revealed that 1 mg l^?1 ALA treatment alone induced the expression of APX, CAT and GR substantially and under water‐deficit stress conditions ALA treatment could induce the expression of POD, CAT and GR to a certain degree. These results indicated that 0.1–1 mg l^?1 ALA could enhance the water‐deficit stress tolerance of oilseed seedlings through improving the biomass accumulation, maintaining a relative high ratio of GSH/GSSG and ASA/DHA, enhancing the activities of the specific antioxidant enzymes and inducing the expression of the specific antioxidant enzyme genes.     

Cultivar Specific Response of CO2 Fertilization on Two Tropical Mung Bean (Vigna radiata L.) Cultivars: ROS Generation,Antioxidant Status,Physiology, Growth,Yield and Seed Quality

Increasing atmospheric carbon dioxide concentration (CO₂) is an important component of global climate change that will have a significant impact on the productivity of crop plants. In recent years, growth and yield of agricultural crop plants have been shown to increase with elevated CO₂ (EC) and have enticed considerable interest due to variation in the response of crop plants. In this study, comparative response of two mung bean cultivars (HUM‐2 and HUM‐6) was evaluated against EC at different growth stages under near‐natural conditions for two consecutive years. The plants were grown in ambient as well as EC (700 ppm) in specially designed open‐top chambers. Under elevated CO₂, marked down‐regulation of reactive oxygen species (ROS) levels, membrane disruption and activities of superoxide dismutase and catalase were noticed in both the cultivars, but the extent of reduction was more in HUM‐6. As compared to ambient CO₂, EC increased total chlorophyll, photosynthetic rate, growth and yield parameters. Cultivar‐specific response was noticed as HUM‐6 showed higher increase in yield attributes than HUM‐2. Under CO₂ treatment, soluble protein and reducing sugars decreased while total soluble sugars and starch showed an opposite trend. Principal component analysis showed that both the cultivars responded more or less similarly to EC in their respective groupings of physiological and growth parameters, but the magnitude of ROS and antioxidative enzymes was variable. The experimental findings depict that both the cultivars of mung bean showed contrasting response against EC and paved the way for selecting the suitable cultivar having higher productivity in a future high‐CO₂ environment.