Influence of a Brassinosteroid Analogue on Antioxidant Enzymes in Rice Grown in Culture Medium with NaCl

We studied the effects of a polyhydroxylated spirostanic brassinosteroid analogue (BB-16) on the activities of antioxidant enzymes in rice seedlings grown in vitro in culture medium supplemented with NaCl. Seedlings were grown in medium with 75 mM NaCl and 0.001 or 0.01 mg dm⁻³ BB-16 for 16 d or 3-d-old seedlings were exposed for 4 d to 0, 0.001 or 0.01 mg dm⁻³ BB-16 then further grown in medium with 75 mM NaCl without BB-16. Seedlings exposed to 0.01 mg dm⁻³ BB-16 for 16 d showed significant increase in the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) and a slight increase in ascorbate peroxidase (APX). On the other hand, 4-d exposure to BB-16 only increased SOD and CAT activities at concentration 0.001 mg dm⁻³. GR activity was not altered by this BB-16 treatment. These results indicated that BB-16, which is structurally modified in the lateral chain in relation to natural brassinosteroids, changes the activity of key antioxidant enzymes, which might confer tolerance to saline stress. This revised version was published online in July 2006 with corrections to the Cover Date.     

干旱胁迫下外源脱落酸和硅对沙枣幼苗叶片水势及保护酶活性的影响

以一年生沙枣幼苗为材料,研究了外源脱落酸和外源硅在干旱（T2:SRWC=35%~40%,处理时间30 d）胁迫下沙枣幼苗叶片相对含水量、叶片水势、质膜相对透性、丙二醛(MDA)含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的影响。结果表明：沙枣幼苗T2干旱处理时,与对照(ck)相比其叶片相对含水量和水势均极显著降低,质膜相对透性有所增大,沙枣幼苗被受到了一定程度的伤害。同时,向T2干旱处理的幼苗使用外源脱落酸(ABA)后,可以极显著提高其叶片相对含水量和过氧化氢酶活性,极显著降低叶片质膜相对透性和丙二醛含量,叶片水势也有所降低,这说明使用外源脱落酸能够减轻干旱胁迫对沙枣幼苗的伤害。同时,向T2干旱处理的幼苗使用外源硅(Si)时,与未使用外源硅的T2相比其叶片相对含水量和超氧化物歧化酶(SOD)活性极显著上升,叶片水势也有下降趋势,这说明使用外源硅在一定程度上能够缓解干旱胁迫对沙枣幼苗的伤害。     

Effects of drought, transgenic expression of a fructan synthesizing enzyme and of mycorrhizal symbiosis on growth and soluble carbohydrate pools in tobacco plants

The effects of three conditions likely to affect soluble carbohydrate pools, namely drought, expression of barley sucrose: fructan 6-fructosyl transferase (6-SFT, EC 2.4.1.10) and the establishment of the arbuscular mycorrhizal symbiosis with Glomus mosseae were studied in a multifactorial experiment using tobacco ( Nicotiana tabacum ). Tobacco, a plant naturally unable to form fructan, accumulated fructan in leaves, and to a larger extent in the roots, when transformed with 6-SFT. Under drought conditions, growth was considerably reduced, but neither expression of 6-SFT nor mycorrhiza formation had an effect on growth rate. However, in response to drought, carbon partitioning was significantly altered towards accumulation of soluble sugars. In plants exposed to drought, pools of sucrose were greater than those of unstressed plants, particularly in their roots. In the transgenic plants expressing 6-SFT, there were also increased contents of the products of 6-SFT, namely fructan, most probably because of the increased availability of the substrate, sucrose. These effects were the same in the presence or absence of mycorrhiza. Hexoses (glucose and fructose) also increased in response to drought, primarily in the leaves. This effect of drought was little affected by the expression of 6-SFT, except that it slightly enhanced drought-induced glucose accumulation in roots. However, the presence of mycorrhiza led to a considerable reduction in drought-induced accumulation of hexoses in the leaves. The content of the fungal disaccharide trehalose was greatly increased in the roots of all mycorrhizal plants upon exposure to drought, particularly in some of the transgenic plants expressing 6-SFT.     

兰科菌根真菌对干旱胁迫下铁皮石斛生长和抗氧化能力及相关基因表达的影响

利用盆栽的方式研究了干旱胁迫下接种兰科菌根真菌(OM)对铁皮石斛生长的影响,并分析了铁皮石斛叶片相对含水量、游离脯氨酸含量、电解质渗透率、丙二醛(MDA)含量、活性氧成分、抗氧化酶活性变化,用定量PCR技术分析了相关抗氧化酶基因的表达特性,以探讨菌根真菌对铁皮石斛干旱胁迫的缓解作用及其机制。结果表明：(1)与正常水分条件相比,干旱胁迫显著降低了铁皮石斛幼苗的生物量和叶片相对含水量,提高了叶片电解质渗透率、脯氨酸含量、MDA含量、O-·2产生速率和H2O2水平。(2)菌根真菌能显著提高干旱胁迫下铁皮石斛叶片相对含水量,降低叶片电解质渗透率、脯氨酸含量、MDA含量、O-·2产生速率和H2O2水平;在不同水分条件下,菌根真菌均能有效促进铁皮石斛幼苗生长,其株高、根重、茎叶重和总生物量均大于未接种组。(3)菌根真菌可诱导干旱胁迫下铁皮石斛超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)基因的表达,提高SOD、POD和CAT的活性,有效缓解干旱胁迫对质膜的过氧化伤害。研究认为,菌根真菌能提高干旱胁迫下铁皮石斛的抗氧化酶活性及其相关基因表达水平,增强铁皮石斛抗氧化防御能力,有效缓解干旱胁迫对铁皮石斛幼苗生长的抑制。     

Antioxidant Enzyme Activities during in vitro Morphogenesis of Gladiolus and the Effect of Application of Antioxidants on Plant Regeneration

Activity of antioxidant enzymes was evaluated during somatic embryogenesis and shoot organogenesis from cultured leaf segments of Gladiolus hybridus Hort. The effect of exogenous antioxidants on somatic embryogenesis and shoot organogenesis has also been monitored. Activity of superoxide dismutase (SOD) gradually increased during somatic embryogenesis. while activities of catalase (CAT) and peroxidase (POX) decreased. In contrast, increase in CAT and POX activity and a concomitant decrease in SOD activity were noted during shoot organogenesis. Exogenous application of antioxidants such as glutathione (GSH), α-tocopherol and ascorbate (AA) inhibited somatic embryogenesis but stimulated shoot organogenesis. The frequency of somatic embryogenesis increased with the addition of H₂O₂. However, H₂O₂ inhibited shoot organogenesis. This revised version was published online in July 2006 with corrections to the Cover Date.     

低温胁迫下不同光照条件对锦熟黄杨抗氧化酶活性的影响

研究了锦熟黄杨（Buxus sempervirens L.）在低温胁迫下不同光照条件（12 h光照/12 h黑暗、24 h全光、24 h全黑）对其抗氧化酶活性的影响,结果表明：低温不同光照条件下细胞膜透性和丙二醛含量均高于对照（20℃ 12 h光照/12 h黑暗）,细胞膜透性和丙二醛含量在5℃ 24 h光照条件下最大;低温胁迫下SOD活性高于对照,并在5℃ 24 h光照条件下达到最高值;CAT的活性仍维持较高水平,5℃ 12 h光照/12 h黑暗显著高于对照及其它处理;在低温有光照条件下,POD活性升高,黑暗条件下POD活性低于对照。低温胁迫下POD、SOD和CAT的活性均呈上升趋势,可能是植株具有较强抗性的原因。     

水分胁迫对芒果(Mangifera indica L.)幼叶细胞活性氧伤害的影响

对芒果进行了水分干旱胁迫处理,结果表明,水分胁迫使芒果幼叶的相对含水量ＲＷＣ（ｒｅｌ－ａｔｉｖｅ ｗａｔｅ ｃｏｎｔｅｎｔ）和叶水势ΨＴ下降,芒果幼叶的超氧离子Ｏ＾－２产生速率随水分胁迫处理强度加大而增加,丙二醛ＭＤＡ（ｍａｌｏｎｄｉａｌｄｅｈｙｄｅ）含量的变化趋势与Ｏ＾－２产生速率的变化趋势相似超氧经歧化酶ＳＯＤ（ｓｕｐｅｒｏｘｉｄｅ ｄｉｓｍｕｔａｃｅ）,这氧化物酶ＰＯＤ（ｐｅｒｏｘｉｄａｓｅ     

干旱胁迫对甘草幼苗保护酶活性及脂质过氧化作用的影响

甘草（Glycyrrhiza uralensis Fisch.)幼苗用PEG6000（－2.5Mpa,-1.5Mpa)模拟干旱处理,测定了4d中叶的MDA含量,膜相对透性及几种保护酶（SOD,POD,ASP,CAT）活性变化情况。结果表明：－2．5Mpa胁迫下,MDA含量总体呈上升趋势;－1．5Mpa胁迫下,前两天略有降低,至第4天时,上升到与处理前基本持平的水平。细胞膜透性在处理前期下降,后期升高,低渗透胁迫较高渗透胁迫变化平缓。几种保护酶活性在干旱处理期间都有变化,POD除第1天降低外,其余几天均呈上升趋势;在处理前期,SOD活性升高,CAT活性下降,而在后期其变化为SOD活性降低,CAT活性升高,ASP活性变化波动较大,－2．5Mpa胁迫下,第1,第3天有两次上升峰,第4天较处理前下降了104．3％。在－1．5Mpa胁迫下的几种保护酶活性变化幅度较小。表明了高渗透胁迫能使膜过氧化而引起膜的损伤,低渗透胁迫程度对细胞膜脂过氧化及膜的透性影响较小,且可能对膜脂过氧化起到一定的防御作用。植物在干旱胁迫下保护酶系统的作用,可能是通过它们之间相互且保持一个稳定的平衡态而进行的。     

NaCl胁迫对甘薯叶片叶绿体超微结构及一些酶活性的影响

随ＮａＣｌ 胁迫浓度的提高,甘薯叶片叶绿体数目逐渐减少, 类囊体膜片层松散、扭曲、破裂并逐渐解体, 叶绿素含量下降。与此同时,Ｈ２Ｏ２ 、ＭＤＡ 含量增加, ＡＳＰ、ＳＯＤ 活性表现出先上升后下降的趋势。耐盐品种在ＮａＣｌ 胁迫下能维持较强的Ｈ２Ｏ２ 清除能力和较低的ＭＤＡ 水平     

干旱胁迫对宁夏枸杞生长及果实糖分积累的影响

文章研究不同干旱胁迫下宁夏枸杞生长及果实糖分积累的变化规律,为宁夏枸杞在干旱地区高产栽培提供参考依据。采用盆栽控水试验,设置正常灌水、轻度干旱、中度干旱和重度干旱处理,研究了干旱胁迫对宁夏枸杞植株生长、生物量分配以及果实糖分积累的影响。结果表明：干旱抑制宁夏枸杞新稍、果实、株高和地径的生长：随着干旱程度加剧,根和茎中干物质分配率逐渐升高,而枝条、叶和果实中干物质分配率大幅降低;轻度干旱有利于果实发育过程中果糖的积累,中度和重度干旱胁迫则不利于成熟期果糖和蔗糖积累;干旱胁迫明显降低成熟期转化酶、蔗糖磷酸合成酶（SPS）和蔗糖合成酶（SS）的活性;果实发育过程中果糖的含量与SPS和转化酶活性存在极显著相关。可见,在果实发育期,土壤含水量为田间持水量55％以上,能促进宁夏枸杞果实中糖分积累,有效提高果实品质。     

渗透胁迫对黑麦幼苗活性氧和抗氧化酶活性的影响

用20%聚乙二醇（PEG 6000）研究了渗透胁迫对黑麦（Secale cereale L.）幼苗活性氧（reactive oxygen species,ROS）和主要抗氧化酶——超氧化物歧化酶（superoxide dismutase,SOD）、过氧化氢酶（catalase,CAT）、抗坏血酸过氧化物酶（ascorbate peroxidase,APX）和谷胱甘肽还原酶（glutathione reductase,GR）活性的影响。结果表明,与对照相比,PEG处理明显提高了叶子和根中丙二醛（malondialdehyde,MDA）的含量、ROS的水平和以上4种抗氧化酶的活性。渗透胁迫下,叶子和根中MDA和ROS水平变化的规律基本相似,但抗氧化酶活性在2种器官中表现不完全相同,叶子中CAT的活性在对照和处理中无显著差异,但在根中差异明显,表明叶子中SOD、APX和GR在植物应答渗透胁迫中起重要作用,而根中这4种抗氧化酶都参与植物对胁迫的反应。GR活性随PEG处理变化幅度显著高于其它抗氧化酶,表明GR在黑麦应答渗透胁迫中所起作用可能强于其它抗氧化酶。     

Decline of Photosynthetic Pigments,Ribulose-1,5-Bisphosphate Carboxylase and Soluble Protein Contents,Nitrate Reductase and Photosynthetic Activities,and Changes in Thylakoid Membrane Protein Pattern in Canopy Shade Grapevine (Vitis Vinifera L. cv. Moscato Giallo) Leaves

In canopy shade leaves of grapevine (Vitis vinifera L. cv. Moscato giallo) grown in the field the contents of chlorophyll (Chl), carotenoids (Car), and soluble protein per fresh mass were lower than in sun leaves. RuBPC activity, in vivo nitrate reductase activity (indicator of nitrate utilisation), apparent electron transport rate, and photochemical fluorescence quenching were also significantly reduced in canopy shade leaves. When various photosynthetic activities were followed in isolated thylakoids, canopy shade leaves exerted a marked inhibition of whole chain and photosystem (PS) 2 activity. Smaller inhibition of PS1 activity was observed even in high-level canopy shade (HS) leaves. The artificial exogenous electron donors, DPC and NH₂OH, significantly restored the loss of PS2 activity in HS leaves. Similar results were obtained when F_v/F_m was evaluated by Chl fluorescence measurements. The marked loss of PS2 activity in canopy shade leaves was due to the loss of 47, 43, 33, 28–25, 23, 17, and 10 kDa polypeptides.     

3种滨藜属牧草苗期叶片解剖结构及生理特性对干旱的响应

通过盆栽控水试验,设置5个干旱胁迫水平,分别为最大田间持水量的80%(CK)、60%(轻度胁迫)、45%(中度胁迫)、30%(重度胁迫)、20%(极重度胁迫),并同步设计充足灌水后自然干旱实验,测定干旱胁迫对3种滨藜属牧草叶片形态解剖结构、叶片相对含水量、叶绿素含量、净光合速率、可溶性糖含量、质膜相对透性和丙二醛含量等生理生化指标的影响,以明确3种滨藜属牧草的抗旱特性,并探索其抗旱机理。结果表明:(1)3种滨藜属牧草均具有适应旱生环境的典型叶片结构特征,即在干旱胁迫条件下叶片组织结构形态表现为叶片栅栏组织逐渐变薄,而海绵组织在胁迫早期先变薄后增厚的现象,叶肉组织结构紧密度也出现了先降低后增高的规律。(2)随着干旱胁迫的加剧,叶片的可溶性糖含量增加,而其相对含水量减少,3种滨藜属牧草在土壤含水量很低的情况下叶片仍能保持高于52%的相对含水量。(3)在干旱胁迫下,3种滨藜属牧草叶片的叶绿素含量、净光合速率、气孔导度和蒸腾速率都发生显著变化,细胞膜受到的伤害程度有明显差异。(4)3种滨藜属牧草抗旱能力均较强,在干旱胁迫下其抗旱性综合表现为灰白滨藜变种1灰白滨藜变种2四翅滨藜。     

Effect of Iron Deficiency Induced Changes on Photosynthetic Pigments,Ribulose-1,5-Bisphosphate Carboxylase,and Photosystem Activities in Field Grown Grapevine (Vitis Vinifera L. cv. Pinot Noir) Leaves

The effect of iron deficiency on photosynthetic pigments, ribulose-1,5-bisphosphate carboxylase (RuBPC), and photosystem activities were investigated in field grown grapevine (Vitis vinifera L. cv. Pinot noir) leaves. The contents of chlorophyll (Chl) (a+b) and carotenoids per unit fresh mass showed a progressive decrease upon increase in iron deficiency. Similar results were also observed in content of total soluble proteins and RuBPC activity. The marked loss of large (55 kDa) and small (15 kDa) subunits of RuBPC was also observed in severely chlorotic leaves. However, when various photosynthetic electron transport activities were analysed in isolated thylakoids, a major decrease in the rate of whole chain (H₂O methyl viologen) electron transport was observed in iron deficient leaves. Such reduction was mainly due to the loss of photosystem 2 (PS2) activity. The same results were obtained when F_v/F_m was evaluated by Chl fluorescence measurements in leaves. Smaller inhibition of photosystem 1 (PS1) activity was also observed in both mild and severely chlorotic leaves. The artificial electron donors, diphenyl carbazide and NH₂OH, markedly restored the loss of PS2 activity in severely chlorotic leaves. The marked loss of PS2 activity was evidently due to the loss of 33, 23, 28-25, and 17 kDa polypeptides in iron deficient leaves.