不同激素对三倍体毛白杨腋芽诱导和增殖效应的研究

在MS基本培养基中附加不同种类和浓度的激素,对三倍体毛白杨腋芽诱导和增殖培养的效果进行了对比试验,结果表明:MS+6-BA0.5～1.0 mg/L+NAA0.05 mg/L作为腋芽诱导培养基效果较好;单一激素对腋芽的增殖不利,将6-BA和GA3配合使用,腋芽增殖效果较好;细胞分裂素是导致植株玻璃化的主要原因;GA3对6-BA有明显的增效作用,它既能促进腋芽的增殖生长,又能防止和减轻玻璃苗的产生.     

EFFECTS OF PHYTOHORMONES ON PROLINE CONTENT AND ANTIOXIDANT ENZYMES OF VARIOUS WHEAT CULTIVARS UNDER SALINITY STRESS

Salinity stress is one of the important agricultural problems in the world. A factorial experiment based on completely randomized design with four replications was conducted to evaluate the effects of phytohormones (gibberellic acid and abscisic acid) on the activity of antioxidant enzymes (peroxidase, superoxide dismutase and catalase), rubisco activity and content, and proline in three wheat cultivars (Gascogen, Zagros, and Kuhdasht) under control and salinity stress (3.5 and 7 dS m^?1). The results showed that salinity stress (3.5 and 7 dS m^?1) decreased the activity of catalase, rubisco, carboxylase, but increased peroxidase, superoxide dismutase activity and proline content. Gibberellic acid caused 58.03% increased in rubisco carboxylase activity in Zagros at 7 dS m^?1 in comparison with abscisic acid under salinity stress compared with the control plants in Kuhdasht. Activity of superoxide dismutase in Kuhdasht cultivar at 7 dS m^?1 salinity level showed 76.43% increased in Gascogen under salinity stress compared with the control plants with gibberellic acid application. The highest proline content as an osmolyte was found in Zagros at 7 dS m^?1 salinity level with abscisic acid (194 μmol g^?1 DM) application. Peroxidase activity increased 83.31% and catalase activity decreased 61.27% compared with the control plants in Zagros. Gibberellic acid application significantly prevented reduction in rubisco content under salinity stress. In conclusion, increased in peroxidase and superoxide dismutase activity and proline content decreased the adverse effects of salinity stress on studied cultivars. Also, the foliage spray of gibberellic acid enhanced and improved the growth condition. In this experiment, Zagros cultivar showed more tolerance to salinity stress than the other two cultivars.     

A synopsis of symbiotic nitrogen fixation and other apparently similar host‐microorganism interactions

Physical, physiological and biochemical processes occurring during colonization, infection, and nodule development and maintenance phases of an effective legume‐rhizobia symtiotic nitrogen fixation system are discussed. Limited knowledge of host reactions to invasion by rhizobia which result in failure to establish a symbiotic nitrogen fixation system are related to more thoroughly researched reactions of resistant host plants to invastion by pathogenic organisms. The most common resistant host responses are an increase in the production of phenolic compounds and phenol oxidizing enzymes. Many of the pheolic compounds or their quinones produced by enzymatic oxidation inhibit the action cell wall degrading enzymes and phytohormones, are antibiotic toward pathogenic organisms, and are phytotoxic to host plant cells. It is postulated that similar host responses result with rhizobia invasion and that the magnitude of these responses determine specificity of legume‐rhizobia symbiosis.     

The role of photoprotection in defence of two wheat genotypes against Zymoseptoria tritici

This study provides new insights into the role of photoprotection in preformed and induced defence of two wheat genotypes with contrasting phenotypes to infection by Zymoseptoria tritici. We investigated the mechanisms of the photoprotective response during early infection, including nonphotochemical quenching (NPQ), β-carotene-derived xanthophylls, reactive oxygen species, and the phytohormones abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA). Furthermore, we quantified the effects of pathogenesis on photosynthesis, stomatal control, and expression of plant defence molecular markers. The photoprotective mechanism of successful defence involved the qI component of NPQ leading to rapid down-regulation of photosystem II quantum yield and chlorophyll a:b, increased biosynthesis of the xanthophyll neoxanthin and ABA, and the expression of chloroplast-specific enzymes to engage in scavenging of O₂^●−. Elevated ABA in the resistant genotype correlated with preformed leaf defence traits including low stomatal density, increased expression of wax biosynthesis, and lignification. Z. tritici exhibited reduced germination and branching on the resistant host genotype and hijacked stomatal control in both genotypes by enhancing stomatal sensitivity to light. Increased biosynthesis of JA and anthocyanins, in contrast to SA, were quantified in the incompatible interaction. Our results indicate that ABA and JA in antagonistic action to SA were associated with defence in the resistant genotype, Cougar, against Z. tritici.     

金叶银杏硬枝扦插繁殖生根过程及其生根机制研究

【目的】研究不同生长调节剂处理对金叶银杏硬枝扦插生根率和成活率的影响,探讨金叶银杏的生根机制,为金叶银杏苗木扦插快繁技术体系的建立提供技术支持和理论指导。【方法】通过NAA和IBA处理金叶银杏硬枝插穗,检测它们对插穗的生根状态、生根指标及IBA对扦插过程中插穗皮部可溶性糖、抗氧化酶、激素含量的影响,探究金叶银杏硬枝扦插繁殖技术和生根机理。【结果】1)金叶银杏插穗愈伤组织诱导期和形成期、不定根发生期和形成期分别在插后的20~26、26~42、42~53、53~79 d。2)800 mg·L^-1 IBA和400 mg·L^-1 NAA+400 mg·L^-1IBA(混合)处理的插穗愈伤组织和不定根出现期及生根率与根数都较其他相应处理的效果好,其中生根率分别达64.4%和51.1%;不定根数分别达8.6条和9.3条。3)插穗生根过程中(500 mg·L^-1 IBA处理)基部韧皮部的SOD、PPO活性在插后40、60 d达到高峰,均比对照提前20 d达到峰值;插穗的POD活性出现上升-下降-升高的趋势,插穗可溶性糖也出现升高-下降-升高的趋势,但时间点不一致;而淀粉的含量出现下降-上升的趋势。4)生根期间插穗基部韧皮部的IAA含量出现了2个峰值和一个谷值;而ZR含量在第40天达到峰值后下降;GA含量先下降后上升;ABA含量在插后的前期高后期低,且值都低于同期对照。IAA/ABA比值在插后的第40天(愈伤组织形成期)达到谷底,后又上升(不定根形成期)。IAA/GA在插后的40~60 d内快速上升,80 d后又开始大幅下降;IAA/ZR值在扦插愈伤组织形成期(40 d)呈下降趋势,到60 d时(不定根发生期)又急剧上升到峰值。【结论】高活性的SOD和POD有利于插穗初期愈伤组织的形成(40 d),高活性的POD与PPO有利于不定根的形成(60 d)。较高的IAA含量是保证愈伤组织形成(20~40 d)的必要条件,不定根形成期(60 d)需要较高的IAA/ZR、IAA/ABA、IAA/GA比值。本研究为金叶银杏扦插繁殖技术和生根机理的研究及金叶银杏苗木的快速繁殖生产提供技术支持。     

热激处理对柰李抗冷性及其内源激素含量的影响

研究6种热激处理（36℃4h，36℃8h，40℃4h，40℃8h，44℃ 0．5h，44℃1h）对柰李贮藏过程中内源1AA（吲哚-3-乙酸），GA3（赤霉素），ABA（脱落酸），ZR（玉米素核苷）的含量的影响及其与柰李冷害发生的关系．结果表明：适当的热激处理（温度为36-40℃；时间约4h）能够诱导IAA，GA3，ABA的产生，但对ZR的诱导效果不明显；内源激素对冷害发生率的作用相对滞后，贮藏0d（热处理后立即测定）的IAA，GA3，ABA含量与贮藏70d的冷害发生率存在显著相关性，相关系数尺为0．999，R^2为0．998，回归方程为：A=30．567—1．057 B—116．08 C-0．907 D-0．1836E，其中，A为冷藏70d柰李的冷害发生率；B，C，D，E分别为冷藏0d的柰李中IAA，ABA，ZR，G13的含量．     

干旱胁迫下几种柑桔植物内源激素含量的变化规律

本文研究了干旱胁迫下枳壳、纽荷尔脐橙和沙田柚内源激素含量的变化规律。结果表明:随着失水率增加,三种植物中吲哚乙酸(IAA)含量逐渐减少,脱落酸(ABA)含量逐渐增加,而赤霉酸(GA3)和玉米素(Z)含量变化有些起伏,但当失水率大于40%时,其含量逐渐减少。     

Floral induction in woody angiosperms

The long juvenile period of trees is a severe impediment to study of reproductive biology and genetic inheritance, and is a serious constraint for traditional breeding programs. Very little effort has been directed toward the development of practical methods for inducing early flowering in most woody angiosperms, particularly members of the genus Populus. This review is intended to stimulate interest in, and provide direction for, future research in this area. An emphasis is placed on techniques that can be applied easily and inexpensively. Inductive treatments discussed include: phytohormones (gibberellins, cytokinins, abscisic acid, ethylene and auxin); growth retardants (paclobutrazol, uniconazole, daminozide, chlormequat and cimecthacarb); physical constraints (girdling, root restriction and shoot training); cultural conditions (photoperiod, mineral nutrition, moisture stress and temperature); and grafting. Recent reports on stimulation of flowering by genetic transformation with floral homeotic genes are also described. Several research avenues which appear promising are proposed for near-term study.     

The control of root hair formation: suggested mechanisms

Little is known about the physiological regulation of root hair development. Though the literature on the topic is fragmentary, with many gaps, it has been used to put forward some proposals for a central regulatory mechanism, taking note especially of the strong physiological influence of environmental factors on root hair formation. A hypothesis which implicates ethylene (ET) in this mechanism is proposed. This hypothesis is supported by numerous indications and observations in the literature about the effect of ET on cell wall formation and cell wall properties during the phase of root expansion and hair formation. It is assumed that environmental conditions control the effective ET concentration in epidermal hair-forming cells; they influence root development and ET production, while, through affecting the rhizosphere, they modify gas exchange at the root surface, accelerating removal of ET thereby limiting its function in hair formation. In such a way the effects of various specific factors (e.g. soil temperature, bulk density, gas exchange at the root surface or the effect of nutrients) might be manifestations of a central regulatory mechanism. The hope is that this hypothesis will stimulate further research and some suggestions are made as to the direction such research might take.     

马铃薯试管薯形成过程中几种内源激素的变化

 以马铃薯早熟品种‘费乌瑞它’脱毒试管苗为材料, 在试管薯形成过程中, 研究其GA₃、IAA、6- 呋喃氨基嘌呤( KT) 、6- 苄氨基嘌呤( BAP) 、ABA 含量的变化。结果表明: 无论是换入试管薯诱导培养基前的试管苗, 还是试管薯诱导形成过程中的母株试管苗, 根内各种内源激素含量始终高于茎叶。随着诱导环境的改变, 以及匍匐茎、试管薯的形成和发育, 各种内源激素含量发生明显变化。转入诱导培养基后的试管苗在光照培养条件下, 茎叶内GA3、IAA、KT、BAP 和根内ABA 含量均有不同程度的增加;黑暗培养3 d 匍匐茎形成时, GA₃、KT、BAP 及茎叶内IAA 含量下降; 黑暗培养7 d 匍匐茎顶端开始膨大时, 茎叶内GA₃、KT、BAP 含量再次增高, 而根内GA₃、BA 含量继续下降, IAA、ABA 含量无明显变化; 黑暗培养14 d 试管块茎基本形成时, IAA、BAP 含量缓慢上升, 根内GA₃ 含量下降, 茎叶GA₃ 含量处于相对稳定状态。