叶面喷施PP_(333)和6-BA对甜荞花芽分化及内源激素的影响

以甜荞品种‘北早生’和‘赤甜荞1号’为材料,利用多效唑(PP_(333))和6-苄基腺嘌呤(6-BA)在不同幼苗时期进行叶片喷施处理,并采用扫描电镜观察花芽分化过程,记录开花时间,调查开花和结实数,通过液质联用方法检测3种内源激素生长素(IAA)、赤霉素(GA_3)、脱落酸(ABA)及人工合成细胞分裂素(6-BA)含量,探究两种植物生长调节剂对甜荞的花芽分化及内源激素含量的影响,为甜荞花期调控提供依据。结果显示:(1)第二片真叶期喷施100mg·L~(-1)PP_(333)和150mg·L~(-1)6-BA能显著提高甜荞结实率和单株产量,两种处理的结实率分别较对照提高49.5%、39.4%,单株产量分别提高41.8%、23.0%。(2)观察甜荞花芽分化过程并将其划分5个时期,分别为生长锥分化前期、生长锥分化期、小花原基分化期、雌雄蕊分化期和雌雄蕊形成期,在第二片真叶期喷施PP_(333)和6-BA均加快了甜荞花芽分化进程,使其开花时间提前。(3)喷施PP_(333)在幼苗期和现蕾期降低了内源IAA、6-BA含量,增加GA_3、ABA含量,而在盛花期增加内源IAA、6-BA含量,降低ABA、GA_3含量;喷施6-BA在幼苗期和现蕾期增加了内源GA_3、IAA含量,在盛花期降低了内源GA_3、IAA含量,3个时期均降低了内源ABA含量,增加了6-BA含量。研究发现,第二片真叶期是调控甜荞小花发育的关键时期,在此时叶面喷施100mg·L~(-1)PP_(333)和150mg·L~(-1)6-BA的调控效果最佳,可加快甜荞花芽分化进程,使开花时间提前,增加单株结实粒数,提高甜荞品种的结实率和单株产量;PP_(333)主要是通过减少甜荞开花数,增强弱势小花活力来提高结实粒数,而6-BA主要是利用增加开花数,提高有效可孕小花数来增加结实粒数。     

Enantioselective Degradation of (2RS, 3RS)‐Paclobutrazol in Rat Liver Microsomes

Paclobutrazol, with two stereogenic centers, but gives only (2R, 3R) and (2S, 3S)‐enantiomers because of steric‐hindrance effects, is an important plant growth regulator in agriculture and horticulture. Enantioselective degradation of paclobutrazol was investigated in rat liver microsomes in vitro. The degradation kinetics and the enantiomer fraction were determined using a Lux Cellulose‐1 chiral column on a reverse‐phase liquid chromatography–tandem mass spectrometry system. The t_1/2 of (2R, 3R)‐paclobutrazol is 18.60 min, while the t_1/2 of (2S, 3S)‐paclobutrazol is 10.93 min. Such consequences clearly indicated that the degradation of paclobutrazol in rat liver microsomes was stereoselective and the degradation rate of (2S, 3S)‐paclobutrazol was much faster than (2R, 3R)‐paclobutrazol. In addition, significant differences between the two enantiomers were also observed in enzyme kinetic parameters. The V_max of (2S, 3S)‐paclobutrazol was more than 2‐fold of (2R, 3R)‐paclobutrazol and the Cl_int of (2S, 3S)‐paclobutrazol was higher than that of (2R, 3R)‐paclobutrazol after incubation in rat liver microsomes. These results may have potential implications for better environmental and ecological risk assessment for paclobutrazol. Chirality 27:344–348, 2015. © 2015 Wiley Periodicals, Inc.     

Plant growth regulator interactions results enhancement of antioxidant enzymes in Catharanthus roseus

Abstract

The present investigation was carried out with the objectives to understand the effect of paclobutrazol, gibberellic acid and Pseudomonas fluorescens on the enzymatic antioxidants like Ascorbate peroxidase (APX, EC: 1.11.1.11), Superoxide dismutase (SOD, EC: 1.15.1.1), Catalase (CAT, EC: 1.11.1.6), Peroxidase (POX, EC 1.11.1.7) and polyphenol oxidase (PPO, Ec 1.10.3.1) activities of Catharanthus roseus plants under field conditions. 10 mg l^?1 paclobutrazol, 5 µM gibberellic acid and 1 mg P. fluorescens concentrations were used for the treatments, and control plants were irrigated with well water. The treatments were given 38, 53, 68 and 83 days after planting (DAP) by soil drenching. The plants were taken randomly 45, 60, 75 and 90 DAP and separated into root, stem, leaves and flowers and used for estimating the antioxidant enzymes. The results showed that these plant growth regulators have significant effects on antioxidant enzymes of C. roseus.     

Gibberellin mediates the development of gelatinous fibres in the tension wood of inclined Acacia mangium seedlings

Background and Aims

Gibberellin stimulates negative gravitropism and the formation of tension wood in tilted Acacia mangium seedlings, while inhibitors of gibberellin synthesis strongly inhibit the return to vertical growth and suppress the formation of tension wood. To characterize the role of gibberellin in tension wood formation and gravitropism, this study investigated the role of gibberellin in the development of gelatinous fibres and in the changes in anatomical characteristics of woody elements in Acacia mangium seedlings exposed to a gravitational stimulus.

Methods

Gibberellin, paclobutrazol and uniconazole-P were applied to the soil in which seedlings were growing, using distilled water as the control. Three days after the start of treatment, seedlings were inclined at 45 ° to the vertical and samples were harvested 2 months later. The effects of the treatments on wood fibres, vessel elements and ray parenchyma cells were analysed in tension wood in the upper part of inclined stems and in the opposite wood on the lower side of inclined stems.

Key Results

Application of paclobutrazol or uniconazole-P inhibited the increase in the thickness of gelatinous layers and prevented the elongation of gelatinous fibres in the tension wood of inclined stems. By contrast, gibberellin stimulated the elongation of these fibres. Application of gibberellin and inhibitors of gibberellin biosynthesis had only minor effects on the anatomical characteristics of vessel and ray parenchyma cells.

Conclusions

The results suggest that gibberellin is important for the development of gelatinous fibres in the tension wood of A. mangium seedlings and therefore in gravitropism.     

The different dissipation behavior of chiral pesticide paclobutrazol in the brine during Chinese cabbage pickling process

Paclobutrazol (PBZ) is a kind of chiral pesticide, which is a plant growth regulator and has fungicidal activity. Because of the steric‐hindrance effect, there are two enantiomers (2S, 3S; 2R, 3R) in the production. This research studied on the dissipation behavior of chiral pesticide PBZ in the brine during the Chinese cabbage pickled process by phase column‐high performance liquid chromatography (HPLC). The result demonstrated the PBZ enantiomers had the different dissipation in the brine. The study on the behavior of chiral pesticide PBZ in food may provide more sufficient data and information for understanding the potential risk in food and evaluating the environmental pollution at the enantiomer level.     

多效唑对花生叶片多胺含量及衰老的调节作用

通过对大田条件下生殖生长期花生喷施不同浓度的多效唑,研究了多效唑对叶片内源多受及其它衰老指标的影响,结果证明多效唑对内源多胺的影响较复杂,多效唑降低了幼嫩叶片的多胺含量,却提高了成熟叶片衰老阶段的多胺含量,并起到延缓衰老的作用,讨论了多效唑影响多胺含量的可能原因。     

Reversing the inhibitory effect of paclobutrazol on seed germination of Amaranthus paniculatus by GA3, ethephon or ACC

The germination of Amaranthus paniculatus seeds was inhibited by applying paclobutrazol, a specific inhibitor of gibberellin biosynthesis. This inhibition was markedly counteracted by gibberellin A₃ (GA₃), suggesting that endogenous gibberellins are required for germination in this species. The inhibitory effect of paclobutrazol was also overcome by ethephon (2-chloroethylphosphonic acid) or the precursor of ethylene biosynthesis, ACC (1-aminocyclopropane-l-carboxylic acid). Thus the physiological effect of gibberellin can be mimicked by ethylene released from ethephon or synthesised from exogenous ACC. It is suggested, that endogenous gibberellins are involved in germination of Amaranthus paniculatus seeds and that action of GA₃ can be substituted by ethylene.Abbreviations ACC 1-aminocyclopropane-l-carboxylic acid - AMO-1618 (2-isopropyl-5methyl-4-trimethylammoniumchloride)-phenyl-l-piperidinium-carboxylate - ancymidol -cyclopropyl--(4-methoxyphenyl)-5-pyrimidine methanol - chloromequat chloride (2-chloroethyl)trimethylammoniumchloride - ethephon 2-chloroethylphosphonic acid - GA gibberellin A₃ - paclobutrazol (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-lyl)pentan-3-ol - Phosphon D 2,4,dichlorobenzyl-tributhylphosphoniumchloride - tetcyclacis 5,(4-chlorophenyl)-3,4,5,9,10-pentaaza-tetracyclo)5,4,1,0,Z,6,0^8,11 dodeca-3,9-diene     

Comparison of the role of gibberellins and ethylene in response to submergence of two lowland rice cultivars, Senia and Bomba

We examined the gibberellin (GA) and ethylene regulation of submergence-induced elongation in seedlings of the submergence-tolerant lowland rice (Oryza sativa L.) cvs Senia and Bomba. Elongation was enhanced after germination to facilitate water escape and reach air. We found that submergence-induced elongation depends on GA because it was counteracted by paclobutrazol (an inhibitor of GA biosynthesis), an effect that was negated by GA₃. Moreover, in the cv Senia, submergence increased the content of active GA₁ and its immediate precursors (GA₅₃, GA₁₉ and GA₂₀) by enhancing expression of several GA biosynthesis genes (OsGA20ox1 and -2, and OsGA3ox2), but not by decreasing expression of several OsGA2ox (GA inactivating genes). Senia seedlings, in contrast to Bomba seedlings, did not elongate in response to ethylene or 1-aminocyclopropane-1-carboxylic-acid (ACC; an ethylene precursor) application, and submergence-induced elongation was not reduced in the presence of 1-methylcyclopropene (1-MCP; an ethylene perception inhibitor). Ethylene emanation was similar in Senia seedlings grown in air and in submerged-grown seedlings following de-submergence, while it increased in Bomba. The expression of ethylene biosynthesis genes (OsACS1, -2 and -3, and OsACO1) was not affected in Senia, but expression of OsACS5 was rapidly enhanced in Bomba upon submergence. Our results support the conclusion that submergence elongation enhancement of lowland rice is due to alteration of GA metabolism leading to an increase in active GA (GA₁) content. Interestingly, in the cv Senia, in contrast to cv Bomba, this was triggered through an ethylene-independent mechanism.     

Nitrate, a signal relieving seed dormancy in Arabidopsis

Nitrate is an important nitrogen source for plants, but also a signal molecule that controls various aspects of plant development. In the present study the role of nitrate on seed dormancy in Arabidopsis was investigated. The effects of either mutations affecting the Arabidopsis nitrate reductase genes or of different nitrate regimes of mother plants on the dormancy of the seeds produced were analysed. Altogether, data show that conditions favouring nitrate accumulation in mother plants and in seeds lead to a lower dormancy of seeds with little other morphological or biochemical differences. Analysis of germination during seed development indicated that nitrate does not prevent the onset of dormancy but rather its maintenance. The effect of an exogenous supply of nitrate on seed germination was tested: nitrate in contrast to glutamine or potassium chloride clearly stimulated the germination of dormant seeds. Data show, moreover, that the Arabidopsis dual affinity nitrate transporter NRT1.1 (CHL1) may be involved in conveying the nitrate signal into seeds. Thus, nitrate provided exogenously or by mother plants to the produced seeds, acts as a signal molecule favouring germination in Arabidopsis. This signalling may involve interaction with the abscisic acid or gibberellin pathway.