<Emphasis Type="Italic">In vitro</Emphasis> shoot multiplication through shoot tip cultures of <Emphasis Type="Italic">Decalepis hamiltonii</Emphasis> Wight &; Arn., a threatened plant endemic to Southern India

Summary An efficient and rapid micropropagation system was developed for a food and medicinally important endangered shrub, Decalepis hamiltonii (‘swallow root’), through shoot multiplication. The influence of 2.5–7.5 μM isopentenyladenine (2iP), 4.4–17.7 μM 6-benzyladenine, 2.3–4.7 μM kinetin, 2.8–6.8 μM thidiazuron, and 2.3–11.4 μM zeatin alone and in combination with 0.3–0.9 μM indole-3-acetic acid (IAA) on in vitro multiple shoot production was studied. The maximum number of multiple shoots (6.5±0.4) was induced from shoot tips cultured on agar-based Murashige and Skoog (MS) medium containing 4.9 μM 2iP. But, both zeatin (9.1 μM) and kinetin (4.7 μM) in combination with IAA (0.6 μM) were able to produce a maximum of 5.0±0.4 and 5.1±0.4 multiple shoots, respectively. Further elongation of shoots and adventitious shoot formation was obtained on medium containing 2.5 μM 2iP and 0.3 μM gibberellic acid. Elongated shoots were separated and rooted on MS medium supplemented with 9.8μM indole-3-butyric acid (IBA) and various phenolic compounds within 5–6 wk. Phloroglucinol and salicylic acid interaction with IBA stimulated in vitro rooting of shoots. Successful field transfer was achieved in rooted plantlets.     

In vitro propagation of the Greek olive cultivar `Chondrolia Chalkidikis'

The effect of basal media (Woody Plant Medium (WPM), Quoirin and Lepoivre (QL) and Olive Medium (OM)) and of various concentrations of cytokinins (6-benzyladenine (BA), zeatin, 6-(,-dimethylallyl-amino) purine (2iP)), solely or in combinations with each other and with gibberellic acid (GA₃), on in vitro shoot proliferation of the greek olive cultivar `Chondrolia Chalkidikis' was investigated. WPM proved to be the most effective one, resulting in better morphological appearance of the microshoots produced. The highest number of new microshoots/explant (1.68), with a 3.0 cm shoot height and a 4.2 proliferation rate, was obtained when this medium was supplemented with 20 M zeatin. The number of microshoots/explant and proliferation rate increased to 1.85 and 6.8, respectively, by using the combination of 5–20 M zeatin with 1 M BA, but shoot height was reduced. 2iP was the least effective of the cytokinins tested. Combination of 20 M zeatin with 10 M GA₃ affected positively shoot proliferation resulting in 1.80 microshoots/explant, 3.0 cm shoot height and 7.0 proliferation rate. However, the same concentration of GA₃ in combination with 1 M BA reduced the number of new microshoots/explant (0.48) as well as the proliferation rate (2.4), although shoot height remained nearly the same (2.7). The effect of indole-3-butyric acid (IBA), -naphthaleneacetic acid (NAA) and putrescine on root induction was also studied. A rooting percentage of up to 70% and 2.3 roots/microshoot were achieved by the combination of 12 M IBA + 3 M NAA, however, abscission of shoot tips and leaves appeared. Both variables were increased, up to 93% and 4.0, respectively, by the addition of 30 M putrescine in the medium, without any undesired side effect. After acclimatization, survival of rooted microshoots was high (90%) while that of non-rooted ones was low (30%).     

Growth and Endogenous Cytokinins of Juniper Shoots as Affected by High Metal Concentrations

The growth and the content of endogenous cytokinins (CKs) of current-year-old shoots from juniper plants (Juniperus communis L.) growing over and off ore site were compared. The juniper shoots from ore site (M plants) had higher metal content and exhibited delayed growth. Less bases and nucleosides of Z- and iP- type CK and more iP-conjugates were present in the M shoots. These changes were probably due to inhibited CK export from the roots and/or altered CK metabolism forming less biologically active CKs.     

Changes in Cytokinin Distribution in the Ovule and Ovary of Taraxacum officinale Web. in Early Stages of Embryogenesis

Quantitative changes in the hormonal status of the ovules and ovaries were first studied in Taraxacum officinale Web. at the early stages of embryogenesis. The plant material was analyzed by ELISA using labeled anti-rabbit antibodies. A new procedure for differential and quantitative determination of the main endogenous cytokinins based on the estimation of the effective zeatin and zeatin riboside concentrations from calibration curves constructed using zeatin and zeatin riboside as standard antigens was developed. It was shown that, at the three initial stages of embryogenesis examined, the concentration of zeatin uniformly increased in T. officinale ovules. The concentration of zeatin riboside, conversely, uniformly decreased. However, their total concentration changed insignificantly. A gradual increase in the concentration of the active and storage hormone forms from the ovary to the ovule was shown.     

玉米素和IAA对番茄子叶再生的影响

高水平的外源ZT抑制番茄子叶不定芽形成,导致畸形芽大量出现,延缓再生芽的生根过程。在低水平的ZT和高浓度的IAA共同作用下,不定芽的再生速度加快,正常芽比例增加,后期生根过程明显加快。     

抗玉米素核苷的单克隆抗体制备及内源玉米素核苷的酶联免疫吸附测定

通过二次成功的细胞融合,共获得三株分泌抗玉米素核苷(ZR)单克隆抗体的稳定杂交瘤系F_2E_6、F_3G_6和F_1B_9。其中F_2E_6分泌的单抗属IgG_1、F_3G_6、F_1B_9分泌的单抗均属IgM。以F_2E_6、F_3G_6单抗为基础的ELISA对ZR的检测灵敏度为0.05pmol(—18pg),线性检测范围为0.05—50pmol。除玉米素(Z)外,F_2E_6、F_3G_6单抗与IPA、6-BA、KT和腺苷几种ZR类似物的交叉反应值都小于0.18％。用ELISA测定F_2E_6单抗与ZR反应的亲和常数为2.36±0.99×10~(-8)M。本文还报道了包埋抗原的ELISA在植物内源细胞分裂素测定中的应用,并用此方法测定了黄化玉米(Zea mays L.)幼苗中ZR的含量。     

Functional and molecular characterization of adenosine transport at the rat inner blood-retinal barrier

The purpose of the present study was to characterize the adenosine transport system(s) at the inner blood-retinal barrier (inner BRB). A conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2), used as an in vitro model of the inner BRB, expresses equilibrative nucleoside transporter 1 (ENT1), ENT2, concentrative nucleoside transporter 2 (CNT2), and CNT3 mRNAs. TR-iBRB2 cells exhibited an Na⁺-independent and concentration-dependent [³H]adenosine uptake with a Michaelis-Menten constant of 28.5 μM and a maximum uptake rate of 814 pmol/(min mg protein). [³H]Adenosine uptake by TR-iBRB2 cells was strongly inhibited by 2 mM adenosine, inosine, uridine, and thymidine. On the other hand, this process was not inhibited by 100 nM nitrobenzylmercaptopurine riboside and dipyridamole. These uptake studies suggest that ENT2 is involved in [³H]adenosine uptake by TR-iBRB2 cells. Quantitative real-time PCR revealed that the expression of ENT2 mRNA is 5.5-fold greater than that of ENT1 mRNA. An in vivo study suggested that [³H]adenosine is transported from the blood to the retina and significantly inhibited by adenosine and thymidine. The results of this study show that ENT2 most likely mediates adenosine transport at the inner BRB and is expected to play an important role in regulating the adenosine concentration in the retina.     

ABA对ZT对小麦叶细胞质膜某些生理特性的影响

激素的原初作用一般与细胞膜的生理变化密切相关,ABA对细胞膜的透性增加,ZT对细胞膜的影响较小;二者对于膜的离子外渗的影响同透性一样,对于叶绿体膜上的Ca^ 2-ATPase,Mg^ 2-ATPase,ABA抑制其活性,ZT则促进其活性的增加。因此,二者可影响叶绿体膜内外离子的交换,改变膜内外质子的平衡,ABA降低光下叶绿体悬浮介质的pH,降低膜的电热值,ZT则增加其电势。两种激素对于膜生理变化的影响是其影响植物细胞衰老,叶绿体光合作用的机制之一。     

Trigonelline biosynthesis and the pyridine nucleotide cycle in Coffea arabica fruits: Metabolic fate of [carboxyl-C]nicotinic acid riboside

Trigonelline is a major component in coffee seeds and may contribute to the bitter taste of the resultant beverage. To determine the trigonelline biosynthetic pathway in coffee fruits, we investigated the metabolic fate of [carboxyl-¹⁴C]nicotinic acid riboside and in situ activity of related enzymes. Exogenously supplied [carboxyl-¹⁴C]nicotinic acid riboside was rapidly converted to nicotinic acid mononucleotide and was utilized for NAD synthesis. Nicotinic acid riboside was also used for trigonelline synthesis, but this process took longer than NAD synthesis. These results indicate that an efficient nicotinic acid riboside salvage system functions in coffee fruits, and that trigonelline is synthesized mainly from nicotinic acid produced by the degradation of NAD.     

Spatial division of phosphoenolpyruvate carboxylase and nitrate reductase activity and its regulation by cytokinins in CAM-induced leaves of Guzmania monostachia (Bromeliaceae)

Crassulacean acid metabolism (CAM) is a physiological adaptation of plants that live in stress environment conditions. A good model of CAM modulation is the epiphytic bromeliad, Guzmania monostachia, which switches between two photosynthetic pathways (C₃–CAM) in response to different environmental conditions, such as light stress and water availability. Along the leaf length a gradient of acidity can be observed when G. monostachia plants are kept under water deficiency. Previous studies showed that the apical portions of the leaves present higher expression of CAM, while the basal regions exhibit lower expression of this photosynthetic pathway. The present study has demonstrated that it is possible to induce the CAM pathway in detached leaves of G. monostachia kept under water deficit for 7 d. Also, it was evaluated whether CAM expression can be modulated in detached leaves of Guzmania and whether some spatial separation between NO₃⁻ reduction and CO₂ fixation occurs in basal and apical portions of the leaf. In addition, we analyzed the involvement of endogenous cytokinins (free and ribosylated forms) as possible signal modulating both NO₃⁻ reduction and CO₂ fixation along the leaf blade of this bromeliad. Besides demonstrating a clear spatial and functional separation of carbon and nitrogen metabolism along G. monostachia leaves, the results obtained also indicated a probable negative correlation between endogenous free cytokinins – zeatin (Z) and isopentenyladenine (iP) – concentration and PEPC activity in the apical portions of G. monostachia leaves kept under water deficit. On the other hand, a possible positive correlation between endogenous Z and iP levels and NR activity in basal portions of drought-exposed and control leaves was verified. Together with the observations presented above, results obtained with exogenous cytokinins treatments, strongly suggest that free cytokinins might act as a stimulatory signal involved in NR activity regulation and as a negative regulator of PEPC activity in CAM-induced leaves of G. monostachia during a diel cycle.