Transport of Ca2+ across the tonoplast of intact vacuoles from Chenopodium album L. suspension cells: ATP-dependent import and inositol-1,4,5-trisphosphate-induced release

The removal of Ca²⁺ from the medium by intact vacuoles and microsomes of Chenopodium album was investigated by measuring INDO-1 fluorescence emission at 400 and 480 nm and the response of Ca²⁺ -selective mini-electrodes. The removal of Ca²⁺ depended on the presence of MgATP, displaying an apparent K _mATP of about 50 μM, a K _mCa of 400–500 nM, and a nucleotide specificity (%) of ATP (100) > CTP (49) > GTP (28) > UTP (20) > ADP = AMP (0). In the presence of saturating MgATP, the vacuoles reduced the [Ca²⁺] of the medium below 30 nM. Part of the Ca²⁺ removed from the medium was released again after adding micromolar concentrations of inositol-1,4,5-trisphosphate. This release of Ca²⁺ was inhibited by heparin. Since digitonin caused the release of the entire amount of Ca²⁺ removed from the medium in the presence of MgATP, we argue that the Ca²⁺ is not bound to membranes or sequestered otherwise, but is transported into the vacuoles (or vesicles) and remains freely mobile there. In accordance with the current literature, we conclude that the plant vacuole is an important store for mobile Ca²⁺ to be released for purposes of signal transduction. Since changes in the trans-tonoplast ΔpH and inhibition of the H⁺-translocating pumps had no significant influence on the ATP-dependent removal of Ca²⁺ from the cytoplasmic side, we argue that in C. album ATP-driven Ca²⁺ transport is the predominant form of Ca²⁺ translocation into the vacuole. Received: 11 July 1996 / Accepted: 18 October 1996     

Effect of solar radiation (UV and visible) at high altitude on CAM‐cycling and phenolic compound biosynthesis in Sedum album

The field experiment was carried out in order to compare the response of a CAM plant, Sedum album L., to solar radiation at a high altitude (2 100 m) with that at a low altitude location with respect to CAM and phenolic content. Treatment sites included (1) sun‐exposed, low altitude, (2) sun‐exposed, high altitude with different light treatments, including UV‐B and UV‐B + A screening, and (3) shade at high altitude. After a 70‐day treatment period, CAM‐cycling and phenolic compound content were analysed, and high altitude treatments were compared to the low altitude control. The sun‐exposed low altitude control was characterized by CAM‐cycling and a low phenolic compound content during the experiment. In plants transplanted to the high altitude, only the shaded group maintained a CAM‐cycling and a phenolic compound content similar to those of the sun‐exposed low altitude control. Samples under UV‐B and UV‐B + A filters showed similar responses, suggesting the absence of a specific UV‐A radiation effect. The screening of UV‐B or UV‐B + A radiation allowed plants to partially maintain a CAM‐cycling and induced a decrease in phenolic compound content. These responses under UV filters were, however, intermediate between those observed in sun‐exposed and shaded groups. These results demonstrate a specific effect of radiation from both visible (400–800 nm) and UV‐B (280–320 nm) bands on both CAM‐cycling and phenolic biosynthesis in S. album L. plants. These light‐dependent effects are discussed on a physiological basis and a possible interaction between CAM‐cycling and phenolic metabolism is suggested.     

湖北土荆芥挥发油化学成分研究

用色谱－质谱联用技术对湖北产土荆芥挥发油的化学成分进行了分析。鉴定了８０种组分。其中主要组分是：薄荷醇（３１．３３１％）α－松油烯（１３．２１０％）,香芹烯醇（８．５２６％）、对伞花烃（８．３４３％）、１,８－桉叶油素（７．４１７％）等５种化合物。被鉴定的８０种成分,共占挥发油总含量的９９．１１２％。     

土荆芥挥发性化感物质诱导蚕豆保卫细胞死亡及信号调节

为了探讨入侵植物土荆芥的化感作用机制,以其入侵地广泛种植的农作物蚕豆叶片下表皮为受试材料,通过对保卫细胞的活性分析,研究了土荆芥挥发油及其两种主要成分α-萜品烯和对伞花素诱导保卫细胞死亡及其信号调节的机制。结果表明:土荆芥挥发油、α-萜品烯、对伞花素具有显著的细胞毒性,随着处理剂量增加,保卫细胞存活率显著下降,细胞核出现了畸形、碎裂和降解等程序性细胞死亡的典型特征;活性氧(Reactive oxygen species,ROS)、一氧化氮合酶(Nitric oxide synthetase,NOS)和Ca~(2+)的组织化学定位显示,在土芥挥发油、α-萜品烯和对伞花素作用下,保卫细胞内ROS、NOS和Ca~(2+)的水平明显高于对照组;活性氧清除剂(AsA)、Ca~(2+)螯合剂(EGTA)和硝酸还原酶抑制剂(NaN——3)均可有效缓解土荆芥挥发油、α-萜品烯和对伞花素的细胞毒性,显著提高了保卫细胞的存活率(P0.05)。上述结果表明,ROS、NO和Ca~(2+)参与了土荆芥挥发油、α-萜品烯和对伞花素诱导蚕豆保卫细胞死亡的信号调节过程。土荆芥挥发油、α-萜品烯和对伞花素诱导的保卫细胞死亡,可能是通过ROS和NO调控保卫细胞内Ca~(2+)水平的变化而引起的。     

土荆芥挥发油化感胁迫对土壤胞外酶活性和微生物多样性的影响

入侵植物释放的化感物质可改变土壤理化性状和微生物群落结构,通过与土壤微生物的互作抑制本土植物生长。为了进一步诠释土荆芥化感作用机制,采用温室培养瓶法,探讨了其挥发油对土壤胞外酶活性和微生物多样性的影响。结果表明:土荆芥挥发油不同程度降低了脲酶、酸性磷酸酶、蔗糖酶和硝酸还原酶的活性(P0.05);较高剂量的挥发油处理组显著促进了过氧化氢酶活性(P0.05)。处理初期挥发油对土壤胞外酶活性影响较大,但随着处理时间延长,其影响逐渐减弱;处理16 d后,较高剂量(20μL和50μL)的挥发油处理组细菌数量显著高于对照(P0.05)。挥发油对土壤放线菌数量的影响表现为低剂量促进,高剂量抑制的效应;PCR-DGGE分析表明,随着挥发油处理剂量增加和处理时间延长,土壤中细菌和真菌的Shannonwiener多样性指数和丰富度指数均增大。结论:土荆芥挥发油可改变土壤微生物群落结构和胞外酶活性,增加土壤微生物多样性。     

Triterpene saponins from Chenopodium quinoa Willd

Twenty triterpene saponins (1-20) have been isolated from different parts of Chenopodium quinoa (flowers, fruits, seed coats, and seeds) and their structures have been elucidated by analysis of chemical and spectroscopic data including 1D- and 2D-NMR. Four compounds (1-4) were identified: 3beta-[(O-beta-d-glucopyranosyl-(1-->3)-alpha-l-arabinopyranosyl)oxy]-23-oxo-olean-12-en-28-oic acid beta-d-glucopyranoside (1), 3beta-[(O-beta-d-glucopyranosyl-(1-->3)-alpha-l-arabinopyranosyl)oxy]-27-oxo-olean-12-en-28-oic acid beta-d-glucopyranoside (2), 3-O-alpha-l-arabinopyranosyl serjanic acid 28-O-beta-d-glucopyranosyl ester (3), and 3-O-beta-d-glucuronopyranosyl serjanic acid 28-O-beta-d-glucopyranosyl ester (4). The following known compounds have not previously been reported as saponin constituents from the flowers and the fruits of this plant: two bidesmosides of serjanic acid (5,6), four bidesmosides of oleanolic acid (7-10), five bidesmosides of phytolaccagenic acid (11-15), four bidesmosides of hederagenin (16-19), and one bidesmoside of 3beta,23,30-trihydroxy olean-12-en-28-oic acid (20). The cytotoxicity of these saponins and their aglycones was tested in HeLa cells. Induction of apoptosis in Caco-2 cells by bidesmosidic saponins 1-4 and their aglycones I-III was determined by flow cytometric DNA analysis. The saponins with an aldehyde group were most active. The relationships between structure and cytotoxic activity of saponins and their aglycones are discussed.     

藜叶中黄酮类化合物体外抗氧化活性研究

为了探讨藜叶中黄酮类化合物的体外抗氧化活性,采用有机溶剂提取法和色谱柱法对藜叶中化学成分进行提取与分离;以Vc作对照,对分离纯化的芦丁、乙酸乙酯浸膏和正丁醇浸膏进行DPPH·、O2^-·和·OH的清除效果试验。结果表明：三者对DPPH·、O2^-·、·OH均具有清除作用,且与浓度呈量效关系,芦丁对·OH清除效果优于Vc,芦丁具有较强的清除DPPH·能力,其IC50为0．05μg／mL。     

藜的光合特性研究

5月中旬选取典型晴天用L I-6400便携式光合仪对藜从第一片完全展开叶倒数第3~5片功能叶进行有关光合参数的测定.结果表明:藜的光合日变化呈双峰型,有明显的“午休”现象,第1个峰值出现在8:30左右,P n达到9.34μm o l CO2.m-2.s-1;第2个峰值出现在16:00左右,P n为4.26μm o l CO2.m-2.-s 1.造成光合午休的主要原因是受气孔调节.在400μm o l.m o-l 1CO2浓度下藜的光饱和点(LSP)为1 350μm o l CO2.m-2.-s 1左右,光补偿点(LCP)为22.5μm o l CO2.m-2.-s 1左右;表观量子效率(AQY)为0.035μm o l CO2.m o-l 1photons.二氧化碳饱和点(CSP)在976μm o l CO2.m o-l 1左右,二氧化碳补偿点(CCP)在40μm o l CO2.m o-l 1左右,羧化效率(CE)为0.113 2μm o l CO2.m-2.-s 1.说明藜是一种具有较强耐荫能力的C3型阳性植物.     

Towards a better understanding of the Chenopodium album aggregate (Amaranthaceae) in the Middle East: A karyological,cytometric and morphometric investigation

The study of variation in nuclear genome size, especially when combined with common garden experiments, significantly contributes to disentangling interspecies relationships within taxonomically complicated plant groups. The Chenopodium album aggregate is among the morphologically most variable groups and consists of many weakly differentiated cosmopolitan entities. We analysed nuclear genome size variation in diploid and polyploid species of the aggregate from Iran using flow cytometry of 282 accessions from 88 populations of 7 species. To this end, we also determined chromosome numbers and performed a morphometric study to reveal the extent of intraspecific morphological variation. We found that Iranian species are exclusively diploid (C. vulvaria), tetraploid (C. novopokrovskyanum, C. strictum, C. sosnowskyi and C. chaldoranicum) or hexaploid (C. album subsp. album, C. album subsp. iranicum and C. opulifolium). Six homogeneous relative genome size groups were distinguished among the species studied. Our morphometric study surprisingly revealed that under similar ecological conditions Chenopodium species are morphologically stable and well distinguishable, exhibited very little morphological variation. Hence, immense variation in leaf shapes, branching and inflorescence organization seen in the field has not been repeated under greenhouse conditions. The only exception was C. album s. str. which exhibited numerous morphotypes, covering the variation of remaining species.     

Plants in a crowded stand regulate their height growth so as to maintain similar heights to neighbours even when they have potential advantages in height growth

Background and Aims

Although being tall is advantageous in light competition, plant height growth is often similar among dominant plants in crowded stands (height convergence). Previous theoretical studies have suggested that plants should not overtop neighbours because greater allocation to supporting tissues is necessary in taller plants, which in turn lowers leaf mass fraction and thus carbon gain. However, this model assumes that a competitor has the same potential of height growth as their neighbours, which does not necessarily account for the fact that height convergence occurs even among individuals with various biomass.

Methods

Stands of individually potted plants of Chenopodium album were established, where target plants were lifted to overtop neighbours or lowered to be overtopped. Lifted plants were expected to keep overtopping because they intercept more light without increased allocation to stems, or to regulate their height to similar levels of neighbours, saving biomass allocation to the supporting organ. Lowered plants were expected to be suppressed due to the low light availability or to increase height growth so as to have similar height to the neighbours.

Key Results

Lifted plants reduced height growth in spite of the fact that they received higher irradiance than others. Lowered plants, on the other hand, increased the rate of stem elongation despite the reduced irradiance. Consequently, lifted and lowered plants converged to the same height. In contrast to the expectation, lifted plants did not increase allocation to leaf mass despite the decreased stem length. Rather, they allocated more biomass to roots, which might contribute to improvement of mechanical stability or water status. It is suggested that decreased leaf mass fraction is not the sole cost of overtopping neighbours. Wind blowing, which may enhance transpiration and drag force, might constrain growth of overtopping plants.

Conclusions

The results show that plants in crowded stands regulate their height growth to maintain similar height to neighbours even when they have potential advantages in height growth. This might contribute to avoidance of stresses caused by wind blowing.