The impact of elevated carbon dioxide on the phosphorus nutrition of plants: a review

Background Increasing attention is being focused on the influence of rapid increases in atmospheric CO₂ concentration on nutrient cycling in ecosystems. An understanding of how elevated CO₂ affects plant utilization and acquisition of phosphorus (P) will be critical for P management to maintain ecosystem sustainability in P-deficient regions.Scope This review focuses on the impact of elevated CO₂ on plant P demand, utilization in plants and P acquisition from soil. Several knowledge gaps on elevated CO₂-P associations are highlighted.Conclusions Significant increases in P demand by plants are likely to happen under elevated CO₂ due to the stimulation of photosynthesis, and subsequent growth responses. Elevated CO₂ alters P acquisition through changes in root morphology and increases in rooting depth. Moreover, the quantity and composition of root exudates are likely to change under elevated CO₂, due to the changes in carbon fluxes along the glycolytic pathway and the tricarboxylic acid cycle. As a consequence, these root exudates may lead to P mobilization by the chelation of P from sparingly soluble P complexes, by the alteration of the biochemical environment and by changes to microbial activity in the rhizosphere. Future research on chemical, molecular, microbiological and physiological aspects is needed to improve understanding of how elevated CO₂ might affect the use and acquisition of P by plants.     

缺锌和HCO_3~-处理对诸葛菜和油菜有机酸特征的影响

以诸葛菜和油菜为材料,水培环境下设置4个不同的缺锌和碳酸氢根离子胁迫处理,分别为+Zn0(含Zn且不加HCO3-的处理组),+Zn10(含Zn且加10 mmol·L-1HCO3-的处理组),-Zn0(缺Zn且不加HCO3-的处理组)和-Zn10(缺Zn且加10 mmol·L-1HCO3-的处理组),利用离子色谱法分析了4个处理的两种植物幼苗器官(根、茎、叶)及根系分泌物中的有机酸特征。结果表明:(1)高浓度碳酸氢根离子处理显著增加了两种植物器官及根系分泌的有机酸总量,尤其是在缺锌和高浓度碳酸氢根离子双重胁迫下(-Zn10处理),诸葛菜器官和根系分泌的有机酸比油菜更敏感,草酸、柠檬酸和苹果酸是诸葛菜器官和根系分泌物中的优势酸,这三种有机酸的含量分别占其有机酸总量的75%及以上;(2)叶片是两种植物有机酸产生的主要器官,有机酸的含量和分配比例从地上部分(叶和茎)到地下部分(根)减少;(3)两种植物器官和根系分泌物中的有机酸变化趋势一致,叶片中有机酸主要来源于暗呼吸过程和光呼吸过程,其他器官和根系分泌物中的有机酸主要来源于暗呼吸过程;(4)诸葛菜对缺锌和高浓度碳酸氢根离子的适应能力强于油菜,为诸葛菜的喀斯特适生性和低锌和高浓度碳酸氢根离子环境(如喀斯特环境)的生态修复提供了理论依据。     

花生根分泌物的鉴定及其化感作用

采用改进的根系分泌物循环收集系统收集花生根系分泌物,利用气相色谱/质谱联用仪(GC-MS)鉴定其结构,并研究了花生根系分泌物对花生青枯病原菌的化感作用.结果表明,花生根系分泌物中主要含有丙三醇、苯甲酸、3,5-二甲基苯甲醛、苯乙酮、硬脂酸、棕榈酸和乳酸等7种物质.7种根系分泌物中只有苯乙酮在浓度低于0.1g·L-1时,对花生青枯病原菌生长才有明显的促进作用.同时还发现,苯乙酮浓度超过0.1 gL-1后对花生青枯病原菌有显著的抑制作用.这一结论为利用苯乙酮调控花生青枯病害的发生提供了可靠的依据.     

黑麦草根系分泌物剂量对污染土壤芘降解和土壤微生物的影响

模拟根际根系分泌物梯度递减效应,研究了黑麦草根系分泌物剂量对污染土壤中芘降解特征和土壤微生物生态特征的影响.结果表明:污染土壤中芘残留量随根系分泌物添加剂量的增加呈现先下降后上升的非线性变化,达到最低芘残留量的添加剂量是总有机碳(TOC) 32.75 mg·kg-1,说明此浓度下根系分泌物显著促进了芘的降解;土壤微生物生物量碳和微生物熵的变化趋势与污染土壤中芘残留量变化趋势相反,表明土壤微生物与污染土壤 中芘残留量存在密切关系.芘污染土壤中微生物群落以细菌占主导地位,且细菌变化趋势与芘降解变化一致,表明芘以细菌降解为主,根系分泌物主要通过影响细菌数量,进而影响芘的降解.能催化有机物质脱氢反应的土壤微生物胞内酶——脱氢酶活性的变化与土壤微生物变化趋势一致,进一步证明微生物及其生物化学特性变化是污染土壤中芘残留量随根系分泌物添加剂量变化的生态机制.     

大蒜根系分泌物的化感作用

以苍山白蒜和蔡家坡紫蒜为材料,采用水培方法收集根系分泌物,研究了2个大蒜品种的根系分泌物对莴苣种子发芽和幼苗生长及对黄瓜枯萎病菌、西瓜枯萎病菌的化感效应.结果表明:2个大蒜品种的根系分泌物对莴苣种子发芽和幼苗生长均表现为低浓度(0.1、0.2 g·mL-1)促进、高浓度(0.4、0.6 g·mL-1)抑制,高浓度时蔡家坡紫蒜的抑制作用大于苍山白蒜;对黄瓜枯萎病菌和西瓜枯萎病菌的菌丝生长及孢子萌发均表现为抑制作用,随着根系分泌物浓度的提高,抑制作用增强,其中黄瓜枯萎病菌较敏感,且蔡家坡紫蒜的抑制作用大于苍山白蒜.     

A chemical investigation by headspace SPME and GC-MS of volatile and semi-volatile terpenes in various olibanum samples

Six different olibanum samples with certified botanical origin were analyzed by headspace SPME-GC/MS in order to define their mono-, sesqui- and diterpenic composition, as pertinent criteria of identification. Boswellia carteri and Boswellia sacra olibanum have quite similar chemical composition, with isoincensole acetate as the main diterpenic biomarker. Although Boswellia serrata olibanum also exhibits this biomarker, the presence of methylchavicol, methyleugenol and an unidentified oxygenated sesquiterpene distinguishes B. serrata olibanum from the two other species. The characteristic chemical compounds of Boswellia papyrifera are the diterpenic biomarkers incensole and its oxide and acetate derivatives, n-octanol and n-octyl acetate. Boswellia frereana olibanum is devoid of diterpenes of the incensole family but contains a high amount of many dimers of alpha-phellandrene. The chemical composition of olibanum, which is demonstrated to be different for each Boswellia species allowed the determination of the taxonomic origin of frankincense samples purchased on various markets in East Africa, in the Near East and in Yemen. Moreover, terpenic fingerprints allowed the botanical origin of olibanum used in traditional incense mixtures to be identified. Furthermore, this study gave us the opportunity to assign a botanical origin to an archaeological frankincense sample.     

Oxidation of gum arabic by soluble colloidal MnO2

In the present work, the oxidative degradation of gum arabic by colloidal manganese dioxide (MnO2) was carried out. Monitoring the disappearance of the MnO2 spectrophotometrically at 375 nm was used to follow the kinetics. The oxidation obeyed fractional-order kinetics with respect to the [gum arabic]. Effect of various experimental parameters such as the initial colloidal [MnO2], [HClO4], temperature, and complexing agents (P2O7(4-), F-, and Mn2+) for the oxidation of gum arabic was studied. The reaction was acid catalyzed. Addition of P2O(7)4-, F-, and Mn2+ ions enhances the rate of oxidation significantly. Gum arabic adsorbs onto the surface of the colloidal MnO2 through the equatorial -OH groups of the rhamnose moiety, and the complex breaks down into products. The Arrhenius equation was valid for the oxidation kinetics between 40 and 60 degrees C. To explain the observed kinetic results, a suitable mechanism and rate law for the reaction taking place at the surface of the colloidal particle has been proposed. The reducing nature of gum arabic is found be due to the presence of -OH group in the skeleton.     

Involvement of CD14 in the inhibitory effects of dimethyl-alpha-cyclodextrin on lipopolysaccharide signaling in macrophages

The potential use of alpha-cyclodextrin and its hydrophilic alpha-cyclodextrin derivatives (alpha-CyDs) as antagonists against lipopolysaccharide (LPS), which stimulates the nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) production as well as nuclear factor-kappaB (NF-kappaB) activation in macrophages was examined. Of three alpha-CyDs used in the present study, 2,6-di-O-methyl-alpha-CyD (DM-alpha-CyD) had greater inhibitory activity than did the other CyDs against NO and TNF-alpha production through an impairment of gene expression in macrophage cell lines and primary macrophages stimulated with LPS and lipid A in a concentration-dependent manner. Concomitantly, DM-alpha-CyD inhibited NF-kappaB translocation into nucleus. These inhibitory effects of DM-alpha-CyD could be attributed to the release of CD14 from lipid rafts caused by an efflux of phospholipids, but not cholesterol. These results suggest that DM-alpha-CyD may have promise as a potent and unique antagonist for excess activation of macrophages stimulated with LPS.     

Arabinogalactans and arabinogalactan-proteins induce embryogenesis in wheat (Triticum aestivum L.) microspore culture

The objective of this study was to improve induction of embryogenesis in wheat microspore culture in order to obtain a high number of regenerable embryos. The arabinogalactan (AG) Larcoll and the arabinogalactan-protein (AGP) from gum arabic were tested on two spring genotypes to see if they could increase microspore viability and induce embryogenesis in the microspore culture. Adding Larcoll significantly decreased microspore mortality in both genotypes regardless of the presence or absence of ovaries in the culture. Similarly, gum arabic had a strong effect on the number of embryos produced and regenerated green plants. In fact, by using only gum arabic we were able to obtain green plants from wheat microspore cultures without the presence of ovaries. In addition to preventing a high mortality rate of the cells, our results show that the induction of embryogenesis in wheat microspore cultures is strongly affected by the use of both AG or AGP.An erratum to this article can be found at