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Isoprenoid metabolism and its derivatives took part in photosynthesis, growth regulation, signal transduction, and plant defense to biotic and abiotic stresses. However, how aluminum (Al) stress affects the isoprenoid metabolism and whether isoprenoid metabolism plays a vital role in the Citrus plants in coping with Al stress remain unclear. In this study, we reported that Al–treatment–induced alternation in the volatilization rate of monoterpenes (α–pinene, β–pinene, limonene, α–terpinene, γ–terpinene and 3–carene) and isoprene were different between Citrus sinensis (Al-tolerant) and C. grandis (Al-sensitive) leaves. The Al-induced decrease of CO 2 assimilation, maximum quantum yield of primary PSII photochemistry (F v /F m), the lower contents of glucose and starch, and the lowered activities of enzymes involved in the mevalonic acid (MVA) pathway and 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway might account for the different volatilization rate of isoprenoids. Furthermore, the altered transcript levels of genes related to isoprenoid precursors and/or derivatives metabolism, such as geranyl diphosphate (GPP) synthase (GPPS) in GPP biosynthesis, geranylgeranyl diphosphate synthase (GGPPS), chlorophyll synthase (CHS) and GGPP reductase (GGPPR) in chlorophyll biosynthesis, limonene synthase (LS) and α-pinene synthase (APS) in limonene and α–pinene synthesis, respectively, might be responsible for the different contents of corresponding products in C. grandis and C. sinensis. Our data suggested that isoprenoid metabolism was involved in Al tolerance response in Citrus , and the alternation of some branches of isoprenoid metabolism could confer different Al-tolerance to Citrus species. [Display omitted] • The emission rate of volatile isoprenoids varied in C. grandis and C. sinensis. • Al treatment downregulated both MVA and MEP pathways in C. grandis leaves. • Al treatment upregulated MEP pathway in C. sinensis leaves. • Isoprenoid metabolism was involved in Al tolerance response in Citrus plants. [ABSTRACT FROM AUTHOR]

Aluminum (Al)-toxicity and boron (B)-deficiency are two major factors limiting crop production in tropical and subtropical areas. Elevating B supply can alleviate the Al-induced inhibition of growth in Citrus grandis . Seedlings of C. grandis were irrigated for 18 weeks with nutrient solutions containing two B levels (2.5 and 20 μM H 3 BO 3 ) and two Al levels (0 and 1.2 mM AlCl 3 ·6H 2 O). By using 2-dimensional electrophoresis (2-DE) based MALDI-TOF/TOF-MS method, this study successfully identified and quantified sixty-one differentially abundant proteins in Citrus roots in response to B-Al interactions. The mechanisms underlying the B-induced alleviation of Al-toxicity unveiled by 2-DE technique could be summarized as follows: a) remodeling of cell wall by reducing the synthesis of lignin (sugar ATP Binding Cassette (ABC) transporter ATPase and cinnamyl alcohol dehydrogenase) and increasing the modification of cell wall (UDP-forming); b) enhancing the abundances of proteasomes and turnover of dysfunctional proteins (proteasome or protease); c) increasing the abundance of stress response proteins, such as alcohol dehydrogenase, S-adenosylmethionine synthetase (SAMS) and glycosyl hydrolase; d) reinforcing cellular biological regulation and signal transduction (calreticulin-1). For the first time, some proteins, such as cell division protein 48 (CDC48), calreticulin and phospholipase, which might be involved in the downstream signaling of Al in Citrus plants, were successfully identified. [ABSTRACT FROM AUTHOR]

Little is known about the physiological and molecular responses of leaves to aluminum (Al)-toxicity. Seedlings of Al-intolerant Citrus grandis and Al-tolerant Citrus sinensis were supplied daily with nutrient solution containing 0 mM (control) and 1.0 mM (Al-toxicity) AlCl 3 ·6H 2 O for 18 weeks. We found that Al-treatment only decreased CO 2 assimilation in C. grandis leaves, and that the Al-induced alterations of gene expression profiles were less in C. sinensis leaves than those in C. grandis leaves, indicating that C. sinensis seedlings were more tolerant to Al-toxicity than C. grandis ones. Al concentration was similar between Al-treated C. sinensis and C. grandis roots, but it was higher in Al-treated C. grandis stems and leaves than that in Al-treated C. sinensis stems and leaves. Al-treated C. sinensis seedlings accumulated relatively more Al in roots and transported relatively little Al to shoots. This might be responsible for the higher Al-tolerance of C. sinensis . Further analysis showed that the following several aspects might account for the higher Al-tolerance of C. sinensis , including: (a) Al-treated C. sinensis leaves had higher capacity to maintain the homeostasis of energy and phosphate, the stability of lipid composition and the integrity of cell wall than did Al-treated C. grandis leaves; (b) Al-triggered production of reactive oxygen species (ROS) and the other cytotoxic compounds was less in Al-treated C. sinensis leaves than that in Al-treated C. grandis leaves, because Al-toxicity decreased CO 2 assimilation only in C. grandis leaves; accordingly, more upregulated genes involved in the detoxifications of ROS, aldehydes and methylglyoxal were identified in Al-treated C. grandis leaves; in addition, flavonoid concentration was increased only in Al-treated C. grandis leaves; (c) Al-treated C. sinensis leaves could keep a better balance between protein phosphorylation and dephosphorylation than did Al-treated C. grandis leaves; and (d) both the equilibrium of hormones and hormone-mediated signal transduction were greatly disrupted in Al-treated C. grandis leaves, but less altered in Al-treated C. sinensis leaves. Finally, we discussed the differences in Al-responsive genes between Citrus roots and leaves. [ABSTRACT FROM AUTHOR]

Little information is available on the molecular mechanisms of boron (B)-induced alleviation of aluminum (Al)-toxicity. ‘Sour pummelo’ ( Citrus grandis ) seedlings were irrigated for 18 weeks with nutrient solution containing different concentrations of B (2.5 or 20 μM H 3 BO 3 ) and Al (0 or 1.2 mM AlCl 3 ·6H 2 O). B alleviated Al-induced inhibition in plant growth accompanied by lower leaf Al. We used cDNA-AFLP to isolate 127 differentially expressed genes from leaves subjected to B and Al interactions. These genes were related to signal transduction, transport, cell wall modification, carbohydrate and energy metabolism, nucleic acid metabolism, amino acid and protein metabolism, lipid metabolism and stress responses. The ameliorative mechanisms of B on Al-toxicity might be related to: (a) triggering multiple signal transduction pathways; (b) improving the expression levels of genes related to transport; (c) activating genes involved in energy production; and (d) increasing amino acid accumulation and protein degradation. Also, genes involved in nucleic acid metabolism, cell wall modification and stress responses might play a role in B-induced alleviation of Al-toxicity. To conclude, our findings reveal some novel mechanisms on B-induced alleviation of Al-toxicity at the transcriptional level in C. grandis leaves. [ABSTRACT FROM AUTHOR]

'Xuegan' (Citrus sinensis) seedlings were fertilized 6 times weekly for 24 weeks with 0.5 or 350 μM CuCl 2 and 2.5, 10 or 25 μM H 3 BO 3. Cu-toxicity increased Cu uptake per plant (UPP) and Cu concentrations in leaves, stems and roots, decreased water uptake and phosphorus, nitrogen, calcium, magnesium, potassium, sulfur, boron and iron UPP, and increased the ratios of magnesium, potassium, calcium and sulfur UPP to phosphorus UPP and the ratios of leaf magnesium, potassium and calcium concentrations to leaf phosphorus concentration. Many decaying and dead fibrous roots occurred in Cu-toxic seedlings. Cu-toxicity-induced alterations of these parameters and root damage decreased with the increase of boron supply. These results demonstrated that B supplementation lowered Cu uptake and its concentrations in leaves, stems and roots and subsequently alleviated Cu-toxicity-induced damage to root growth and function, thus improving plant nutrient (decreased Cu uptake and efficient maintenance of the other nutrient homeostasis and balance) and water status. Further analysis indicated that the improved nutrition and water status contributed to the boron-mediated amelioration of Cu-toxicity-induced inhibition of seedlings, decline of leaf pigments, large reduction of leaf CO 2 assimilation and impairment of leaf photosynthetic electron transport chain revealed by greatly altered chlorophyll a fluorescence (OJIP) transients, reduced maximum quantum yield of primary photochemistry (F v /F m), quantum yield for electron transport (ET o /ABS) and total performance index (PI abs,total), and elevated dissipated energy per reaction center (DI o /RC). To conclude, our findings corroborate the hypothesis that B-mediated amelioration of Cu-toxicity involved reduced damage to roots and improved nutrient and water status. Principal component analysis showed that Cu-toxicity-induced changes of above physiological parameters generally decreased with the increase of B supply and that B supply-induced alterations of above physiological parameters was greater in 350 μM Cu-treated than in 0.5 μM Cu-treated seedlings. B and Cu had a significant interactive influence on C. sinensis seedlings. • B supply lowered Cu uptake and Cu level in C. sinensis leaves, stems and roots. • Cu-toxicity-induced root damage decreased with the increase of B supply. • B supply improved nutrition and water status of Cu-toxic seedlings. • B and Cu had a significant and interactive influence on C. sinensis seedlings. [ABSTRACT FROM AUTHOR]

Limited data are available on metabolic responses of plants to copper (Cu)-toxicity. Firstly, we investigated Cu-toxic effects on metabolomics, the levels of free amino acids, NH 4 +-N, NO 3 --N, total nitrogen, total soluble proteins, total phenolics, lignin, reduced glutathione (GSH) and malondialdehyde, and the activities of nitrogen-assimilatory enzymes in 'Shatian' pummelo (Citrus grandis) leaves. Then, a conjoint analysis of metabolomics, physiology and transcriptomics was performed. Herein, 59 upregulated [30 primary metabolites (PMs) and 29 secondary metabolites (SMs)] and 52 downregulated (31 PMs and 21 SMs) metabolites were identified in Cu-toxic leaves. The toxicity of Cu to leaves was related to the Cu-induced accumulation of NH 4 + and decrease of nitrogen assimilation. Metabolomics combined with physiology and transcriptomics revealed some adaptive responses of C. grandis leaves to Cu-toxicity, including (a) enhancing tryptophan metabolism and the levels of some amino acids and derivatives (tryptophan, phenylalanine, 5-hydroxy- l -tryptophan, 5-oxoproline and GSH); (b) increasing the accumulation of carbohydrates and alcohols and upregulating tricarboxylic acid cycle and the levels of some organic acids and derivatives (chlorogenic acid, quinic acid, d -tartaric acid and gallic acid o -hexoside); (c) reducing phospholipid (lysophosphatidylcholine and lysophosphatidylethanolamine) levels, increasing non-phosphate containing lipid [monoacylglycerol ester (acyl 18:2) isomer 1] levels, and inducing low-phosphate-responsive gene expression; and (d) triggering the biosynthesis of some chelators (total phenolics, lignin, l -trytamine, indole, eriodictyol C-hexoside, quercetin 5-O-malonylhexosyl-hexoside, N-caffeoyl agmatine, N′-p-coumaroyl agmatine, hydroxy-methoxycinnamate and protocatechuic acid o -glucoside) and vitamins and derivatives (nicotinic acid-hexoside, B 1 and methyl nicotinate). Cu-induced upregulation of many antioxidants could not protect Cu-toxic leaves from oxidative damage. To conclude, our findings corroborated the hypothesis that extensive reprogramming of metabolites was carried out in Cu-toxic C. grandis leaves in order to cope with Cu-toxicity. [Display omitted] • Citrus leaves underwent extensive metabolic reprograming under Cu-toxicity. • Cu impaired N assimilation in leaves, thus lowering Cu-tolerance. • Cu increased carbohydrates and alcohols levels and upregulated TCA cycle in leaves. • Cu triggered the biosynthesis of some chelators, vitamins and derivatives in leaves. • MDA accumulated in Cu-toxic leaves despite increased levels of some antioxidants. [ABSTRACT FROM AUTHOR]

Waste classification is regarded as one of the most important strategies for waste management, and its success depends on the active participation of the public. Based on the theory of planned behavior (TPB) and attitude-behavior-condition (A-B-C) theory, this research investigated the key factors affecting residents' domestic waste classification intention (WCI) and waste classification behavior (WCB), and explored the moderating effects of three external factors including infrastructure (INF), government publicity (GP), and incentive measures (IM) on the intention-behavior relationship. The valid data were collected from 584 residents via conducting a face-to-face interview in Chengdu, a pilot city of waste classification in China, and analyzed by using the structural equation model (SEM). Results showed that residents' WCI and WCB had a significant discrepancy with the average values of 4.07 and 2.81, respectively. Attitude (AT), perceived behavior control (PBC) and classification knowledge (CK) were significantly related to residents' WCI, with AT (β = 0.65, P < 0.001) having the greatest direct impact. Meanwhile, CK and INF had a stronger impact on the WCB than WCI. GP indirectly affected WCB through the intermediary effect of CK. In addition, INF and GP had a positively moderating effect on residents' waste classification intention-behavior relationship and can facilitate the intention-behavior conversion. By contrast, IM failed to promote the conversion of residents' classification intention into behavior, and had no direct significant influence on residents' WCB. Finally, some relevant policy suggestions were put forward for the new pilot cities of waste classification in China. • Key factors affecting residents' WCI and WCB were investigated. • Moderating effects of external factors on intention-behavior relation was explored. • Attitude had the greatest direct influence on residents' WCI. • CK and Infrastructure had a stronger impact on WCB than WCI. • Infrastructure and GP can strengthen the intention-behavior conversion. [ABSTRACT FROM AUTHOR]

Abstract: Poly(N-isopropylacrylamide) (PNIPAM) is a common thermo-responsive, water-soluble polymer, while Hercosett is a cationic resin commonly employed in the paper industry. In this paper, Hercosett™ and poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were used to prepare composite films that show thermo-responsive behavior and swelling–shrinking properties in water. First, size-controlled PNIPAM hydrogel nanoparticles were synthesized. These were then embedded within a matrix of the cationic resin Kymene 577H by film casting. The distribution of nanoparticles in the resin film was investigated. The thermo-responsive properties of the as-synthesized PNIPAM hydrogel nanoparticles and of the composite films were characterized together with the repeatability of the swelling–shrinking cycles. The presence of nanoparticles endowed the film with highly enhanced water retention (in comparison with resin-only films) and, most importantly, thermo-responsiveness. A very fast optical and morphological response was in fact observed. Due to the dual (optical and morphological) response, this new system is suitable for applications in optical or morphological actuation and gating. [Copyright &y& Elsevier]