Sour Pummelo Research Articles

Effects of different fertilizer ratios on the growth and physiology of sour pomelo seedlings

To reduce the usage of inorganic fertilizers and to protect the soil environment, a new approach was implemented. This approach incorporated using ‘special substrate & a little inorganic fertilizer’ to study the growth of sour pomelo seedlings. There were 7 treatments, all had processed substrates, and 6 with different ratios of fertilizers as the test group and one as a control (CK), which only had processed substrate. From the experiment we discovered that all the test groups are better than CK on majority of the indicators, and W3(N:P2O5=1:0.25) was more efficient for container seedlings of sour pummelo in many aspects. For the growth parameters of W3, the average leaf area was 22.04 cm2 and the average of leaf number 26.20; for the physiological indicators, the content of chlorophyll is 62.39 SPAD, the content of soluble sugar 4.49 mg/g and the content of soluble protein 10.95 mg/g, all the different treatments of W3 were nearly significant or highly significant levels when compared to the CK (18,6 cm2, 9.6, 51.68 SPAD; 2.77 mg/g and 7.05 mg/g). Moreover, we find that the treatment which is combined with two or more fertilizers is better than the treatment with one fertilizer, so we suggest that we should choose the fertilizer ratio of N:P2O5:K2O=1:0.25 as the optimum combination.

A Study of Scion Phenotypes in Pummelo Grafted onto a New Citrus Rootstock Citrus junos ‘Pujiang Xiangcheng’

Citrus is one of the most important fruit crops in the world. Citrus junos Siebold ex Tanaka cv. Pujiang Xiangcheng is a new rootstock with a good grafting affinity and multiple abiotic stress tolerance. In this study, the effects of ‘Pujiang Xiangcheng’ and two commonly used rootstocks for Citrus maxima (Burm.) Merrill cv. Guanxi Miyou, considering their growth, photosynthetic performance, phytohormones and fruit quality, were evaluated. There was little difference between three graft combinations in the height and diameter of the scions. However, the rootstock ‘Pujiang Xiangcheng’ can cause an up-regulated photosynthetic capacity. In addition, ‘Guanxi Miyou’ on ‘Pujiang Xiangcheng’ had the highest total sugar (TS) content (129.28 mg·g−1) and the lowest titratable acid (TA) content (0.78 g·100 mL−1) in 2020 and the highest TSS (11.84%) in 2021. There was no significant difference in the TSS-to-acid ratio between the fruit of ‘Guanxi Miyou’ on trifoliate orange (13.41) and ‘Pujiang Xiangcheng’ (15.68), but it was significantly higher than that of ‘Guanxi Miyou’ on sour pummelo (11.61). Moreover, the comprehensive fruit quality of ‘Guanxi Miyou’ on ‘Pujiang Xiangcheng’ was better than on sour pummelo and trifoliate orange based on two-year statistics. We suggest that ‘Pujiang Xiangcheng’ might be the appropriate rootstock of ‘Guanxi Miyou’ in production compared with sour pummelo and trifoliate orange.

Influence of Citrus Rootstocks on Scion Growth, Hormone Levels, and Metabolites Profile of ‘Shatangju’ Mandarin (Citrus reticulata Blanco)

Dwarfing rootstocks are a valuable genetic resource for managing high-density plantations. The selection of the appropriate scion/rootstock combination is key to improving crop performance and sustainable production in a particular environment and specific training systems. ‘Shatangju’ mandarin scion cultivar grafted onto ‘Flying Dragon’ rootstock tends to be dwarfing and develops short stature plants. To obtain insight into potential mechanisms underlying rootstock-induced dwarfing effects, we conducted a rootstock trial to examine the influence of 11 different rootstocks based on their growth vigor, antioxidants, and hormonal levels of the scion cultivar. The phenotypic observations revealed that size reduction in the ‘Flying Dragon’ rootstock is due to lower node number, shorter internodal length, and a reduced trunk diameter of the scion compared with more vigorous rootstocks. Antioxidant analysis showed that ‘Shatangju’ mandarin grafted onto ’Flying Dragon’ and ‘Trifoliate Orange’ rootstock had significantly lower peroxidase (POD) activity than other tested rootstocks. The hormonal analysis indicated that there were markedly lower amounts of abscisic acid (ABA) in ‘Shatangju’ mandarin grafted with ‘Flying Dragon’ rootstock. In addition, trees grafted with ‘Sour Pummelo’ and ‘Flying Dragon’ depicted minimum amounts of gibberellins (GA24). Moreover, several metabolites associated with organic acids, flavonoids, amino acids, and alkaloids responded differently in plants grafted with ‘Flying Dragon’ (dwarfing) and ‘Shatang Mandarin’ (vigorous) rootstocks. This study concluded that ‘Flying Dragon’ rootstock with a strong dwarfing effect has been proposed to improve high-density cultivation methods. These findings will provide useful insights for future research associated with rootstock-mediated dwarfing mechanisms of citrus rootstocks.

Long-term manganese-toxicity-induced alterations of physiology and leaf protein profiles in two Citrus species differing in manganese-tolerance

Manganese (Mn)-intolerant ‘Sour pummelo’ (Citrus grandis) and Mn-tolerant ‘Xuegan’ (Citrus sinensis) seedlings were irrigated for 17 weeks with 2 (control) or 600μM (Mn-toxicity or −excess) MnSO4. C. sinensis had higher Mn-tolerance than C. grandis, as indicated by the higher photosynthesis rates in Mn-excess C. sinensis leaves. Under Mn-toxicity, Mn levels were similar between C. sinensis and C. grandis roots, but lower in C. sinensis leaves than in C. grandis leaves. This might be responsible for C. sinensis Mn-tolerance. Using two-dimensional electrophoresis, we identified more differentially abundant proteins (DAPs) in Mn-excess C. grandis than in Mn-excess C. sinensis leaves, which agrees with the higher Mn levels in Mn-excess C. grandis leaves. DAPs were mainly related to carbohydrate and energy metabolism, stress response, and protein and amino acid metabolism. DAPs involved in the cytoskeleton and signal transduction were found only in Mn-excess C. grandis leaves. We isolated more photosynthesis-related proteins with decreased abundances in Mn-excess C. grandis leaves than in Mn-excess C. sinensis leaves, which might account for the larger decrease in photosynthesis rates in C. grandis leaves. The abundances of proteins involved in reactive oxygen species (ROS) scavenging and photorespiration were increased in Mn-excess C. grandis leaves, while only proteins involved in ROS detoxification were increased in Mn-excess C. sinensis leaves. This agrees with the increased requirement for dissipating the excess absorbed light energy, which was higher in Mn-excess C. grandis leaves than Mn-excess C. sinensis leaves because Mn-toxicity inhibited photosynthesis to a greater degree in C. grandis leaves.

Effects of Low pH on Photosynthesis, Related Physiological Parameters, and Nutrient Profiles of Citrus.

Seedlings of “Xuegan” (Citrus sinensis) and “Sour pummelo” (Citrus grandis) were irrigated daily with a nutrient solution at a pH of 2.5, 3, 4, 5, or 6 for 9 months. Thereafter, the following responses were investigated: seedling growth; root, stem, and leaf concentrations of nutrient elements; leaf gas exchange, pigment concentration, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and chlorophyll a fluorescence; relative water content, total soluble protein level, H2O2 production and electrolyte leakage in roots and leaves. This was done (a) to determine how low pH affects photosynthesis, related physiological parameters, and mineral nutrient profiles; and (b) to understand the mechanisms by which low pH may cause a decrease in leaf CO2 assimilation. The pH 2.5 greatly inhibited seedling growth, and many physiological parameters were altered only at pH 2.5; pH 3 slightly inhibited seedling growth; pH 4 had almost no influence on seedling growth; and seedling growth and many physiological parameters reached their maximum at pH 5. No seedlings died at any given pH. These results demonstrate that citrus survival is insensitive to low pH. H+-toxicity may directly damage citrus roots, thus affecting the uptake of mineral nutrients and water. H+-toxicity and a decreased uptake of nutrients (i.e., nitrogen, phosphorus, potassium, calcium, and magnesium) and water were likely responsible for the low pH-induced inhibition of growth. Leaf CO2 assimilation was inhibited only at pH 2.5. The combinations of an impaired photosynthetic electron transport chain, increased production of reactive oxygen species, and decreased uptake of nutrients and water might account for the pH 2.5-induced decrease in CO2 assimilation. Mottled bleached leaves only occurred in the pH 2.5-treated C. grandis seedlings. Furthermore, the pH 2.5-induced alterations of leaf CO2 assimilation, water-use efficiency, chlorophylls, polyphasic chlorophyll a fluorescence (OJIP) transients and many fluorescence parameters, root and leaf total soluble proteins, H2O2 production, and electrolyte leakage were all slightly greater in C. grandis than in C. sinensis seedlings. Hence, C. sinensis was slightly more tolerant to low pH than C. grandis. In conclusion, our findings provide novel insight into the causes of low pH-induced inhibition of seedling growth and leaf CO2 assimilation.

Effects of High Toxic Boron Concentration on Protein Profiles in Roots of Two Citrus Species Differing in Boron-Tolerance Revealed by a 2-DE Based MS Approach.

Citrus are sensitive to boron (B)-toxicity. In China, B-toxicity occurs in some citrus orchards. So far, limited data are available on B-toxicity-responsive proteins in higher plants. Thirteen-week-old seedlings of “Sour pummelo” (Citrus grandis) and “Xuegan” (Citrus sinensis) was fertilized every other day until dripping with nutrient solution containing 10 μM (control) or 400 μM (B-toxicity) H3BO3 for 15 weeks. The typical B-toxic symptom only occurred in 400 μM B-treated C. grandis leaves, and that B-toxicity decreased root dry weight more in C. grandis seedlings than in C. sinensis ones, demonstrating that C. sinensis was more tolerant to B-toxicity than C. grandis. Using a 2-dimensional electrophoresis (2-DE) based MS approach, we identified 27 up- and four down-accumulated, and 28 up- and 13 down-accumulated proteins in B-toxic C. sinensis and C. grandis roots, respectively. Most of these proteins were isolated only from B-toxic C. sinensis or C. grandis roots, only nine B-toxicity-responsive proteins were shared by the two citrus species. Great differences existed in B-toxicity-induced alterations of protein profiles between C. sinensis and C. grandis roots. More proteins related to detoxification were up-accumulated in B-toxic C. grandis roots than in B-toxic C. sinensis roots to meet the increased requirement for the detoxification of the more reactive oxygen species and other toxic compounds such as aldehydes in the former. For the first time, we demonstrated that the active methyl cycle was induced and repressed in B-toxic C. sinensis and C. grandis roots, respectively, and that C. sinensis roots had a better capacity to keep cell wall and cytoskeleton integrity than C. grandis roots in response to B-toxicity, which might be responsible for the higher B-tolerance of C. sinensis. In addition, proteins involved in nucleic acid metabolism, biological regulation and signal transduction might play a role in the higher B-tolerance of C. sinensis.

Identification of manganese-toxicity-responsive genes in roots of two citrus species differing in manganese tolerance using cDNA-AFLP

We identified more Mn-toxicity-responsive genes from Mn-intolerant Citrus grandis than from Mn-tolerant Citrus sinensis roots. These findings increased our understanding of the molecular mechanisms on plant Mn toxicity and Mn tolerance. Manganese (Mn) toxicity is the most important factor limiting crop production after aluminum toxicity in acidic soils. However, little is known about Mn-toxicity-induced alterations of gene expression profiles in woody plants. Using cDNA-AFLP, we identified 87 and 63 Mn-toxicity-responsive genes from Mn-intolerant ‘Sour pummelo’ (Citrus grandis) and Mn-tolerant ‘Xuegan’ (Citrus sinensis) roots. Among these genes, only 22 genes with the same accession number were shared by both. Protein phosphorylation/dephosphorylation-related genes were upregulated in C. sinensis roots, and downregulated in C. grandis roots except for one differentially expressed gene. Sulfur metabolism-related genes were repressed only in Mn-toxic C. grandis roots. Obviously, great differences existed in Mn-toxicity-induced alterations of gene expression profiles between C. sinensis and C. grandis roots. Genes related to protein phosphorylation/dephosphorylation (i.e., cyclin-dependent kinase-activating kinase assembly factor-related protein and PP2A regulatory subunit TAP46), cellular transport (i.e., Ca-transporting ATPase 1), and nucleic acid (i.e., ethylene-responsive transcription factor ERF109-like, structural maintenance of chromosomes protein 4-like, RNA-binding protein and DEAD-box ATP-dependent RNA helicase 21), cell wall (i.e., pectin methylesterase 1 and invertase/pectin methylesterase inhibitor family protein) and fatty acid (i.e., carboxylesterase 20) metabolisms might play a role in C. sinensis Mn tolerance. In addition, cell wall materials were increased in Mn-toxic C. sinensis and C. grandis roots, especially in the former. Interestingly, lignin content was increased in Mn-toxic C. sinensis roots, while a reverse trend was displayed in Mn-toxic C. grandis roots. In conclusion, our results provided novel clues to the molecular mechanisms on Mn toxicity and Mn tolerance in higher plants.

Root iTRAQ protein profile analysis of two Citrus species differing in aluminum-tolerance in response to long-term aluminum-toxicity.

BackgroundLimited information is available on aluminum (Al)-toxicity-responsive proteins in woody plant roots. Seedlings of ‘Xuegan’ (Citrus sinensis) and ‘Sour pummelo’ (Citrus grandis) were treated for 18 weeks with nutrient solution containing 0 (control) or 1.2 mM AlCl3 · 6H2O (+Al). Thereafter, we investigated Citrus root protein profiles using isobaric tags for relative and absolute quantification (iTRAQ). The aims of this work were to determine the molecular mechanisms of plants to deal with Al-toxicity and to identify differentially expressed proteins involved in Al-tolerance.ResultsC. sinensis was more tolerant to Al-toxicity than C. grandis. We isolated 347 differentially expressed proteins from + Al Citrus roots. Among these proteins, 202 (96) proteins only presented in C. sinensis (C. grandis), and 49 proteins were shared by the two species. Of the 49 overlapping proteins, 45 proteins were regulated in the same direction upon Al exposure in the both species. These proteins were classified into following categories: sulfur metabolism, stress and defense response, carbohydrate and energy metabolism, nucleic acid metabolism, protein metabolism, cell transport, biological regulation and signal transduction, cell wall and cytoskeleton metabolism, and jasmonic acid (JA) biosynthesis. The higher Al-tolerance of C. sinensis may be related to several factors, including: (a) activation of sulfur metabolism; (b) greatly improving the total ability of antioxidation and detoxification; (c) up-regulation of carbohydrate and energy metabolism; (d) enhancing cell transport; (e) decreased (increased) abundances of proteins involved in protein synthesis (proteiolysis); (f) keeping a better balance between protein phosphorylation and dephosphorylation; and (g) increasing JA biosynthesis.ConclusionsOur results demonstrated that metabolic flexibility was more remarkable in C. sinenis than in C. grandis roots, thus improving the Al-tolerance of C. sinensis. This provided the most integrated view of the adaptive responses occurring in Al-toxicity roots.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2133-9) contains supplementary material, which is available to authorized users.

Two-dimensional gel electrophoresis data in support of leaf comparative proteomics of two citrus species differing in boron-tolerance.

Here, we provide the data from a comparative proteomics approach used to investigate the response of boron (B)-tolerant ‘Xuegan’ (Citrus sinensis) and B-intolerant ‘Sour pummelo’ (Citrus grandis) leaves to B-toxicity. Using two-dimensional gel electrophoresis (2-DE) technique, we identified 50 and 45 protein species with a fold change of more than 1.5 and a P-value of less than 0.05 from B-toxic C. sinensis and C. grandis leaves. These B-toxicity-responsive protein species were mainly involved in carbohydrate and energy metabolism, antioxidation and detoxification, stress responses, coenzyme biosynthesis, protein and amino acid metabolism, signal transduction, cell transport, cytoskeleton, nucleotide metabolism, and cell cycle and DNA processing. A detailed analysis of this data may be obtained from Sang et al. (J. Proteomics 114 (2015))[1].

CDNA-AFLP analysis reveals the adaptive responses of citrus to long-term boron-toxicity.

BackgroundBoron (B)-toxicity is an important disorder in agricultural regions across the world. Seedlings of ‘Sour pummelo’ (Citrus grandis) and ‘Xuegan’ (Citrus sinensis) were fertigated every other day until drip with 10 μM (control) or 400 μM (B-toxic) H3BO3 in a complete nutrient solution for 15 weeks. The aims of this study were to elucidate the adaptive mechanisms of citrus plants to B-toxicity and to identify B-tolerant genes.ResultsB-toxicity-induced changes in seedlings growth, leaf CO2 assimilation, pigments, total soluble protein, malondialdehyde (MDA) and phosphorus were less pronounced in C. sinensis than in C. grandis. B concentration was higher in B-toxic C. sinensis leaves than in B-toxic C. grandis ones. Here we successfully used cDNA-AFLP to isolate 67 up-regulated and 65 down-regulated transcript-derived fragments (TDFs) from B-toxic C. grandis leaves, whilst only 31 up-regulated and 37 down-regulated TDFs from B-toxic C. sinensis ones, demonstrating that gene expression is less affected in B-toxic C. sinensis leaves than in B-toxic C. grandis ones. These differentially expressed TDFs were related to signal transduction, carbohydrate and energy metabolism, nucleic acid metabolism, protein and amino acid metabolism, lipid metabolism, cell wall and cytoskeleton modification, stress responses and cell transport. The higher B-tolerance of C. sinensis might be related to the findings that B-toxic C. sinensis leaves had higher expression levels of genes involved in photosynthesis, which might contribute to the higher photosyntheis and light utilization and less excess light energy, and in reactive oxygen species (ROS) scavenging compared to B-toxic C. grandis leaves, thus preventing them from photo-oxidative damage. In addition, B-toxicity-induced alteration in the expression levels of genes encoding inorganic pyrophosphatase 1, AT4G01850 and methionine synthase differed between the two species, which might play a role in the B-tolerance of C. sinensis.ConclusionsC. sinensis leaves could tolerate higher level of B than C. grandis ones, thus improving the B-tolerance of C. sinensis plants. Our findings reveal some novel mechanisms on the tolerance of plants to B-toxicity at the gene expression level.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0284-5) contains supplementary material, which is available to authorized users.

Nitric oxide protects sour pummelo (Citrus grandis) seedlings against aluminum-induced inhibition of growth and photosynthesis

Limited data are available on the amelioration of nitric oxide (NO) on aluminum (Al)-toxicity. Sour pummelo (Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 0 and 1.2mM AlCl3·6H2O×0 and 10μM sodium nitroprusside (SNP, an NO donor). Under Al stress, SNP increased root phosphorus (P) and Al, but decreased shoot Al. Al decreased photosynthesis, maximum quantum yield of primary photochemistry (Fv/Fm) and total performance index (PItot,sbs), but increased inactivation of oxygen-evolving complex (OEC), K-band and relative variable fluorescence at I-steps (VI). SNP alleviated Al-induced changes for all these parameters. SNP stimulated Al-induced secretion of malate and citrate by excised roots from Al-treated seedlings, while Al did not increase their contents in roots. Antioxidant system in leaves and roots was up- and down-regulated by Al, respectively. SNP prevented Al-induced accumulation of malondialdehyde (MDA) in roots and leaves. In conclusion, SNP alleviates Al-induced inhibition of growth and impairment of the whole photosynthetic electron transport chain. This occurs through increasing Al-immobilization and P level in roots and Al-induced secretion of malate and citrate from roots, and decreasing Al accumulation in shoots. Thus, the decrease of photosynthesis is prevented. Increased P level and Al-immobilization in roots through SNP may be effected through enhanced secretion of malate and citrate.

Differential expression of genes involved in alternative glycolytic pathways, phosphorus scavenging and recycling in response to aluminum and phosphorus interactions in Citrus roots

The objective was to determine the possible links between the expression levels of genes involved in alternative glycolytic pathways, phosphorus (P) scavenging and recycling and Citrus tolerance to aluminum (Al) and/or P-deficiency. 'Xuegan' (Citrus sinensis) and 'Sour pummelo' (Citrus grandis) seedlings were irrigated for 18weeks with nutrient solution containing 0 and 1.2mM AlCl(3)·6H(2)O×0, 50 and 200μM KH(2)PO(4). C. sinensis displayed more tolerant to Al and P-deficiency than C. grandis. Under Al stress, C. sinensis accumulated more Al in roots and less Al in shoots than C. grandis. P concentration was higher in C. sinensis shoots and roots than in C. grandis ones. C. sinensis roots secreted more malate and citrate than C. grandis ones when exposed to Al. Al-induced-secretion of malate and citrate by excised roots from Al-treated seedlings decreased with increasing P supply. Al-induced-secretion of malate and citrate from roots and Al precipitation by P in roots might be responsible for Al-tolerance of C. sinensis. qRT-PCR analysis showed that Al-activated malate transporter (ALMT1), ATP-dependent phosphofructokinase (ATP-PFK), pyrophosphate-dependent phosphofructokinase (PPi-PFK), tonoplast adenosine-triphosphatase subunit A (V-ATPase A), tonoplast pyrophosphatase (V-PPiase), pyruvate kinase (PK), acid phosphatase (APase), phosphoenolpyruvate carboxylase (PEPC), malic enzyme (ME) and malate dehydrogenase (MDH) genes might contribute to the tolerance of Citrus to Al and/or P-deficiency, but any single gene could not explain the differences between the two species. Citrus tolerance to Al and/or P-deficiency might be caused by the coordinated regulation of gene expression involved in alternative glycolytic pathways, P scavenging and recycling.

Boron-aluminum interactions affect organic acid metabolism more in leaves than in roots of Citrus grandis seedlings

Sour pummelo (Citrus grandis) seedlings were irrigated with nutrient solution containing four boron concentrations (i.e., 2.5, 10, 25 and 50 μM H3BO3) and two aluminum concentrations [i.e., 0 (-Al) and 1.2 mM AlCl3 . 6 H2O (+Al)]. It was found that B did not affect, but Al increased, the Al content in the roots. The Al and citrate contents in the -Al leaves either did not change or slightly increased with increasing B concentration. On the other hand, the Al and citrate contents in the +Al leaves rapidly decreased as B concentration increased from 2.5 to 50 μM, then decreased at the highest B concentration. The Al and citrate contents were higher in the +Al than in the -Al leaves, except for at 25 μM B when they were similar. The leaf malate content did not change in response to B or Al, except for an increase in the +Al leaves and a decrease in the -Al leaves at 2.5 μM B. Similarly, the root malate and citrate contents did not change in response to B with or without Al, except for a decrease in the malate and citrate contents in the +Al roots at 50 μM B and an increase in the citrate content in the -Al roots at 50 μM B. The activities of acid-metabolizing enzymes were less affected by B-Al interactions in the roots than in the leaves.

Effects of manganese-excess on CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase, carbohydrates and photosynthetic electron transport of leaves, and antioxidant systems of leaves and roots in Citrus grandis seedlings.

BackgroundVery little is known about the effects of manganese (Mn)-excess on citrus photosynthesis and antioxidant systems. Seedlings of sour pummelo (Citrus grandis) were irrigated for 17 weeks with nutrient solution containing 2 μM (control) or 500 μM (excess) MnSO4. The objective of this study were to understand the mechanisms by which Mn-excess leads to a decrease in CO2 assimilation and to test the hypothesis that Mn-induced changes in antioxidant systems differ between roots and leaves.ResultsMn-excess decreased CO2 assimilation and stomatal conductance, increased intercellular CO2 concentration, but did not affect chlorophyll (Chl) level. Both initial and total ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity in Mn-excess leaves decreased to a lesser extent than CO2 assimilation. Contents of glucose, fructose, starch and total nonstructural carbohydrates did not differ between Mn-excess leaves and controls, while sucrose content was higher in the former. Chl a fluorescence (OJIP) transients from Mn-excess leaves showed increased O-step and decreased P-step, accompanied by positive L- and K-bands. Mn-excess decreased maximum quantum yield of primary photochemistry (Fv/Fm) and total performance index (PItot,abs), but increased relative variable fluorescence at I-steps (VI) and energy dissipation. On a protein basis, Mn-excess leaves displayed higher activities of monodehydroascorbate reductase (MDAR), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) and contents of antioxidants, similar ascorbate peroxidase (APX) activities and lower dehydroascorbate reductase (DHAR) activities; while Mn-excess roots had similar or lower activities of antioxidant enzymes and contents of antioxidants. Mn-excess did not affect malondialdehyde (MDA) content of roots and leaves.ConclusionsMn-excess impaired the whole photosynthetic electron transport chain from the donor side of photosystem II (PSII) up to the reduction of end acceptors of photosystem I (PSI), thus limiting the production of reducing equivalents, and hence the rate of CO2 assimilation. Both the energy dissipation and the antioxidant systems were enhanced in Mn-excess leaves, while the antioxidant systems in Mn-excess roots were not up-regulated, but still remained high activity. The antioxidant systems in Mn-excess roots and leaves provided sufficient protection to them against oxidative damage.

Phosphorus alleviates aluminum‐induced inhibition of growth and photosynthesis in Citrus grandis seedlings

Limited data are available on the effects of phosphorus (P) and aluminum (Al) interactions on Citrus spp. growth and photosynthesis. Sour pummelo (Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 50, 100, 250 and 500 microM KH(2)PO(4)x 0 and 1.2 mM AlCl(3). 6H(2)O. Thereafter, P and Al in roots, stems and leaves, and leaf chlorophyll (Chl), CO(2) assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and Chl a fluorescence (OJIP) transients were measured. Under Al stress, P increased root Al, but decreased stem and leaf Al. Shoot growth is more sensitive to Al than root growth, CO(2) assimilation and OJIP transients. Al decreased CO(2) assimilation, Rubisco activity and Chl content, whereas it increased or did not affect intercellular CO(2) concentration. Al affected CO(2) assimilation more than Rubisco and Chl under 250 and 500 microM P. Al decreased root, stem and leaf P, leaf maximum quantum yield of primary photochemistry (F(v)/F(m)) and total performance index (PI(tot,abs)), but increased leaf minimum fluorescence (F(o)), relative variable fluorescence at K- and I-steps. P could alleviate Al-induced increase or decrease for all these parameters. We conclude that P alleviated Al-induced inhibition of growth and impairment of the whole photosynthetic electron transport chain from photosystem II (PSII) donor side up to the reduction of end acceptors of photosystem I (PSI), thus preventing photosynthesis inhibition through increasing Al immobilization in roots and P level in roots and shoots. Al-induced impairment of the whole photosynthetic electron transport chain may be associated with growth inhibition.

Antagonistic actions of boron against inhibitory effects of aluminum toxicity on growth, CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase, and photosynthetic electron transport probed by the JIP-test, of Citrus grandisseedlings

BackgroundLittle information is available on the amelioration of boron (B) on aluminum (Al)-induced photosynthesis inhibition. Sour pummelo (Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 4 B levels (2.5, 10, 25 and 50 μM H3BO3) × 2 Al levels (0 and 1.2 mM AlCl3·6H2O). The objectives of this study were to determine how B alleviates Al-induced growth inhibition and to test the hypothesis that Al-induced photosynthesis inhibition can be alleviated by B via preventing Al from getting into shoots.ResultsB had little effect on plant growth, root, stem and leaf Al, leaf chlorophyll (Chl), CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Chl a fluorescence (OJIP) transient and related parameters without Al stress except that root, stem and leaf B increased with increasing B supply and that 50 μM B decreased slightly root dry weight. Al-treated roots, stems and leaves displayed a higher or similar B. B did not affect root Al under Al stress, but decreased stem and leaf Al level. Shoot growth is more sensitive to Al stress than root growth, CO2 assimilation, Chl, Rubisco, OJIP transient and most related parameters. Al-treated leaves showed decreased CO2 assimilation, but increased or similar intercellular CO2 concentration. Both initial and total Rubisco activity in Al-treated leaves decreased to a lesser extent than CO2 assimilation. Al decreased maximum quantum yield of primary photochemistry and total performance index, but increased minimum fluorescence, K-band, relative variable fluorescence at J- and I-steps. B could alleviate Al-induced increase or decrease for all these parameters. Generally speaking, the order of B effectiveness was 25 μM > 10 μM ≥ 50 μM (excess B) > 2.5 μM.ConclusionWe propose that Al-induced photosynthesis inhibition was mainly caused by impaired photosynthetic electron transport chain, which may be associated with growth inhibition. B-induced amelioration of root inhibition was probably caused by B-induced changes in Al speciation and/or sub-cellular compartmentation. However, B-induced amelioration of shoot and photosynthesis inhibition and photoinhibitory damage occurring at both donor and acceptor sides of photosystem II could be due to less Al accumulation in shoots.

Changes in organic acid metabolism differ between roots and leaves of Citrus grandis in response to phosphorus and aluminum interactions

Seedlings of sour pummelo (Citrus grandis) were irrigated daily for 18 weeks with nutrient solution containing four phosphorus (P) levels (50, 100, 250 and 500 microM KH2PO4) and two aluminum (Al) levels [0 (-Al) and 1.2 mM AlCl3 x 6H2O (+Al)]. Both malate and citrate concentrations in +Al leaves decreased with increasing P supply, but their concentrations in -Al leaves did not change in response to P supply. The concentrations of malate under 50 microM P and of citrate under 50 and 100 microM P were higher in +Al leaves than in -Al ones, but malate concentration was lower in +Al leaves than in -Al ones under 500 microM P. There was no difference in root malate and citrate concentrations among different P and Al combinations except for an increase in malate and citrate under 50 microM P+0 mM Al and a slight decrease in malate under 50 microM P+1.2 mM Al. The activities of acid-metabolizing enzymes (citrate synthase, aconitase, phosphoenolpyruvate carboxylase, NADP-isocitrate dehydrogenase, phosphoenolpyruvate phosphatase, NAD-malate dehydrogenase, NADP-malic enzyme and pyruvate kinase) in most cases were less affected by P and Al interactions in roots compared to the leaves. Our results support the hypothesis that changes in organic acid metabolism differ between roots and leaves of C. grandis in response to P and Al interactions.

酵素免疫測定法による食物・生薬中のフラノクマリン類含量のスクリーニング

Furanocoumarin derivatives such as bergamottin and 6',7'-dihydroxybergamottin are inhibitors of CYP3A4 and have been isolated from grapefruit juice. We developed a sensitive and specific enzyme-linked immunosorbent assay for these furanocoumarin derivatives and used it for screening a large number of citrus fruits, vegetables and crude drugs for them. On testing the juice and peel of 25 citrus fruits, significant reactivity was observed with the juice of 4 of them : sweetie, melogold, banpeiyu pummelo and red pummelo and in the case of peel, significant reactivity was observed for 4 fruits : sweetie, melogold, sour pummelo and natsudaidai. For most of the citrus fruits, the peel showed a stronger reaction than the juice. Seven vegetables were tested and only slight reactivity was observed for 4 of them : parsley, celery, Italian parsley and mitsuba. Among the twenty crude drugs tested, significant reactivity was observed for 2 : angelica dahurica root (byakushi) and bitter orange peel (touhi). These findings suggest that 4 of the citrus fruits and 2 of the crude drugs tested would exhibit strong drug interactions.