Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E–) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E– plants. Endophyte infection increased specific root length at 17 and 50 mg P kg-1soil. At soil P level of 17 mg P kg-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E– plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg-1 but declined again at 96 mg P kg-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue. 相似文献
The influence of environmental factors on the indole alkaloid content and biomass of the roots of Tabernaemontana pachysiphon and Rauvolfia mombasiana, two species of considerable local medicinal use in tropical East Africa, was investigated. Both species, belonging to the Apocynaceae, are frequent constituents of the residual tropical forests, prefering sites of different ecological conditions. Experimental plants, raised from seeds, were grown for 16 months in a temperature- and humidity-controlled greenhouse. Environmental factors at variance were water and nutrient supply, and light intensity. At sufficient water and nutrient supply, the more drought and nutrient shortage-tolerating heliophilous Rauvolfia mombasiana showed increased alkaloid accumulation, concurrently with reduced root biomass. Under the same conditions, the drought-sensitive and higher levels of nutrient-requiring ombrophilous Tabernaemontana pachysiphon produced more root biomass but accumulated less alkaloids in the roots. The results indicate that the accumulation of indole alkaloids in the roots, as well as biomass allocation to the roots, is influenced in an opposite manner by the nutrient and water supply to the heliophilous and the ombrophilous species. 相似文献
Studies on the alkaloids from the leaves of Rhazya stricta have afforded a new alkaloid to which the structure 2-methoxy-1,2-dihydrorhazimine has been assigned. 相似文献
Lupin genotypes accumulate alkaloids that act as feeding deterrents for several kinds of herbivores. Breeding sweet (low alkaloid) genotypes resulted in a greater dependence on pesticides. Besides the concentration of defensive chemicals, plants possess another way to deal with herbivory, to allocate post-damage resources to growth in order to reach compensation in biomass (tolerance).
These two ways to deal with herbivores were postulated as alternative strategies, as scarce resources allocated to one function (growth or secondary metabolism) would not be available for the other function. Genotypes could differ in the way they respond to herbivory; identifying those genotypes with greater ability to overcome the damage would be useful to decrease the use of pesticides.
The aim of this work was to compare tolerance to herbivory in Lupinus albus and Lupinus angustifolius genotypes with contrasting alkaloid concentration. Tolerance was evaluated by comparing growth and grain yield of field-grown cut and uncut plants. Cutting treatments were performed at flowering by cutting 50% of the upper shoot biomass (including the main apex, stems, flowers and leaves). Differences between species were found in their tolerance to herbivory. While L. angustifolius showed full compensation in growth or grain yield that allowed cut plants to equal controls biomass or yield after damage, simulated herbivory reduced growth and grain yield in L. albus. 相似文献
Investigation of the Red Sea marine tunicate Symplegma rubra Monniot, 1972 gave three new purine alkaloids namely 6-methoxy-7,9-dimethyl-8-oxoguanine (1), 6-methoxy-9-methyl-8-oxoguanine (2), and 2-methoxy-7-methyl-8-oxoadenine (4) together with seven known compounds: 6-methoxy-7-methyl-8-oxoguanine (3), 9-methyl-8-oxoadenine (5), 7-methyl-8-oxoadenine (6), 8-oxoadenine (7), 3-methylxanthine (8), inosine (9), and homarine (pyridinium-2-carboxylic acid-1-methyl) (10). Compound 6 was reported here for the first time from a natural source. The structure determination of the compounds was accomplished by extensive interpretation of their spectroscopic data including 1D (1H and 13C) and 2D (1H–1H COSY, HSQC, and HMBC) NMR and high-resolution mass spectral data. The isolated compounds were evaluated for their protein kinase inhibitory activity against different kinases (CDK5, CK1, DyrK1A, and GSK3) at 10 μg/mL. The compounds showed moderate activity against these kinases. 相似文献
Strictosidine synthase (STR1) catalyzes the stereoselective formation of 3α(S)‐strictosidine from tryptamine and secologanin. Strictosidine is the key intermediate in the biosynthesis of 2,000 plant monoterpenoid indole alkaloids, and it is a key precursor of enzyme‐mediated synthesis of alkaloids. An improved expression system is described which leads to optimized His6‐STR1 synthesis in Escherichia coli. Optimal production of STR1 was achieved by determining the impact of co‐expression of chaperones pG‐Tf2 and pG‐LJE8. The amount and activity of STR1 was doubled in the presence of chaperone pG‐Tf2 alone. His6‐STR1 immobilized on Ni‐NTA can be used for enzymatic synthesis of strictosidines on a preparative scale. With the newly co‐expressed His6‐STR1, novel 3α(S)‐12‐azastrictosidine was obtained by enzymatic catalysis of 7‐azatryptamine and secologanin. The results obtained are of significant importance for application to chemo‐enzymatic approaches leading to diversification of alkaloids with novel improved structures. 相似文献