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991.
A new sterol isolated from Costus species roots has been characterized as 5α-stigmast-9(11)-en-3β-ol by spectroscopic data and chemical studies. 相似文献
992.
Summary The uptake of Na and K by perennial ryegrass from flowing solution culture with monitored concentrations of Na and K was followed
in two experiments. In the first, when only 50 and 10 per cent of the K uptake by one set of plants, grown with K held constant
at 2.5 μeq 1−1, was supplied to two other linked sets of plants and the balance supplied as Na, there was a rapid decrease in K, and an
increase in Na, concentration in the shoots over a 20-day period. However, when compared with the plants grown in K in solution
held constant, there was not a complete replacement of Na for K. In the second experiment the concentration of K in the culture
solution was held constant at 2 μeq 1−1 and Na at 0, 5, 25, 50 and 100 μeq 1−1. Although uptake of Na increased with increasing concentration in solution the contents in the plants were low,i.e. less than 0.19 per cent and decreased with time. There was an increase in the yield of both shoots and roots with increasing
Na in the solution; it was suggested that, during the early stages of growth there may have been an inadequate supply of K
and that Na may have substituted for K in some of the non-specific roles of K in the plants. There was evidence in both experiments
that a flux of H-ions was involved in the uptake of Na. 相似文献
993.
Charles L. Stinemetz 《Plant Growth Regulation》1967,16(1):83-92
The curvature of roots in response to gravity is attributed to the development of a differential concentration gradient of IAA in the top and bottom of the elongation region of roots. The development of the IAA gradient has been attributed to the redistribution of IAA from the stele to cortical tissues in the elongation region. The gravistimulated redistribution of IAA was investigated by applying [3H]IAA to the cut surface of 5 mm apical primary root segments. The movement of label from the stele-associated [3H]IAA into the root, tip, root cap, and cortical tissues on the top and bottom of the elongation region was determined in vertically growing roots and gravistimulated roots. Label from the stele moved into the region of cell differentiation (root tip) prior to accumulating in the elongation region. Little label was observed in the root cap. Gravistimulation did not increase the amount of label moving from the stele; but gravistimulation did increase the amount of label accumulating in cortical tissues on the lower side of the elongation region, and decreased the amount of label accumulating in cortical tissues on the upper side of the elongation region. Removal of the cap prior to or immediately following gravity stimulation rendered the roots partially insensitive to gravity and also prevented gravity-induced asymmetric redistribution of label. However, removal of the root cap following 30 min of gravistimulation did not alter root curvature or the establishment of an IAA asymmetry across the region of root elongation. These results suggest that a signal originating in the root cap directs auxin redistribution in tissues behind the root cap, leading to the development of an asymmetry of IAA concentration in the elongation region that in turn causes the differential growth rate in the elongation region of a graviresponding root. 相似文献
994.
995.
Yi Yang-Hua 《Phytochemistry》1991,30(12):4179-4181
A new triterpenoid, esculentagenin, and its glycoside, esculentoside M, were isolated from the roots of Phytolacca esculenta and characterized as 11-oxo-3-O-methyloleanata-12-en-2β,3β,23-trihydroxy-28-oic acid and 3-O-[β -
-glucopyranosyl (1→4)-β-
-Xylopyranosyl]-28-O-β-
-glucopyranosyl-11-oxo-30-methyloleanate-12-en-2β,3β,23-trihydroxy-28-oic acid by spectral and chemical evidence. 相似文献
996.
Adventitious roots were observed on 3 wild perennialGlycine species, in short-poddedG. clandestina, G. latifolia and mostG. tabacina (2x, 4x, 6x), while other species lacked adventitious roots. This suggests that the adventitious roots trait is associated with B genome species. Intra- and interspecific F1 hybrids reveal that adventitious roots apparently are inherited recessively. The presence of adventitious roots or short-poddedG. clandestina, coupled with infertility with longer-poddedG. clandestina, and enzymatic and leaflet morphology differences between the twoG. clandestina subgroups, supports segregation of the short-podded form as a separate taxon. 相似文献
997.
R. J. Robins J. D. Hamill A. J. Parr K. Smith N. J. Walton M. J. C. Rhodes 《Plant cell reports》1987,6(2):122-126
The addition of exogenous nicotinic acid, nicotinamide or nicotine was studied with reference to their effects on growth and alkaloid production by hairy root cultures of Nicotiana rustica. Nicotinic acid and nicotinamide were toxic (50% phytostatic dose being 2.4 and 9 mM respectively) while nicotine was not toxic below 10 mM. Nicotinic acid (up to 5 mM) was found to be phytostatic rather than phytotoxic. Roots exposed to increasing nicotinic acid or nicotinamide levels had altered alkaloid accumulation patterns relative to the controls. The principal effects were to increase the intracellular and extracellular levels of anatabine and nicotine, with a markedly greater proportion of anatabine being produced. The use of nicotinic acid as a selection agent for the recovery of higher alkaloid-producing lines is identified and discussed. 相似文献
998.
Two synthetic oligonucleotide probe mixtures, whose sequences were inferred from two separate stretches of amino acids, one
closer to the carboxy terminal and the other closer to the amino terminal, of ferredoxin I protein ofAzotobacter vinelandii, were used to select ferredoxin I gene clones from a cosmid gene library ofAzotobacter vinelandii. Restriction analysis revealed that 7 out of 10 selected clones were of the same type. All these clones were found to hybridize
withfixABCX genes ofRhizobium meliloti. 相似文献
999.
Pathways of assimilation and transfer of fixed nitrogen in coralloid roots of cycad-Nostoc symbioses
Freshly detached coralloid roots of several cycad species were found to bleed spontaneously from xylem, permitting identification of products of nitrogen transfer from symbiotic organ to host. Structural features relevant to the export of fixed N were described for Macrozamia riedlei (Fisch. ex Gaud.) Gardn. the principal species studied. Citrulline (Cit), glutamine (Gln) and glutamic acid (Glu), the latter usually in a lesser amount, were the principal translocated solutes in Macrozamia (5 spp.), Encephalartos (4 spp.) and Lepidozamia (1 sp.), while Gln and a smaller amount of Glu, but no Cit were present in xylem sap of Bowenia (1 sp.),and Cycas (2 spp.). Time-course studies of 15N enrichment of the different tissue zones and the xylem sap of 15N2-pulse-fed coralloid roots of M. riedlei showed earlier 15N incorporation into Gln than into Cit, and a subsequent net decline in the 15N of Gln of the coralloid-root tissues, whereas Cit labeling continued to increase in inner cortex and stele and in the xylem sap. Hydrolysis of the 15N-labeled Cit and Gln consistently demonstrated much more intense labeling of the respective carbamyl and amide groups than of the other N-atoms. Coralloid roots of M. riedlei pulse-fed 14CO2 in darkness showed 14C labeling of aspartic acid (Asp) and Cit in all tissue zones and of Cit of xylem bleeding sap. Lateral roots and uninfected apogeotropic roots of M. riedlei and M. moorei also incorporated 14CO2 into Cit. The 14C of Cit was restricted to the carbamyl-C. Comparable 15N2 and CO2-feeding studies on corallid roots of Cycas revoluta showed Gln to be the dominant product of N2 fixation, with Asp and alanine as other major 14C-labeled amino compounds, but a total absence of Cit in labeled or unlabeled form.Abbreviations Ala
alanine
- Asp
aspartic acid
- Cit
citrulline
- Gln
glutamine
- Glu
glutamic acid
- Orn
ornithine 相似文献
1000.
Summary The two main types of fibrous flagellar roots present in the flagellar apparatus of green algae (system I and system II fibers) are immunologically distinct as indicated by the localization of a Ca2+-modulated contractile protein (centrin) exclusively in one type (system II fibers) but not in the other type (system I fibers). A polyclonal antibody generated against the major protein of the striated flagellar roots (system II fibers) of the quadriflagellate green algaTetraselmis striata was used to localize centrin by immunofluorescence and pre- and postembedding immunogold electron microscopy in the flagellar apparatus ofSpermatozopsis similis, S. exsultans, Chlamydomonas reinhardtii, Dunaliella bioculata, Polytomella parva and gametes ofMonostroma grevillei andEnteromorpha sp. Whereas the antibody recognizes centrin in connecting fibers and system II fibers, no labeling occurs in system I fibers in all taxa investigated. This study presents the first evidence that system I fibers lack centrin and indicates that the two main types of fibrous flagellar roots in green algae are biochemically distinct. 相似文献