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181.
Epidermal and mesophyll tissues of Commelina communis L. andVicia faba L. were analysed by atomic absorption spectrometryfor the major plant inorganic cations and anions (K, Na, Ca,Mg, P, NO3-N, Cl) when stomata of the leaf were open and closed.Water-soluble and residual levels of the elements were estimatedand a charge balance of the soluble fraction made. The major portion of K, Na, Cl, and P was extracted in the water-solublefraction of the epidermal and mesophyll tissues of both species.In both species the bulk of Ca remained in the insoluble residueof the epidermis whereas in mesophyll tissue it was equallydistributed be-between the two fractions in C. communis butmainly in the insoluble residue in V. faba. Magnesium was predominantlyfound in the water-soluble fraction of V. faba mesophyll tissueand distributed approximately equally between the two fractionsin the epidermal tissue. In C. communis Mg was slightly moreabundant in the water-soluble fraction of both mesophyll andepidermis. In both species no statistically significant differences inthe levels of the elements could be detected between epidermaland mesophyll tissues from leaves with open stomata and thesame tissues from leaves with closed stomata, suggesting thatthere was no major flux of ions between mesophyll and epidermisduring stomatal movements. Regardless of whether the stomata were open or closed, therewere considerably more water-soluble inorganic cations thananions present in all tissues of both species with K being themajor cation and Cl being the major anion. In V.faba and C-communis epidermis there was 4953 per cent and 56%68per cent excess cation respectively. In the mesophyll tissuethe excess cation was 6375 per cent and 75%78 per centin V.faba and C. communis respectively. When the partitioning of the levels of the elements betweenepidermis and mesophyll of a leaf is considered, except forNO3-N in both species and Na in V. faba, 20 per cent or lessof each element was present in the epidermis. 相似文献
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EDWARD J. KLEKOWSKI JR. F.L.S. 《Botanical journal of the Linnean Society. Linnean Society of London》1970,63(2):153-169
Gametophytes of the fern Ceratopteris thalictroides originating from four different geographic areas were studied morphologically and genetically. Intraspecific variability was found among the collections for gametophyte morphology and the frequency of lethal sporophytic genotypes. The differences in gametophyte morphology were shown to result in a different mating system for each collection. 相似文献
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Nucleotide sequence analysis of the lemur beta-globin gene family: evidence for major rate fluctuations in globin polypeptide evolution 总被引:1,自引:0,他引:1
Lemur beta-related globin genes have been isolated and sequenced. Orthology
of prosimian and human epsilon-, gamma-, and beta-related globin genes was
established by dot-matrix analysis. All of these lemur globin genes
potentially encode functional beta-related globin polypeptides, though
precisely when the gamma-globin gene is expressed remains unknown. The
organization of the 18-kb brown lemur beta-globin gene cluster (5'
epsilon-gamma-[psi eta-delta]-beta 3') is consistent with its evolution by
contraction via unequal crossing-over from the putative ancestral mammalian
beta-globin gene cluster (5' epsilon-gamma- eta-delta-beta 3'). The dwarf
lemur nonadult globin genes are arranged as in the brown lemur. Similar
levels of synonymous (silent) nucleotide substitutions and noncoding DNA
sequence differences have accumulated between species in all of these
genes, suggesting a uniform rate of noncoding DNA divergence throughout
primate beta-globin gene clusters. These differences are comparable with
those observed in the nonfunctional psi eta pseudogene and have therefore
accumulated at the presumably maximal neutral rate. In contrast,
nonsynonymous (replacement) nucleotide substitutions show a significant
heterogeneity in distribution for both the same gene in different lineages
and different genes in the same lineage. These major fluctuations in
replacement but not silent substitution rates cannot be attributed to
changes in mutation rate, suggesting that changes in the rate of globin
polypeptide evolution in primates is not governed solely by variable
mutation rates.
相似文献
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