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51.
This study was the first attempt to extract RNA from black willow (Salix nigra Marshall) that contains numerous secondary products and to examine the photosynthetic gene expression of black willow under
a wide range of soil moisture regimes. Black willow cuttings were grown under control, continuous flooding, periodic flooding
and periodic drought for 42 d. A modified lithium chloride precipitation method was used for RNA extraction. Results of real-time
polymerase chain reaction showed reduced gene expression of oxygen evolving complex, large subunit of ribulose-1,5-bisphosphate
carboxylase/oxygenasse and ferredoxin on day 7 as well as the latter two on day 14 in response to flooding. Therefore, decreased
expression of these three genes may have contributed to the observed reduced photosynthetic capacity in response to flooding. 相似文献
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In the southern United States, much of the emphasis in bottomland restoration is placed on establishing an oak-dominated forest. Artificial regeneration is an alternative for restoration on cleared lands and where a desirable seed source is not present. Currently the standard procedure for seedling preparation is to prune the roots prior to transplanting in the field. It is not fully known what effect(s) root pruning has on transplanted seedlings. In addition, bottomland restoration efforts inherently take place on floodplains. The potential interaction between root pruning and flooding on seedling performance is not known. This study consisted of two separate but related laboratory experiments. The purpose of the first experiment was to quantify the effects of various percentages of root removal and varying soil moisture regimes on transplanted Nuttall oak seedlings (Quercus nuttallii Palmer). Root pruning treatments consisted of removal of roots at 0%, 25% and 75% while soil moisture regime was maintained at non-flooded or periodically flooded conditions. Plant gas exchange, growth, and survival were measured. Root pruning alone had adverse effects on height growth during the first 72 days following transplanting. Periodic flooding also produced adverse effects on stomatal conductance (p = 0.0002), height growth (p = 0.005), and survival (p = 0.02). Photosynthetic data indicated that as pruning intensified in the periodically flooded seedlings, photosynthetic rates decreased. In contrast, as pruning intensified in the non-flooded seedlings, photosynthesis increased. This demonstrated that pruning rate had a varying effect on photosynthesis dependent upon soil moisture condition. Experiment 2 focused on the effects of varying degrees of root pruning on new root formation. The seedlings were grown under laboratory conditions, harvested at 0, 10, 20, and 30 days after treatment initiation, and analyzed for new root formation. Results of Experiment 2 indicated no difference in new root formation, root length, or root biomass due to the pruning treatment. Overall, our results from both experiments indicated that root pruning had no detectable long-term adverse effects on growth and survival of seedlings under drained soil conditions; however, as results from Experiment 1 demonstrated, if seedlings were planted in periodically flooded conditions, root pruning produced adverse effects. Thus, in restoration efforts utilizing Nuttall oak seedlings, the planting strategy and pruning rate should be carefully evaluated based on the knowledge of sites' hydrology. Alternatively, on sites with unpredictable flooding both pruned and unpruned seedlings may be utilized to ensure survival. 相似文献
55.
Collier RJ Annen-Dawson EL Pezeshki A 《Animal : an international journal of animal bioscience》2012,6(3):403-414
The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period. 相似文献
56.
We quantified the physiological responses of black willow to four soil moisture regimes: no flooding (control, C), continuous flooding (CF), periodic flooding (PF), and periodic drought (PD). Stomatal limitation was one of the factors that led to the reduced photosynthetic capacity in CF cuttings. Under PD, stomatal closure, decreased leaf chlorophyll content, and increased dark fluorescence yield contributed to photosynthetic decline. CF cuttings accumulated the lowest shoot biomass while the final height and root growth were most adversely affected by PD. PF cuttings tended to allocate more photoassimilates to root growth than to shoots. 相似文献
57.
Tallury SP Hilu KW Milla SR Friend SA Alsaghir M Stalker HT Quandt D 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2005,111(7):1229-1237
Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but
the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic
relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic
information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related
to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited
genomic regions show promise in understanding genome types and relationships in Arachis. 相似文献
58.
The simple repeat poly(dT-dG).poly(dC-dA) common to eukaryotes is absent from eubacteria and archaebacteria and rare in protozoans 总被引:5,自引:0,他引:5
Genomic DNA from a wide variety of prokaryotic and eukaryotic organisms has
been assayed for the simple repeat sequence poly(dT-dG).poly(dC-dA) by
Southern blotting and DNA slot blot hybridizations. Consistent with
findings of others, we have found the simple alternating sequence to be
present in multiple copies in all organisms in the animal kingdom (e.g.,
mammals, reptiles, amphibians, fish, crustaceans, insects, jellyfish,
nematodes). The TG element was also found in lower eukaryotes
(Saccharomyces cerevisiae, Neurospora crassa, and Dictyostelium discoideum)
and at a much lower frequency in protozoans (Oxytricha fallux and
Tetrahymena thermophila). The sequence was also repeated in high copy
number in a higher plant (Zea mays) as well as at very high levels in a
unicellular green alga (Chlamydomonas reinhardi). Although the copy number
of the repeat per haploid genome was generally proportional to genome size,
there was a greater-than-1,000-fold variation in the number of
(TG)25/100-kb genomic DNA. By contrast, no eu-or archaebacterium--including
Myxococcus xanthus, whose life cycle is very similar to that of the slime
mold Dictyostelium discoideum, and Halobacter volcanii, whose genome
contains other repeated sequences-- was found whose genomic DNA contained
this sequence in detectable amounts. A computer search also failed to find
the TG element in human mitochondrial DNA.
相似文献
59.
Interaction among sediment anaerobiosis, nitrogen uptake and photosynthesis of Spartina alterniflora
Spartina alterniflora Lois. plants were grown under controlled sediment-pH-redox conditions. Uptake of added 15 NH4 -nitrogen and subsequent photosynthetic activity under different redox conditions in the plant root rhizosphere were measured. Data for total plant nitrogen and 15 N concentration indicated that nitrogen allocation was not altered by anaerobic conditions of the sediment. However, average net photosynthesis was reduced by up to 35% for plants under anaerobiosis. The results indicate that anaerobiosis in the root rhizosphere, rather than limiting nitrogen uptake, influences photosynthesis and growth of S. alterniflora under anaerobic conditions. 相似文献
60.
Protein evolution in different cellular environments: cytochrome b in sharks and mammals 总被引:4,自引:0,他引:4
DNA sequences for the mitochondrial cytochrome b gene were determined for
13 species of sharks. Rates and patterns of amino acid replacement are
compared for sharks and mammals. Absolute rates of cytochrome b evolution
are six times slower in sharks than in mammals. Bivariate plots of the
number of nonsynonymous and silent transversions are indistinguishable in
the two groups, however, suggesting that the differences in amino acid
replacement rates are due primarily to differences in DNA substitution
rates. Patterns of amino acid replacement are also similar in the two
groups. Conserved and variable regions occur in the same parts of the
cytochrome b gene, and there is little evidence that the types of amino
acid changes are significantly different between the groups. Similarity in
the relative rates and patterns of protein change between the two groups
prevails despite dramatic differences in the cellular environments of
sharks and mammals. Poor penetrance of physiological differences through to
rates of protein evolution provides support for the neutral theory and
suggests that, for cytochrome b, patterns of evolution have been relatively
constant throughout much of vertebrate history.
相似文献