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C3-C4 intermediate photosynthetic characteristics of cassava (Manihot esculenta Crantz) 总被引:1,自引:0,他引:1
James H. Cock Nestor M. Riaño Mabrouk A. El-Sharkawy López F. Yamel Gonzalo Bastidas 《Photosynthesis research》1987,12(3):237-241
Cassava, bean and maize leaves were fed with14CO2 in light and the primary products of photosynthesis identified 5 and 10 seconds after assimilation. In maize, approximately three quarters of the labelled carbon was incorporated in C4 acids, in beans about two thirds in PGA, and in cassava approximately 40–60% in C4 acids with 30–50% in PGA. These data indicate that cassava possesses the C4 photosynthetic cycle, however due to the lack of typical Kranz anatomy appreciable carbon assimilation takes place directly through the Calvin-Benson-Bassham cycle. 相似文献
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Hernández-Barrera A Ugartechea-Chirino Y Shishkova S Napsucialy-Mendivil S Soukup A Reyes-Hernández BJ Lira-Ruan V Dong G Dubrovsky JG 《Planta》2011,234(6):1163-1177
An indeterminate developmental program allows plant organs to grow continuously by maintaining functional meristems over time. The molecular mechanisms involved in the maintenance of the root apical meristem are not completely understood. We have identified a new Arabidopsis thaliana mutant named moots koom 1 (mko1) that showed complete root apical meristem exhaustion of the primary root by 9?days post-germination. MKO1 is essential for maintenance of root cell proliferation. In the mutant, cell division is uncoupled from cell growth in the region corresponding to the root apical meristem. We established the sequence of cellular events that lead to meristem exhaustion in this mutant. Interestingly, the SCR and WOX5 promoters were active in the mko1 quiescent center at all developmental stages. However, during meristem exhaustion, the mutant root tip showed defects in starch accumulation in the columella and changes in auxin response pattern. Therefore, contrary to many described mutants, the determinate growth in mko1 seedlings does not appear to be a consequence of incorrect establishment or affected maintenance of the quiescent center but rather of cell proliferation defects both in stem cell niche and in the rest of the apical meristem. Our results support a model whereby the MKO1 gene plays an important role in the maintenance of the root apical meristem proliferative capacity and indeterminate root growth, which apparently acts independently of the SCR/SHR and WOX5 regulatory pathways. 相似文献
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María Consuelo Marín-Togo Tiberio C. Monterrubio-Rico Katherine Renton Yamel Rubio-Rocha Claudia Macías-Caballero Juan Manuel Ortega-Rodríguez Ramón Cancino-Murillo 《Biodiversity and Conservation》2012,21(2):451-473
Ecological niche models provide useful predictions of species distributions, but may fail to detect reductions in distribution
due to factors other than habitat loss, such as hunting or trade. From 2001 to 2009, we conducted field-surveys along the
Mexican Pacific coast to obtain presence–absence data for nine Psittacidae species. We applied Genetic Algorithm for Rule
set Prediction (GARP) ecological niche modeling, using field-survey presence data to determine the potential current distribution
of each species, and incorporated absence data to delineate extirpation areas. All parrot species showed a reduced current
distribution, ranging from 9.6 to 79% reduction of estimated original distribution. The threatened and endemic species of
Amazona
oratrix, Amazona
finschi, and Forpus
cyanopygius suffered the greatest distribution reduction, higher than previously estimated by habitat-based models, suggesting that capture
for trade may have caused extirpation of these species. The greatest extent of current distribution was occupied by Aratinga
canicularis, Amazona
albifrons and Ara
militaris, which continue to occur throughout most of their original distribution. Amazona
auropalliata, Aratinga
strenua, and Brotogeris
jugularis also occur throughout their restricted distribution in coastal Chiapas, and show a relatively small distribution reduction,
but had the highest proportion of modified lands within their current distributions. Our results highlighted the regions of
coastal Guerrero, northern Nayarit, and southern Sinaloa where parrot species have been extirpated even though GARP models
predicted suitable habitat available. Ideally distribution models should be verified in the field to determine conservation
priorities, and efforts should be directed to maintain populations of species with greatest distribution reductions. 相似文献
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Yamel Ugartechea-Chirino Ranjan Swarup Kamal Swarup Benjamin P��ret Morag Whitworth Malcolm Bennett Sue Bougourd 《Annals of botany》2010,105(2):277-289
Background and Aims
The root meristem of the Arabidopsis thaliana mature embryo is a highly organized structure in which individual cell shape and size must be regulated in co-ordination with the surrounding cells. The objective of this study was to determine the role of the AUX1 LAX family of auxin import carriers during the establishment of the embryonic root cell pattern.Methods
The radicle apex of single and multiple aux1 lax mutant mature embryos was used to evaluate the effect of this gene family upon embryonic root organization and root cap size, cell number and cell size.Key Results
It was demonstrated here that mutations within the AUX1 LAX family are associated with changes in cell pattern establishment in the embryonic quiescent centre and columella. aux1 lax mutants have a larger radicle root cap than the wild type and this is associated with a significant increase in the root-cap cell number, average cell size, or both. Extreme disorganization of the radicle apex was observed among quadruple aux1 lax1 lax2 lax3 mutant embryos, but not in single aux1 null or in lax1, lax2 and lax3 single mutants, indicating redundancy within the AUX1 LAX family.Conclusions
It was determined that the AUX1 LAX family of auxin influx facilitators participates in the establishment of cell pattern within the apex of the embryonic root in a gene-redundant fashion. It was demonstrated that aux1 lax mutants are affected in cell proliferation and cell growth within the radicle tip. Thus AUX1 LAX auxin importers emerge as new players in morphogenetic processes involved in patterning during embryonic root formation.Key words: AUX1 LAX genes, auxin, Arabidopsis thaliana, embryogenesis, meristem, radicle development, cell pattern establishment 相似文献5.
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