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Independent Evolution of Leaf and Root Traits within and among Temperate Grassland Plant Communities
Steven W. Kembel,James F. Cahill Jr.
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0019992
Abstract: In this study, we used data from temperate grassland plant communities in Alberta, Canada to test two longstanding hypotheses in ecology: 1) that there has been correlated evolution of the leaves and roots of plants due to selection for an integrated whole-plant resource uptake strategy, and 2) that trait diversity in ecological communities is generated by adaptations to the conditions in different habitats. We tested the first hypothesis using phylogenetic comparative methods to test for evidence of correlated evolution of suites of leaf and root functional traits in these grasslands. There were consistent evolutionary correlations among traits related to plant resource uptake strategies within leaf tissues, and within root tissues. In contrast, there were inconsistent correlations between the traits of leaves and the traits of roots, suggesting different evolutionary pressures on the above and belowground components of plant morphology. To test the second hypothesis, we evaluated the relative importance of two components of trait diversity: within-community variation (species trait values relative to co-occurring species; α traits) and among-community variation (the average trait value in communities where species occur; β traits). Trait diversity was mostly explained by variation among co-occurring species, not among-communities. Additionally, there was a phylogenetic signal in the within-community trait values of species relative to co-occurring taxa, but not in their habitat associations or among-community trait variation. These results suggest that sorting of pre-existing trait variation into local communities can explain the leaf and root trait diversity in these grasslands.
Closed soilless growing system for producing strawberry bare root transplants and runner tips
Giménez, Gustavo;Andriolo, Jer?nimo Luiz;Janisch, Djeimi;Godoi, Rodrigo;
Pesquisa Agropecuária Brasileira , 2008, DOI: 10.1590/S0100-204X2008001200016
Abstract: the objective of this work was to test a closed soilless growing system for producing bare root transplants and runner tips of two strawberry clones, using two categories of substrates. the system used corrugated roofing panels of fiber-cement, over which a substrate layer was used as a growing bed. the nutrient solution was pumped from a reservoir toward the upper end of the roofing panels and drained back to a reservoir. plant growth and development were determined for two advanced strawberry clones, grown in sand or in plantmax organic substrate. growth of the stock plants and the number and dry mass of bare root transplants were similar in the substrates, but bare roots differed in their crown diameters by substrate. for number of runner tips, no significant differences were found in total, small, and medium categories in the substrates. a mean production of about 590 runner tips per square meter and 145 bare root transplants per square meter was obtained. for both clones, a large number of bare root transplants and runner tips of adequate size were produced in the closed soilless growing system using sand or organic substrate.
Role of acetylcholine on plant root-shoot signal transduction
Hengbin Wang,Shuqiu Zhang,Xuechen Wang,Chenghou Lou
Chinese Science Bulletin , 2003, DOI: 10.1360/03tb9121
Abstract: The role of acetylcholine (ACh) on plant rootshoot communication was investigated using the root-split system of Vicia faba L. In the experiments, slight osmotic stress caused the decrease of ACh content in root tips and the xylem sap transported up per time unit from root tip to the shoot when the water potential of the shoot was kept unchanged. It also caused the decrease of ACh content in the abaxial epidermis. The decrease was highly correlative to the changes of transpiration rate, suggesting that the decrease of ACh content probably functions as a signal to regulate stomatal behavior. The effect of osmotic stress might be mainly through the inhibition of the ACh synthesis in root tip; thus further influences the ACh content in root tip, xylem sap and abaxial epidermis and resulting in the changes of stomatal behavior. These results provide new evidence that plants transduce positive and negative signals among roots and shoots to coordinate stomatal behavior and adapt to variable environments.
Concentration-dependent effects of narciclasine on cell cycle progression in Arabidopsis root tips
Xiaofan Na, Yanfeng Hu, Kun Yue, Hongxia Lu, Pengfei Jia, Huahua Wang, Xiaomin Wang, Yurong Bi
BMC Plant Biology , 2011, DOI: 10.1186/1471-2229-11-184
Abstract: Results showed that the inhibition of NCS on cell division in Arabidopsis root tips and its effects on cell differentiation are concentration-dependent; at low concentrations (0.5 and 1.0 μM) NCS preferentially targets mitotic cell cycle specific/cyclin complexes, whereas at high concentration (5.0 μM) the NCS-stimulated accumulation of Kip-related proteins (KRP1 and RP2) affects the CDK complexes with a role at both G1/S and G2/M phases.Our findings suggest that NCS modulates the coordination between cell division and differentiation in Arabidopsis root tips and hence affects the postembryonic development of Arabidopsis seedlings.The growth and development of multicellular organisms depends on the spatiotemporal coordination of cell proliferation, cell differentiation, and subsequent cell specialization [1]. During plant postembryonic development, meristematic tissues provide new cells for growth at both ends of the main body axis. Stem cells in the root meristem generate transit-amplifying cells, which undergo additional divisions in the proximal meristem, and differentiate in the meristem transition zone that encompasses the boundary between dividing and expanding cells in different cell files. The balances between cell proliferation, cell cycle arrest and differentiation to maintain the organogenetic program depend on the coordination of gene expression, posttranslational modification, and specific proteolysis of cell cycle regulators. The retinoblastoma (RB)-E2F pathway is one of the most important regulatory pathways that control and couple cell division and cell differentiation [2,3]. The E2F and DP proteins interact to form active transcription factors that bind to various gene promoters and regulate the expression of genes required for cell cycle progression. The RB protein binds to E2F proteins, masking the transactivation region and blocking the transcriptional activity. This repression can be released by phosphorylation of the RB protein, catalyzed by cy
Role of acetylcholine on plant root-shoot signal transduction
Hengbin Wang,Shuqiu Zhang,Xuechen Wang,Chenghou Lou,
WANGHengbin
,ZHANGShuqiu

科学通报(英文版) , 2003,
Abstract: The role of acetylcholine (ACh) on plant root- shoot communication was investigated using the root-split system of Vicia faba L. In the experiments, slight osmotic stress caused the decrease of ACh content in root tips and the xylem sap transported up per time unit from root tip to the shoot when the water potential of the shoot was kept un-changed. It also caused the decrease of ACh content in the abaxial epidermis. The decrease was highly correlative to the changes of transpiration rate, suggesting that the decrease of ACh content probably functions as a signal to regulate stomatal behavior. The effect of osmotic stress might be mainly through the inhibition of the ACh synthesis in root tip; thus further influences the ACh content in root tip, xy-lem sap and abaxial epidermis and resulting in the changes of stomatal behavior. These results provide new evidence that plants transduce positive and negative signals among roots and shoots to coordinate stomatal behavior and adapt to variable environments.
Iron fractions in the apoplast of intact root tips of Zea mays L. seedlings affected by nitrogen form
Chunqin Zou,Fusuo Zhang,H. E. Goldbach
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9164
Abstract: The effects of ammonium (NH 4 + -N) and nitrate (NO 3 -N) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0–3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture by using short-term experiment under controlled Fe deficiency conditions (containing high HCO 3 concentration in preculture solution). The results showed that Fe(II) concentrations in root tip apoplast of maize were only 20–40 nmol/g FW which accounted for 7%–13% of total Fe. Most of Fe in root tips existed as Fe(III) compounds. Imposition of the roots to NH 4 ±N or NO 3 N for 60 min led to an increase of Fe(II) in root tip apoplast. NH 4 ±N led to an increased concentration of Fe(II) and exchangeable Fe (Fe(II) and Fe (III)) in root tips, while NO 3 -N increased FeCN reductase activity. The relationship between pH and Fe fractions, FeCN reductase activity was also discussed.
Iron fractions in the apoplast of intact root tips of Zea mays L. seedlings affected by nitrogen form

ZOU Chunqin,ZHANG Fusuo,H E Goldbach,

科学通报(英文版) , 2002,
Abstract: The effects of ammonium (NH 4 + -N) and nitrate (NO 3 -N) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0–3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture by using short-term experiment under controlled Fe deficiency conditions (containing high HCO 3 concentration in preculture solution). The results showed that Fe(II) concentrations in root tip apoplast of maize were only 20–40 nmol/g FW which accounted for 7%–13% of total Fe. Most of Fe in root tips existed as Fe(III) compounds. Imposition of the roots to NH 4 ±N or NO 3 N for 60 min led to an increase of Fe(II) in root tip apoplast. NH 4 ±N led to an increased concentration of Fe(II) and exchangeable Fe (Fe(II) and Fe (III)) in root tips, while NO 3 -N increased FeCN reductase activity. The relationship between pH and Fe fractions, FeCN reductase activity was also discussed.
Physiological and genetic basis of plant tolerance to excess boron  [PDF]
Kastori Rudolf R.,Maksimovi? Ivana V.,Kraljevi?-Balali? Marija M.,Kobiljski Borislav ?.
Zbornik Matice Srpske za Prirodne Nauke , 2008, DOI: 10.2298/zmspn0814041k
Abstract: Boron (B) deficit as well as excess may significantly limit the organic production in plants. In extreme cases they may kill the affected plants. Boron excess occurs primarily in arid and semiarid regions, in saline soils or in consequence to human action. Excessive boron concentrations retard plant growth and cause physiological and morphological changes (chlorosis and necrosis) first of all in leaf tips and then in marginal or intercostal parts of the lamina. Physiological mechanisms of plant tolerance to boron excess have not been studied in sufficient detail. The predominant opinion holds that they are based on restricted uptake and accumulation of boron in the root and aboveground plant parts. Significant differences in boron excess tolerance have been observed not only between different crops but even between different genotypes of the same crop. This has enabled the breeding of crop genotypes and crops adapted to growing on soils rich in available boron and intensified the research on the inheritance of plant tolerance to high B concentration. Sources of tolerance to high B concentration have been found in many crops (wheat, mustard, pea, lentil, eucalypt). Using different molecular techniques based on PCR (RAPD, SRAP), plant parents and progenies have been analyzed in an attempt to map as precisely as possible the position of B-tolerant genes. Small grains have been studied in greatest detail for inheritance of B tolerance. B tolerance in wheat is controlled by at least four additive genes, Bo1, Bo2, Bo3 and Bo4. Consequently, there exists a broad range of tolerance levels. Studies of Arabidopsis have broadened our understanding of regulation mechanisms of B transport from roots to above ground parts, allowing more direct genetic manipulations.
Evaluation of the lengths and angles of the tips of rotatory files in root canal preparations
Drago, Mariana Aleluia;Pereira, Rosana de Souza;Schettino Junior, Miguel ?ngelo;
Revista Odonto Ciência , 2012, DOI: 10.1590/S1980-65232012000100011
Abstract: purpose: to detect changes in the angles and lengths of the tips of rotary nickel-titanium files after use. methods: forty human teeth were prepared with eight sets of rotary protaper? universal nickel-titanium files with a length of 25 mm and rotation of 350 rpm. the files were evaluated in a scanning electron microscope (sem) at three different times: group a - before use; group b - after using each file in the preparation of three molars; and group c - after using each file in the preparation of five molars. the length of the tip was determined by measuring the length of a straight line drawn parallel to the file axis, from the apex of the tip to its posterior border. the sem software provided the angle measurements. data were analyzed by using paired t-tests and wilcoxon tests. results: there were no differences between the groups for the s1 file. there was a decrease in length when the f2 file was used to prepare three and five molars, whereas decreases in length were seen when f5 files were used to prepare three or five molars. conclusion: the results suggest that the tips of the rotary instruments showed significant changes in length and angle even with relatively low use.
Structural Changes in Root Tips of Wheat (Triticum aestivum L.) in Response to Olive Oil Mill Wastewater  [PDF]
M. Aybeke,U. Sidal,G. Huseyin
Pakistan Journal of Biological Sciences , 2008,
Abstract: Toxic effects of the wastewater were investigated ultrastructurally in root tips of Triticum aestivum. As a result, wall and nuclear degradations, disruptions in all cytoplasmic membranes, irregular nucleus shapes and cellular organization defects were densely detected. Besides, germination ratio, total protein contents, DNA contents and root-shoot growth were found to be decreased significantly when compared to the control group. Results were compared with those of recent studies regarding excessive Na+, Fe+2, P, polyphenols and acidic pH toxicity.
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