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1.
Summary The mechanism of water movement across roots is, as yet, not well understood. Some workable black box theories have already been proposed. They, however, assumed unrealistic cell membranes with low values of , or were based on a poor anatomical knowledge of roots. The role of root stele in solute and water transport seems to be especially uncertain. An attempted explanation of the nature of root exudation and root pressure by applying the apoplast canal theory (Katou andFurumoto 1986 a, b) to transport in the root stele is given. The canal equations are solved for boundary conditions based on anatomical and physiological knowledge of the root stele. It is found that the symplast cell membrane, cell wall and net solute transport into the wall apoplast are the essential constituents of the canal system. Numerical analysis shows that the canal system enables the coupled transport of solutes and water into a xylem vessel, and the development of root pressure beyond the level predicted by the osmotic potential difference between the ambient medium and the exudate. Observations on root exudation and root pressure previously reported seem to be explained quite well. It is concluded that the movement of water in the root stele although apparently active is essentially osmotic.Abbreviations J
v
ex
volume exudation per root surface
- J0
non-osmotic exudation
- Lr
overall radial hydraulic conductivity of an excised root
-
reflection coefficient
- Cs
difference in the osmotic concentration between the bathing medium and the exudate
- R
gas constant
- T
absolute temperature
- CK
molar concentration of K+
- CCl
molar concentration of Cl–
- Cj
molar concentration of ion species j
- Pj
membrane permeability of ion j
- zj
valence of ion j
- F
Faraday constant
- Vix
intracellular electric potential with reference to the canal 相似文献
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6.
Summary There are many contradictory observations on the mechanohydraulic relation of growing higher plant cells and tissues. Graphical analysis of the simultaneous equations which govern irreversible wall yielding and water absorption has made more comprehensive the understanding of this relation when relative growth rate is plotted against turgor pressure. It suggests that some respiration-dependent and auxin sensitive process might regulate the difference of osmotic potential between cells and water source. Based on anatomical and electrophysiological knowledge of the pea stem xylem, we propose the wall canal system as the mechanism of respiration-dependent water uptake which is sensitive to auxin. This system consists of the xylem apoplastic walls, the xylem proton pumps, active solute uptake system and cell membranes. In the simplest case, third-order simultaneous differential equations are involved. Numerical analysis showed that net uptake of solutes enables water to be taken up against an opposing gradient of water potential. The behaviour of this wall canal system describes well the mechano-hydraulic relation of enlarging plant cells and tissues. Recent typical, but incompatible, interpretations of this relation are critically discussed based on our model.Abbreviations V
the volume of enlarging symplast
-
the average extensibility of the wall
- Pi
turgor pressure
- Y
the yield threshold of the wall
- L
the relative hydraulic conductance
-
the solute reflection coefficient of the plasmamembrane
- Ci
the osmotic concentration of the symplast cells
- Cx
the osmotic concentration of the xylem vessels
- Px
hydrostatic pressure in the xylem vessels
- R
the gas constant
- T
absolute temperature
- o
water potential of xylem fluid
- i
water potential of symplast cells 相似文献
7.
Summary
Panax ginseng hairy root cultures were established by infecting petiole segments with Agrobacterium rhizogenes strain 15834. Hairy root segments including root tips placed onto phytohormone-free 1/2 Murashige and Skoog solid medium and stored at 4 °C in the dark for 4 months, resumed elongation when the temperature was raised to 25 °C in the dark. For cryopreservation, a vitrification method was applied. Root tips precultured with 0.1 mg/l 2,4-D for 3 days and dehydrated with PVS2 solution for 8 minutes prior to immersion into liquid nitrogen had a survival rate of 60 % and could regenerate. The hairy roots regenerated from cryopreserved root tips grew well and showed the same ginsenoside productivity and patterns as those of the control hairy roots cultured continuously at 25 °C. The conservation of T-DNAs in the regenerated hairy roots was proved by PCR analysis.Abbreviations 1/2 MS
a half strength Murashige and Skoog (1962)
- B5
Gamborg B5 (Gamborg et al. 1968)
- WP
woody plant (Lloyd and McCown 1980)
- RC
root culture (Thomas and Davey 1982)
- RCI
root culture medium containing 100 mg/l myoinositol
- HF
phytohormone-free
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- TIBA
2,3,5-triiodobenzoic acid
- PCR
polymerase chain reaction
- PVS2
plant vitrification solution 2 (Sakai et al., 1990)
- FDA
fluorecein diacetate 相似文献
8.
Mondher Jaziri Kayo Yoshimatsu Jacques Homès Koichiro Shimomura 《Plant Cell, Tissue and Organ Culture》1994,38(2-3):257-262
Hairy root cultures of Atropa belladonna L. were established by infection either with Agrobacterium rhizogenes ATCC 15834 or MAFF 03-01724, and transgenic plants were obtained from both hairy root cultures. Doubly transformed roots were induced by re-infection of the leaf segments of transgenic Atropa belladonna plants (A. rhizogenes 15834) with MAFF 03-01724. Shoots and viviparous leaves were regenerated from the doubly transformed roots. The genetic transformation was determined by the opine assay (agropine, mannopine and/or mikimopine) and polymerase chain reaction. Physiological changes and tropane alkaloid biosynthesis in the hairy roots (singly and doubly transformed) were investigated. The alkaloid content in the doubly transformed root strain was intermediate as compared to the root strains which were singly transformed. On the other hand endogenous IAA levels in doubly transformed roots were significantly decreased compared to both singly transformed roots.Abbreviations BA
benzyladenine
- IAA
indoleacetic acid
- NAA
naphthaleneacetic acid
- PCR
polymerase chain reaction
-
t-ZR
trans-zeatin 相似文献
9.
Kayo Kobayashi Yasuhiro Kamei Masato Kinoshita Thomas Czerny Minoru Tanaka 《Genesis (New York, N.Y. : 2000)》2013,51(1):59-67
We established three lines of transgenic medaka, a heat‐shock element (HSE) monitor line (hse‐GFP line), heat‐inducible driver lines (hse‐cre lines), and effector lines (gapdh‐loxP[DsRed]‐GFP lines). We employed these to comprehensively analyze gene induction at different time points in various tissues. These analyses demonstrate a good response of synthetic HSEs by heat treatment during embryogenesis and the mosaic gene induction by cre/loxP‐mediated recombination, thus providing practical information regarding the feasibility of a heat‐inducible cre/loxP‐mediated system in medaka. We also activated recombination by local heat‐treatment using a metal probe and an infrared laser. Our results collectively indicate that these lines allow us to perform lineage tracing and mosaic analysis and provide the platform to investigate gene functions at later developmental stage and adult. genesis 51:59–67, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
10.
Mitsuhide Hamaguchi Hironari Kamikubo Kayo N. Suzuki Yoshihisa Hagihara Itaru Yanagihara Ikuhiro Sakata Mikio Kataoka Daizo Hamada 《PloS one》2013,8(8)
Enterohaemorrhagic E. coli (EHEC) induces actin reorganization of host cells by injecting various effectors into host cytosol through type III secretion systems. EspB is the natively partially folded EHEC effector which binds to host α-catenin to promote the actin bundling. However, its structural basis is poorly understood. Here, we characterize the overall structural properties of EspB based on low-resolution structural data in conjunction with protein dissection strategy. EspB showed a unique thermal response involving cold denaturation in the presence of denaturant according to far-UV circular dichroism (CD). Small angle X-ray scattering revealed the formation of a highly extended structure of EspB comparable to the ideal random coil. Various disorder predictions as well as CD spectra of EspB fragments identified the presence of α-helical structures around G41 to Q70. The fragment corresponding to this region indicated the thermal response similar to EspB. Moreover, this fragment showed a high affinity to C-terminal vinculin homology domain of α-catenin. The results clarified the importance of preformed α-helix of EspB for recognition of α-catenin. 相似文献