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81.
82.
Causes of root growth retardation induced by ultraviolet-B irradiation of shoots in Barley seedlings
I. N. Ktitorova O. V. Skobeleva E. V. Kanash T. E. Bilova E. I. Sharova 《Russian Journal of Plant Physiology》2006,53(1):85-95
In barley seedlings (Hordeum vulgare L.) during two days after irradiation of shoots with UV-B (0.5 W/m2, 6 h), the rate of elongation of primary roots decreased 2–3 times compared to that in control plants. The modulus of elasticity of roots (ε) increased at most twofold in 12 h after the onset of irradiation; the hydraulic conductivity (L p) diminished by a factor of two in 12 h, and the root osmotic pressure gradually decreased by 0.08 MPa in 24 h. Changes in ε and L p were shown to be related to oxidative stress in growing roots, which was evidenced from the increase in H2O2 level up to 15-fold increase in 6 h and in activity of guaiacol peroxidase (3.5-fold in 12 h). After 48 h, the characteristics of oxidative metabolism and root characteristics ε and L p became identical in untreated and treated plants. On the third day, the rate of root growth in treated plants reached its initial value. It is concluded that the main causes of retardation of root growth under these conditions were as follows: the increase in cell wall rigidity related to formation of oxidative cross-links in the apoplast and the decrease in root osmotic pressure due to limited transport of assimilates from irradiated leaves. After the intensity of UV-B irradiation applied to shoots was enhanced (1.6 W/m2, 4 h), another physiological status of roots was observed on the 2nd day characterized by twofold increase in L p, tenfold decreased root elongation rate, and by a progressing increase of root diameter in growing roots. The comparison of root responses induced by irradiation of shoots with the root responses to sodium salicylate and ABA suggests that both agents might participate in the transmission of signals from irradiated leaves to roots. 相似文献
83.
A chlorophyll deficient mutant of Hordeum vulgare L. was investigated with respect to its transpiration response to light pulses. Broad band blue light. 380–500 nm, caused a significant transpiration response, while broad band red light did not. The transpiration response to changes in the ambient CO2-concentration was the same in the chlorophyll deficient mutant as in green plants. The absence of a transpiration response to red light in the mutant was therefore not the result of a defective CO2-response. It is concluded that the specific blue light response is not mediated via photosynthetic CO2-fixation. The nature of the blue light response is discussed. 相似文献
84.
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86.
Background and Aims
Aluminium is toxic in acid soils because the soluble Al3+ inhibits root growth. A mechanism of Al3+ tolerance discovered in many plant species involves the release of organic anions from root apices. The Al3+-activated release of citrate from the root apices of Al3+-tolerant genotypes of barley is controlled by a MATE gene named HvAACT1 that encodes a citrate transport protein located on the plasma membrane. The aim of this study was to investigate whether expressing HvAACT1 with a constitutive promoter in barley and wheat can increase citrate efflux and Al3+ tolerance of these important cereal species.Methods HvAACT1
was over-expressed in wheat (Triticum aestivum) and barley (Hordeum vulgare) using the maize ubiquitin promoter. Root apices of transgenic and control lines were analysed for HvAACT1 expression and organic acid efflux. The Al3+ tolerance of transgenic and control lines was assessed in both hydroponic solution and acid soil.Key Results and Conclusions
Increased HvAACT1 expression in both cereal species was associated with increased citrate efflux from root apices and enhanced Al3+ tolerance, thus demonstrating that biotechnology can complement traditional breeding practices to increase the Al3+ tolerance of important crop plants. 相似文献87.
The gradients in photosynthetic and carbohydrate metabolism which persist within the fully expanded second leaf of barley ( Hordeum vulgare ) were examined. Although all regions of the leaf blade were green and photosynthetically active, the basal 5 cm, representing approximately 20% of the leaf area, retained some characteristics of sink tissue. The leaf blade distal from the leaf sheath exhibited characteristics typical of source tissue; the activities of sucrolytic enzymes (invertase and sucrose synthase) were relatively low, whilst that of sucrose phosphate synthase was high. These regions of the leaf accumulated sucrose throughout the photoperiod and starch only in the second half of the photoperiod whilst hexose sugars remained low. By contrast the leaf blade proximal to the leaf sheath retained relatively high activities of sucrolytic enzymes (especially soluble, acid invertase) whilst sucrose phosphate synthase activity was low. Glucose, as well as sucrose, accumulated throughout the photoperiod. Although starch accumulated in the second half of the photoperiod, a basal level of starch was present throughout the photoperiod, by contrast with the rest of the leaf. The 14 CO2 feeding experiments indicated that a constant amount of photosynthate was partitioned towards starch in this region of the leaf irrespective of irradiance. These findings are interpreted as the base of the leaf blade acting as a localized sink for carbohydrate as a result of sucrose hydrolysis by acid invertase. 相似文献
88.
Stress-induced degradation of D1 protein and its photoprotection by DCPIP in isolated thylakoid membranes of barley leaf 总被引:1,自引:0,他引:1
Effects of various stress treatments such as NaCl, hydrogen peroxide, hydroxyl free radical, and high irradiance (HI, 1 000
μmol m−2 s−1) on the photosystem (PS) 2 mediated electron transport rate and the degradation of D1 protein in the thylakoid membranes
of barley were studied. The applied stresses caused significant reduction in the PS 2-mediated electron transport and a degradation
of D1 protein that was highest during the HI-treatment. Presence of 2,6-dichlorophenol indophenol (DCPIP), which is an artificial
electron acceptor from water, significantly minimizes the HI-induced deleterious effect on the PS 2-mediated electron transport
rate, disarrangement of PS machinery, and degradation of the D1 protein. HI in the absence of an acceptor resulted in production
of reactive oxygen species due to electron transfer to oxygen. 相似文献
89.
Summary Differences in the activity and structure of the vacuolar H+-ATPase (V-ATPase, EC 3.6.1.3) were investigated in the C3/CAM intermediate plantKalanchoë blossfeldiana Poellnitz cv. Tom Thumb, with lower or higher expression of CAM, andHordeum vulgare cv. Carina, grown with or without 150 mM NaCl. InK. blossfeldiana ATP-hydrolysis and H+-transport activity were higher with higher expression of CAM than in plants with very weak CAM. This was mainly due to a larger amount of V-ATPase. Statistical analysis of the diameter of intramembrane particles (IMPs) on freeze-fractures of tonoplast vesicles showed that IMPs were larger in tonoplast vesicle preparations ofK. blossfeldiana with strong CAM expression (9.1 nm) than in preparations ofK. blossfeldiana with low CAM expression (7.3 nm). As there is evidence that the majority of IMPs on freeze-fractures of tonoplast vesicles corresponds to the V0 domain of V-ATPase, the higher activity of V-ATPase inK. blossfeldiana with stronger CAM could be a result of additional structural changes in its membrane-integral domain. The higher activity of V-ATPase inK. blossfeldiana with stronger CAM is discussed in relation to the requirement for a higher proton pumping capacity for nocturnal malate accumulation in the vacuole. The ATP-dependent H+-pumping activity inH. vulgare was higher under salt stress than in control plants, while the rates of ATP-hydrolysis and the size of IMPs were not affected by the salt treatment. The data presented here indicate that different mechanisms might increase the transport capacity of V-ATPase to meet the higher requirements of secondary active transport related to CAM expression and adaptation to salt stress.Abbrevations ATP
adenosine triphosphate
- CAM
crassulacean acid metabolism
- IMP
intramembrane particles
- V-ATPase
vacuolar proton-translocating adenosine triphosphatase
- V0
domain membrane-integral domain of V-ATPase
- V1
domain membrane-peripheral domain of V-ATPase
Dedicated to Prof. Dr. Eberhard Schnepf on the occasion of his retirement 相似文献
90.
Martin Wood 《Plant and Soil》1987,97(3):303-314
Summary Laboratory data for the loss of root material by barley and field data for the growth of barley plants in Syria and in England
have been combined to predict the amount of material lost by barley roots during a season, and to predict the resulting microbial
biomass in the rhizosphere. The predicted microbial biomass C in the rhizosphere ranged from 10–34% of the total plant biomass
C depending mainly upon the value used for rate of loss of root material. Total loss of root material predicted during a season
in England constituted 7.7–25.4 percent of C fixed by photosynthesis. The major assumptions made in these calculations are
considered, and the predicted values discussed in relation to reported values for soil microbial biomass, CO2 fluxes from soil and associative nitrogen fixation. 相似文献